Physiological Psychology Flashcards
1
Q
Brenda Milner
A
British-Canadian neuropsychologist who has contributed extensively to the research literature on various topics in the field of clinical neuropsychology, and is sometimes referred to as the founder of neuropsychology. In particular, she studied the severe anterograde amnesia of H. M.
2
Q
Limitations of Schachter and Singer’s
Two-Factor Theory of Emotion
A
Schachter and Singer’s two-factor theory has attracted a good deal of controversy, as some studies have corroborated their findings but others have not. Overall, it now appears that one limited but important conclusion can be drawn: When people are unclear about their own emotional states, they sometimes interpret how they feel by watching others. The “sometimes” is important. For other people to influence your emotion, your level of physiological arousal cannot be too intense or else it will be experienced as aversive, regardless of the situation. Also, other people must be present before the onset of arousal.
3
Q
Schachter-Singer Two-Factor Theory of Emotion
A
Stanley Schachter and J. E. Singer proposed that the subjective experience of emotion is based on the interaction between changes in physiological arousal and cognitive interpretation of that arousal, which is influenced by the situational context. They conducted a famous experiment in which they injected subjects with epinephrine (under various conditions of disclosure or misinformation) and had a confederate model behavior that was either euphoric or angry. The results supported the hypothesis: drug-uninformed participants reported feeling relatively happy or angry depending on the confederate’s performance.
4
Q
Cannon-Bard Theory of Emotion
A
Walter Cannon and Philip Bard, objecting to the James-Lange Theory, argued that physiological changes and subjective feeling of an emotion are separate and independent; arousal does not have to occur before the emotion. In particular, they proposed that emotional expression results from the function of hypothalamic structures, while emotional feeling results from stimulations of the dorsal thalamus. The Cannon-Bard theory is also referred to as the thalamic theory of emotion. Cannon discovered that any activation of the sympathetic nervous system essentially produces the same physiological response. Cannon and Bard thus argued that subjective experience of emotion implicates specific neural circuits in the brain, with different circuits corresponding to different emotions, and that emotional feeling can be simultaneous with physiological arousal.
5
Q
James-Lange Theory of Emotion
A
William James and Carl Lange proposed the James-Lange theory of emotion during the late 19th century, arguing that we become aware of our emotion after we notice our physiological reactions to some external event. James wrote that “we feel sorry because we cry, angry because we strike, afraid because we tremble.” In formal terms, a temporal sequence is posited:
- Event (for example, a frightening situation)
- Appraisal (the cognitive aspect)
- Action (the behavioral aspect, including physiology)
- Emotional feeling (the feeling aspect)
6
Q
During what phase of sleep do sleepwalking, sleep talking, and night terrors (experiences of intense anxiety which lead people to awaken screaming in terror) typically occur?
A
Non-REM Sleep (NREM)
7
Q
Insomnia, Narcolepsy, and Sleep Apnea
A
Insomnia is a disturbance affecting the ability to fall asleep and/or stay asleep. Narcolepsy is a condition characterized by lack of voluntary control over the onset of sleep. The narcoleptic has sudden, brief episodes of sleep. Sleep apnea is an inability to breathe during sleep, sometimes for more than a minute. People with sleep apnea awaken often during the night in order to breathe.
8
Q
REM Rebound
A
When people are specifically deprived of REM sleep, but are allowed to sleep during all other sleep stages, they tend to become irritable during waking states. They also report having trouble concentrating. After people who have been deprived of REM sleep are allowed to sleep without being distrubed, they compensate for the loss of REM sleep by spending more time than usual in REM sleep. This phenomenon is called REM Rebound.
9
Q
Summary of Sleep
(Narrative)
A
When you fall asleep, you start in N1 and slowly progress through stages N2, N3, and N4, in order, although loud noises or other intrusions can interrupt the sequence. After ~ one hour of sleep, you begin to cycle back from stage 4 through stages 3, 2, and then REM. The sequence repeats, with each cycle lasting ~ 90 minutes. Early in the night, stages 3 and 4 predominate. Toward morning, REM occupies an increasing percentage of time. The amount of REM depends more on the time of day than on how long you have been asleep. That is, if you go to sleep later than usual, you will still increase your REM at about the same time that you would have ordinarily.
10
Q
REM and Dreams
A
Shortly after the discovery of REM, researchers believed it was almost synonymous with dreaming. William Dement and Nethaniel Kleitman (1957) found that people who were awakened during REM reported dreams 80 – 90% of the time. Later research, however, found that people awakened during NREM sleep also sometimes report dreams. REM dreams are more likely than NREM dreams to include visual imagery and complicated plots, but not always. Some people continue to report dreams despite an apparent lack of REM. In short, REM and dreams are not the same thing.
11
Q
Paradoxical / REM Sleep
A
Researchers use the term REM sleep for humans but prefer the term paradoxical sleep for nonhuman species that lack eye movements. During REM, the EEG shows irregular, unsynchronized, low-voltage fast waves that indicate increased neuronal activity. However, the postural muscles of the body are more relaxed during REM than in other stages. REM is associated with erection in males and vaginal moistening in females. Heart rate, blood pressure, and breathing rate are more variable in REM than in N2, N3, or N4. In addition to its steady characteristics, REM sleep has intermittent characteristics such as facial twitches and eye movements. Associated with dreaming.
12
Q
Summary of Sleep
(Brain Waves)
A
- Awake: Beta and Alpha waves
- Stage 1: Theta waves
- Stage 2: Theta waves
- Stage 3: Delta waves
- Stage 4: Delta waves
- REM: “Similar to Waking”
13
Q
N1 or Sleep Stage 1
A
A time of drowsiness or transition from being awake to falling asleep. Brain waves and muscle activity begin slowing down in this stage. People in N1 sleep may experience sudden muscle jerks, preceded by a falling sensation. In N1 sleep, the EEG is dominated by irregular, jagged, low-voltage waves. Brain activity is less than in relaxed wakefulness but higher than in other sleep stages. Theta waves begin to occur––slower in frequency and greater in amplitude than alpha waves.
14
Q
N2 or Sleep Stage 2
A
Period of light sleep during which eye movements stop. Spontaneous periods of muscle tone mixed with periods of muscle relaxation. Heart rate slows. In the brain, the most prominent characteristics of N2 sleep are sleep spindles and K-complexes. A sleep spindle consists of 12 – 14Hz waves during a burst that lasts at least half a second. Sleep spindles result from oscillating interactions between cells in the thalamus and cortex. A K-complex is a sharp wave associated with a temporary inhibition of neuronal firing. Characterized by theta waves––slower in frequency and greater in amplitude than alpha waves.
15
Q
N3 and N4, Stages 3 and 4, or
Slow-Wave Sleep (SWS)
A
During N3 and N4, heart rate, breathing rate, and brain activity decrease, whereas slow, large-amplitude waves become more common. N3 and N4 differ only in the prevalence of these slow waves. Slow waves indicate that neuronal activity is highly synchronized. The technical term for these slow waves is delta waves.
16
Q
Brain Waves Characteristic of a Waking State
A
Beta and alpha waves characterize brain wave activity when we are awake. Beta waves have a high frequency and occur when we are alert or attending to some mental task that requires concentration. Beta waves are unsynchronized. Alpha waves occur when we are awake but relaxing with our eyes closed, and are somewhat slower than beta waves. Alpha waves are also more synchronized than beta waves.
17
Q
Polysomnography
(PSG)
A
A multiparametric test used in the study of sleep and as a diagnostic tool in sleep medicine. The test result is called a polysomnogram. The test may include an EEG, eye-movement records, skeletal muscle activation, and heart rhythm (ECG) during sleep.
18
Q
EEG and Sleep
A
The EEG records an average of the electrical potentials of the cells and fibers in the brain areas nearest each electrode on the scalp. If half the cells in some area increase their electrical potentials while the other half decrease, they cancel out. The EEG record rises and falls when most cells do the same thing at the same time. You might compare it to a record of the noise in a sports stadium. It shows only slight fluctuations until some event gets everyone yelling at once. The EEG enables brain researchers to monitor brain activity during sleep.
19
Q
Circadian Rhythm
A
Our daily cycle of waking and sleeping is regulated by an internally generated circadian rhythm. In humans and other animals, the circadian rhythm approximates a 24-hour cycle; in humans, it is slightly longer than 24 hours: ~ 24 hours + 15 minutes, on average. However, the cycle is recalibrated, or “snapped into place,” by external cues, particularly night and day, called zeitgebers. Still, in experiments where there is no alternation between light and dark, humans and other animals appear to maintain the same roughly 24-hour cycle of waking and sleeping, although with no light / dark alternation, this cycle may be slightly longer or shorter than 24 hours.
20
Q
Reticular Formation
A
Neural structure in the brainstem (the midbrain and hindbrain together comprise the brainstem) that keeps our cortex awake and alert. If the reticular formation is disconnected from the cortex (for example, because the connecting fibers are damaged in an accident), the result will be that the person sleeps for most of the day.
21
Q
Broca’s Aphasia and Wernicke’s Aphasia
A
Language disorders associated with Broca’s area and Wernicke’s area, respectively. Broca’s aphasia refers to impairments in speaking ability, and is associated with damage to Broca’s area. Wernicke’s aphasia refers to impairments in understanding written and spoken language, and is associated with damage to Wernicke’s area. “Aphasia” comes from the Greek for “not speech.”
22
Q
Neurocognitive Disorders
A
Neurocognitive disorders (formerly known as dementias in the DSM-4) are neurological disorders characterized by a loss of intellectual functioning. One example is Alzheimer’s disease, primarily associated with progressive memory loss. Patients with Huntington’s chorea (aka Huntington’s disease) and Parkinson’s disease also present symptoms of neurocognitive disorder. However, cognitive decline progresses at a much slower rate, and the resulting cognitive deficits are less severe than in Alzheimer’s. The motor symptoms in Huntington’s chorea (loss of motor control) and Parkinson’s disease (resting tremors, muscle rigidity) are quite severe, however.
23
Q
Anterograde Amnesia
A
Damage or surgical removal of the hippocampus, a brain structure in the limbic system, is associated with anterograde amnesia, or a loss of the ability to create new memories, which leads to a partial or complete inability to recall the recent past.
24
Q
Agnosia
A
The Greek roots for agnosia mean “not knowing.” In general, agnosia is an impairment of perceptual recognition. In visual agnosia, there is an impairment in visual recognition. That is, although the person can see an object, let’s say a comb, he or she is unable to know or recognize what it is. Visual perception is registered in the projection area of the visual cortex, whereas visual recognition is processed in nearby association areas. Therefore, damage to these association areas impairs a person’s ability to recognize visual objects without interfering with his or her ability to see.
25
Apraxia
An impairment in the organization of motor action. The Greek derivation means "inability to act." **Apraxia** is characterized by an inability to execute learned (familiar) movements on command, even though the command is understood and there is a willingness to perform the movement. Both the desire and the capacity to move are present but the person simply cannot execute the act. In apraxia, the projection areas in the motor cortex, which send motor impulses down to the muscles, remain more or less intact. The problem seems to arise from damage to the nearby association areas, which organize simple motor movements into predictable voluntary acts.
26
Alexander Romanovich Luria
| (A. R. Luria)
Russian neuropsychologist, often credited as a father of modern neuropsychological assessment. He developed an extensive and original battery of neuropsychological tests during his clinical work with brain-injured victims of World War II, which are still used in various forms.
27
rCBF
**Regional cerebral blood flow**. Can be measured with PET or fMRI, for example. When a specific cognitive function, such as listening to music, activates specific areas of the brain, the blood flow to that region increases. In this example, blood flow to the right auditory cortex increases because that is where music is processed in most people's brains.
28
Functional Magnetic Resonance Imaging
A modified version of MRI based on hemoglobin (the blood protein that binds oxygen) instead of water. Hemoglobin with oxygen reacts to a magnetic field differently than hemoblobin without oxygen. Researchers set the fMRI scanner to detect the amount of hemoglobin with oxygen. When a brain area becomes more active, two relevant changes occur. First, blood vessels dilate to allow more blood flow to the area. Second, as the brain area uses oxygen, the percentage of hemoglobin with oxygen decreases. An fMRI scan responds to both of these processes.
29
Magnetic Resonance Imaging
| (MRI)
Based on the fact that any atom with an odd-numbered atomic weight, such as hydrogen, has an axis of rotation. An MRI device applies a powerful magnetic field (~ 25,000 times the magnetic field of the Earth) to align all the axes of rotation, and then tilts them with a brief radio frequency. When the radio frequency field is turned off, the atomic nuclei release electromagnetic energy as they relax and return to their original axes. By measuring that energy, MRI devices form an image of the brain––MRI shows anatomical details smaller than a millimeter in diameter. One drawback is that the person must lie motionless in a confining, noisy apparatus.
30
Computerized Axial Tomography
| (CT or CAT)
Dye is injected into the blood (to increase contrast in the image) and then the person's head is placed into a CT scanner. X-rays are passed through the head and recorded by detectors on the opposite side. The CT scanner is rotated slowly until a measurement has been taken at each angle over 180 degrees. From the measurements, a computer constructs images of the brain. CT scans help detect tumors and other structural abnormalities.
31
Positron-Emission Tomography
| (PET)
PET scans provide a high-resolution image of activity in a living brain by recording the emission of radioactivity from injected chemicals. First, the person receives an injection of glucose or some other chemical containing radioactive atoms. Glucose use increases in the most active brain areas. When a radioactive atom decays, it releases a positron that immediately collides with a nearby electron, emitting 2 gamma rays in exactly opposite directions. The person's head is surrounded by a set of gamma ray detectors. When two detectors record gamma rays at the same time, they identify a spot halfway between those detectors as the point of origin of the gamma rays. A computer uses this info to determine how many gamma rays came from each spot in the brain and therefore how much of the radioactive chemical is located in each area. PET scans use radioactive chemicals with a short half-life, made in a device called a cyclotron. Because cyclotrons are expensive, PET is available only at research hospitals. Furthermore, PET requires exposure to radioactivity. PET has now been mostly replaced with fMRI.
32
Electroencephalograph
| (EEG)
An apparatus for detecting and recording brain waves. The technique involves placing several electrodes on the surface of the head. Broad patterns of electrical activity can thus be detected and recorded. The machine is called an **electroencephalograph**. The machine produces an **electroencephalogram**. Because it is noninvasive, EEG is commonly used with human subjects. Sleep research relies heavily on EEG.
33
Problem with studying human brain lesions
Human brain lesions are rarely isolated to specific brain structures. When several brain structures are damaged, it becomes difficult to attribute a specific functional impairment to any one brain region.
34
Studying brain lesions in animals
The advantage of studying brain lesions in animals is that precisely defined brain lesions can be created. **Ablation** (or **extirpation**) refers to any surgically induced brain lesion. Researchers can produce lesions by applying heat, cold, or electricity to specific brain regions. The device used to locate brain areas when electrodes (for example) are implanted to make lesions or stimulate nerve cell activity is called a **stereoscopic instrument**.
35
Stereoscopic Instrument
Device used to locate brain areas when electrodes (for example) are implanted to make lesions or stimulate nerve cell activity.
36
Wilder Penfield
With his colleague **Herbert Jasper**, invented the **Montreal Procedure**, in which he treated patients with severe epilepsy by destroying nerve cells in the brain where the seizures originated. Before operating, he would stimulate the brain with electrical probes while the patient was conscious on the operating table (under only local anesthesia), and observe their responses. In this way he could more accurately target the areas of the brain responsible, reducing the side-effects of the surgery. This technique also allowed him to create maps of the sensory and motor cortices of the brain (**cortical homunculi**) showing their connection to the various limbs and organs of the body. These maps are still used today, practically unaltered.
37
Cortical Homunculus
| (plural Homunculi)
A distorted representation of the human body, based on a neurological "map" of the areas and proportions of the human brain dedicated to processing motor functions, or sensory functions, for different parts of the body. The word "homunculus" is Latin for "little man," and was a term used in alchemy and folklore long before it appeared in scientific literature.
38
Using eletrodes in lab animals to study deeper regions of the brain (deeper, that is, than the cortical homunculi)
Depending on where electrodes are implanted, researchers have found that brief bursts of electrical current can elicit sleep, sexual arousal, rage, or terror. Once the electrode is turned off, these behaviors cease.
39
David Hubel and Torsten Wiesel
Used single-cell recording, in which individual neurons are recorded by inserting ultrasensitive microelectrodes into single brain cells. They applied this procedure to the visual cortex of cats, and their results formed a neural basis for **feature detection theory**, which suggests that certain cells in the cortex are maximally sensitive to certain features of stimuli. They distinguished 3 different types of cells: **simple**, **complex**, and **hypercomplex**.
40
Neuropsychology
**Neuropsychology** is the term used to refer to the study of functions and behaviors associated with specific regions of the brain. It is mostly applied in research settings, where researchers attempt to associate very specific areas in the brain to behavior, and clinical settings where patients are treated for brain lesions. Neuropsychology has its own experimental methodology and technology.
41
Testosterone
Produced in the testes. Stimulates production of sperm, maturation of male genitalia, and growth of facial / pubic hair.
42
Hormones produced by the _ovaries_
The ovaries produce **estrogen**, which stimulates female sex characteristics, and in the menstrual cycle is associated with the maturation and release of the egg or ovum from the ovary. The ovaries also produce **progesterone**, which prepares the uterus for implantation of the embryo.
43
Adrenal Medulla
Inner part of the adrenal glands. Produces adrenaline (epinephrine), which increases sugar output of the liver; also increases heart rate; crucial in "fight or flight" response.
44
Thyroid
Affects metabolism rate, growth, and development.
45
Female Reproductive Cycle
(The female reproductive cycle is called the **menstrual cycle** in humans and primates, and the **estrus cycle** in other mammals.) First, the pituitary secretes a hormone called **follicle-stimulating hormone (FSH)**, which stimulates the growth of an ovarian follicle, which is a small-protective sphere surrounding the egg or ovum. **Luteinizing hormone (LH)**, also produced by the pituitary, is associated with ovulation, which is the release of the egg from one of the ovaries. At various stages during this cycle the ovaries manufacture and secrete two hormones: **estrogen** and **progesterone**. Increasing levels of estrogen are associated with the maturation and release of the egg or ovum from the ovary. The function of progesterone is to prepare the uterus for implantation of the fertilized egg. If an ovum is fertilized by a sperm cell, the ovum begins to divide and soon attaches itself to the uterine wall. If the ovum is not fertilized, estrogen and progesterone levels decrease, at which point menstruation begins.
46
Sexual Development
Hormones that are regulated by the hypothalamus and anterior pituitary play a role in initiating, maintaining, and halting development of primary and secondary sex characteristics. There are two kinds of sex chromosomes: X and Y. At conception, the embryo always inherits an X chromosome from the mother but may receive either an X or a Y chromosome from the father. When a fetus inherits two X chromosomes, it is genetically female; when it inherits an X and a Y, it is genetically male. The genetic sex of a child is determined upon fertilization; however, the development of physical characteristics of the fetus occurs later. Male development, for example, requires the presence of hormones called androgens during critical stages of development. The most important androgen to remember is **testosterone**. Just after conception, the Y chromosome initiates production of androgens. Normal development of the testes and penis then proceeds. During puberty, the pituitary gland produces and releases gonadotropic hormones, also called gonadotropins. These chemical messengers activate a dramatic increase in production of hormones by the testes or ovaries. In males, they stimulate the testes to produce sperm. They also stimulate a surge in testosterone which leads to facial hair and deepening voice. In females, they stimulate the ovaries to secrete estrogen which accelerates development of female genitalia and has a role in the menstrual cycle.
47
The _Default_ is _Female_
If a genetically male fetus does not produce or cannot use androgens, development will follow the female pattern (regardless of chromosomal genetic sex). For example, **androgen-insensitivity syndrome**. Anatomic development of a female fetus does not require female hormones, but merely the absence of androgens.
48
Primary vs. Secondary Sex Characteristics
Primary sex characteristics are present at birth: sex organs, or gonads (ovaries and testes), and external genitalia. In contrast, secondary sex characteristics do not appear until puberty––for females, enlarged breasts and widened hips; for males, facial hair and a deeper voice.
49
Glands and Hormones
The endocrine system shares many functions with the hypothalamus. (remember the 4 "Fs") The hypothalamus works directly with the **pituitary gland**, the so-called "master gland." The pituitary gland, located at the base of the brain, is divided into two parts: **anterior** and **posterior**. It is the anterior pituitary that is the master since it releases hormones that regulate activities of endocrine glands. However, the hypothalamus controls the anterior pituitary. The pituitary secretes various hormones into the bloodstream that travel to other endocrine glands located elsewhere in the body to activate them. Once activated by the pituitary, a given endocrine gland manufactures and secretes its own characteristic hormone into the bloodstream. This chemical messenger then signals a specific internal organ like the heart or liver to change its functioning.
50
Hypothalamus
Structure within the forebrain, subdivided into **lateral**, **ventromedial**, and **anterior** regions. Serves homeostatic functions (receptors in the hypothalamus regulate metabolism, temperature, and water balance––**osmoregulation** is performed by **osmoreceptors** in the hypothalamus). The hypothalamus is important in _drive_ behaviors, including hunger, thirst, and sexual behavior. Crucial for the fight or flight response. Also involved in sleep. 4 Fs: feeding, fighting, flighting, fucking. The hypothalamus is the _link_ between the _endocrine_ and _nervous systems_. It produces _releasing_ and _inhibiting_ _hormones_, which stop and start the production of other hormones throughout the body. (In general, the hypothalamus is involved in emotional experience during high-arousal states.)
51
Medulla Oblongata
Part of the **hindbrain**. Often called simply the "medulla." The lowest portion of the brainstem and the point where the spinal cord connects to the brainstem. It contains a number of important tracts and nuclei that are necessary for maintaining vital functions like heart rate, blood pressure and respiration.
52
Reticular Formation
Extends from the **hindbrain** into the **midbrain** and is composed of a number of interconnected nuclei. Regulates arousal, alertness, and attention (sleeping and waking). Anasthetics cause unconsciousness in part by depressing activity of the reticular formation.
53
Thalamus
Structure within the forebrain that serves as an important relay station for incoming sensory information, including all senses _except smell_. After receiving incoming sensory impulses, the thalamus sorts them, then transmits them to the appopriate areas of the cerebral cortex.
54
Cerebral Cortex
Part of the **forebrain**. The outer layer of the cerebrum, and the most recent evolutionary development of the human brain. In humans, the cerebral cortex is associated with everything from language processing to problem solving, impulse control, and long-term planning. The cerebral cortex is composed of gray matter (outside) and white matter (inside).
55
Ganglia vs. Nuclei
Ganglia are clusters of nerve cell bodies in the PNS, whereas nuclei are clusters of nerve cell bodies in the CNS.
56
Walter Cannon
(1871 – 1945) Performed pioneering work on the autonomic nervous sytem. Coined the term "**fight or flight response"**; expanded on **Claude Bernard's concept of homeostasis**; and with **Philip Bard**, proposed the **Cannon-Bard theory of emotions**.
57
Somatic Nervous System
Consists of sensory and motor neurons distributed throughout the skin and muscles. Sensory neurons transmit information through **afferent fibers**. Motor impulses, in contrast, travel along **efferent fibers**.
58
Lateral Hypothalamus (LH)
The _hunger center_: has special detectors that detect when your body needs more food or fluids. When the LH is destroyed in lab rats, they refuse to eat or drink and would die if not force-fed through tubes. This disorder is called **aphagia**. The root word _phagos_ means "eating." The same root word appears in **esophagus**, the tube leading from mouth to stomach. To remember the association between "lateral hypothalamus" and "aphagia," think **_L**_acking _**H**_unger, or LH, which are also the initials for _**L**_ateral _**H_**ypothalamus. _Additionally, the LH plays a role in rage and fighting behaviors._
59
Ventromedial Hypothalamus
| (VMH)
The _satiety center_. The VMH tells you when you've had enough to eat. Brain lesions to the VMH usually lead to obesity. A name for this disorder is **hyperphagia**, or excessive eating. To remember the connection between the "ventromedial hypothalamus" and "hyperphagia," remember that hyperphagia refers to being **_V_**ery **_H_**ungry (the initials VH can also stand for **_V_**entromedial **_H_**ypothalamus).
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Removal of the cerebral cortex, or both the cerebral cortex _and_ hypothalamus, in cats:
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
Note: apparently they also removed just the hypothalamus, but only the conclusion is given (page 146).
In the 1920s, when researchers removed the cat's cerebral cortex but left the hypothalamus in place, the cat displayed a pattern of pseudo-aggressive behavior called "**sham rage**"––rage that was spontaneous or triggered by the mildest touch. The researchers concluded that the cortex typically inhibits this type of response. When the researchers removed the cat's cortex and hypothalamus together, the cat no longer showed any signs of sham rage, and much rougher stimulation was required before the cats showed defensive behavior. So without the cerebral cortex, animals have little or no control over defensive / aggressive behavior; without the hypothalamus, animals seem to lack the ability to defend themselves against threats; without both the cortex and hypothalamus, the cats lacked the ability to coordinate emotional responses.
61
Hippocampus
Plays a vital role in learning and memory. Researchers originally discovered the connection between memory and the hippocampus when parts of the temporal lobes––including most of the amygdala and hippocampus––were removed in a famous patient now known as H. M. This surgery was performed in order to control epileptic seizures. After surgery, H. M.'s intelligence was largely intact but he suffered a drastic and irreversible loss of memory for anything new. This kind of memory loss is called **anterograde amnesia** and is characterized by not being able to establish new long-term memories, whereas memory for distant events is usually intact. The opposite kind of memory loss, **retrograde amnesia**, refers to memory loss of events that transpired before brain injury. It is now clear that the hippocampus should not be removed to control epileptic seizures. **Brenda Milner** described H. M.'s memory problems in detail.
62
Cerebral Cortex
The outer surface of the brain––in Latin, "cortex" means "bark." The cortex is sometimes called the **neocortex**, because the cortex was the most recent brain region to evolve. The cortex has numerous bumps and folds called **convolutions**, which allow for increased cellular mass. Seen from above, the cortex has two halves, or **cerebral hemispheres**. The surface of the cortex is divided into four lobes––**frontal**, **parietal**, **occipital**, and **temporal**.
63
Amygdala
Structure of the limbic system that plays an important role in defensive and aggressive behaviors. Based on studies of animals and humans with brain lesions, when the amygdala is damaged, _aggression_ and _fear reactions_ are markedly reduced. Lesions to the amygdala result in _docility_ and _hypersexual states_. **Heinrick Klüver** and **Paul Bucy** performed studies that linked the amygdala with defensive and aggressive behavior in monkeys. They identified changes that resulted from bilateral removal of the amygdala as **Klüver-Bucy syndrome**. (Note: most of H. M.'s amygdala was removed along with most of his hippocampus.)
64
Septal Nuclei
Part of the limbic system and one of the primary pleasure centers in the brain (although not the only pleasure center). Mild stimulation of the septal nuclei is reported to be intensely pleasurable and sexually arousing. **James Olds** and **Peter Milner** discovered this phenomenon in the 1950s. They demonstrated that when rats could stimulate their septal nuclei at will, the rats found it so pleasurable that they preferred it to eating, even after going 24 hours without food. The septal nuclei also acts to inhibit aggression. If the septal nuclei are damaged, aggressive behavior goes unchecked, resulting in vicious behavior known as **septal rage**.
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3 Basic Subdivisions of the Human Brain
* **Hindbrain** (also called **Rhombencephalon**): Located where the brain meets the spinal cord, the hindbrain's primary functions include balance, motor coordination, breathing, digestion, and general arousal processes such as sleeping and waking. In other words, the hindbrain manages vital functioning necessary for survival.
* **Midbrain** (also called **Mesencephalon**): Manages sensorimotor reflexes that are also crucial for survival. Associated with vision, hearing, motor control, sleep / wake cycles, arousal (alertness), and temperature regulation.
* **Forebrain** (**Proencephalon**): Largest part of the brain. Regulates skeletal movement and other higher motor functions. Regulates visceral functions including temperature, reproductive functions, eating, sleeping, emotions, decision-making, memory, learning, and in general, complex perceptual, cognitive, and behavioral processes.
66
7 Components of the Forebrain
* Cerebrum
* Basal ganglia (base of forebrain, top of midbrain)
* Pituitary gland (base of brain)
* Limbic system
* Thalamus
* Hypothalamus
* Olfactory bulb
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Composition of the Midbrain
The midbrain is associated with involuntary reflex responses triggered by visual or auditory stimuli. There are several prominent nuclei in the midbrain, two of which are collectively called **colliculi**. The **superior colliculus** receives visual sensory input, and the **inferior colliculus** receives auditory sensory input.
68
Brain Diagram
See physical flashcard.
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How the prefrontal cortex works
In memory, for example, the role of the prefrontal cortex is not to store any memory traces, but rather to remind you that you have something to remember. To regulate attention and alertness, the prefrontal cortex communicates with the reticular formation in your brainstem, telling you either to wake up or relax, depending on the situation.
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Frontal Lobe
Comprised of two basic regions: **prefrontal cortex** and **motor cortex**. The prefrontal cortex serves an executive function in which it supervises and directs the operations of other brain regions. In particular, the prefrontal cortex supervises processes associated with percetion, memory, emotion, impulse control, and long-term planning. The prefrontal cortex thus governs and integrates numerous cognitive and behavioral processes.
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Broca's Area
A part of the frontal lobe that is vital for speech production. Broca's area is usually found in only one hemisphere, the so-called "dominant" hemisphere, which for most people is the left hemisphere.
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Parietal Lobe
The **parietal lobe** contains the **somatosensory cortex**. This projection area is the destination for all incoming sensory signals for touch, pressure, temperature, and pain. Despite certain differences, the somatosensory cortex and motor cortex are very closesly related––so much so that they are sometimes described as a single unit: the **sensorimotor cortex**. The central region of the parietal lobe is associated with spatial processing and manipulation. This region makes it possible for you to orient yourself in 3-dimensional space and do spatial-orientation skills such as those required for map reading.
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Occipital Lobe
Contains the **visual cortex**, which is sometimes called the **striate cortex**. "Striate" means "furrowed" or "striped," which is how the visual cortex appears under a microscope. Researchers understand the visual cortex better than many other brain regions. Important advances are credited in particular to **David Hubel** and **Torsten Wiesel** (who found a neural basis for **feature detection theory**). Areas in the occipital lobe have also been implicated in _learning_ and _motor control_.
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Interrelation of Brain Areas
The lobes of the brain, although having seemingly independent functions, are not really independent. For example, often a sensory modality is represented in more than one area.
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Motor Cortex
Initiates voluntary motor movements by sending neural impulses down the spinal cord toward the muscles. As such, it is considered a projection area in the brain. The neurons in the motor cortex are arranged systematically according to the parts of the body to which they are connected. Because certain sets of muscles require more motor control than others, they take up more space in the motor cortex than you would expect from their relative size in the body.
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Contralateral
vs.
Ipsilateral
For most functions, one side of the brain communicates with the opposite side of the body, and we say the cerebral hemispheres communicate **contralaterally**. For example, the motor neurons on the left side of your brain activate movements on the right side of your body. But for some functions (smell, for example), cerebral hemispheres communicate with the same side of the body, and we say they communicate **ipsilaterally**.
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Damage to the prefrontal cortex...
...impairs its overall supervisory functions. A person with a prefrontal lesion may be more impulsive and generally less in control of his or her behavior, or depressed. It is not unusual for someone with a prefrontal lesion to make vulgar and inappropriate sexual remarks, or to be apathetic. In the 1950s, **prefrontal lobotomies** were used to treat schizophrenia. Surgeons would insert a scalpel through a hole in the skull and disconnect the frontal lobe from the limbic system and hypothalamus, both of which are associated with mood and emotion.
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Limbic System
The **limbic system** is a part of the **forebrain** that evolved after the brainstem but before the cerebral cortex. It is located in the oldest part of the cerebral hemispheres. The limbic system is a group of neural structures primarily associated with emotion and memory. Aggression, fear, pleasure, and pain all involve the limbic system. Its primary components are the **septal nuclei**, **amygdala**, and **hippocampus**, although it also includes portions of the **hypothalamus** and **cortex**.
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Relative amounts of
_association_ vs. _projection_ _areas_
In humans, the amount of cortex devoted to association areas is substantially larger than the amount devoted to projection areas. In other mammals, however, projection areas are generally larger than association areas.
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Association Area
vs.
Projection Area
Because it integrates information from different cortical regions, the prefrontal cortex is a good example of an **association area** (an area that combines input from diverse brain regions). Association areas are generally contrasted with **projection areas**, which receive incoming sensory information or send out motor-impulse commands. Examples of projection areas include the **visual cortex**, which receives visual input from the retina, and the **motor cortex**, which sends out motor commands to the muscles.
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Temporal Lobe
The **auditory cortex**, **Wernicke's area**, and the **hippocampus** are all located within the temporal lobe. Wernicke's area is the comprehension center for both spoken and written language, receiving input from the auditory cortex and visual cortex, respectively. The temporal lobe (in general) serves in _memory processing_, _emotional control_, and _language_. Studies have shown that electrical stimulation of the temporal lobe can evoke memories of past events. This makes sense given that the hippocampus is located within the temporal lobe.
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Wernicke's Area
Area in the temporal lobe which serves as the comprehension center for both spoken and written language, receiving input from the auditory cortex and visual cortex, respectively.
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Roger Sperry and Michael Gazzaniga
Studied the effects of severing the **corpus callosum** (a large collection of fibers connecting the left and right hemispheres) in an effort to limit the convulsive seizures of epileptic patients. In a "split brain" patient, each hemisphere has its own function and specialization that is no longer accessible to the other. (Associate **_sp_**lit brain with **_Sp_**erry and Gazzaniga.)
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Role of the nondominant hemisphere in language
The nondominant hemisphere (usually the right hemisphere) serves a less prominent role in language. It is more sensitive to the emotional tone of spoken language, and permits us to recognize whether people are happy, depressed, or anxious just by the sound of their voice. The dominant hemisphere thus screens incoming language to analyze its content, while the nondominant hemisphere interprets it according to its emotional tone. Thus the minor (nondominant) hemisphere plays a supportive role.
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Note about hemispheric dominance and handedness
The left hemipshere is "dominant" in right-handed people. For left-handed people, "dominant" functions (language, complex movement, etc.) may be associated with the right side of the brain.
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3 kinds of nerve cells
| (not necessarily the only kind)
* **Sensory neurons** (also known as **afferent neurons**) transmit sensory information from receptors to the spinal cord and brain.
* **Motor neurons** (also known as **efferent neurons**) transmit motor information from the brain and spinal cord to the muscles.
* **Interneurons** are found between other neurons and are the most numerous of the 3 types of neurons. They exist exclusively in the central nervous system and play a vital role in reflexive behavior.
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Reflexes
A reflex, or reflex action, is an involuntary and nearly instantaneous movement in response to a stimulus. A reflex is made possible by neural pathways called **reflex arcs** which can act on an impulse before that impulse reaches the brain. Behavior that is crucial to survival is controlled by reflexes.
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What happens when you step on a nail, i.e. the reflex arc
When receptors in the foot detect pain, the pain signal is transmitted via sensory neurons up to the spinal cord. At that point, the sensory neurons connect with interneurons, which relay pain impulses up to the brain. However, as soon as the impulses arrive at the spinal cord, (other) interneurons immediately transmit information to the motor neurons. Without wasting any time, the motor neurons tell your foot to step away from the nail. Note that the original sensory information still makes its way up to the brain. But by the time it arrives, the muscles have already responded to the pain, thanks to the reflex arc.
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John Dewey's criticism of reflex analysis
Functionalists such as John Dewey criticized the breaking down of reflex processes into separate stimuli and responses. Functionalists preferred to study the process as a whole. To break down the reflex arc into different motor and sensory phases was, for Dewey, an artifical separation.
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Structure of the Human Nervous System
See physical flashcard.
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Function of the Autonomic Nervous System
The ANS regulates heartbeat, respiration, digestion, and glandular secretions. In other words, the ANS manages the involuntary functions associated with many internal organs and glands. The ANS also helps regulate body temperature by activating sweating or shivering, depending on whether we are too hot or too cold. The main thing to understand about these functions is that they are automatic, or independent of conscious control.
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Sympathetic vs. Parasympathetic
Nervous System
Act in opposition to one another, meaning they are **antagonistic**. For example, the sympathetic nervous system acts to accelerate heart rate and inhibit digestion, while the parasympathetic nervous system acts to decelerate heart rate and promote digestion.
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Parasympathetic Nervous System
The main role of the parasympathetic nervous system is to conserve energy. It is associated with resting and sleeping states, and acts to reduce heart and respiration rates. The parasympathetic nervous system is also responsible for managing digestion. Thus, the parasympathetic nervous system promotes _resting and digesting_. The neurotransmitter responsible for parasympathetic responses in the body is **acetylcholine**.
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John Dewey
(1859 – 1952) Along with **William James**, was an originator of **functionalism**. His 1896 article is seen as its inception. This article criticized the concept of the **reflex arc**, which breaks the process of reacting to stimulus into discrete parts. Dewey believed that psychology should focus on the study of the organism as a whole as it functions to adapt to the environment.
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Marie Jean Pierre Flourens
In the early 19th century, was the first person to study the functions of the major sections of the brain. He did this by **extirpation** (also called **ablation**). In extirpation, various parts of the brain are surgically removed, and the behavioral consequences are observed. (Flourens did most of his work on pigeons.) Flouren's work led to his assertion that the brain has specific parts for specific functions, and that the removal of one part weakens the whole brain.
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Franz Gall
(1758 – 1828) One of the earliest to propose that behavior, intellect, and even personality might be linked to brain anatomy. He developed the theory of **phrenology**. The basic idea was that if a particular trait were well developed, then the part of the brain responsible for that trait would expand, and in so doing would push the adjacent area of the skull outward and therefore cause a bulge on the head in a specific location. Although phrenology was quickly shown to be false, it did generate serious research on brain functions, and was the impetus for the work of **Marie Jean** **Pierre Flourens** in the early 19th century.
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Cerebellum
Located at the top of the **hindbrain**, mushrooming out of the **pons**. Helps maintain posture and balance and coordinates body movements. Damage to the cerebellum causes clumsiness, slurred speech, and loss of balance (alcohol impairs the functioning of the cerebellum). Also has a role in memory, cognition, and emotion.
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Anterior Hypothalamus
Electrical stimulation of the hypothalamus causes an increase in aggressive sexual behavior––lab animals are willing to mount just about anything, including inanimate objects. In many species, damage to the anterior hypothalamus leads to permanent inhibition of sexual activity. A useful mnenomic is that damage to the **_a_**nterior hypothalamus results in **_a_**sexual behavior.
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Role of the non-dominant hemisphere besides in language
The nondominant hemisphere (usually the right hemisphere) is associated with intuition, creativity, music, and spatial processing. The nondominant hemisphere simultaneously processes the pieces of a stimulus and assembles them into a holistic image. The nondominant hemisphere is good at recognizing emotions in facial expression and in tone of voice.
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Dominant vs. Nondominant
Hemispheres
Because the brain mostly communicates contralaterally with the body, the dominant hemisphere is generally located opposite to the hand used for writing. It's estimated that the left hemisphere is dominant in about 97% of all people (although ~ 10 – 12% of people are left-handed). The dominant hemisphere (usually the left) is primarily analytic in function; language, logic, and math skills are all centered in the dominant hemisphere (Broca's area and Wernicke's area are located in the dominant hemisphere). The dominant hemisphere also controls complex voluntary movement.
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Anatomy and function of a neuron
All neurons have 4 basic parts: **cell body** (also called **soma**), **dendrites**, **axon**, and **terminal buttons**. The cell body contains the nucleus of the cell, making it the neuron's energy center. Dendrites branch out from the cell body to receive incoming information from other neurons via postsynaptic receptors. External stimulation of the dendrites can lead a neuron to "fire," or generate an electrical impulse. The end of the axon branches out into numerous terminal buttons, each containing tiny vesicles, or sacs, filled with **neurotransmitter****s**. These neurotransmitters are chemical substances that the vesicles release whenever the neuron "fires." When released, they flow into the tiny space separating terminal buttons of one neuron from the dendrites of adjacent neurons (the synapse). All information passing between neurons via neurotransmitters must make it across the synapse. Depending on which neurotransmitters are released into the synapse, these chemicals may stimulate a neural impulse in an adjacent neuron. The entire cycle then repeats itself in the second neuron.
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Difference between _dendrites_ and _axons_
Dendrites differ from axons in 3 crucial ways:
1. Dendrites are typically receivers of information, whereas axons are generally the communication avenue of a nerve cell.
2. The branching pattern of dendrites can change significantly throughout a person's lifetime, whereas axons typically remain stable with aging. When damaged, dendrites can regenerate new branches and thereby replace neural connections that might otherwise be lost; axons cannot regenerate, so the branching of an axon is kept fairly constant.
3. Most axons are myelinated; dendrites are not myelinated.
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Glial Cells
Nonneural cells that provide neurons with logistical support: _nutrients_, _oxygen_, _insulation_, and _protection from pathogens_. The most important function of glial cells is to insulate axons by enclosing individual axons in a protective **myelin sheath** (not all axons are myelinated). One purpose of this myelin sheath is to insulate nerve fibers from one another. Myelination also plays an important role in the conduction velocity or speed of an impulse. The myelin sheath is divided into myelinated areas punctuated with unmyelinated nodes (called **nodes of Ranvier**), which allows an impulse to quickly skip down the axon in a process called **saltatory conduction**. Saltatory conduction is faster than conduction along an unmyelinated axon.
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Electrical vs. Chemical
Processes of Neurons
Neural conduction _within_ the neuron, including among the dendrites, cell body, and axon is an _electrical_ process. Neural transmission _between_ neurons is a _chemical_ process that always occurs at the synapse.
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Cell Membrane
| (of a neuron)
The cell membrane (of a neuron) is a thin layer of fatty molecules that separates the inside of the neuron from the outside. This membrane is **semipermeable**; it's a partial barrier that allows some substances to pass through but blocks the passage of others. (An alternative term, perhaps a better one, is **selectively permeable**.)
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Sodium-Potassium Pump
Oxygen, CO2, urea (the chief nitrogenous end product of the metabolic breakdown of proteins in all mammals and some fishes), and water cross the cell membrane freely through channels that are always open. Several important ions, including sodium, potassium, calcium, and chloride, cross through membrane channels (or gates) that are sometimes open and sometimes closed. When the membrane is at rest, the Na+ and K+ channels are closed, permitting almost no flow of Na+ and only a small flow (outflow) of K+. The **sodium-potassium pump**, a protein complex, repeatedly transports 3 Na+ out of the cell while drawing 2 K+ into it. The sodium-potassium pump is an active transport that requires energy. As a result of the sodium-potassium pump, Na+ is 10 times more concentrated outside the membrane than inside, and K+ is similarly more concentrated inside than outside. The pump is effective only because of the selective permeability of the membrane, which prevents Na+ pumped out of the neuron from leaking right back in again. When Na+ are pumped out, they stay out. However, some of the K+ in the neuron slowly leak out, carrying a positive charge with them. That leakage increases the electrical gradient across the membrane. The pump helps maintain the resting potential.
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Resting Potential
The **resting potential** is a slight electrical charge (a _negative_ charge) stored inside the neuron's cell membrane––a charge just waiting to be transformed into a nerve impulse. Because this energy potential is present when the neuron is at rest, it is called a resting potential. The **cell membrane** plays an important role in the resting potential, which is why it is sometimes called the **membrane potential**. Negatively charged proteins inside the cell are responsible for the resting potential, although the **sodium-potassium pump** also helps to maintain it.
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Action Potential
Stimulation beyond the **threshold** **of excitation** causes the sodium channels to open, permitting sodium ions to flow into the cell and resulting in a massive depolarization of the membrane. The K+ channels also open, but at first that makes little difference, because for K+ the concentration and electrical gradients are almost in balance. At the peak of the action potential, the Na+ gates snap shut. The K+ channels remain open and, driven by both a concentration gradient and an electrical gradient (the inside of the cell now has a slight positive charge), K+ flows out of the cell until a temporary hyperpolarization is achieved. Then the resting potential is restored, but with slightly more sodium ions and slightly fewer potassium ions inside the cell than before. Then the pump restores the initial balance of ions. 4 Steps:
1. Resting potential (~ -70 mV)
2. Depolarization (threshold ~ -50 mV)
3. Action potential spike (voltage inside cell becomes positive)
4. Hyperpolarization (membrane briefly overshoots resting potential)
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All-or-None Law
When depolarization reaches the critical threshold (~ -50 mV), the neuron fires, each and every time. The **all-or-none law** states that the amplitude and velocity of an action potential are independent of the intensity of the stimulus that initiated it, provided that the stimulus reaches the threshold.
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Axon Hillock
The action potential originates at the **axon hillock**, a small elevation on a neuron where the axon meets the cell body. It is at the axon hillock that the **graded potential** in the cell body is converted into the all-or-none potential of the axon. The action potential is then transmitted as an electrical impulse along the axon toward its ultimate destination, the terminal buttons.
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Refractory Period
Immediately after an action potential, the cell enters a **refractory period** during which it resists the production of further action potentials. In the first part of this period, which is called the **absolute refractory period**, the membrane cannot produce another action potential, regardless of the stimulation. The absolute refractory period corresponds to depolarization (the inrush of Na+). During the second part, which is called the **relative refractory period**, a stronger-than-usual stimulus is necessary to initiate an action potential. The relative refractory period corresponds to repolarization (caused by K+ rushing out, eventually resulting in hyperpolarization).
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Graded Potentials
"Felt" at the dendrites. Intensity is proportional to external stimulation.
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Excitatory Postsynamptic Potentials
| (EPSPs)
"Felt" at the dendrites. EPSPs increase the likelihood of an action potential.
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Inhibitory Postsynpatic Potentials
| (IPSPs)
"Felt" at the dendrites. IPSPs decrease the likelihood of an action potential.
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Saltatory Conduction
The basic function of myelin is to insulate the axon and to speed up conduction. Conduction along a myelinated axon is called **saltatory conduction**. The myelin sheath along an axon is not continuous; it has gaps called **nodes of Ranvier** where the axon is unmyelinated. The depolarization actually occurs at the nodes, the conduction jumpting from node to node. When the action potential reaches one node, it triggers a new action potential at the node next to it. Skipping from node to node is faster than having a single impulse travel continuously down the axon. Also, by regenerating the action potential at each node, the neural impulse moves down the axon without losing any of its intensity. (The thicker the myelination, the faster the conduction.)
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Neurotransmission at the Synapse
The membrane of the terminal button that faces the synapse is known as the **presynaptic membrane**. Inside this membrane are tiny sacs called **vesicles** that store neurotransmitters. On the other side of the synapse, or **synaptic cleft**, within the dendrite, is the **postsynapatic membrane** of an adjacent neuron that has **receptors** on it. When an action potential releases the neurotransmitters, these chemicals flood into the synapse. Within the synapse, three things can happen to the neurotransmitters: a) they can attach themselves to receptor sites on the postsynaptic membrane (called **binding**); b) they can remain in the synapse, where they are destroyed and washed away by other biochemical substances; or c) they can be drawn back into the vesicles of the terminal buttons via a process called **reuptake**. Neurotransmitters fit into receptor sites like keys into locks. If you don't have the right key, it won't fit into the receptor-site lock. After a neurotransmitter binds to a postsynaptic receptor, the neurotransmitter is eliminated from the synapse through either reuptake or by being destroyed.
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Postsynaptic Potentials
Once a neurotransmitter binds to a receptor site on the dendrite, it generates a tiny electrical charge called a postsynaptic potential, or PSP. Depending on the transmitter and the receptor site, one of two things can happen. It can make the neuron more likely to fire or less likely to fire. When the postsynaptic potential makes it more likely that a neuron will fire, it is known as an **excitatory postsynaptic potential**, or **EPSP**. When the postsynaptic potential makes the neuron less likely to fire, it is called an **inhibitory postsynaptic potential**, or **IPSP**. Postsynaptic potentials in the dendrites are **graded potentials**, which means their voltage can vary in intensity. Postsynaptic potentials are thus not subject to the all-or-none law that characterizes action potentials in axons. In graded potentials, the voltage depends directly on how much the receptor sites are stimulated by neurotransmitters. If relatively few transmitters bind to the receptor sites, the resulting PSP will be weak. If more transmitters bind, the PSP will be stronger. Another characteristic of graded potentials is that as they spread out from the original site of stimulation, their voltage gradually weakens as they travel along the dendrites. By contrast, action potentials retain their strength as they travel along the axon.
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Eric Kandel
Studied simple neural networks in **aplysia**, which are _sea snails_ with large, easily identifiable nerve cells. Kandel studied neural activity associated with reflexes that govern the movement of the aplysia's gills. When lightly touched, aplysia normally withdraw their gills automatically. As the sea snails gradually learned that this stimulation was harmless, they stopped withdrawing their gills: this is called **habituation**. Kandel found that after aplysia learned to ignore stimulation of their gills, the neurons governing the gill-withdrawal reflex released smaller amounts of neurotransmitters than before. In other words, Kandel demonstrated that changes in synaptic transmission underlie changes in behavior. This finding was important because it identified specific changes in the neuron that explain a simple learned behavior.
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GABA
| (gamma-amino butyric acid)
The neurotransmitter GABA (gamma-amino butryic acid) produces inhibitory postsynaptic potentials and is thought to play an important role in stabilizing neural activity in the brain. GABA exerts its effects by causing hyperpolarization in the postsynaptic membrane. Low levels of GABA or serotonin have been linked to anxiety.
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Serotonin
Along with the catecholamines, **serotonin** is classified as a monoamine or biogenic-amine transmitter. Serotonin is thought to play roles in regulating mood, eating, sleeping, and arousal. Like norepinephrine, serotonin has been implicated in depression and mania. An oversupply of serotonin is thought to produce manic states; an undersupply is thought to produce depression. Hence the class of antidepressants known as **selective serotonin reuptake inhibitors (SSRIs)**, such as Prozac. In addition, low levels of serotonin or GABA have been linked to anxiety.
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Dopamine, Schizophrenia, and Parkinson's Disease
Dopamine is a neurotransmitter that plays an important role in movement and posture as well as in reward systems, sleep, memory, learning, and concentration. Imbalances in dopamine transmission have been found to play a role in schizophrenia. The **dopamine hypothesis of schizophrenia** argues that delusions, hallucinations, and agitation associated with schizophrenia arise from either too much dopamine or from an oversensitivity to dopamine in the brain. Parkinson's disease, meanwhile, is thought to result from a loss of dopamine-sensitive neurons in the basal ganglia (specifically, in the substantia nigra, a part of the basal ganglia). (Recall that the basal ganglia is a group of brain structures that help make our movements smooth and our posture steady.)
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Dopamine Hypothesis of Schizophrenia
The dopamine hypothesis argues that delusions, hallucinations, and agitation associated with schizophrenia arise from either too much dopamine or from an oversensitivity to dopamine in the brain. Evidence for this theory comes from different sources. Drugs like amphetamines enhance the action of dopamine at the synapse. If taken over a long period of time, amphetamines produce excessive dopamine activity that can result in amphetamine psychosis, a disorder closely resembling paranoid schizophrenia. Second, antipsychotic medications, such as a class of drugs called **phenothiazines**, are thought to reduce the sensitivity of dopamine receptors. The less sensitive the receptors are to dopamine, the less likely the person is to experience schizophrenic symptoms. Although the dopamine hypothesis of schizophrenia is an important theory, it is not conclusive; researchers continue to explore the origins of the disease.
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Parkinson's Disease and Dopamine
Parkinson's is thought to result from a loss of dopamine-sensitive neurons in the basal ganglia (specifically, in the substantia nigra, a part of the basal ganglia). Disruptions of dopamine transmission lead to resting tremors and jerky motor movements. Consequently, when antipsychotic medication is adminstered over a long period of time, schizophrenic patients begin to show side effects resembling the motor disturbances seen in Parkinson's. This side effect of antipsychotic medication is called **tardive dyskinesia**. Motor disturbances in Parkinson's can be treated with a drug called **L-dopa**, a synthetic substance that increases dopamine levels in the brain. Before the discovery of L-dopa, researchers tried giving Parkinson's patients oral doses of dopamine, but this technique did not work because the dopamine was blocked from entering the brain by the **blood-brain barrier**. Unlike dopamine, L-dopa can make it past the blood-brain barrier to increase production of dopamine in the brain. Unfortunately, L-dopa can have unwanted side effects––when L-dopa leads to an oversupply of dopamine in the brain, it can produce psychotic symptoms in Parkinson's patients.
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Acetylcholine
A neurotransmitter found in both the central and peripheral nervous systems. In the parasympathetic nervous system (a subdivision of the autonomic nervous system), acetylcholine is used to transmit nerve impulses to the muscles. In the central nervous system, acetylcholine has been linked to **Alzheimer's disease**. Alzheimer's disease is specifically associated with a loss of acetylcholine in neurons that connect with the hippocampus.
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Peptides
Studies suggest that **peptides**, which are two or more amino acids joined together, are also involved in neurotransmission. The synaptic action of **neuropeptides** (also called **neuromodulators**) involves a more complicated chain of events in the postsynaptic cell than that of regular neurotransmitters. Generally speaking, a neurotransmitter is used for neuron-to-neuron communication, whereas a neuromodulator affects the neurotransmission of a whole group of neurons. Neuromodulators are relatively slow and have longer effects on the postsynaptic cell than neurotransmitters. The **endorphins** and **enkephalins** are endogenous analgesic peptides that are very similar in structure to morphine and other opiates.
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Monoamine Neurotransmitters
**Epinephrine**, **norepinephrine**, and **dopamine** are 3 closely related neurotransmitters known as catecholamines. They also belong to the broader category of **monoamines**, or **biogenic amines**. Another important monoamine neurotransmitter is **serotonin**. The monoamines are involved in the experience of emotions.
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Ventricles
The ventricles are fluid-filled cavities in the middle of the brain that link up with the spinal canal that runs down the middle of the spinal cord. The ventricles and the spinal canal are filled with the same **cerebrospinal fluid**. Researchers have linked abnormally enlarged ventricles with a pattern of symptoms often seen in schizophrenia––social withdrawal, flat affect, and catatonic states.
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Phylogeny or Phylogenesis
The evolutionary development and diversification of a species or group of organisms, or of a particular feature of an organism.
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Hermann von Helmholtz
(1821 – 1894) First to measure the speed of a nerve impulse (in terms of reaction), and is often credited with the transition of psychology into the field of the natural sciences.
Also developed **Young-Helmholtz trichromatic theory of color vision**, as well as **place-resonance theory of pitch perception**. Was a German physician (like Ernst Weber) and also a physicist.
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Sympathetic Nervous System
Activated whenever you face stressful situations (both mild and severe). Closely associated with fight or flight response. Activation results in elevated heart rate, blood-sugar level, and respiration; reduced digestion; dilated pupils (to increase the amount of visual information reaching the retina); and a rush of the neurotransmitter adrenaline (epinephrine and norepinephrine) into the bloodstream. An "adrenaline rush" gives you more energy than usual to contend with emergencies.
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Sir Charles Sherrington
(1857 – 1952) Around the turn of the 20th century, effectively resolved the debate between "neurons with synapses" and "reticular theory" in mammals. (Reticular theory stated that everything in the nervous system, including the brain, is a single continuous network.) Many of Sherrington's conclusions have held over time––with one notable exception. He thought that synaptic transmission was an electrical process. We now know that it is primarily a chemical process.
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Neurotransmitters associated with mania and depression
**Epinephrine** and **norepinephrine** (also called adrenaline and noradrenaline) are important for alertness. They have also been implicated in mood disorders such as depression and mania. One theory holds that too much epinephrine and norepinephrine results in **mania**, which is characterized by intense euphoria and impaired judgment. When there is too little epinephrine and norepinephrine, the result is depression. Another neurotransmitter, **serotonin**, has also been linked to depression (not enough serotonin) and mania (too much serotonin). These theories are sometimes collectively called the **monoamine theory of depression**.
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Psychopharmacology
**Psychopharmacology**, a subdiscipline of physiological psychology, is the science of how drugs affect behavior. Psychoactive drugs, which include both psychiatric and illegal drugs, produce their main effects by modifying neurotransmission. Psychopharmacology is also concerned with the development of medications to treat mental illness.
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Sedative-Hypnotics
In general **sedative-hypnotic drugs**, also known as **depressants**, act to slow down the functioning of the central nervous system. At low doses, these drugs reduce anxiety; at medium doses, they produce sedation; and at high doses, they induce anesthesia or coma. Sedative-hypnotic drugs are **synergistic**, meaning when two different drugs are taken together, their combined effect is greater than the sum of their individual effects. The sedative-hypnotics include the **benzodiazepines** and **barbiturates**. Both facilitate / enhance the action of **GABA**, which stabilizes brain activity. Today barbiturates are used mostly as an anesthetic in medical settings, while benzodiazepines are often prescribed for anxiety under trade names such as Valium and Xanax. Another common sedative-hypnotic is **alcohol**. Alcohol abuse can result in memory disturbances, such as blackouts. Chronic alcoholics sometimes suffer **anterograde amnesia** (memory loss for anything new). **Korsakoff's syndrome** doesn't arise directly from drinking too much alcohol. It is traced to a vitamin deficiency in **thiamin**, also known as **B1**. This vitamin deficiency arises from malnutrition that often occurs in chronic alcoholics.
Korsakoff's syndrome is characterized by memory impairment, specifically short-term memory loss (i.e., the inability to form new memories or retain new information). Some affected individuals may also have random loss of long-term memories. It usually results from a deficiency of thiamin (vitamin B1), which may be caused by alcohol abuse, dietary deficiencies, prolonged vomiting, eating disorders, or the effects of chemotherapy.
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Antipsychotic Drugs
**Thorazine**, **chlorpromazine**, **phenothiazine**, and **haloperidol** (**Haldol**) are **antipsychotic drugs**, and are effective in treating the delusional thinking, hallucinations, and agitation commonly associated with **schizophrenia**. Most are thought to block receptor sites for dopamine (all are thought to inhibit dopamine action in some way). **Lithium carbonate** is presribed to treat **bipolar disorder** (it is specifically an anti-manic agent). Lithium carbonate is an effective mood stabilizer and eliminates 70 – 90% of symptoms associated with bipolar disorder.
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Narcotics
**Narcotics** have historically been used to refer to a number of mind-altering substances as well as to provide a broad legal designation for a range of illicit drugs; today, the Drug Enforcement Administration (DEA) more specifically defines narcotic drugs as those that relieve pain and dull the senses, and the use of the word is most commonly associated with opioid drugs.
**Opium**, **heroin**, and **morphine** are narcotics, and are among the most effective pain-relieving drugs available. Many narcotics bind directly to opiate receptors in the brain, which normally respond to the body's own naturally produced painkillers: **endorphins** and **enkephalins**.
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Behavioral Stimulants
A class of drugs that increase behavioral activity by increasing motor activity or by counteracting fatigue. **Amphetamines** speed up the central nervous system in ways that mimic the action of the sympathetic nervous system. They stimulate receptors for norepinephrine, dopamine, and serotonin. **Methylphenidate**, also known as **Ritalin**, is an amphetamine used to treat children with ADHD. It increases alertness and decreases motor activity (contradiction?) in hyperactive children. Its mechanism of action involves dopamine. **Antidepressants** are used to treat symptoms of clinical depression. Antidepressants often elevate mood, increase overall activity level and appetite, and improve sleep patterns. The main antidepressants to know about are the tricyclics, the monoamine oxidase (MAO) inhibitors, and the selective serotonin reuptake inhibitors (SSRIs). **Tricyclic antidepressants** are believed to block the reuptake of the monoamine neurotransmitters, including norepinephrine and serotonin (but not dopamine), thus facilitating their transmission. Tricyclics are also thought to block the action of acetylcholine. They are called "tricyclic" because of their chemical structure. **MAO inhibitors** inhibit the action of an enzyme called MAO, which normally breaks down norepinephrine, serotonin, and dopamine in the synapse––thus increasing the supply of these transmitters. **SSRIs**, such as Prozac, selectively inhibit the reuptake of serotonin, thus increasing its supply in the synapse.
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Detailed Brain Diagram
See physical flashcard.
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Narcolepsy
Condition characterized by brief attacks of deep sleep often occuring with **cataplexy** (sudden loss of muscle power) and **hypnagogic hallucinations** (hypnagogic means of, relating to, or occurring in the period of drowsiness immediately preceding sleep). Narcolepsy may be treated with **amphetamines**.
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The Endocrine System
The other internal communication network in the body (besides the nervous system). It uses chemical messengers called **hormones**. The endocrine system is somewhat slower than the nervous system because hormones travel to their target destinations through the bloodstream. The endocrine system is involved in slow and continuous bodily processes––for example, thyroid hormones regulate general body growth. But the endocrine system does respond quickly when we face life-threatening situations. For example, one endocrine gland, the adrenal gland, produces the hormone **adrenaline** (aka **epinephrine**) that increases energy available for "fight or flight" reactions. Recall that adrenaline also acts as a neurotransmitter. Epinephrine is, therefore, a chemical that can act as both a neurotransmitter and a hormone. The endocrine system also regulates sexual arousal and other functions associated with sexual reproduction.
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Phineas Gage
An early and famous example of the relation between brain lesions and functional behavior. In 1848, Gage was injured when an explosive charge sent an iron rod through the front of his skull. Gage survived the injury with relatively minor physical impairments. However, there were noticeable differences in his personality. Before the injury, he was a persistent and energetic employee––afterwards he was unpredictable, profane, and intolerant. These changes make sense given what we now know about the functions of the prefrontal cortex.
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Paul Broca
Around 1860, Paul Broca examined the behavioral deficits of people with brain damage. He was the first person to demonstrate that specific **functional impairments** could be linked with specific brain lesions. Broca found that a man who could not talk was unable to do so because of a lesion in a specific area of the left frontal lobe. This area of the brain is referred to as **Broca's area**.
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William James
(1842 – 1910) One of the originators of **functionalism**, a system of thought in psychology that was concerned with studying how mental processes help individuals adapt to their environments. He also developed an important theory on the link between physiology and emotional experience.
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Basal Ganglia
A group of subcortical nuclei situated at the base of the forebrain and on top of the midbrain. Associated with a variety of functions, including control of voluntary motor movements, procedural learning, habit learning, eye movements, cognition, and emotion. The basal ganglia coordinate muscle movement as they receive information from the cortex and relay it (via the **extrapyramidal motor system**) to the brain and spinal cord. The extrapyramidal motor system gathers info about body position (from areas such as the basal ganglia) and carries it to the brain and spinal cord. This system helps to make our movements smooth and our posture steady. One chronic disease associated with the basal ganglia is **Parkinson's disease**, characterized by jerky movements and uncontrolled resting tremors. The basal ganglia may also play a role in **schizophrenia**.
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Johannes Müller
In 1835, proposed the **law of specific nerve energies**. As Müller articulated it, this law states that the nature of perception is defined by the pathway over which the sensory information is carried. Hence, the origin of the sensation is not important. For example, pressing on the eye elicits sensations of flashes of light, despite the mechanical nature of the sensory input. Müller's original law differs from its modern form in one key way. Müller attributed the quality of an experience to some specific quality of the energy in the nerves. In 1912, **Lord Edgar Douglas Adrian** showed that all neurons carry the same energy in the form of action potentials. Thus, the quality of an experience depends on the part of the brain to which nerves deliver their action potentials.
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Pons
Part of the **hindbrain**. Lies above the medulla and contains a collection of various tracts and nuclei, all with their own functions.
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Brainstem
The first part of the brain to develop; sometimes referred to as the most primitive region of the brain. The brainstem is composed of the hindbrain and midbrain.
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4 Components of the Hindbrain
* Cerebellum
* Pons
* Medulla oblongata
* Reticular formation
