Lab 1 Flashcards
EEG
Electroencephalogram;
Records electrical activity of neurons, or brain waves
EEG signals are affected by the state of arousal of cerebral cortex and show characteristic changes in different stages of sleep
EEG signals are affected by stimulation from the external environment
EEG is used in the diagnosis of epilepsy, sleep disorders, and the diagnosis of brain death
Brain waves
Patterns of neuronal electrical activity recorded
Generated by synaptic activity at the surface of the cortex, rather than by action potentials in the white matter
EEG made and recorded
EEG is made by placing electrodes on the scalp and then connecting the electrodes to an apparatus that measures electrical potential differences between various cortical areas
EEG is recorded by small voltage signals
Signals are small because recording electrodes are separated from the brain’s surface by the scalp, skull, and a layer of cerebrospinal fluid
Electrodes must be made of the right material and they must be connected properly
Might record artifacts
Artifacts
A range of unwanted interfering influences that may spoil Electroencephalogram (EEG) recordings
Origin of EEG
EEG results from slow changes in the membrane po-
tentials of cortical neurons, especially the excitatory and
inhibitory postsynaptic potentials (EPSPs and IPSPs)
Little contribution normally comes from action potentials propagated along nerve axon
EEG reflects the algebraic sum of the electrical potential changes occurring from large populations of cells; Therefore, large amplitude waves require
the synchronous activity of a large number of neurons
Components of EEG waveform
Amplitude
Frequency
Brain waves
Frequency
The number of peaks in one second; Expressed in hertz (Hz); A frequency of 1 Hz means that one peak occurs each second
Sleep induces lower amplitudes of brain waves
Amplitude
Amplitude or intensity of any wave is represented by how high the wave peaks rise and how low the troughs dip
Amplitude of brain waves reflects the synchronous activity of individual neurons
Usually, brain waves are complex and have low amplitude
Sleep induces higher amplitudes of brain waves
Alpha brain waves
8-13 Hz; amplitude 30-50uV
Relatively regular and rhythmic, low-amplitude, synchronous waves
Indicate a brain that is “idling” – a calm, relaxed state of wakeful-
ness; Alpha rhythm is seen when the eyes are closed and
the subject relaxed
It is abolished by eye opening and by mental effort such as doing calculations or concentrating on an idea
It is thus thought to indicate the degree of cortical activation where, the greater the cortical activation, the lower the alpha wave activity
Alpha waves are strongest over the occipital cortex (back of the head) and the frontal cortex
Beta brain waves
14-30 Hz; amplitude <20 uV
Beta waves are also rhythmic, but they are not as regular
as alpha waves and have a higher frequency
Beta waves occur when we are mentally alert, as when concentrating on some problem or visual stimulus
In awake, alert individuals with their eyes open, the dominant rhythm is beta
It may be absent or reduced in areas of cortical damage
and can be accentuated by sedative-hypnotic drugs such
as benzodiazepines and barbiturates
The greater the cortical activity, the higher the beta wave activity will be
Theta brain waves
4-7 Hz; amplitude <30 uV
Theta waves are still more irregular
Though common in awake children (up to adolescent age), theta waves are
uncommon in awake adults but may appear when concentrating
It is normal during sleep at all ages
(Note, however, that some researchers separate this frequency band into two components, low theta (4 - 5.45 Hz) activity that they correlate with decreased arousal and in-
creased drowsiness, and high theta (6 - 7.45 Hz) activity
claimed to be enhanced during tasks involving working
memory.)
Delta brain waves
4 or less Hz; amplitude up to 100-200 uV
Delta waves (4Hz or less) are high-amplitude waves
seen during deep sleep and when the reticular activating
system is damped, such as during anesthesia
In awake adults, they indicate brain damage
Delta rhythm is the dominant rhythm in sleep stages 3 and 4 but is not seen in the conscious adult. This rhythm tends to have the highest amplitude of any of the component EEG waves
Note that EEG artifacts caused by movements of jaw and neck
muscles can produce waves in the same frequency band
Gamma brain waves
30-50 Hz
Some people also recognize gamma waves but their
existence and importance is controversial
These waves may be associated with higher mental activity, including perception and consciousness and they disappear under general anesthesia
One suggestion is that the gamma rhythm reflects the mental activity involved in integrating various aspects of an object (color, shape, movement, etc) to form a coherent picture
Interestingly, recent research has shown that gamma waves are enhanced in Buddhist
monks during meditation and are absent in schizophrenic
Amplitude vs frequency relationship
In general, the more active the brain, the higher the frequency and the lower the amplitude of the EEG
Conversely, the more inactive the brain, the lower the frequency and the higher
the amplitude of the signal
Flat EEG
Spontaneous brain waves are always present, even during unconsciousness and coma
Their absence is clinical evidence of brain death
Consciousness
Encompasses conscious perception of sensations, voluntary initiation and control of movement, and capabilities associated with higher mental processing (memory, logic, judgment, perseverance, and so on)
Clinically, consciousness is defined on a continuum that
grades behavior in response to stimuli as: (1) alertness,
(2) drowsiness or lethargy (which proceeds to sleep), (3)
stupor, and (4) coma
Syncope
Fainting
A brief loss of consciousness and is usually caused by inadequate blood flow to the brain due to low blood pressure
Sleep
A state of partial unconsciousness from which a person can be aroused by stimulation
Cortical activity is depressed during sleep, but brain stem functions, such as control of respiration, heart rate, and blood pressure, continue
Even environmental monitoring continues to some extent, as illustrated by the fact that strong stimuli (i.e. things that go bump in the night) immediately arouse us
Coma
A state of unconscious-
ness for an extended period of time from which a person
cannot be aroused by even the most vigorous stimuli
Types of sleep
Two major types of sleep, which through most of the sleep cycle, are non-rapid movement (NREM) sleep and rapid eye movement (REM)
Sleep patterns
24-hour circadian rhythm
Hypothalamus is responsible for timing of sleep cycle
Suprachiasmatic nucleus (a biological clock) regulates its preoptic nucleus (a sleep-inducing center)
By inhibiting the brain stem’s reticular activating system (RAS), the preoptic nucleus puts the cerebral cortex to sleep
RAS centers maintain the awake state but also mediate some sleep stages, especially dreaming sleep
Orexins
Peptides released by hypothalamic neurons which act as “wake-up” chemicals
Certain neurons of brain stem reticular formation fire at maximal rates, arousing the sleepy cortex
Sleep stages
Stage 1: Associated with decreasing beta activity, alpha activity becomes less obvious, and the emergence of theta activity
Stage 2: Irregular theta activity, short bursts of sleep spindles, and sudden increases in wave amplitude
Stages 3 and 4: Delta activity predominates although there is delta activity for 50% of the time in Stage 3; Deep sleep
Stage 4: When bed-wetting, night terrors, and sleepwalking may occur
REM: Lasts from 20-60 minutes; Occurs about 90 minutes after sleep begins after NREM Stage 4; Brain change is coupled with increases in heart rate, respiratory rate, and blood pressure and a decrease in gastrointestinal motility; Eyes move rapidly under lids, but body’s skeletal muscles are actively inhibited
Sleep importance
NREM Stages 3 and 4: Presumed to be restorative; Deprivation of sleep leads to more time in slow-wave sleep
REM: Work through emotional problems and analyze day’s events; Reverse learning
Reverse learning
Accidental, repetitious, and meaningless communications continually occur, and they must eliminated from neural networks by dreaming if the cortex is to remain an efficient thinking system; Dream to remove unneeded synaptic connections/communications or to “forget”
Drugs and suppression of sleep stages
Suppress REM: Alcohol and some sleep medications (barbiturates and others); Does not suppress slow-wave sleep
Suppress slow-wave sleep: Certain tranquilizers, such as diazepam; Does not suppress REM sleep
Narcolepsy
Will fall abruptly into REM sleep from the awake state
Hypothalamic cells that make orexins are damaged in patients with narcolepsy, likely due to the autoimmune destruction of these cells
Insomnia
Chronic ability to get sufficient quality sleep needed by an individual to function adequately during the day
Psychological disturbances are the most common cause
Broca’s area
Part of left side association cortex
Involved with speaking language but not necessarily with understanding it
Aphasia
Inability to produce coherent language
Affects Broca’s area
Wernicke’s area
Part of left side association cortex
Area of the brain is involved with understanding and producing sentences that are structured with logical thought
Procedural memory
Skill memory such as that
used to play the piano or type on a keyboard
This type of memory is practiced over and over and over again by professional athletes to reinforce their procedural memory as they prepare for their sport through the ability to very accurately repeat the same procedure repeatedly (such as
the procedure to accurately shoot a ball at a basket)
Motor memory
The memory associated with the
ability to repeat the same muscle movements
This is different from the procedure or order and exact positions of a process in that this is the memory of how to control the muscles themselves to repeat an action
This is also a memory that athletes practice most every day so that they can, for example, ride a bike in the same way every time so that they can cover a distance in the fastest time they possibly can
Emotional memory
Memory associated with the
sentiments of an event such as the memory of the feelings
felt the last time you visited your parents or the emotions
felt as you left home to begin college
Declarative memory
The memory of facts such as
words, names, faces, and dates
Declarative memory is
formed through two stages, short-term and then long-
term memory
Short-term memory
Limited to 7-8 parts of information
Evolved to process memory to begin to store it in this way most likely to remember directions for tasks essential to survival
Why long sequences of information can be better remembered if grouped into chunks
Long-term memory
Transfer from short-term to long-term memory can be influenced by rehearsing, repeating, and looping new information to older information already stored in long-term memory
Emotional state can affect how much is committed to long-term memory
More memory is committed natural to long-term memory when surprised, aroused, or otherwise stimulated into an emotional state
Bilateral damage to medial temporal lobes and hippocampuses greatly inhibits the ability to transfer information from short-term to long-term memory
Seizures
A torrent of electrical discharges from groups of brain neurons that interrupts the normal functioning of these neurons such that during this uncontrolled activity no other information can be processed through these neurons
Seizure
A burst of uncontrolled electrical activity between neurons
Epilepsy can make people susceptible to brain abnormalities
Diseases that cause chemical imbalances in the brain can cause seizures
During a seizure the person might experience sensory hallucinations just before the seizure begins
Absence seizures
A mild form during which the person is no longer conscious of their environment as their expression goes blank for a few seconds
Epilepsy
A pathologic neurological disorder that makes people susceptible to brain abnormalities like seizures
When a person experiences epilepsy, it is often associated with sensory disturbances, loss of consciousness, abnormal uncontrolled movements, and/or full-on convulsions, in the form of an epileptic seizure, with potential loss of bowel and bladder control
Can be genetically inherited or can be caused by injuries such as those due to stroke, tumors, infections, or blows to the head
Tonic-clonic seizures
Most severe form and result in convulsions
The person loses consciousness, bowel, and bladder control, and the seizure might last for a few minutes during which it is very common for the person to sustain considerable injuries such as broken bones
Psychophysiology
A branch of science that is concerned with the physiological bases of psychological processes
Psychophysiologists typically measure
Skin conductance, or the electrodermal response (EDR), skin temperature, heart rate, heart rate variability, muscle activity through electromyograms (EMGs), eye movements through electrooculograms (EOGs), blood pressure, and respiratory system
Stress
Upon stress, sympathetic nervous system signals to the adrenal medulla to release catecholamines (epinephrine and norepinephrine)
Hormones drive the initial fight or flight responses which include an increase in cellular energy use, a change in blood localization, a reduction in digestive activity, an increase in heart rate and respiration, and an increase in sweat production
Another response to stress is production of the catabolic steroid cortisol
Cortisol drives the resistance reaction to stress during which energy stores are mobilized, gluconeogenesis occurs, glucose is conserved along with salts and water, and the immune system is depressed
Electrodermal Response (EDR)
Psychophysiological measure using eccrine sweat glands
Electromyography (EMG)
Technique that measures the electrical activity of the skeletal muscles and therefore reflects the activity of the nerves controlling them
Lobes of brain
Frontal lobe: Consciousness, how to initiate activity in response to environment and judgements made about what occurs in daily activities
Parietal lobe: Location for visual attention as well as goal directed voluntary movements and manipulation of objects
Occipital lobe: Vision and ability to locate objects in environment and identify colors
Temporal lobe: Controls hearing ability, memory acquisition, and visual perceptions
Brain stem and cerebellum: Controls vision reflexes and coordination of voluntary movement, respectively
Two ways brain pays attention
Top-down: Willful, goal-oriented attention, such as when focusing to read
Bottom-up: Reflexive attention to sensory information, such as loud noises, bright colors, or threatening animals
Distraction
Divided attention of an individual from a particular task onto the source of the distraction
Inattentive blindness
Occurs when someone is distracted and becomes “blinded” to sensory information they would likely process without the distraction
