Week 6 Readings Flashcards
What two main metabolites does the brain use, delivered via the blood?
Oxygen and glucose.
Despite being only 2% of our total body weight, what percentage of the oxygen and calories we consume does the brain use?
20%
Can a lack of “brain fuel” explain our limited cognitive capacity?
No, as long as we are not oxygen-deprived or malnourished, we have more than enough oxygen and glucose to fuel the brain.
Is it true that humans use only 10% of their brain?
No, this is a myth. Modern neuroimaging shows that we use all parts of the brain at different times and certainly more than 10% at any given time.
If we have enough brain fuel and neurons, what most likely explains our limited cognitive abilities?
The way neurons are wired up, especially the competitive behavior among neurons.
What is an example of competitive behavior among neurons in the brain?
In the visual cortex, neurons are wired to inhibit each other, meaning when one neuron fires, it suppresses the firing of nearby neurons.
When two neurons that are wired in an inhibitory way both fire, neither neuron can fire as vigorously as it would on its own, limiting the brain’s response to visual information.
What is the most likely cause of our limited capacity for cognitive tasks?
The complex way in which neurons communicate and inhibit each other, rather than the depletion of resources like oxygen or glucose.
What are the three parts that we divide the brain into (for simplicity in this course)?
The brain stem, cerebellum and cerebral hemispheres
Which part is referred to as the “trunk” of the brain?
The brainstem
What essential functions does the brain stem regulate?
Respiration (breathing), heart rate, and digestion.
What happens if a patient sustains severe damage to the brain stem?
The patient will require life support to stay alive.
In many countries, what condition defines a person as “brain dead”?
How do other countries define “brain death”?
Loss of brain stem function.
Other countries require significant tissue loss in the cortex, which is responsible for conscious experience.
What regions make up the brain stem?
The medulla, pons, midbrain, and diencephalon (which includes the thalamus and hypothalamus).
What additional functions (other than respiration, heart rate and digestion) are the brain stem regions involved in?
The sleep–wake cycle, some sensory and motor functions, growth, and other hormonal behaviors.
What is the cerebellum, and where is it located?
The cerebellum is the distinctive structure at the back of the brain, often referred to as the “small brain.”
Who referred to the cerebellum as the “small brain,” and why?
The Greek philosopher Aristotle referred to it as the “small brain” to distinguish it from the “large brain,” or cerebrum.
What are the primary functions of the cerebellum?
The cerebellum is critical for coordinated movement and posture.
In addition to movement and posture, what other abilities has neuroimaging implicated the cerebellum in?
Neuroimaging studies have implicated the cerebellum in a range of cognitive abilities, including language.
Why is it not surprising that the cerebellum influences more than just movement and posture?
Because the cerebellum contains the greatest number of neurons of any structure in the brain.
What are the cerebral hemispheres responsible for?
They are responsible for our cognitive abilities and conscious experience.
What structures make up the cerebral hemispheres?
The cerebral cortex, white matter, and subcortical structures (including the basal ganglia, amygdala, and hippocampal formation).
What is the cerebral cortex?
The largest and most visible part of the brain, consisting of two hemispheres and giving the brain its characteristic gray, convoluted appearance.
“The outermost gray matter of the cerebrum; the distinctive convolutions characteristic of the mammalian brain.”
What term did Aristotle coin for the cerebral cortex, and why?
He coined the term “cerebrum” (Latin for “large brain”) to distinguish it from the “small brain” (cerebellum).
What are the folds and grooves of the cerebral cortex called?
The folds are called gyri (singular: gyrus) and the grooves are called sulci (singular: sulcus).
How many hemispheres does the cerebral cortex consist of?
Two hemispheres.
What does subcortical mean?
Structures that lie beneath the cerebral cortex, but above the brain stem.
What are gyri and sulci?
Gyri: (plural) Folds between sulci in the cortex.
Gyrus: (plural form, gyri) A bulge that is raised between or among fissures of the convoluted brain.
Sulci: (plural) Grooves separating folds of the cortex.
Sulcus: (plural form, sulci) The crevices or fissures formed by convolutions in the brain.
What are the four lobes of the cerebral hemispheres?
The occipital, temporal, parietal, and frontal lobes.
What is the primary function of the occipital lobe?
Vision.
Which lobe is involved in vision, auditory processing, memory, and multisensory integration?
The temporal lobe.
Besides vision, what else is the temporal lobe responsible for?
Auditory processing, memory, and the convergence of multisensory information (e.g., vision and audition).
What is the parietal lobe responsible for?
It houses the somatosensory cortex (body sensations), is involved in visual attention, and contains multisensory convergence zones.
Where is the motor cortex located, and what other functions are associated with this lobe?
The motor cortex is located in the frontal lobe, which is also involved in motor planning, language, judgment, and decision-making.
Which lobe is proportionally larger in humans compared to other animals, and why?
The frontal lobe, because it is involved in higher cognitive functions like judgment, decision-making, and motor planning.
An area of the cerebrum that lies below the lateral sulcus; it contains auditory and olfactory (smell) projection regions.
Temporal lobe
An area of the cerebrum just behind the central sulcus that is engaged with somatosensory and gustatory sensation.
Parietal lobe
Define the somatosensory cortex
The region of the parietal lobe responsible for bodily sensations; the somatosensory cortex has a contralateral representation of the human body.
Define the motor cortex
Region of the frontal lobe responsible for voluntary movement; the motor cortex has a contralateral representation of the human body.
Why are subcortical structures so named?
Because they reside beneath the cortex.
What are the basal ganglia?
Subcortical structures of the cerebral hemispheres involved in voluntary movement.
What is the limbic system?
A loosely defined network of nuclei in the brain involved with learning and emotion.
What is the primary function of the basal ganglia?
The basal ganglia are critical to voluntary movement.
Which structures do the basal ganglia make contact with?
The cortex, the thalamus, and the brain stem.
Which subcortical structures are part of the limbic system?
The amygdala and hippocampal formation.
What is the limbic system involved in?
It plays an important role in emotion, particularly in aversion and gratification.
Does the limbic system include only subcortical structures?
No, it also includes some cortical structures.
What does contralateral mean/signify?
Literally “opposite side”; used to refer to the fact that the two hemispheres of the brain process sensory information and motor commands for the opposite side of the body (e.g., the left hemisphere controls the right side of the body).
What does it mean to say “functions are lateralized”?
To the side; used to refer to the fact that specific functions may reside primarily in one hemisphere or the other (e.g., for the majority individuals, the left hemisphere is most responsible for language).
What is a callosotomy?
Surgical procedure in which the corpus callosum is severed (used to control severe epilepsy).
What is a split-brain patient?
A patient who has had most or all of his or her corpus callosum severed.
What is the visual hemifield?
The half of visual space (what we see) on one side of fixation (where we are looking); the left hemisphere is responsible for the right visual hemifield, and the right hemisphere is responsible for the left visual hemifield.
What connects the two cerebral hemispheres?
A dense bundle of white matter tracts called the corpus callosum.
How is sensory and motor function represented in the two hemispheres?
They have a contralateral representation; the left hemisphere controls the right side of the body and vice versa.
What is meant by lateralized functions in the brain?
Some functions reside primarily in one hemisphere or the other.
In most right-handed and many left-handed individuals, which hemisphere is most responsible for language?
The left hemisphere.
What happens when the corpus callosum is severed or not fully developed?
It leads to split-brain patients, who can help us understand the functioning of the two hemispheres.
How does contralateral representation affect a split-brain patient’s perception of objects in their visual field?
If an object is placed in only the left or right visual hemifield, only the respective hemisphere will see it.
Why might a split-brain patient deny seeing a picture presented to the right hemisphere?
Because language is often localized in the left hemisphere, which did not see the picture.
How can a split-brain patient demonstrate that the right hemisphere perceives an image?
If asked to press a button when seeing an image, the left hand (controlled by the right hemisphere) will respond.
What advantages do split-brain patients have compared to those with a fully functional corpus callosum?
They can search simultaneously in both visual fields and perform tasks that require coordination of both hemispheres, exhibiting less competition between them.
What is gray matter?
Composes the bark or the cortex of the cerebrum and consists of the cell bodies of the neurons.
What is white matter?
Regions of the nervous system that represent the axons of the nerve cells; whitish in color because of myelination of the nerve cells.
What is myelin?
Fatty tissue, produced by glial cells that insulates the axons of the neurons; myelin is necessary for normal conduction of electrical impulses among neurons.
What is gray matter primarily composed of?
Neuronal cell bodies (soma).
What are the main functions of the cell body in gray matter?
The cell body contains the genes of the cell, is responsible for metabolism (keeping the cell alive), and synthesizes proteins.
What is the primary composition of white matter?
The axons of neurons, particularly those covered with a sheath of myelin.
What is the function of axons in white matter?
Axons conduct electrical signals from the cell and are critical for cell communication.
What does the expression “use your gray matter” refer to?
It encourages a person to think harder, likely referencing the cerebral hemispheres more generally and the gray cortical sheet.
Why are both gray and white matter important?
Both are critical to the proper functioning of the mind; losses in either can result in deficits in language, memory, reasoning, and other mental functions.
Which is on the “outside”, grey or white matter?
Outer grey matter, inner white matter
What provides the strongest evidence for a specific role or function of a particular brain area?
Converging evidence—similar findings reported from multiple studies using different methods.
What was phrenology, and when was it popular? What assumption did phrenologists make about the brain and the skull? What has been proven wrong about phrenology?
Phrenology was an organized attempt to study brain functions in the first half of the 19th century.
They assumed that features of the brain, such as its uneven surface, are reflected on the skull.
The assumption that the skull reflects the underlying brain structure.
How did phrenologists attempt to correlate brain functions?
They correlated bumps and indentations of the skull with specific functions of the brain, claiming, for example, that artistic people have different skull ridges compared to those good at spatial reasoning.
Despite its inaccuracies, how did phrenology impact modern neuroscience?
It influenced the understanding that different parts of the brain are devoted to specific functions that can be identified through scientific inquiry.
What advancements have improved the method of brain dissection?
The discovery of various staining techniques that can highlight particular cells
Why is brain dissection especially useful for studying specific groups of neurons?
Because the brain can be sliced very thinly, examined under a microscope, and particular cells can be highlighted, allowing for high spatial resolution.
What changes can dissections help scientists study?
Changes in the brain that occur due to various diseases or experiences, such as exposure to drugs or brain injuries.
What is virtual dissection, and how is it conducted?
Virtual dissection studies with living humans use imaging techniques like computerized axial tomography (CAT) or MRI scanners to visualize brain structures.
What do CAT and MRI scans reveal about the brain?
They reveal various brain structures with very high precision and can help detect changes in gray or white matter.
How can changes in the brain detected by imaging correlate with behavior?
Changes in the brain can be correlated with behaviors such as performance on memory tests, implicating specific brain areas in certain cognitive functions.
What is spatial resolution?
A term that refers to how small the elements of an image are; high spatial resolution means the device or technique can resolve very small elements; in neuroscience it describes how small of a structure in the brain can be imaged.
What are lesions?
A region in the brain that suffered damage through injury, disease, or medical intervention.
What does the term to ablate mean?
Surgical removal of brain tissue.
What is transcranial magnetic stimulation (TMS)?
A neuroscience technique whereby a brief magnetic pulse is applied to the head that temporarily induces a weak electrical current that interferes with ongoing activity.
What is temporal resolution?
A term that refers to how small a unit of time can be measured; high temporal resolution means capable of resolving very small units of time; in neuroscience it describes how precisely in time a process can be measured in the brain.
What is transcranial direct current stimulation (tDCS)?
A neuroscience technique that passes mild electrical current directly through a brain area by placing small electrodes on the skull.
What is the purpose of inducing lesions or ablating parts of the brain in animal research?
To infer that the removed structure is important for specific behaviors if the animal’s behavior changes after the lesion.
In human studies, what types of patients are examined for brain lesions?
Patients who have lost a brain region due to a stroke or injury, or who have had surgical removal of a structure to treat a disease (e.g., callosotomy for epilepsy).
How can brain function be inferred from patient case studies?
By measuring changes in the behavior of patients before and after the lesion
What does transcranial magnetic stimulation (TMS) involve?
Applying a brief magnetic pulse to the head to temporarily induce a weak electrical current in the brain.
How are the effects of TMS described, and what is its primary function?
They are referred to as temporary virtual lesions, but it’s more accurate to describe them as interference with normal neuronal communication.
What is the temporal resolution of TMS, and what are its limitations?
TMS allows precise study of when events in the brain happen, but its application is limited to the surface of the cortex and cannot reach deep areas of the brain.
How does transcranial direct current stimulation (tDCS) differ from TMS?
tDCS uses electrical current directly applied via electrodes on the skull, while TMS induces current with magnetic pulses.
What effects has tDCS shown when combined with cognitive training?
It has been shown to improve performance in various cognitive functions such as mathematical ability, memory, attention, and coordination.
What is positron emission tomography (PET)?
A neuroimaging technique that measures brain activity by detecting the presence of a radioactive substance in the brain that is initially injected into the bloodstream and then pulled in by active brain tissue.
What is the purpose of neuroimaging tools?
To study the brain in action while it is engaged in specific tasks.
What does positron emission tomography (PET) measure?
PET records blood flow in the brain by detecting a radioactive substance injected into the bloodstream.
How does a PET scanner determine which brain areas are active during a task?
More blood and radioactive substance flow into active neuron populations, allowing researchers to infer activity in specific brain regions.
What is functional magnetic resonance imaging (fMRI) used for?
To measure changes in oxygen levels in the blood without requiring any substance to be injected.
How do PET and fMRI compare in terms of spatial resolution?
Both tools have good spatial resolution, although not as precise as dissection studies.
What is a limitation of PET and fMRI regarding temporal resolution?
They have poorer temporal resolution (compared to dissection studies) because it takes several seconds for blood to arrive in active areas of the brain, so they do not provide precise timing of when activity occurred.
How does a PET scanner measure brain activity during a task?
The PET scanner detects a radioactive substance injected into the bloodstream of the participant before or while performing a task (e.g., adding numbers). Active neuron populations require metabolites, leading to increased blood flow and more radioactive substance in those regions. By detecting this substance in specific brain areas, researchers can infer that those areas were active during the task.
What does electroencephalography (EEG) measure?
EEG measures the electrical activity of the brain.
How does the temporal resolution of EEG compare to that of PET or fMRI?
EEG has much greater temporal resolution, providing millisecond precision, whereas PET and fMRI have a temporal resolution of seconds.
What is used to measure electrical activity through EEG during a task?
Electrodes are placed on the participant’s head to measure electrical activity while they perform a task.
Why does EEG have poor spatial resolution?
EEG has poor spatial resolution because the electrical activity detected at any electrode can originate from anywhere in the brain, giving only a rough idea of the activity’s source.
What is electroencephalography (EEG)?
A neuroimaging technique that measures electrical brain activity via multiple electrodes on the scalp.
What does diffuse optical imaging (DOI) measure to provide information about brain activity?
DOI measures the infrared light that is shined into the brain and reflects back out, analyzing how the light properties change when it interacts with oxygenated blood or active neurons.
How does DOI provide high spatial and temporal resolution?
When DOI is configured to directly detect active neurons, it achieves both high spatial and temporal resolution.
What happens to DOI’s temporal resolution when it is set up to detect changes in blood oxygen levels?
The temporal resolution becomes low and is comparable to that of PET or fMRI.
What can researchers infer from the properties of the collected light in DOI?
Researchers can infer which regions of the brain were engaged by the task based on the changes in light properties.
What is diffuse optical imaging (DOI)?
A neuroimaging technique that infers brain activity by measuring changes in light as it is passed through the skull and surface of the brain.
Why is converging evidence crucial in understanding brain functions, and what does it suggest about the complexity of the brain?
Converging evidence from multiple studies using various tasks and neuroimaging tools strengthens our belief in the role of specific brain areas, such as the hippocampal formation in memory. This complexity indicates that only ongoing advances in brain research will reveal whether the brain can truly understand itself.
Describe the key factors of the parietal lobe (what it is, where it is, what its involved with, etc)
The parietal lobe is located between the frontal and occipital lobes.
- It is involved in bodily sensations, visual attention, and integrating the senses.
- The parietal lobe is home to the somatosensory (body sensations) cortex and structures involved in visual attention and multisensory convergence zones.
Describe the key factors of the temporal lobe (what it is, where it is, what its involved with, etc)
The temporal lobes are located laterally (right behind your ears).
- The temporal lobe is responsible for vision, along with the occipital lobe.
- It is also involved in auditory processing, memory, and multisensory integration (e.g., the convergence of vision and audition).
Describe the key factors of the frontal lobe (what it is, where it is, what its involved with, etc)
The frontal lobe is the forward-most region in the cerebrum (closest to the forehead).
- As the motor cortex is located within the frontal lobe, it is responsible for motor output, planning, language, judgment, and decision-making.
- The frontal lobe is proportionally larger in humans than in any other animal.
Describe the key factors of the occipital lobe (what it is, where it is, what its involved with, etc)
The occipital lobe is the back most (posterior) part of the cerebellum.
It is involved in vision, as is much of the temporal lobe.
Describe the key factors of the cerebellum (what it is, where it is, what its involved with, etc)
The cerebellum is the distinctive structure at the back of the brain.
- It contains the greatest number of neurons of any structure in the brain.
- The cerebellum is critical for coordinated movement and posture.
- Recent research findings have implicated the cerebellum in a range of cognitive abilities, including language.
Describe the key factors of the brain stem (what it is, where it is, what its involved with, etc)
The brain stem is sometimes referred to as the “trunk” of the brain.
- It is responsible for many of the neural functions that keep us alive, including regulating our respiration (breathing), heart rate, and digestion.
- It includes the medulla, pons, midbrain, and diencephalon (which consists of thalamus and hypothalamus). Collectively, these regions are involved in our sleep–wake cycle, some sensory and motor function, as well as growth and other hormonal behaviors.
The single most basic part of the human brain – a part that is seen in other, less-evolved animals - is the ______. This essential area helps to regulate such critical functions as breathing, digestion, and the beating of your heart.
brainstem
Which of the following would NOT be considered a structure that is part of the limbic system?
the pituitary gland.
the hypothalamus.
the thalamus.
the amygdala.
the medulla.
the medulla
The thick bundle of neurons that connects the left and right cerebral hemispheres is called the ______. This structure allows those hemispheres to communicate with each other.
corpus callosum
