Neurobiology Exam 3

There are 6 layers in neocortex. What defines these layers?

Layer one contains neuropil with very few cell bodies. Layers two and three contain small pyramidal neurons that form from corticocortical connections. Layer four is rich in stellate cells which is the primary input region from the thalamus. Layers five and six contain larger pyramidal cells that often project out of the cortex

What stains contributed to the identification of neocortical layers? How do these stains differ?

Golgi stains label the entire cell body and all processes allowing for cell shape visualization. Nissl stain label the cells body which is used for determining shape, size, and density of neurons with different layers. Wiegert stains label myelin to reveal horizontal and vertical connections

Describe the general function of the association cortex as a whole

The association cortex is responsible for complex integrated processing between sensory and motor systems.

Briefly describe the functions of the 4 main regions of association cortex

complex visual processing to perceive color and movement

Briefly describe the function of the temporal association cortex

identification and recognition of items, sounds, objects (basically what things are)

Briefly describe the function of the parietal association cortex

important in the ability to attend to stimuli and determine where objects are located in space

Briefly describe the function of the frontal association cortex

Important for selecting, planning, and evaluating options and responses.

Most of the input to association cortex comes from where?

other cortical areas both ipsilateral and contralateral

Relative to sensory information received by the primary sensory cortices, what is different about the information that reaches the association cortices via the thalamus?

information from the thalamus has already been processed by the primary sensory cortex

What thalamic regions project to the frontal and parietal association areas?

the frontal association area receives projections from the medial dorsal nuclei. the parietal association area primarily receives information from the pulvinar

There is diffuse neuromodulatory input into the association cortices. What are they? What processes do these inputs influence and what happens if there is dysfunction in these circuits?

Neuromodulatory circuits originate from the brainstem and project to all areas of the association cortex. Dopaminergic inputs influence motivation, drives, and the ability to pay attention. Noradrenergic, cholinergic, and serotonergic inputs are associated with regulating sleep and wakefulness. Dysfunction is correlated with mental health disorders

After processing in the occipital association cortex, what are the two main areas that receive this processed visual information?

information is sent to the parietal association cortex in the dorsal stream and the temporal association cortex in the ventral stream

Describe some symptoms if a person has damage to occipital association cortex

symptoms include cerebral ankinetopsia (inability to detect movement) and achromatopsia (cortical color blindness)

What types of information does the parietal association cortex process?

largely multimodal to integrate visual, auditory, and somatosensory information

What is the role of parietal association cortex?

mediates spatial location and the ability to attend to stimuli

Damage to the inferior parietal association cortex and superior posterior temporal association cortex can lead to a variety of problems, including Contralateral Neglect Syndrome. Describe the symptoms associated with this syndrome.

visuospatial deficits, neglecting one side of the body, spatial disorientation, and specific apraxia

Describe the 4 broad functional areas of the temporal lobe cortex & the function of each

the primary auditory cortex handles initial processing, the unimodal auditory association area specializes in refined processing including voice recognition, the unimodal visual association area is important for recognition of complex objects and faces, the multimodal association cortex integrates information for face to face communication

Visual information flows from the visual cortex into dorsal and ventral streams. What is the general purpose of each stream?

The dorsal stream goes to the parietal association cortex and mediates the ability to attend to stimuli and determine spatial location. The ventral stream goes to the temporal association cortex for identification and recognition of objects, words, and faces

Intrinsic optical imaging is an indirect way of studying neuronal activity by recording optical changes caused by changes in the blood flow to an area and by changes in the oxygenated state of hemoglobin in an area. Using this method, researchers showed that a group of cortical cells in the inferior temporal cortex displays increased activity when the individual looks at a profile of a particular face. When that same face is turned a bit toward a more frontal view, what region will show increased activity (look at the lecture slide)? Is the second region different, or the same as the first region? Do they overlap?

While the second region is different, it is not entirely separate; there is an overlap where some neurons respond to both profile and frontal orientations. This is known as population coding, where different subsets of neurons represent specific views of a face

What is visual agnosia, what cortex is associated with it?

inability to identify objects by sight due to damage in the right temporal association cortex

What is auditory agnosia, what cortex is associated with it?

inability to identify objects based on the sound they make due to damage in the temporal association cortex

What is tactile agnosia, what cortex is associated with it?

inability to identify objects by touch due to damage in the parietal association cortex

What is prosopagnosia? Damage to what specific region in the temporal association cortex leads to this disorder?

face blindness due to damage in the fusiform face area of the fusiform gyrus (typically on the right side)

What things/events can lead to the inability to recognize faces?

stroke, tumors, TBI and congenital disorders affecting the fusiform face area

Describe the range of deficits that can be seen in people with Prosopagnosia or face blindness.

There is a wide range with most patients only being able to identify individual features but unable to combine them to form a holistic image.

What kinds of information do we process & with what regions, to insure successful face-to-face communication?

we integrate information in the temporal association cortex to communicate. We use visual cues combined with auditory (emotional) stimuli . When these are misaligned we become confused

The Superior temporal sulcus (STS) contains neurons that are sensitive to voice stimuli. Which area(s) are especially important for voice recognition?

anterior regions are critical for voice recognition

Describe the 2 models presented in class that propose how the temporal association cortex organizes information to recognize a person based on both voice and facial features.

The indirect combination model describes how the voice and face recognition area project to a third separate multimodal region where information is combined. The direct communication model describes how the voice and face recognition areas directly communicate with each other

How does Magnetic Resonance Diffusion Tractography work? What is being characterized in these types of studies?

MRI tracks diffusion of water because it diffuses parallel to the axons. These studies provide an indirect measure of white matter tracts in the brains of living individuals

MR diffusion tractography studies support which of the 2 models you described above for person recognition in the temporal cortex? Why would this be advantageous?

MR diffusion tractography studies support the Direct Communication Model The data revealed a robust anatomical connection between the anterior superior temporal sulcus and the fusiform face area. This direct connection is advantageous because it is faster than projecting to a separate intermediate area

What differences are seen between right and left temporal association cortex damage?

right side is associated with agnosias while left side is associated with language deficits

Describe the over-all function of the frontal association cortex.

The frontal association cortex is responsible for integrating complex information. It is essential for the appreciation of self relative to the world aka personality

What is the relationship between the frontal association cortex and the temporal and parietal association cortices?

The frontal association cortex receives information from the temporal and parietal association cortices to guide complex decision making

What are the effects of frontal lobe damage? Are these effects specific and consistent for each person, or variable?

Frontal lobe damage affects personality and ability to react appropriately to social stimuli. These effects are variable depending on the person and size of the damage

So why was neurosurgical destruction of the frontal lobes used as an attempt to treat certain psychiatric disorders in the 1930s?

lobotomies occasionally made patients more placid even though it resulted in lots of damage

List 4 possible cognitive disabilities that can result from frontal lobe damage.

impaired restraint, disordered thought, behavioral repetition, inability to plan appropriate actions

Describe the function of the dorsolateral prefrontal cortex (dIPFC)

crucial for working memory and the ability to organize and plan flexible future behaviors

Describe the function of the ventrolateral prefrontal cortex

Important for flexibility and making good decisions by integrating new information as it comes

Describe the function of the dorsomedial prefrontal cortex

Involved in forming socially relevant impression and the ability to evaluate if we trust other people by the way they are acting

Describe the function of the orbitofrontal cortex

helps estimate the value of an opinion and social restraint

Describe the function of the ventromedial prefrontal cortex

important in assessing the value of items and situations, particularly in weighing options

Describe the Wisconsin card sorting task and what cognitive abilities are necessary for the task

Cards are sorted based on a rule that is not stated, After the participant learns the rule the investigator changes it without warning. This requires working memory, flexibility, social restraint, and synthesis of multimodal information

What is “working memory”? Which region of the frontal association cortex is involved in working memory?

the ability to keep information held in short term memory to guide behavior (remembering directions while walking) and primarily associated with the dorsolateral prefrontal cortex

Babies as young as 2 months old produce anticipatory behaviors in response to repeating patterns True or False? Give an example.

True, they make anticipitory eye movements in response to a tennis match

Violations of patterns evoke activation in what prefrontal cortex regions? How could this be determined?

it activates the dorsolateral and ventrolateral prefrontal cortex. This was determined by fMRI to record blood flow changes while subjects respond to stimuli that break established sequences

What is different about the sensory information that reaches the association cortices relative to that which is received by the primary sensory cortex?

The sensory information reaching the primary sensory cortex is a relatively direct relay from the thalamus. In contrast, the information reaching the association cortices has already been processed by the primary sensory cortex, making it much more complex and refined.

What are the benefits of sleeping? In people, what are the effects of sleep deprivation for brief periods?

Sleep replenishes brain glycogen levels, consolidates memories, clears metabolites via the glymphatic system and overall conserves energy

Studies with mice show that longer periods of sleep deprivation lead to what symptoms? What happens if sleep deprivation continues?

Longer periods of sleep deprivation result in increased body temperature and food intake but decreased body weight. Continuous deprivation compromises the immune system and eventually leads to death

Describe the glymphatic system and what changes occur during sleep that promote waste clearance from the brain.

the interstitial space increases which increases CSF flow by 60%. Increased flow of CSF promotes clearance of metabolites and waste including beta-amyloid and tau plaques

Briefly describe Electroencephalography (EEG) and what the electrode is measuring.

EEG surface electrodes measure the extracellular field potentials of thousands of pyramidal neurons in cortical layers 2 and 3.

Describe the advantageous and disadvantageous of EEGs

EEGs have good temporal resolution (changes over time) and are non-invasive. However, EEGs have low spatial resolution and therefore cant record activity from specific deep nuclei

Why are EEG recordings from awake individuals are lower amplitude and higher frequency than those from a person in non-REM sleep?

Because neurons are firing irregularly and are desynchronized while processing input. In non-REM sleep neurons become synchronized

Describe the changes in body temperature, growth hormone and cortisol levels during a 24 hour period in a person.

Body temperature peaks when people are awake and decreases as people sleep. GH levels are low during the day and peak in the middle of the night. Cortisol levels are higher during the day and reach their lowest point right after midnight.

Describe the stages of sleep that a healthy person would go through in a 2 hour time period, beginning with eyes open and awake. Include a description (drowsy, light sleep, deep sleep, etc.) the main characteristics of the EEG during that stage (synchronized or not, high or low amplitude, high or low frequency)

Awake people have beta waves that are irregular with high frequency and low amplitude. Eyes closed are characterized by alpha waves. Stage one sleep shows theta waves and the frequency becomes lower. Stage two sleep is characterized by the appearance of sleep spindles. Deep sleep is characterized by delta waves and rem sleep shows more activity resembling the awake stages

For a typical 8 hour sleeping period approximately how many cycles of stage I sleep are there?

approximately 5-6

For a typical 8 hour sleeping period approximately how many cycles of stage IV sleep are there?

typically two

For a typical 8 hour sleeping period what happens to the REM stage of sleep as sleep continues through the night?

periods get progressively longer

For a typical 8 hour sleeping period when is Heart, temperature, respiration and penile erection the lowest? The highest?

Heart rate and respiration are at their lowest during non-REM sleep. Penile erection is at its highest during REM sleep

What happens in the absence of cues about the day/night environment?

In the absence of day/night cues, the internal clock is freerunning. The individual remains on an endogenous rhythm of approximately 24 to 26 hours, resulting in them waking up later and later each day

Describe 2-3 unique features of intrinsically photosensitive retinal ganglion cells compared to cone photoreceptor cells.

pRGCs contain melanopsin, depolarize in response to light and do not required input from a bipolar or retinal ganglion cell

Intrinsically photosensitive retinal ganglion cell bodies are in the retina. Where do the axons of these neurons project?

suprachiasmatic nucleus of the hypothalamus

What does the pineal gland produce and when is the product at the highest level?

the pineal gland produces melatonin whose levels are highest at night

What is the main role of the suprachiasmatic nucleus of the hypothalamus? Describe 4 features/characteristics of this nucleus or of the neurons in this nucleus

the SCN contains about 10,000 neurons with an intrinsic rhythm. When cells touch (in cell culture) their activity synchronizes. Rhythm is maintained by feed forward and feedback loops (DRAW)

Describe the production and flow of cerebral spinal fluid (CSF) in the cranial vault. Where is CSF located?

CSF is produced by choroid plexus in the ventricles where it drains out of the fourth ventricle into the subarachnoid space and central canal of the spinal cord to the venous system

Briefly describe the mouse experiments that showed that CSF penetrates deeper into the brain tissue during sleep.

researchers injected a fluorescent tracer into brain cavities containing CSF. In awake mice very little tracer penetrated brain tissue but in asleep mice there was a significant increase in braces movement into deep areas of the brain

In the absence of external cues, what happens to the sleep/wake periods in people?

in the absence of external cues individuals wake up later and later each day but maintain and intrinsic 24 hr rhythm

What forms the basis for the molecular mechanism of the biological clock in neurons of the suprachiasmatic nucleus?

molecular looks that rely on time delays involved in the production of mRNA, translation into proteins, and dimerization of those proteins to form feedback inhibition loops

List 5 genes whose expressions regulate the SCN clock or rhythm. What else regulates the SCN clock?

Clock, Bmal1, Per, Cryptochrome, and ccgs. In addition to these proteins, light information and melatonin release regulates the SCN clock

Is the activity of SCN neurons high (depolarized, firing action potentials) or low during the subjective day?

the activity of SCN neurons is high during subjective day. Neurons are more depolarized and fire action potential more frequently