Cognition and Association Cortices

Question 1

What is cognition?

Answer 1

it’s basically our inner life

perception, attention, memory, language, emotion, planning and consciousness

Question 2

What is the default network and when is it active?

Answer 2

The default network is the combination of brain regions that are more active during “rest” as opposed to during tasks

it’s involved in daydreaming or mind wandering, autobiographical memories, envisioning the future and moral decisions

It contrasts with the “task positive network”

Question 3

What is the status of the default network in schizophrenia, depression, and autism?

Answer 3

schizophrenia = doesn’t turn off properly when the task network is on

depression = default network is way overactive (rumination)

autism = default network is hypoactive

Question 4

What are the two basic types of association cortex?

Answer 4

unimodal (dealing with only one sensory modality)

multimodal (incorporates multiple modalities)

Question 5

WHat are the 4 primary sensory areas?

Answer 5

1. motor
2. auditory
3. somatosensoty
4. visual

Question 6

What’s technically the motor association cortex?

Answer 6

the premotor area

Question 7

What is the general pathway of sensory informaiton flow through the association cortices?

Answer 7

1. primary sensory cortex
2. unimodal association cortex
3. multimodal association cortex
4. premotor cortex
5. motor cortex (to respond)

Question 8

How many layers of cortex are there?

Answer 8

6

Question 9

How does the primary visual cortex (and other sensory cortices) differ cytoarchtecturally from the primary motor cortex?

Answer 9

primary visual cortex - thinner, but layer 4 is much thicker (this is a granular layer - receives info from the thalamus)

primary motor cortex - thicker, but layer 4 is thin and layer 5 is especially thicker (this is the pyramidal layer for output)

Question 10

What cell type is located throughout the layers of the cortex? What cell type is really only in layer 4?

Answer 10

pyrmidal cells are everywhere

stellate cells are in layer 4

Question 11

The primary sensory cortices receive input from what? Into what layer?

Answer 11

from the thalamus into layer 4

Question 12

What 4 areas of the thalamus provide input to the primary sensory cortices?

Answer 12

lateral geniculate - visual info

medial geniculate - auditory info

ventral posterior medial - somatosensory

ventral posterior lateral - somatosensory

Question 13

Where do the association cortices get input from? To what layer?

Answer 13

From the MULTIMODAL thalamic nuclei, to layer 4

Question 14

What are the 4 multimodal thalamic nuclei?

Answer 14

1. pulvinar - visual
2. medial dorsal - supeerior colliculus, olfaction, amygdala, ventral pallidum
3. lateral posterior - association cortex, anterior cingulate, retina
4. anterior - hypothalamus, hippocampus, cingulate

Question 15

What layers receive input from other areas of the cortex (not thalamus)?

Does this differ between the primary and association cortices?

Answer 15

1, 2, 3, and 5

it differs in that the association cortices just get a lot more information than the primary cortices

Question 16

From what two layers do the sensory and assocition cortices send output to other cortical areas?

Answer 16

2 and 2

Question 17

Which two layers project out of the primary and association cortices to the thalamus? Which one also provides output to the other subcortical areas like the basal ganlgia, mdibrain, brainstem and spinal cord?

Answer 17

5 and 6

5 is the one that goes to the thalamus and other subcortial areas

Question 18

Therefore, what layer of the cortex gives you motor function?

Answer 18

layer 5

Question 19

What layer receives MODULATORY input from the thalamus?

Answer 19

layer 1

Question 20

Wall cortical layers receive modulatory input from the brain stem with what NTs?

Answer 20

5HT, DA, NE and ACh

Question 21

How does the function of the parietal association cortex differ based on what hemisphere its in?

Answer 21

nondominant hemisphere = attention, visupspatial localization (where’s waldo”, spatial relationships

dominant hemisphere = skilled movements, right-left orientation

Question 22

Specifically, where is the seat of attention based?

Answer 22

in the nondominant posterior parietal cortex (also called the inferolateral parietal cortex)

Question 23

What is the physiological basis for selective attention found in the posterior parietal?

Answer 23

recordsing in monkey parietal association cortex are only active when they attend to a certain target

this allows selective attention - blocking out stimulus we don’t need to pay attention to

Question 24

What mental disorder has a marked deficiency in selective attention?

Answer 24

schizophrenia

Question 25

What neuropsych test is used to test selective attention?

Answer 25

stroop test

Question 26

Damage to the nondominant posterior parietal cortex will result in what?

Answer 26

spatial neglect (left-sided neglect)

Question 27

Damage in the dominant posteiorr parietal cortex will result in what?

Answer 27

motor apraxias

Question 28

What are some characteristics of spatial neglect?

Answer 28

it's a failure to acknowledge half of the world. note that it's not an issue of the sensory system or of perception - it's an attention problem applies to emviornment, patient's own body, and even memory and visualizations

Question 29

What is the incidence of spatial neglect in right-hemisphere strokes?

Answer 29

nearly 50%!

Question 30

Damage to what areas of the brain will result in motor apraxias?

Answer 30

anywhere in the motor cortex obviously, but also in the interparietal sulcus

Question 31

What is a motor apraxia?

Answer 31

it's a loss of ability to perform SKILLED motions when sensory and general motor systems are still intact

Question 32

Specifically, what is ideomotor apraxia?

Answer 32

apraxia in which the patient can't use gestures (waving goodbye) or tools (fork and knife for examples)

Question 33

How can you test for ideomotor apraxia, and what is a positive result?

Answer 33

you have the patients pantomime use of imaginary tools, imitate action, or use actual tools the test is positive if they can't do this, obviously. but also positive if patient uses the hand in place of an imaginary tool - like using hand to brush the teeth instead of using the hand to pretend to use a tool to brush the teeth

Question 34

What can't a patient do in orofacial apraxia?

Answer 34

They can't make specific facial meovements (usually in stroke near the language areas on the left)

Question 35

What can't a patient do in ideational apraxia?

Answer 35

they can't sequence actions so they'll put on their shoes before their socks, etc. (usuallyf rontal cortex damage - common in dementia)

Question 36

Where is the temporal association cortex (2 parts) and what does it specialize in?

Answer 36

the superior temporal sulcus - specializes in language and social attention inferior temporal cortex (deep) - expert recognition

Question 37

What special neurons are located in the inferior temporal cortex on the left?

Answer 37

it's the fusiform face area with face neurons

Question 38

Through what kind of encoding do face neurons convey recognition?

Answer 38

it's not thorugh a "grandmother" neuron it's thorugh population coding - each neuron responds to a particular feature and together they build up a unified image of grandma

Question 39

Recognition of wat else will occur like it does int he fusiform face area?

Answer 39

any category of highly salient objects - like birds in bird watchers

Question 40

What do you call a general deficit in recognition?

Answer 40

agnosia

Question 41

Damage to what area causes an inability to recognize faces? What is it called?

Answer 41

prosopagnosia bilateral lesions of the inferior temporal cortex

Question 42

What happens in a visual agnosia? Where is the damage?

Answer 42

inability to recognize an oject by SIGHT - you can still recognize them by using other senses (so they look at a cup and can't name it, they put the cup in their hand and they can name it) this is from damage to the UNIMODAL visual association cortex

Question 43

Wha thappens in astereognosia? Where is the damage?

Answer 43

this is an inability to reocgnize an object by touch alone - but they can do so with other senses like vision (put cup in hand wiht eyes closed and can't name it, open eyes and can name it) damage to unimodal somatosensory cortex

Question 44

What happens in ASSOCIATIVE visual agnosia?

Answer 44

you can identify something, but not name it this is from damage to the posterior parietal cortex (for example, they can say, it's what you comb your hair with, but they can't say it's a comb)

Question 45

What happens in finger agnosia? Where ist he damage?

Answer 45

they can't name their fingers! damge to the angular gyrus of the dominant parietal cortex

Question 46

What syndrome does finger agnosia often occur in? WHat are the other symptoms?

Answer 46

Gertmann syndrome finger agnosia acalculia agraphia right-left confusion

Question 47

WHat neuropsych test is useful for testing prefrontal function?

Answer 47

wisconsin card sort

Question 48

How does the cortex change during the first few years of life?

Answer 48

it starts out with distinct motor, sensory and prefrontal networks that are not yet integrated and a rudimentary default network rapidly, it will overproduce synaptic density during the first few years myelination will occur gray matter will become thicker for the first few years

Question 49

During the first few years of life, in what direction does the maturation usually go and what does this mean for degeneration?

Answer 49

usually goes form posterior to anterior basically the last areas to mature are often the first to degenerate

Question 50

What happens to the brain through maturation after the first few years of life?

Answer 50

1. synapses are pruned down to what's necessary 2. the grey matter becoems thinner - partially due to loss of excess synapses, and also as myelination expands, you just lose grey matter by definition