Cerebral Cortex -Bales

Question 1

What are the layers from superficial to deep of the cortex?

Answer 1

1. molecular layer
2. external granular layer
3. external pyramidal layer
4. internal granular layer
5. internal pyramidal layer
6. multiform layer

Question 2

What are the regions of homotypical cortex?

Answer 2

relatively proportional layers

e.g. primary sensory

Question 3

What are the regions of heterotypical agranular cortex?

Answer 3

pyramidal layers (3 and 5) are enlarged

e.g. primary motor cortex

Question 4

What are the regions of heterotypical granular cortex?

Answer 4

layer 4 is enlarged

e.g. association cortex

Question 5

What are some key features of pyramidal neurons?

Answer 5

• 75% of neurons
• small to large triangular bodies
• apex points to surface; apical dendrites extend to layer 1
• basal dendrites from each corner spread out more locally
• dendrites are spiny (spines receive synaptic input)
• all excitatory
• axon from center of base projects to white matter; often with collateral branches

Question 6

Where are the largest pyramidal cells?

Answer 6

Betz cells in layer 5 of the primary motor cortex (BA4)

Question 7

Where do abnormal products accumulate in Alzheimer disease?

Answer 7

In the pyramidal cells

association cortex and hippocampal pyramidal neurons are especially vulnerable

Question 8

What are some properties of cortical interneurons?

Answer 8

• all smooth (except the spiny interneuron
• mostly inhibitory
• most small, irregular

Question 9

What exists in layer 1?

Answer 9

afferent axon terminals and dendrites of pyramidal neurons

Question 10

What exists in layer 2?

Answer 10

mostly small granular interneurons

Question 11

What exists in layer 3?

Answer 11

• has the most terminations of cortical intrahemispheric association fibers
• plus significant callosal fiber input (interhemispheric)
• pyramidal cells project to cortex via callosal or association pathways

Question 12

Which 2 layers have callosal fibers (inter hemispheric)?

Answer 12

layers 3 and 4

Question 13

What exists in layer 4?

Answer 13

• significant callosal input
• main termination layer for specific thalamocortical fibers
• mostly small (granular) interneurons (not a main output layer)
• horizontal branches (of thalamocortical input) which form the “outer band of Baillarger”

Question 14

Which layer is the stripe of Genarri found in?

Answer 14

layer 4

this is the outer band of Baillarger in the primary visual cortex (BA17=”striped cortex”)

Question 15

What exists in layer 5?

Answer 15

• major output projection layer
• mostly medium-to-large-to-giant (Betz) pyramidal cells
• main output (corticofugal) layer to most subcortical targets

Question 16

Which layer projects to all of the cortico paths?

Answer 16

layer 5

corticospinal, corticobulbar, corticopontine, corticostriate, corticorubral

Question 17

What exists in layer 6?

Answer 17

• small pyramidal and modified pyramidal (fusiform) neurons

- main output layer for corticothalamic fibers

Question 18

Which 2 reticular nuclei function in cortical arousal and alertness? What neurotransmitters do they produce?

Answer 18

Raphe nuclei are serotoninergic

locus ceruleus is norepinephrinergic

Question 19

What is a major source of Ach neurons to the cortex?

Answer 19

Basal nuclear of meynert

fascilitates cortical memory functions

Question 20

The majority of cortical interneurons are _______ to the pyramidal cells

Answer 20

inhibitory (GABAergic)

Question 21

What is the most important cortical interneuron? Why?

Answer 21

the chandelier cell synapses strongly at the initial segment of the axon and is the last control point before the action potential

Question 22

How many pyramidal axons can one chandelier cell axon terminate on?

Answer 22

MANY!

they are the principle regulators of cortical output

Question 23

What would a lesion of the dominant left temporal lobe cause?

Answer 23

fluent aphasia due to the loss of wernickes

• can’t process auditory input
• inability to repeat a command
• can’t read aloud

Question 24

What would a lesion of the right temporal lobe cause?

Answer 24

• amusia–> loss of musical ability
• loss of ability to appreciate the variable aspects of speech which add emotional and other non-word features (aprosodia)

Question 25

What would an occipital lesion cause?

Answer 25

visual agnosia (inability to recognize familiar objects) or alexia (inability to recognize words)

Question 26

What would an inferior occipital-temporal lobe lesion cause?

Answer 26

prosopagnosia–> inability to recognize faces

Question 27

What is a Jacksonian march?

Answer 27

a seizure along the pre central gyrus which will begin with involuntary movement along the motor homunculus

the initial body part that moved would localize the origin of the seizure

Question 28

What would a frontal lobe lesion cause?

Answer 28

apraxias: inability to perform a voluntary motor act in the absence of paralysis

Voluntary control of micturition seems to occur in a medial premotor area

Question 29

What would a lesion to the frontal eye field cause? Stimulation?

Answer 29

lesion: horizontal deviation to the lesion side
stimulation: horizontal deviation to the opposite side

Question 30

What are some believed functions of the insula?

Answer 30

• visceral homeostasis (both motor and sensory functions)
• crude (unlocalized) pain and temperature sense (collateral path of ALS)
• primary gustatory cortex (solitariothalamocortical pathway)
• vestibular cortex (among other places)
• limbic and olfactory association cortex

Question 31

What is Gerstmann’s syndrome? What can cause it?

Answer 31

angular gyrus syndrome

Lesions, especially focused on angular gyrus, cause multiple affects including inability to write (agraphia), inability to do math (acalculia), inability to recognize and name individual fingers (finger agnosia) and inability to tell right-from left

Question 32

What will a lesion of the right inferior parietal lobe cause?

Answer 32

astereognosis –> inability to recognize objects

Question 33

What will a lesion of the right superior parietal lobe cause?

Answer 33

hemineglect of the left side of the body and world

Question 34

What happens in Pick’s disease?

Answer 34

frontal and temporal lobes degenerate

“frontotemporal dementia”