Cortex

Question 1

Types of cortex

Answer 1

• archicortex (oldest, hippocampal formation)
• paleocortex (olfactory areas)
• neocortex (newest, 95% of cortex, 6 layers)

Question 2

Layers of cortex

Answer 2

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

Question 3

Roles of cortical layers

Answer 3

L2: granule cells receive input from other cortical areas (L3).
L3: pyramidal cells send output to other cortical areas (L2).
L4: granule cells receive input from outside of cortex (eg. thalamus).
L5: pyramidal cells send output to outside of cortex (corticopontine, spinal, bulbar tracts).
L6: pyramidal cells send feedback to thalamus.

Question 4

Agnosia

Answer 4

Caused by lesion of posterior unimodal sensory association areas for a particular sense.
- asterognosia (objects by touch)
- akinetopsia (motion)
- achromatopsia (colour)
- prosopagnosia (faces)
- phonagnosia (familiar voices)

Question 5

Lesion of POT association area

Answer 5

• receptive aphasia (lesion to Wernicke’s, unable to understand speech or make sense when talking)
• contralateral neglect (loss of spatial attention on contralateral side)

Question 6

Apraxia

Answer 6

Lesion of anterior unimodal motor association areas, inability to perform purposeful movement.
- expressive aphasia (lesion of Broca’s, can’t put words together)
- difficulty in programming motor sequences

Question 7

Lesion of multimodal prefrontal cortex

Answer 7

• ventromedial prefrontal cortex: major personality changes
• dorsolateral prefrontal cortex: working memory, planning, problem solving damaged

Question 8

Aphasia

Answer 8

Often due to left hemisphere lesion.
- expressive aphasia
- receptive aphasia
- conduction aphasia (damage to arcuate fasciculus, cannot repeat words/phrases)
- global aphasia (damage to inf frontal gryus and parieto-temporal cortex, unable to produce/understand speech)

Question 9

Aprosodia

Answer 9

Often occur from right hemisphere lesion.
- motor aprosodia (unable to produce prosody (tone, rhythm) in speech)
- sensory aprosodia (unable to understand differences in time, rhythm, etc.)

Question 10

Types of cortical layers

Answer 10

• homotypical (granular = pyramidal)
• heterotypical granular (granular > pyramidal)
• heterotypical agranular (pyramidal > granular)