prefrontal cortex

Question 1

describe the cellular architecture in the prefrontal cortex

Answer 1

prefrontal cortex has very strong inputs into layer IV

layer IV contains inhibitory GABAergic neurons which express parvalbumin and somatostatin

these make inputs into layer V (thick/thin tufted pyramidal)
• thick → sub-cortical areas + back to inhibitory interneurons
• thin → through corpus callosum to other hemisphere + collaterals back to inhibitory interneurons

excitatory pyramidal cells in layer II/III synapse onto thick tufted pyramidal cells

Question 2

which thalamic nuclei project to the prefrontal cortex?

Answer 2

medio-dorsal
ventral anterior
anterior complex

Question 3

where does the prefrontal cortex project to?

Answer 3

has wide projections:
– medio-dorsal thalamus
– basal ganglia
– hippocampus
– association cortices
– amygdala
– hypothalamus
– cerebellum
– brainstem
– other areas in premotor cortex

• not connected to primary motor or sensory areas

Question 4

describe the role of dopamine inputs to the PFC

Answer 4

dopamine projects from the ventral tegmental area (midbrain) to interneurons + pyramidal neurons in layer IV and V of the PFC

high dopamine release inhibits cortical inputs onto basal dendrites, allowing thalamic inputs onto to apical dendrites to dominate ∴ communication to other areas

low dopamine release allows cortical inputs to predominate ∴ communication with self

this is important in goal-orientated behaviours

Question 5

what are the three regions of the prefrontal cortex?

Answer 5

ORBITAL
• emotional behaviour

MEDIAL
• emotional behaviour

LATERAL
• speech
• reasoning

Question 6

what are the consequences of an orbital PFC lesion?

Answer 6

• impulsivity / engaging in high risk behaviour
• disregard for social principles
• euphoria / hyperactivity
• irritability
• perseveration (persisting even when action is not going to work)

Question 7

what are the consequences of a medial PFC lesion?

Answer 7

• loss of motility, unable to initiate movement or speech
• loss of spontaneity
• apathy, disinterest
• unaware of own condition

Question 8

what are the consequences of a lateral PFC lesion?

Answer 8

• depression
• cognitive deficits involving time integration and organisation
• impaired attention
• impaired short-term memory
• unable to plan + carry out sequences of actions (motor and language)

Question 9

what is a test that can be used to test PFC function?

Answer 9

Wisconsin Card Sorting Test

subjects told to match cards be either colour, number or shape

tester will tell subject if match is correct and subject must infer the rule being used