PFC functions

Question 1

Routine

Answer 1

Established, Well learned stimulus response associations.

Arise due to connections between unimodal association cortex and premotor cortex. Repitition lowers placement in hierarchy, no need for PFC

Also reason why lesioned PFC patients show behaviour thats automatized for them (non-smokers would push away, smokers would smoke)

Question 2

Flexibility

Answer 2

New and flexible stimulus response associations

made possible by polymodal association cortex and PFC. High in the hierarchy

Enabled by PFC due to :
1. Working memory (long stimulus response contingencies are held in WM, allowing delayed response)
2. inhibition of direct response
3. Adding value to choice options

Question 3

PFC connections

Answer 3

PFC is connected to the dorsomedial nucleus of the thalamus.

Bidirectional with most of the brain
- Cortical (parietal, temporal, occipital)
- Subcortical (thalamus, basal ganglia, cerebellum etc)
- Frontal (motor/premotor)

Coordinates a large region of the CNS

Question 4

Working memory task

Answer 4

Similar to associative, but there you learn a certain rule/association between stimulus and target

In WM task, there is a delayed response, where location of target has to be remembered.

Lesion to lateral/pre-frontal cortex
= Impaired performance on WM task, but not associative memory task
- Also in delayed alteration task

Question 5

Wisconsin CST

Answer 5

Requires flexibility to discard previously learned rule

Pre-frontal patients persevere with the first rule

Question 6

N-back task

Answer 6

PF patients fail this as well, can’t keep it in memory. Memory load is too high

Also seen in ‘normal’, the more N-back the more activity in PFC

Question 7

Delay activity

Answer 7

Seen in monkeys where neural activity is measured in WM task.

Delay activity is neurons that fire during the delay. Typically location specific.

More recently, found that its not only where, but also what, object identity

Some neurons encode the what information
Some neurons encode the where information

The idea however, is that it works through feedback loops (where that info is stored anyway)

Question 8

Evidence for feedback loop theory

Answer 8

You’d expect activity in the cortex where the info is stored, but this is not the case. Visual cortex eg is not active

BUT, primary visual cortex size does determine WM capacity, and it could be that it’s possible to decode a pattern from the baseline activity.