Prefrontal Cortex (9b) Flashcards
(16 cards)
What is the frontal lobe
The frontal lobe is the largest of the four main lobes of the human brain, located at the front of each cerebral hemisphere. It is responsible for a wide range of important functions
Compared to lots of other animals - the HUMAN frontal lobe is a lot bigger
–> so there must be something important in humans
Outline the developmental changes in the brain
Between age 5 and 20, the GRAY MATTER THINS OUT over the whole brain
–> however some of the biggest reductions seem to be happening in the frontal lobe
What are frontostriatal loops
Some of the strongest connections occur between regions in the PFC and the basal ganglia (or striatum) which is a collection of old, subcortical structures including the caudate, putamen, globus, pallidus, and ventral striatum
These loops seem to occur in parallel, with different loops connecting different PFC regions and hypothesised to play different roles
–> eg. a reward processing loop that connects the ventral striatum to the OFC and an executive control loop that connects the DLPFC to the dorsal striatum
Anatomy of the frontal lobe: outline the lateral, medial, and orbital surface
Lateral Surface: Outer side of the frontal lobe, involved in movement control, language, and higher thinking.
Medial Surface: Inner side facing the midline, involved in emotions, decision-making, and self-awareness.
Orbital Surface: Bottom side above the eyes, involved in decision-making, emotional regulation, and smell.
History: describe the story of Phineas Gage
Worker who had metal bar shot up into his face
- he could still speak, interact, move etc.
BUT
- appeared to be an abstract element that had broken
- personality changes, control and behv organisation change
History - Ryland 1939: Outline ‘dysexecutive syndrome’
Shallice - Supervisory Attention System (SAS)
Characterised problems with frontal lobe injuries as ‘dysexecutive syndrome’
- involving problems with attention, abstraction, and novelty
Supervisory Attention System (SAS)
- a system in charge of the control of action and or coping with novelty (Norman and Shallice, 1980)
- required in situations where the routine selection of actions in unsatisfactory and cognitive control or executive function is required
Classic Executive Function Tasks: outline the Wisconsin Card Sorting Task
The Wisconsin Card Sorting Task (WCST) is a neuropsychological test that assesses cognitive flexibility, problem-solving, and executive functioning.
Brief Outline:
Materials: A set of cards with different symbols, colors, and shapes (e.g., red triangles, green stars).
Task: The participant is asked to sort cards according to an unknown rule, which can be based on color, shape, or number.
Feedback: After each sort, the participant is told whether their choice is correct or incorrect.
Rule Changes: Periodically, the sorting rule changes without warning, requiring the participant to adapt.
Measures: Performance is assessed based on the number of correct responses, errors, and the ability to shift to new rules.
What are the problems with the Normal and Shallice supervisory attention system (SAS) theory of the frontal lobe
Who controls the controller - explains what is controlled but not HOW control is exercised
Patients with frontal lesions tend to perform poorly on complex tasks
–> complex tasks tend to require lots of different cognitive processes (like planning, inhibition, selective attention, WM)
Overview: what was the Miyake et al. (2000) factor analysis of executive function
1. task 1
2. task 2
3. task 3
4. factor analysis
A big factor analysis of executive function
- Task-switching (subjects perform two tasks eg. odd v even)
- Letter memory task - requires subjects to remember letters but also to update letters in memory
- Stop signal reaction time task - requiring ppts to withhold prepotent responses
Factor Analysis of Executive Function
- found three distinct variables that accounted for performance on the 9 task differences
A) shifting (shifting between task sets)
B) updating (updating the contents of WM)
C) inhibition (updating prepotent responses)
There is general consensus that regions in the lateral/medial PFC are doing something different from the orbitofrontal cortex (OFC)
- describe the cold v hot cognition argument
Cold Cognition
- functions that do not involve emotional or value based judgements
- response inhibition, task switching, error monitoring, attention, WM
Hot Cognition
- functions that do involve emotional or value-based judgements
- value based decision making
- emotion guided decision making
- counterfactual thinking,
- gambling
Outline the research by Stuss (2007) looking at whether there is a dysexecutive syndrome
Tested frontal lobe patients on a range of neuropsychological tasks
–> brain lesions were mapped out and location of brain damage defined
–> focus on parts involved in ‘cold’ cognition (ventrolateral PFC and ACC)
Found that:
- Right lateral PFC is for monitoring (checking the task over time for quality control and behavioural adjustment) similar to ‘updating’
- Left lateral PFC for task-setting (ability to set a stimulus-response relationship) similar to ‘shifting’
Left medial PFC: energising - the process of initiation and sustaining of any response
Research: Aron (2003) - evidence that the right frontal cortex is a response inhibition ‘module’
Demonstrated the importance of the right inferior frontal cortex for response inhibition
–> gave patients with brain lesions a SSRT task
–> found that performance was STRONGLY CORRELATION to size of inferior frontal gyrus lesion
–> bigger the lesion = worse patient was at inhibition
Right Frontal Cortex Module: How have imaging studies supported these findings
Showing increased activation in right inferior frontal cortex during response inhibition
==> activation in right inferior frontal cortex is consistently higher for no-go trials than it is for go trials - suggesting a specific role for this region in inhibiting a prepotent response
HOWEVER: this may be due to a role in attention
Alternative Perspective: what is the idea that the Frontoparietal cortex as a ‘multiple demand’ network
Not everyone believes it is possible to fractionate the PFC into seperate processes
–> meta-analysis found that different processes all activated similar regions
–> no clear separation - was a network of regions activated during difficult cognitive tasks
‘Multiple demand network’ - reflecting the idea that this is a ‘multi-purpose’ network of brain regions that underlies cognitive performance in multiple different types of demanding tasks
What does the ‘multiple demand’ network do
Construction of ‘attentional episodes’
- adaptive coding: PFC neurons adapt their responses depending on task demands
HOWEVER: study by Woolgar suggested PFC may perform a more complex role
- demonstrated primary role of PFC is encoding the information about abstract task performance
- could be claimed it is not a simple redirection of attention, but a complex function being performed
Key lecture points: what is the role of the PFC, what are the ideas about modularity
- PFC plays a key role in organised, goal-directed behaviour
- Its structure, connections, and functional architecture make it well suited to playing a key role in intelligent human behaviour
- Some evidence that the PFC can be fractioned into different functions but also disagreement - even about what the fundamental executive functions are
- multiple demand network hypothesis: integrated network involved in performing cognitively demanding tasks
