Lecture 5 Flashcards
Concept of executive functions
- Needed in situations that require coordination
- Strongly linked to PFC
- Controlled behaviour relies on executive function
- Planning, predicting, correlating, abstract ideas
Anatomy of prefrontal cortex
- Connected to almost all the rest of the brain
- 3 surfaces: lateral, medial and orbital
- Lateral surfaces (dorsal–> ventral) implicated in cold processes (cognitive processing of info independent of emotion)
- Orbito-frontal (above eyes) and medial (between 2 hemispheres) implicated in hot control (person’s thinking influenced by emotions)
General situations requiring executive functions
Normal and Shallice: identify 5 cognitive scenarios in which automatic behaviour will not be adequate”
- Situations involving planning or decision making
- Situations involving error correction or trouble shooting –> PFC damage = fail to update the rule and exhibit preservation behaviour (cease behaviour)
- Situations where responses are not well-learned or contain novel sequences of actions
- Situations judged to be dangerous or technically difficult
- Situation that require the overcoming of a strong habitual response or resisting temptation –> studies suggest involvement of anterior cingulate cortex and pre-SMA (supplementary motor area)
Non-unitary: Role of ACC in executive functions
ACC = anterior cingulate cortex
- Detection of errors and response conflict
- Monkeys with ACC lesion = more errors following error trial because they cant correct themselves
Non-unitary: Petrid’s theory of working memory
- Ventral and dorsal PFC involved in maintenance (retention) vs updating (manipulation) rather than processing different types of content
- PFC involved in retrieving or manipulating
Non-unitary: Self-ordered pointing task
- Patients with PFC damage
- Array of 8 words or pictures, required to pick any 1 on first trial, then asked to pick a different one on next trial, requires updating and maintaining on which items have been picked
- Found patients with PFC damage strongly impaired
- Similar task done in monkeys - found dorso-lateral PFC was important for updating
Non-unitary: left dorsolateral PFC
- Region responsible for selecting plausible responses
- Region active in free will e.g. choosing which finger to move
- TMS over region disrupts random digit generation
Non-unitary: right dorsolateral PFC
- Important in monitoring and sustained attention
- For externally presented information and internally generated info
- Activity greatest in conditions of uncertainty
- Evidence comes from the N-back test
Theories of executive functions: unitary accounts
-Argues there are no executive functions just one general underlying function (intelligence)
Unitary accounts: Goldman-Rakic’s working memory model
- Assumes a unitary executive control whose main task is refreshing of information in working memory
- Single cell recording of PFC neurones in monkeys in delayed response task, monkey required to maintain location of target during delay period, PFC neurones active during period
- Assumes division into spatial and object base working memory, these regions hold location vs object information
- Some research shows involvement of both the ventral and dorsal neurones in spatial or object encoding
Unitary accounts: The multiple demand network
Duncan and Owen
- Multiple demand network = single set of fronto-parietal brain regions that is active during all tasks involving executive functions
- Multiple demand network divides complex tasks into sequence of attentional episodes
Evidence for multiple demand networks
- 80 patients with focal, adult-onset brain lesions
- More lesions within the MD system showed greater deficit in fluid intelligence e.g. problem solving
- Relationship didn’t exist for lesion within language network
Investigating cold control processes
Planning and decision making
-Tower of London task: ppts move beads from initial to goal position, challenge is to reach goal in as few moves, performance measured in total time and number of moves and requires planning
Error correction and trouble shooting
-Wisconsin card sorting task: ppts need to sort cards according to one of three features but not told which feature, after each task given feedback (trial and error)
Overcoming habitual response
-Stroop task: naming colour of printed word
