Executive Function Ref: Banich pp (skim “Cognitive estimation”), pp

Behaviour Involves "Control" Taking initiativeTaking initiative Focusing a single task, ignoring distractionsFocusing a single task, ignoring distractions “Multi-tasking” (switching between tasks)“Multi-tasking” (switching between tasks) Planning, organising behaviour towards goalsPlanning, organising behaviour towards goals Thinking and acting flexiblyThinking and acting flexibly Reasoning, drawing inferencesReasoning, drawing inferences These skills often referred to as “executive functions”

Prefrontal Cortex (PFC) = frontal lobes excluding primary and secondary motor areas: = frontal lobes excluding primary and secondary motor areas: Rich interconnections with other cortical/subcortical regionsRich interconnections with other cortical/subcortical regions Primary Motor Cortex Secondary Motor Cortex Prefrontal Cortex

Three Major Subdivisions Dorsolateral Prefrontal Cortex Orbitomedial Prefrontal Cortex Anterior Cingulate

Three Major Subdivisions 1.Dorsolateral - key role in executive functions (today) 2.Anterior cingulate - evaluating one’s behaviour (Weds.) 3.Orbitomedial - emotional aspects of control (Thurs.)

Some functions discussed earlier: Working memory Working memory Memory for temporal order Memory for temporal order Source memory Source memory Dorsolateral Prefrontal Cortex

Different regions specialised for different types of informationDifferent regions specialised for different types of information e.g. verbal span - region anterior to Broca's area in left hemisphere Working Memory Cells in dorsolateral PFC can sustain activity over short delaysCells in dorsolateral PFC can sustain activity over short delays Working memory may underlie many “executive functions”: goal-oriented behaviour involves keeping the goal in mindgoal-oriented behaviour involves keeping the goal in mind reasoning involves manipulating information “on line”reasoning involves manipulating information “on line”

Other PFC Functions However, other PFC functions may go beyond working memory: 1.Initiating new plans, activities (and knowing when to stop!) 2.Attending to one activity, filtering out others (“dynamic filtering”) 3.Task switching 4.Flexibility - suppressing habitual responses when inappropriate

1. Initiation, Cessation of Action P's with damage to dorsolateral PFC may exhibit Psychological inertia:P's with damage to dorsolateral PFC may exhibit Psychological inertia: Dr. P was a successful surgeon, who while undergoing a simple operation, suffered a brief hypoxia. After the surgery, standard IQ tests revealed Dr. P's intelligence to be, for the most part, in the superior range. Yet, he could not handle many simple day-to-day activities... For example, his sister-in-law had to tell him to change his clothes... He did not initiate any activities or ask questions about his existence, being content to spend his free time watching television. A waitress explaining why she had lost her job after frontal lobe surgery said, "You have to have a "push" to wait on several tables at once, and I just didn't have it any more"

1. Initiation, Cessation of Action Another common feature of damage to this region is Perseveration:Another common feature of damage to this region is Perseveration:

Other PFC Functions However, other PFC functions may go beyond working memory: 1.Initiating new plans, activities (and knowing when to stop!) 2.Attending to one activity, filtering out others (“dynamic filtering”) 3.Task switching 4.Flexibility - suppressing habitual responses when inappropriate

2. Dynamic Filtering e.g. Stroop task: e.g. Stroop task: Give the name of the colour this word is written in:Give the name of the colour this word is written in: Red Failed by P’s with dorsolateral PF lesionsFailed by P’s with dorsolateral PF lesions

2. Dynamic Filtering Wisconsin Card Sorting Task: Cards can be sorted on three dimensions: i. colourii. shapeii. number P must sort on one dimension, ignore others P must sort on one dimension, ignore others

Other PFC Functions However, other PFC functions may go beyond working memory: 1.Initiating new plans, activities (and knowing when to stop!) 2.Attending to one activity, filtering out others (“dynamic filtering”) 3.Task switching 4.Flexibility - suppressing habitual responses when inappropriate

3. Task Switching Trail-Making Test: Must switch between two types of sequencing Begin End 4 C 1 B 2 3 A D

3. Task Switching Wisconsin Card Sorting Task: Following initial sort, P must change his/her sorting rule

Other PFC Functions However, other PFC functions may go beyond working memory: 1.Initiating new plans, activities (and knowing when to stop!) 2.Attending to one activity, filtering out others (“dynamic filtering”) 3.Task switching 4.Flexibility - suppressing habitual responses when inappropriate

P’s with dorsolateral PFC damage may exhibit Environmental dependency syndrome:P’s with dorsolateral PFC damage may exhibit Environmental dependency syndrome: a)Utilisation behaviour b)Imitative behaviour 4. Flexibility/Inhibitory Control Professor Lhermitte would place a hammer, nail and picture on a table in the entryway to his office. On seeing this array of objects, the frontal lobe patient might pick up the hammer and nail and hang the picture on the wall. a)Utilisation behaviour:

4. Flexibility/Inhibitory Control b) Imitative behaviour: Lhermitte sat opposite a patient and, without explanation, produced gestures. Some were innocuous: folding paper, combing his hair, or tapping his leg. Others were socially inappropriate: thumbing his nose, chewing paper or kneeling in prayer. The patients with frontal lobe lesions mimicked these actions.

4. Flexibility/Inhibitory Control P’s may also have problems with Cognitive Flexibility Alternate uses test: "Think of as many uses as you can for these objects" e.g. brick, pencil, paper, clip, toothpick Verbal Fluency: “Say as many words as you can that start with ‘f’”

Executive Control: Issues Many "Frontal" tasks can be described in >1 way:Many "Frontal" tasks can be described in >1 way: e.g. Wisconsin Card Sorting Task: dynamic filtering, task switching or cognitive flexibility? Problem of circularityProblem of circularity How can we describe what the frontal lobes do in a way that is directly testable?How can we describe what the frontal lobes do in a way that is directly testable? Thursday - more on this issueThursday - more on this issue