Executive Function III Ref: Theories: Gazzaniga pp. 526-529

Prefrontal Cortex: 3 Major Regions Dorsolateral Prefrontal Cortex Key role in executive function Anterior Cingulate Evaluating own behaviour Orbitomedial Prefrontal Cortex Social/emotional mediation of behaviour

Today Review of dorsolateral PFC, anterior cingluate Discussion of orbitomedial PFC Theories of executive function

Dorsolateral PFC Key role in Working Memory Other Functions: Initiation, cessation of action Dynamic filtering (e.g. Stroop task) Task switching (e.g. Trail making test) Flexibility - response inhibition, cognitive flexibility (e.g. alternate uses test)

Prefrontal Cortex: 3 Major Regions Dorsolateral Prefrontal Cortex Anterior Cingulate Orbitomedial Prefrontal Cortex

Anterior Cingulate Strongly activated in highly demanding tasks e.g divided attention Also especially active when errors occur Generally, participates in situations requiring close monitoring, where there is response conflict Acts in tandem with dorsolateral PFC to ensure that the necessary attentional resources are effectively deployed

Prefrontal Cortex: 3 Major Regions Dorsolateral Prefrontal Cortex Anterior Cingulate Orbitomedial Prefrontal Cortex

Orbitomedial PFC Social and Emotional Mediation of Behaviour Phineas Gage: Before the accident he had been their most capable and efficient foreman, one with a well-balanced mind, and who was looked on as a shrewd smart business man. He was now fitful, irreverent, and grossly profane, showing little deference for his fellows. He was also impatient and obstinate, yet capricious and vacillating, unable to settle on any of the plans he devised for future action. His friends said he was "No longer Gage."

Orbitomedial PFC: Features Two key features of damage to orbitomedial PFC: No initiative, flattened affect: (“pseudodepression”) Elliott: After removal of a brain tumour that bilaterally invaded the brain's orbital surface, Elliott performed well on standard IQ tests and even outperformed most age-matched control subjects on the WCST. Nonetheless, he had great difficulties coping with the real world. He lost his job, and eventually went bankrupt. As striking as Elliott's lost sense of social norms was his personal detachment from his problems. He had no difficulty recounting the minutest details of his many failings, but spoke of them as if he were a dispassionate observer.

Lack of social restraint (“pseudopsychopathy’) Orbitomedial PFC: Features Lack of social restraint (“pseudopsychopathy’) Patient Y: A high velocity missile had entered the patient's left temple and emerged through the right orbit. Prior to injury, Patient Y had been quiet, intelligent, proper, and hard-working. Subsequent to this injury, he was outspoken, facetious, brash and disrespectful. There was no evidence of self-pity, although he frequently made rather morbid jokes about his condition. When asked about how his injury had affected him, he showed some awareness of some aspects of his problems (e.g. no sense of taste), but little concern, often commenting "To tell you the truth, it's a blessing this way".

Orbitomedial PFC: What does it do? Somatic Marker Hypothesis (Damasio): Orbitomedial PFC binds memories to their emotional and neurophysiological associations normals: an “emotional” picture (e.g. accident victim) evokes a learned emotional response. This is measurable. P’s with Orbitomedial PFC lesions: can describe picture in detail, but no strong emotional response Explains: flattened affect, lack of concern for social conventions

Theories of Executive Function Problems with describing role of PFC in executive function: Many "Frontal" tasks are complex and can be described in >1 way Problem of circularity Also terms such as “control” too vague to be tested How can we describe what the frontal lobes do in a way that is directly testable? Answer: we must develop a proper theory

Contention Scheduling Theory Shallice and Norman (1989) Schemas Two Major Components Supervisory Attentional System Schemas: well-practised routines or action plans e.g. stop at red light are developed with practice are "activated" by external stimuli OR internal cues e.g. stop at red light schema -> red light remain active until "switched off"

Contention Scheduling Theory Supervisory Attentional System (SAS): overrides normal activation levels of schemas turns on, switches off schemas when no other cues creates program of action when no schema avail., or when task has special demands Schemas are stored in posterior cortical regions The SAS is in prefrontal cortex

Contention Scheduling Theory Explains: Inability to initiate or cease an action (psychological inertia, perseveration) Difficulties dynamic filtering Poor task switching Inability to inhibit habitual responses Lack of cognitive flexibility Inability to formulate goals

Contention Scheduling - Problems Theory is highly cognitive. It proposes one central system - BUT PFC shows regional specialisation Very powerful - predicts just about anything, so is difficult to test Doesn’t deal with working memory

Alternatives Miller & Cohen (2001): PFC maintains patterns of activity that represent goals These patterns modulate processing in posterior cortex e.g. resolve competition, inhibit inappropriate responses Similar to Contention Scheduling, but more anatomically- based, allows for the possibility of regional specialisation Also, gives a primary role to working memory BUT still a problem with power??

Conclusion The executive functions of prefrontal cortex still poorly understood Research is in its infancy The next decade (even the next few years) is likely to change this significantly Advances will depend as much on cognitive theories, as they do on research technology