Models of frontal lobe functioning

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Key names and ideas that might show up on a multiple choice question. (From Grafman, J. Chapter 19 in Miller, B.L., & Cummings, J.L (Eds.) The Human Frontal Lobes (1999). Guilford).


Contents

Norman & Shallice’s Framework:

2 basic “control” mechanisms that determine how we monitor our activities

  • The automatic contention scheduler (ACS)- automatic & direct priming of stored knowledge by stimuli in environment or conceptual thought
  • Supervisory attention system (SAS): conscious awareness of what we know that set the priorities for action. SAS can override ACS.
    • In frontal lobe dysfunction, the SAS goes down


Goldman-Rakic and Primate Working Memory

  • Based on electrophysiological studies of monkeys
  • Developed concept of working memory by noting that prefrontal cortical neurons fired only during delay between presentation of stimulus to remember and stimulus to recall. The prefrontal cortical cells were also specifically linked to where in space the stimulus was seen.


Fuster’s Temporal Processing Model

  • The prefrontal cortex is principally involved with representing the “temporal structure of behavior” i.e., the coding of place within a sequence of actions or perceptual observations.
  • Action sequences tend to be goal related (i.e., conceptually driven).
  • To encode temporal aspects of behaviors, the prefrontal cortex must be involved in the formation of “cross-temoral contingencies” i.e., ties between events that are related to other, not only in time, but because they have a common goal.
  • These temporal operations are unique to the prefrontal cortex according to Fuster


Stuss & Benson’s Behavioral/Anatomical Theory

They divide the functions of the frontal lobes into two groups

  • The first group is concerned with sequencing behaviors, forming mental sets, and integrating various behaviors.
    • Associated with dorsolateral prefrontal cortex activation
  • The second is concerned with more primitive processes such as drive, motivation, and will.
    • Associated with ventromedial prefrontal cortex activation
    • Lately, Stuss and colleagues have distinguished a large set of top-down attentional processes subserved by the frontal cortex.


Luria’s view: Problem solving & the frontal lobe

  • Luria’s approach was qualitative and relied on the analysis of verbal protocols of pts. trying to solve multistep problems
  • Impaired programming and regulation of behavior were the principle deficits, resulting in impulsivity and difficulty switching problems solving strategies.
  • FL Pts. can access fragmentary operations but cannot combine them into an overall schema
  • Luria believed that focal lesions could dissocicate types of problem-solving failures.


Damasio’s Somatic Marker Theraory

  • Pts. with inappropriate social behavior as a result of frontal lobe lesions fail to behave appropriately due to a “defect in the activation of somatic markers”
  • This somatic signal binds to social behaviors and modulates social decisions
  • Based on observation that pts with ventromedial frontal lesions have diminished GSRs (i.e., diminished somatic marker) during tasks which normals find arousing.


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