m8ta
You are not authenticated, login.
text: sort by
tags: modified
type: chronology
{1077}
hide / / print
ref: Frank-2007.11 tags: horses PD STN DBS levodopa decision learning science date: 01-25-2012 00:50 gmt revision:5 [4] [3] [2] [1] [0] [head]

PMID-17962524[0] Hold your horses: impulsivity, deep brain stimulation, and medication in parkinsonism.

  • While on DBS, patients actually sped up their decisions under high-conflict conditions. Wow!
    • This impulsivity was not effected by dopaminergic medication status.
    • Impulsivity may be the cognitive equivalent of excess grip force {88}.
  • Mathematical models of decision making suggest that individuals only execute a choice once the 'evidence' in its favor crosses a critical decision threshold.
    • people can adjust decision thresholds to meet current task demands
    • One theory is that the STN modulates decision thresholds (6) and delays decision-making when faced with a conflict. Wanted to test this in a conflict situation.
    • Record from the STN in conflict task to see ??
  • Second wanted to test negative learning.
    • Dopamine replacement therapy impairs patient's ability to learn from the negative outcomes of their decisions (11 - 13), which may account for pathological gambling behavior (14).
    • PD patients did indeed score worse on avoidance, slightly less accurate on AB choice, and about the same for the rest.
  • Made a network model.
    • Found that preSMA and STN coactivation is associated with slowed reaction times under decision conflict (25).
    • And that STN-DBS reduces coupling between cingulate and basal ganglia output (27).
    • Their model they either lesioned STN or overloaded it with high frequency regular firing.
      • either one showed the same faster response in high-conflict decisions.
  • STN dysfunction does not lead to impulsivity in all behavioral situations.
    • STN lesioned rats show enhanced preference for choices that lead to large delayed rewards compared to those that yield small immediate rewards (32,33). (This is not conflict, though -- rather reward -- but nonetheless illuminating)
  • Dopaminergic medication, by tonically elevating dopamine levels and stimulating D2 receptors, prevents learning from negative decision outcomes (11, 13, 18). Hence pathological gambling behavior (14).
  • Other studies show DBS-induced impairments in cognitive control (27 PMID-17119543, 36 PMID-15079009).

____References____

[0] Frank MJ, Samanta J, Moustafa AA, Sherman SJ, Hold your horses: impulsivity, deep brain stimulation, and medication in parkinsonism.Science 318:5854, 1309-12 (2007 Nov 23)