Decision-making and addiction (part I): impaired activation of somatic states in substance dependent individuals when pondering decisions with negative future consequences
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Abstract
Some substance dependent individuals (SDI) suffer from a decision-making impairment
akin to that seen in neurological patients with lesions of the ventromedial (VM) prefrontal
cortex. The somatic-marker hypothesis posits that decision-making is a process that
depends on emotion and that deficits in emotional signaling will lead to poor decision-making.
In this study, we tested the hypothesis that SDI who perform disadvantageously on
a decision-making instrument, the gambling task (GT), have a deficit in the somatic
signals that help guide their decision in the advantageous direction. Since deficits
in decision-making/somatic markers can also result from dysfunctional amygdala, we
asked indirectly (i.e. via tests sensitive to VM or amygdala dysfunction) whether
such a deficit in SDI is restricted to VM dysfunction or includes the amygdala. Using
the GT, and skin conductance response (SCR) as an index of somatic state activation,
we studied groups of SDI (n=46), normal controls (n=49), and VM patients (n=10). A
subgroup of SDI showed defective performance on the GT coupled with impaired anticipatory
SCR, but normal SCR to punishment, and normal acquisition of conditioned SCR to an
aversive loud sound. This supports the hypothesis that the poor decision-making in
some SDI is associated with defective somatic state activation that is linked to a
dysfunctional VM cortex. Thus, the dysfunctional VM cortex underlying the "myopia"
for the future in some SDI may be one of the principle mechanisms underlying the transition
from casual substance taking to compulsive and uncontrollable behavior.