Separate Prefrontal-Subcortical Circuits Mediate Different Components of Risk-Based Decision Making
Jennifer R. St. Onge, Colin M. Stopper, Daniel S. Zahm, and Stan B.
J. Neurosci. 2012;32 2886-2899
リスク下の意思決定（Risky/Large 対 Safe/Small reward；ラット損傷研究）。扁桃体と側坐核の結合を遮断するとRisky/Largeを選ぶ頻度が減少し、前頭前野から扁桃体の結合を遮断するとRisky/Largeを選ぶ頻度が増加する（一方、前頭前野と側坐核の結合を遮断すると反応時間が長くなる）。リスク下の意思決定は異なる「皮質・皮質下の回路」の競合によって行われている。http://www.jneurosci.org/content/32/16/5631
Choosing between smaller, assured rewards or larger, uncertain ones requires reconciliation of competing biases toward more certain or riskier options. We used disconnection and neuroanatomical techniques to reveal that separate, yet interconnected, neural pathways linking the medial prefrontal cortex (PFC), the basolateral amygdala (BLA), and nucleus accumbens (NAc) contribute to these different decision biases in rats. Disrupting communication between the BLA and NAc revealed that this subcortical circuit biases choice toward larger, uncertain rewards on a probabilistic discounting task. In contrast, disconnections between the BLA and PFC increased choice of the Large/Risky option. PFC–NAc disconnections did not affect choice but did increase choice latencies and trial omissions. Neuroanatomical studies confirmed that projection pathways carrying axons from BLA-to-PFC transverse a distinctly different route relative to PFC-to-BLA pathways (via the ventrolateral amydalofugal pathway and ventromedial internal capsule, respectively). We exploited these dissociable axonal pathways to selectively disrupt bottom-up and top-down communication between the BLA and PFC. Subsequent disconnection studies revealed that disruption of top-down (but not bottom-up) information transfer between the medial PFC and BLA increased choice of the larger, riskier option, suggesting that this circuit facilitates tracking of actions and outcomes to temper urges for riskier rewards as they become less profitable. These findings provide novel insight into the dynamic competition between these cortical/subcortical circuits that shape our decision biases and underlie conflicting urges when evaluating options that vary in terms of potential risks and rewards.