2013年12月27日金曜日

Effects of Amygdala Lesions on Reward-Value Coding in Orbital and Medial Prefrontal Cortex

Peter H. Rudebeck, Andrew R. Mitz, Ravi V. Chacko, Elisabeth A. Murray
Neuron, Volume 80, Issue 6, 1519-1531, 18 December 2013

サル電気生理/損傷研究。
扁桃体を損傷すると(つまり、扁桃体からの情報が届かなくなる)、前頭皮質での報酬情報の処理がどのように変わるか?
損傷前は眼窩前頭皮質と内側前頭前皮質、両方の領域のニューロンが報酬情報を保持しているが、前者の方が報酬情報を処理しているニューロンの比率が高い。
一方、扁桃体を損傷すると、眼窩前頭皮質で報酬情報を処理しているニューロンが減り、二つの脳領域で比率の差がなくなる。
つまり、報酬情報の処理において扁桃体は、主に「眼窩前頭皮質に報酬情報を送る」という役割を担っていると考えられる。

We examined the contribution of the amygdala to value signals within orbital prefrontal cortex (OFC) and medial prefrontal cortex (MFC). On each trial, monkeys chose between two stimuli that were associated with different quantities of reward. In intact monkeys, as expected, neurons in both OFC and MFC signaled the reward quantity associated with stimuli. Contrasted with MFC, OFC contained a larger proportion of neurons encoding reward quantity and did so with faster response latencies. Removing the amygdala eliminated these differences, mainly by decreasing value coding in OFC. Similar decreases occurred in OFC immediately before and after reward delivery. Although the amygdala projects to both OFC and MFC, we found that it has its greatest influence over reward-value coding in OFC. Notably, amygdala lesions did not abolish value coding in OFC, which shows that OFC’s representations of the value of objects, choices, and outcomes depends, in large part, on other sources.

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