2014年4月2日水曜日

Disentangling neural representations of value and salience in the human brain

Thorsten Kahnt, Soyoung Q Park, John-Dylan Haynes, and Philippe N. Tobler
Proceedings of the National Academy of Sciences 1 April 2014; Vol. 111, No. 13

脳内での「価値(value)」と「顕著性(salience)」の処理。後部頭頂皮質の中で、上部が価値、下部が顕著性をコードしている。また、眼窩前頭皮質は価値をコードしている. http://www.pnas.org/content/111/13/5000

A large body of evidence has implicated the posterior parietal and orbitofrontal cortex in the processing of value. However, value correlates perfectly with salience when appetitive stimuli are investigated in isolation. Accordingly, considerable uncertainty has remained about the precise nature of the previously identified signals. In particular, recent evidence suggests that neurons in the primate parietal cortex signal salience instead of value. To investigate neural signatures of value and salience, here we apply multivariate (pattern-based) analyses to human functional MRI data acquired during a noninstrumental outcome-prediction task involving appetitive and aversive outcomes. Reaction time data indicated additive and independent effects of value and salience. Critically, we show that multivoxel ensemble activity in the posterior parietal cortex encodes predicted value and salience in superior and inferior compartments, respectively. These findings reinforce the earlier reports of parietal value signals and reconcile them with the recent salience report. Moreover, we find that multivoxel patterns in the orbitofrontal cortex correlate with value. Importantly, the patterns coding for the predicted value of appetitive and aversive outcomes are similar, indicating a common neural scale for appetite and aversive values in the orbitofrontal cortex. Thus orbitofrontal activity patterns satisfy a basic requirement for a neural value signal.

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