Single neuronal substrate responsible for emotions underlying reward-seeking

科学研究費助成事業(学術研究助成基金助成金)研究成果報告書：若手研究(B)2011-2012課題番号：2370050

Neurons in the monkey orbitofrontal cortex mediate reward value computation and decision-making

Choice reflects the values of available alternatives; more valuable options are chosen more often than less valuable ones. Here we studied whether neuronal responses in orbitofrontal cortex (OFC) reflect the value difference between options, and whether there is a causal link between OFC neuronal activity and choice. Using a decision-making task where two visual stimuli were presented sequentially, each signifying a value, we showed that when the second stimulus appears many neurons encode the value difference between alternatives. Later when the choice occurs, that difference signal disappears and a signal indicating the chosen value emerges. Pharmacological inactivation of OFC neurons coding for choice-related values increases the monkey’s latency to make a choice and the likelihood that it will choose the less valuable alternative, when the value difference is small. Thus, OFC neurons code for value information that could be used to directly influence choice

Differential Encoding of Factors Influencing Predicted Reward Value in Monkey Rostral Anterior Cingulate Cortex

Background: The value of a predicted reward can be estimated based on the conjunction of both the intrinsic reward value and the length of time to obtain it. The question we addressed is how the two aspects, reward size and proximity to reward, influence the responses of neurons in rostral anterior cingulate cortex (rACC), a brain region thought to play an important role in reward processing. Methods and Findings: We recorded from single neurons while two monkeys performed a multi-trial reward schedule task. The monkeys performed 1–4 sequential color discrimination trials to obtain a reward of 1–3 liquid drops. There were two task conditions, a valid cue condition, where the number of trials and reward amount were associated with visual cues, and a random cue condition, where the cue was picked from the cue set at random. In the valid cue condition, the neuronal firing is strongly modulated by the predicted reward proximity during the trials. Information about the predicted reward amount is almost absent at those times. In substantial subpopulations, the neuronal responses decreased or increased gradually through schedule progress to the predicted outcome. These two gradually modulating signals could be used to calculate the effect of time on the perception of reward value. In the random cue condition, little information about the reward proximity or reward amount is encoded during the course of the trial before reward delivery, but when the reward is actually delivered the responses reflect both the reward proximity and reward amount

時間の不確実性が行動選択に与える効果とそのニューロン活動基盤

科学研究費助成事業 研究成果報告書：基盤研究(C)2013-2015課題番号 : 2535099

Percentage of neurons showing significant task-related activity.

<p>Percentage of neurons showing significant task-related activity.</p

Average firing rate of rACC neurons in <b>Fig. 4</b>.

<p>Colors mean reward amount as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0030190#pone-0030190-g004" target="_blank">Figure 4</a>. A, Decreasing type activity. B, Increasing type I activity. C, Increasing type II activity.</p