Roesch Matthew R, Olson Carl R
Center for the Neural Basis of Cognition, Mellon Institute, University of Pittsburgh, Pennsylvania, USA.
J Neurophysiol. 2005 Oct;94(4):2457-71. doi: 10.1152/jn.00373.2005. Epub 2005 Jun 15.
Neurons in monkey orbitofrontal cortex (OF) are known to respond to reward-predicting cues with a strength that depends on the value of the predicted reward as determined 1) by intrinsic attributes including size and quality and 2) by extrinsic factors including the monkey's state of satiation and awareness of what other rewards are currently available. We pose here the question whether another extrinsic factor critical to determining reward value-the delay expected to elapse before delivery-influences neuronal activity in OF. To answer this question, we recorded from OF neurons while monkeys performed a memory-guided saccade task in which a cue presented early in each trial predicted whether the delay before the monkey could respond and receive a reward of fixed size would be short or long. OF neurons tended to fire more strongly in response to a cue predicting a short delay. The tendency to fire more strongly in anticipation of a short delay was correlated across neurons with the tendency to fire more strongly before a large reward. We conclude that neuronal activity in OF represents the time-discounted value of the expected reward.
已知猴子眶额皮质（OF）中的神经元会对奖励预测线索做出反应，其反应强度取决于预测奖励的价值，该价值由以下因素决定：1）包括大小和质量在内的内在属性；2）包括猴子的饱足状态以及对当前其他可用奖励的认知在内的外在因素。我们在此提出一个问题，即另一个对确定奖励价值至关重要的外在因素——预期奖励交付前的延迟——是否会影响眶额皮质中的神经元活动。为了回答这个问题，我们在猴子执行记忆引导扫视任务时记录眶额皮质神经元的活动，在每次试验早期呈现的线索预测猴子做出反应并获得固定大小奖励之前的延迟是短还是长。眶额皮质神经元对预测短延迟的线索往往反应更强。在预期短延迟时反应更强的趋势在神经元之间与在大奖励之前反应更强的趋势相关。我们得出结论，眶额皮质中的神经元活动代表预期奖励的时间折扣价值。
