Center for Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA.
J Neurophysiol. 2013 Jul;110(1):75-85. doi: 10.1152/jn.00784.2012. Epub 2013 Apr 3.
Dopamine neurons of the ventral tegmental area (VTA) signal the occurrence of a reward-predicting conditioned stimulus (CS) with a subsecond duration increase in post-CS firing rate. Important theories about reward-prediction error and reward expectancy have been informed by the substantial number of studies that have examined post-CS phasic VTA neuron activity. On the other hand, the role of VTA neurons in anticipation of a reward-predicting CS and analysis of prestimulus spike rate rarely has been studied. We recorded from the VTA in rats during the 3-choice reaction time task, which has a fixed-duration prestimulus period and a difficult-to-detect stimulus. Use of a stimulus that was difficult to detect led to behavioral errors, which allowed us to compare VTA activity between trials with correct and incorrect stimulus-guided choices. We found a sustained increase in firing rate of both putative dopamine and GABA neurons during the pre-CS period of correct and incorrect trials. The poststimulus phasic response, however, was absent on incorrect trials, suggesting that the stimulus-evoked phasic response of dopamine neurons may relate to stimulus detection. The prestimulus activation of VTA neurons may modulate cortical systems that represent internal states of stimulus expectation and provide a mechanism for dopamine neurotransmission to influence preparatory attention to an expected stimulus.
腹侧被盖区（VTA）的多巴胺神经元通过在 CS 后发射率的短暂持续增加来预测奖励性条件刺激（CS）的发生。大量研究检查了 CS 后 VTA 神经元的活动，这些研究为奖励预测误差和奖励预期的重要理论提供了信息。另一方面，VTA 神经元在预测奖励性 CS 和分析刺激前尖峰率方面的作用很少被研究。我们在大鼠进行 3 选择反应时间任务期间记录 VTA 的活动，该任务具有固定持续时间的预刺激期和难以检测的刺激。使用难以检测的刺激会导致行为错误，这使我们能够在具有正确和不正确的刺激引导选择的试验之间比较 VTA 活动。我们发现，在正确和不正确试验的预 CS 期间，假定的多巴胺和 GABA 神经元的放电率都持续增加。然而，在不正确的试验中，刺激后的相位反应缺失，这表明多巴胺神经元的刺激诱发的相位反应可能与刺激检测有关。VTA 神经元的刺激前激活可能调节代表刺激预期的内部状态的皮质系统，并为多巴胺神经传递影响对预期刺激的预备注意提供了一种机制。
