National Institute on Drug Abuse, Intramural Research Program, Neuronal Networks Section, Baltimore, Maryland 21224, USA.
J Neurosci. 2011 May 18;31(20):7471-6. doi: 10.1523/JNEUROSCI.5731-10.2011.
It is widely accepted that midbrain dopamine (DA) neurons encode actual and expected reward values by phasic alterations in firing rate. However, how DA neurons encode negative events in the environment is still unclear because some DA neurons appear to be depressed and others excited by aversive stimuli. Here, we show that exposing fear-conditioned rats to stimuli predicting electrical shock elicited three types of biphasic responses, each of which contained an inhibitory pause, in neurochemically identified ventral tegmental area (VTA) DA neurons. The duration of the inhibitory pause in these responses of VTA DA neurons was in direct proportion to the increase in respiratory rate reflecting the level of conditioned fear. Our results suggest that the duration of inhibition of VTA DA neurons encodes negative emotional values of signals predicting aversive events in the environment.
人们普遍认为，中脑多巴胺（DA）神经元通过放电频率的相位变化来编码实际和预期的奖励值。然而，DA 神经元如何编码环境中的负面事件尚不清楚，因为一些 DA 神经元似乎被厌恶刺激所抑制，而另一些则被兴奋。在这里，我们表明，使恐惧条件反射的大鼠暴露于预测电击的刺激下，会在神经化学鉴定的腹侧被盖区（VTA）DA 神经元中引发三种双相反应，每种反应都包含抑制性停顿。这些 VTA DA 神经元反应中的抑制性停顿持续时间与反映条件性恐惧程度的呼吸率增加成正比。我们的结果表明，VTA DA 神经元的抑制持续时间编码了预测环境中厌恶事件的信号的负面情绪值。
