Schoenbaum Geoffrey, Setlow Barry
Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, Maryland 21218, USA.
J Neurosci. 2003 Oct 29;23(30):9833-41. doi: 10.1523/JNEUROSCI.23-30-09833.2003.
Nucleus accumbens (NAcc) is critical for encoding and using information regarding the learned significance of cues predictive of reward. However, its role in processing information about cues predictive of aversive outcomes is less well studied. Here, we examined the effects of NAcc lesions in an odor-guided discrimination task in which rats use odor cues predictive of either appetitive or aversive outcomes to guide responding. Rats with sham or neurotoxic lesions of NAcc were trained on a series of two-odor discrimination problems. Performance on each problem was assessed by monitoring accuracy of choice behavior and by measuring latency to respond for fluid reinforcement after odor sampling. After acquisition of four problems, rats were trained on serial reversals of the final problem. Rats with NAcc lesions exhibited normal choice performance relative to controls on both acquisition and reversal of the discrimination problems (indeed, lesioned rats exhibited a mild facilitation on the first discrimination problem). Despite normal choice performance, however, lesioned rats failed to show normal changes in response latency during discrimination learning, particularly on trials involving the aversive outcome. These findings are consistent with a deficit in processing cue-outcome associations. These results are compared with those obtained from studies of basolateral amygdala and orbitofrontal cortex lesions in this task and suggest that NAcc integrates the motivational value of both appetitive and aversive cues to bias or modulate the vigor of subsequent responding.
伏隔核（NAcc）对于编码和利用有关预测奖励线索的习得意义的信息至关重要。然而，其在处理有关预测厌恶结果线索的信息方面的作用研究较少。在此，我们在一项气味引导的辨别任务中研究了伏隔核损伤的影响，在该任务中大鼠利用预测奖励或厌恶结果的气味线索来指导反应。对具有伏隔核假损伤或神经毒性损伤的大鼠进行了一系列双气味辨别问题的训练。通过监测选择行为的准确性以及测量气味采样后对液体强化物做出反应的潜伏期来评估每个问题的表现。在掌握了四个问题后，对大鼠进行最后一个问题的系列反转训练。在辨别问题的习得和反转过程中，与对照组相比，伏隔核损伤的大鼠表现出正常的选择表现（实际上，损伤大鼠在第一个辨别问题上表现出轻微的促进作用）。然而，尽管选择表现正常，但损伤大鼠在辨别学习过程中未能表现出反应潜伏期的正常变化，尤其是在涉及厌恶结果的试验中。这些发现与线索 - 结果关联处理缺陷一致。将这些结果与在此任务中对基底外侧杏仁核和眶额皮质损伤的研究结果进行比较，结果表明伏隔核整合了奖励和厌恶线索的动机价值，以偏向或调节后续反应的强度。
