Joseph Michael H, Datla Krishna, Young Andrew M J
Behavioural Neuroscience Group, School of Psychology, University of Leicester, University Road, Leicester LE1 7RH, UK.
Neurosci Biobehav Rev. 2003 Oct;27(6):527-41. doi: 10.1016/j.neubiorev.2003.09.001.
Psychopharmacological studies have implicated the dopaminergic innervation of the nucleus accumbens (NAC) in reward and reinforcement, in the actions of addictive drugs, and in the control of the symptoms of schizophrenia. Recent developments in in vivo dialysis, and other in vivo neurochemical techniques have permitted a more direct analysis of the behavioural correlates of increased dopamine release in rats, and have largely confirmed these findings in relation to reward, and drugs of abuse potential. However, dopamine release has also been found to be increased by many other stimuli/situations including aversive stimuli, stimuli conditioned to aversive stimuli, complex novel stimuli, and in the process of conditioning itself. These results contrast with electrophysiological data obtained in the behaving monkey, where rewarding stimuli, or stimuli predictive of reward are associated with increased firing of presumptive dopamine neurones projecting to the NAC (and indeed to the striatum), but mild aversive stimuli are not, leading to the suggestion that this system subserves a more purely reward function, or indeed that it provides a reward error signal. Further exploration of these issues will depend upon a comparison of increased dopamine cell firing and increased dopamine release, and an analysis of the behavioural effects of blocking these increases in dopamine transmission. One suggestion, deriving from work on latent inhibition, is that the significance of dopamine release by salient stimuli is to allow learning about stimuli which would otherwise be excluded on the basis of familiarity. This suggests that in addition to a role in some types of learning about salient stimuli, dopamine release in NAC may have a role in controlling the attention paid to familiar stimuli. Since it is difficult to see a connection between simple learning about rewards, and the symptoms of schizophrenia, this provides a more convincing link between the dopamine theory of schizophrenia, and the attentional difficulties held by many theorists to underlie schizophrenic symptoms.
精神药理学研究表明，伏隔核（NAC）的多巴胺能神经支配与奖赏和强化、成瘾性药物的作用以及精神分裂症症状的控制有关。体内透析及其他体内神经化学技术的最新进展，使得对大鼠体内多巴胺释放增加的行为相关性进行更直接的分析成为可能，并且在很大程度上证实了这些与奖赏及具有滥用潜力药物相关的发现。然而，人们还发现，许多其他刺激/情况也会导致多巴胺释放增加，包括厌恶刺激、与厌恶刺激相关的条件刺激、复杂的新异刺激以及条件作用本身的过程。这些结果与在行为猴身上获得的电生理数据形成对比，在行为猴中，奖赏刺激或预示奖赏的刺激与投射到NAC（实际上是纹状体）的假定多巴胺神经元的放电增加有关，但轻度厌恶刺激则不然，这表明该系统具有更纯粹的奖赏功能，或者实际上它提供了一个奖赏误差信号。对这些问题的进一步探索将取决于对多巴胺细胞放电增加和多巴胺释放增加的比较，以及对阻断多巴胺传递增加所产生的行为效应的分析。从潜伏抑制研究中得出的一个观点是，显著刺激引起的多巴胺释放的意义在于允许对那些否则会因熟悉度而被排除的刺激进行学习。这表明，除了在某些类型的对显著刺激的学习中发挥作用外，NAC中的多巴胺释放可能在控制对熟悉刺激的注意力方面发挥作用。由于很难看出简单的奖赏学习与精神分裂症症状之间的联系，这就在精神分裂症的多巴胺理论与许多理论家认为是精神分裂症症状基础的注意力障碍之间提供了一个更有说服力的联系。
