Jones G H, Marsden C A, Robbins T W
Department of Experimental Psychology, University of Cambridge, U.K.
Behav Brain Res. 1991 Apr 18;43(1):35-50. doi: 10.1016/s0166-4328(05)80050-6.
Isolation-reared rats were compared to those reared in social groups on the acquisition of a conditional visual discrimination (Expt. I), a simultaneous (simple) light/dark discrimination and serial reversal learning (Expt. II). In Expt. I, rats reared in social isolation made more errors during the acquisition of the conditional discrimination but did reach a level of accurate performance which was comparable with that of socially-reared rats. Discrimination performance in isolates was less disruptable by manipulations of the task requirements. Reducing the number of stimulus lights or the introduction of a distracting stimulus increased the number of errors committed by socially-reared rats but did not significantly affect accuracy in isolates. Performance in isolated rats was also remarkably resistant to changes in motivational variables. Isolates responded more frequently during conditions of extinction and were virtually unaffected by pre-feeding prior to testing. In Expt. II, isolation-reared rats were not impaired in the acquisition of a simultaneous discrimination but unlike socially-reared rats isolates failed to show improvement with successive reversals of this discrimination. Isolates exhibited stronger position habits than socially-reared rats following reversal of the contingencies. These results of these two experiments combined have demonstrated a specific impairment in rule learning in isolates. Isolated rats were not impaired on a simultaneous discrimination in which accurate performance can be achieved simply by approaching the stimulus associated with reinforcement, but performed worse than controls on both the conditional discrimination and on serial reversal learning, another form of conditional task. In both of these latter tasks each stimulus becomes equally associated with reward and therefore performance can be improved by learning a rule. Post-mortem neurochemical measurements made at the completion of Expt. II revealed selective alterations in dopaminergic, serotoninergic and cholinergic markers in isolated rats. Correlational analyses indicated specific relationships between neurochemical and behavioural measurements.
将隔离饲养的大鼠与群居饲养的大鼠在条件性视觉辨别学习（实验一）、同时性（简单）明暗辨别及连续反转学习（实验二）方面进行了比较。在实验一中，隔离饲养的大鼠在条件性辨别学习过程中犯的错误更多，但最终达到的准确表现水平与群居饲养的大鼠相当。隔离饲养大鼠的辨别表现受任务要求操纵的干扰较小。减少刺激光的数量或引入干扰刺激会增加群居饲养大鼠犯错误的数量，但对隔离饲养大鼠的准确性没有显著影响。隔离饲养大鼠的表现对动机变量的变化也具有显著的抗性。隔离饲养的大鼠在消退条件下反应更频繁，并且在测试前预先喂食对其几乎没有影响。在实验二中，隔离饲养的大鼠在同时性辨别学习方面没有受损，但与群居饲养的大鼠不同，隔离饲养的大鼠在这种辨别连续反转时没有表现出改善。在 contingencies 反转后，隔离饲养的大鼠比群居饲养的大鼠表现出更强的位置习惯。这两个实验的结果共同证明了隔离饲养大鼠在规则学习方面存在特定损伤。隔离饲养的大鼠在同时性辨别任务中没有受损，在该任务中，仅通过接近与强化相关的刺激就能实现准确表现，但在条件性辨别和连续反转学习（另一种条件性任务形式）中，其表现均比对照组差。在这后两种任务中，每个刺激与奖励的关联程度相同，因此通过学习规则可以提高表现。在实验二完成后进行的死后神经化学测量显示，隔离饲养的大鼠中多巴胺能、5-羟色胺能和胆碱能标记物存在选择性改变。相关分析表明神经化学测量与行为测量之间存在特定关系。
