STRIATAL LESIONS PRODUCE DISTINCTIVE IMPAIRMENTS IN REACTION-TIME PERFORMANCE IN 2 DIFFERENT OPERANT CHAMBERS

The dorsal striatum plays a crucial role in mediating voluntary moveme nt. Excitotoxic striatal lesions in rats have previously been shown to impair the initiation but not the execution of movement in a choice r eaction time task in an automated lateralised nose-poke apparatus (the ''nine-hole box''), Conversely, when a conceptually similar reaction time task has been applied in a conventional operant chamber (or ''Ski nner box''), striatal lesions have been seen to impair the execution r ather than the initiation of the lateralised movement. The present stu dy was undertaken to compare directly these two results by training th e same group of rats to perform a choice reaction time task in the two chambers and then comparing the effects of a unilateral excitotoxic s triatal lesion in both chambers in parallel. Particular attention was paid to adopting similar parameters and contingencies in the control o f the task in the two test chambers, After striatal lesions, the rats showed predominantly contralateral impairments in both tasks, However, they showed a deficit in reaction time in the nine-hole box but an ap parent deficit in response execution in the Skinner box, This finding confirms the previous studies and indicates that differences in outcom e are not simply attributable to procedural differences in the lesions , training conditions or tasks parameters, Rather, the pattern of reac tion time deficit after striatal lesions depends critically on the app aratus used and the precise response requirements for each task. (C) 1 998 Elsevier Science Inc.