Anticipatory errors after unilateral lesions of the subthalamic nucleus inthe rat: Evidence for a failure of response inhibition

The nature of anticipatory responding in rats with unilateral subthalamic n ucleus lesions was examined. Rats were trained to respond toward visual tar gets that were preceded by 1 of 4 different cues. For normal rats, a cue in vokes an involuntary attentional orienting that enhances processing of the target at the location of attention. The cue is also a salient stimulus to which a response must be suppressed. Therefore, this task was used to inves tigate possible attentional impairments, as well as the ability of a lesion ed rat to suppress competing motor programs. Responding under target contro l was not affected by the lesion. Then was an increase in anticipatory resp onses before target onset, which could be accounted for by a failure to inh ibit contralateral responses.