UNILATERAL LESIONS OF THE DORSAL STRIATUM IN RATS DISRUPT RESPONDING IN EGOCENTRIC SPACE

Rats were trained in a specially designed, multichoice operant chamber on a visual choice reaction time task designed to assess performance on each side of the rat's body. The task required animals to sustain a nose poke in a central hole, until a brief light stimulus was present ed in either of two holes that were located on the same side of the bo x. Once the rats were trained to perform the task to both sides indepe ndently they received unilateral injections of quinolinic acid into th e dorsal striatum. Postoperatively, lesioned animals were impaired whe n performing the task on the side contralateral to the lesion. The tim e taken to initiate contralateral responses was increased. Contralater al responses were also exclusively biased toward the nearer of the two response locations, regardless of the location of the stimulus. This was interpreted as a specific impairment in generating responses in co ntralateral space. In contrast, no comparable deficit was seen when th e animals performed the task on the side ipsilateral to the lesion. Ad ditional postoperative challenges, in which response options were pres ented bilaterally, showed this response deficit to be defined in egoce ntric coordinates, with the severest response deficits for the most co ntralateral locations.