Rule-based learning impairment in rats with lesions to the dorsal striatum

The present study examined the effects of lesions to the dorsal striatum (D S) in Sprague-Dawley rats, when tested on the acquisition and successive sh ifts in the position of a goal arm in an eight-arm radial maze. In the proc edure we used, rats had to retrieve the location of one baited arm among th e eight arms of the maze after it had just been presented as a sample durin g a forced trial. After attainment of a fixed learning criterion, rats were submitted to five successive shifts in the goal location. Results showed t hat DS rats were able to learn the position of the goal arm during the acqu isition phase as efficiently as sham-operated rats. In contrast, when the p osition of the goal arm was shifted, although DS rats were able to learn it s new position, they made significantly more errors and required more sessi ons to reach criterion than sham-operated rats. These results suggested tha t both groups did not solve the task using the same behavioral strategy. Th e analysis of responses made suggested that sham-operated rats solved the t ask using the pairing rule between the forced and the free run (matching-to -sample rule), while DS rats solved the task using only visuospatial proces sing. These data therefore suggest that the dorsal striatum plays an import ant role in rule-learning ability. (C) 1999 Academic Press.