Elsevier

Neuroscience

Volume 136, Issue 2, 2005, Pages 387-395
Neuroscience

Behavioural neuroscience
Lesions of the dorsolateral striatum impair the acquisition of a simplified stimulus-response dependent conditional discrimination task

https://doi.org/10.1016/j.neuroscience.2005.08.021Get rights and content

Abstract

The dorsal striatum has long been thought to be important for some types of learning and memory, especially stimulus-response learning. Recently, we demonstrated that selective lesions of the dorsolateral striatum, but not dorsomedial striatum in rats, retarded the acquisition of two instrumental discrimination tasks thought to require stimulus-response learning. However, since these studies investigated the effects of dorsal striatal lesions on task acquisition, which can be confounded by differences in level of reinforcement and motor impairment caused by the lesion, the interpretation of these findings was somewhat problematic. The present experiment was designed to address these issues by assessing the effects of lesions of the dorsolateral striatum on a simplified version of the conditional discrimination task, in which the importance of reinforcement and motor factors was minimized. Animals with lesions of the dorsolateral striatum showed marked impairments in learning this task, a finding that is in agreement with the notion that the dorsolateral striatum is necessary for stimulus-response learning.

Section snippets

Subjects

Subjects were male Long Evans rats (Charles Rivers, Saint-Constant, Quebec), weighing between 300 and 450g. Rats were housed individually in clear plastic cages, in a room designed to maintain temperature between 20 and 22°C. Animals were maintained on a 12-h light/dark cycle (lights off 08:00–20:00 h). All procedures were carried out in accordance with the Canadian Council on Animal Care and the institutional animal care committee as well as the National Institutes of Health Guide for the Care

Histology

A total of seven sham and 12 lesioned animals were used. Three animals in the lesioned group were removed due to damage outside of the dorsolateral striatum. Thus, a total of nine lesioned animals were included in the final analyses. Fig. 1 depicts the extent of damage in lesioned animals, while Fig. 2 depicts photomicrographs of a typical dorsolateral lesion and sham control. Photomicrographs were digitally scanned from original photos and no manipulations were performed.

Response rate during VI training

Fig. 3 depicts

Discussion

Animals with lesions of the dorsolateral striatum showed a substantial deficit in accuracy throughout the course of training. Similar to what was found in our earlier experiments (Featherstone and McDonald, 2004a), animals started off at a low rate of accuracy, and, despite some improvement over the course of training, failed to reach a level of performance comparable to that of sham animals. These results are compatible with the notion that the dorsolateral striatum is necessary for

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