Deficient acquisition and retention of a visual-tactile discrimination task in rats with medial thalamic lesions

The effects of unilateral and bilateral medial thalamic lesions on discrimination learning in the rat

“…While our previously reported observation that rats with bilateral MT lesions are deficient on acquisition of visualtactile discrimination (Means, Huntley, Anderson, & Harrell, 1973) was replicated, we found no evidence that unilateral lesions produce a deficit on visual-tactile discrimination. Thus, while many studies have shown that bilateral destruction of the MT impairs acquisition (Delacour, 1971;Vanderwolf, 1971), it appears that the MT need only be intact unilaterally for normal acquisition of a two-choice discrimination.…”

“…The bilateral lesions are similar to those reported earlier (Means, Hunt, Whiteside, & Bates, 1973;Means, Huntley, Anderson, & Harrell, 1973). The lesions were centered on the dorsomedi81 nucleus, but bilaterally invaded several of the midline and MT nuclei.…”

“…Discrimination training was done in a previously described maze (Means, Huntley, Anderson, & Harrell, 1973). The maze was equipped with guillotine doors to prevent retracing and had two interchangeable goalboxes, one having 25-mm-wide black and white stripes and a smooth wooden floor and the other having a solid !…”

“…Thus, rats with sham operations, unilateral MT leSions, and bilateral MT lesions were tested on acquisition of a visual-tactile maze discrimination, a task on which we have previously found bilaterally MT lesioned animals to be deficient (Means, Huntley, Anderson, & Harrell, 1973; Waring & Means, Note 1).…”

Chlorpromazine reduces avoidance performance deficit in rats with dorsomedial thalamic lesions

“…Rats with lesions of the dorsomedial area of the thalamus (DMT) have been shown to be deficient in the acquisition of several appetitive tasks (Means, Harrington, & Miller, 1975;Means, Hunt, Whiteside, & Bates, 1973;Means, Huntley, Anderson, & Harrell, 1973). It has been proposed that DMT-1esioned rats will be deficient on any complex task which requires them to form new associations and where stimulus conditions are changed from trial to trial (Means, Harrell, Mayo, & Alexander, 1974).…”