Discrimination learning in turtles after lesions of the dorsal cortex or basal forebrain

Abstract

The basal forebrain of turtles contains cholinergic neurons that project to the dorsal cortex, a three-layered structure on the surface of the cerebral hemispheres. This experiment was designed to examine whether the basal forebrain is involved in associative function in reptiles, as has been shown in mammals. Three groups of turtles—a sham-lesioned control group, a group given aspiration lesions of the dorsal cortex, and a group given ibotenic acid lesions of the basal forebrain—were trained in an operant chamber on a simultaneous pattern discrimination and its reversal. The stimuli to be discriminated were horizontal and vertical stripes. Relative to controls, lesions of either the dorsal cortex or the basal forebrain disrupted acquisition and reversal of the discrimination. The results suggest that the basal forebrain systems of reptiles and mammals function in a similar way. © 1989, Psychonomic Society, Inc.. All rights reserved.