Effects of medial and dorsal cortex lesions on spatial memory in lizards

In mammals and birds, the hippocampus is a major learning and memory center that plays a prominent role in spatial memory, the use of distal cues to g uide navigation. The role of reptilian hippocampal homologues, the medial a nd dorsal cortex, in spatial memory has not been thoroughly investigated. T he medial and dorsal cortex of reptiles is known to play a role in learning both tasks that are hippocampally dependent and tasks that are not hippoca mpally dependent in mammals and birds. In order to examine the specific rul e of the medial and dorsal cortex in spatial memory, we trained medial cort ex, dorsal cortex, and sham lesioned Cnemidophorus inornatus lizards to loc ate the one heated rock of four identical rocks spaced evenly around the pe rimeter of a circular, sand filled, arena in a cool room. We used probe tri als to examine the strategies used by lizards to locate the goal. Medial co rtex lesions and dorsal cortex lesions slowed acquisition and altered the s trategies used to locate the goal. However, none of the lizards adopted a s patial strategy to locate the goal suggesting that the dorsal cortex and me dial cortex are involved in using non-spatial strategies for navigation. (C ) 2001 Elsevier Science B.V. All rights reserved.