Lesions of the Posterior Insular Cortex Impair Water Maze Performance in the Rat

Abstract

Performance of rats in the Morris water maze was measured after small excitotoxic lesions were produced bilaterally in two areas in the insular cortex, 0.3 and 2.3 mm posterior to bregma in the upper bank of the rhinal sulcus. The rats were trained and tested in two successive days to find an underwater platform. Compared to intact animals groups with lesions at AP-0.3 and AP-2.3 were impaired as measured by latency. These animals also did not prefer the correct quadrant while searching for the platform. There were no differences between the groups in percentage of time spent in periphery and speed of swimming. The results do not support the hypothesis that the destruction of an autonomic center at AP-0.3 will impair performance while the destruction of a more posterior part of the insular cortex will not. and are interpreted as further evidence for multifactor sensitivity of the water maze task.

Key Words:

• Morris water maze
• insular cortex
• excitotoxic lesion
• spatial memory
• navigation
• learning
• rat