Memory impairments following basal forebrain lesions.

The functional contribution of the nucleus basalis magnocellularis (NBM) and medial septal area (MSA) to memory was evaluated in 4 behavioral tasks. The tasks were postoperative acquisition of a win-stay spatial discrimination in a T-maze, a win-shift spatial discrimination on a radial arm maze, active avoidance in a shuttle box, and passive avoidance in a shuttle box. Bilateral lesions were made by injecting ibotenic acid (IBO) into the NBM or MSA. Control rats received operations in which no neurotoxin was injected. When compared to controls, rats with lesions in either the NBM or MSA had significantly impaired choice accuracy in the T-maze and radial maze tasks, took significantly fewer trials to reach criterion in the acquisition, but not the retention of an active avoidance task, and significantly more trials to reach criterion in the passive avoidance task. The results show that equivalent behavioral changes are obtained from lesions in the NBM and MSA in tasks that vary in their type of motivation, reinforcement, response-reinforcement contingency, and response. These behavioral changes suggest that the NBM and MSA may both be involved in memory.