Behavioral recovery following bilateral lesions of the nucleus basalis does not occur spontaneously

Recent studies have shown that rats given bilateral ibotenic acid lesions of the nucleus basalis (NBM) exhibit significant impairments on tasks requiring recent or trial-specific memory. However, despite the persistence of cholinergic deficiencies in the cortical projection area, the memory impairments gradually recover over a period of several months of training. Moreover, in one study, the behavioral recovery on a radial arm maze retention task was shown to generalize to a completely different behavior paradigm (passive avoidance) on which the animals had received no prior experience. The present study was performed to determine the extent to which this generalized recovery of performance on memory tasks is dependent upon extensive post-lesion training. Rats were given ibotenic acid lesions of the NBM and were then passively detained in their home cages for six months. Contrary to animals which had received post-surgical radial arm maze experience, the animals detained in their home cages displayed a significant retention impairment when tested on the passive avoidance task, suggesting that the experience the animals receive is an important factor for whether post-lesion functional recovery occurs. This study also confirms that the loss of cholinergic markers following bilateral, NBM lesions persists for at least several months, or longer.