Young, Lauriann E.; Wray, Samuel R.
Author Affiliation, Ana.
Department of Basic Medical Sciences
Learning dysfunction produced by mesolimbic deficits
Alzheimer's Disease Review
Date of Publication
Developments in the last decade have drawn attention to the functional role of the mesolimbic system or nucleus accumbens septi (NAS) in brain reward as evidenced by its association with drug abuse. The present study was designed to evaluate the role of the NAS in avoidance learning, which is a negative form of reinforcement or reward. Felame Wistar rats were subjected to a series of electric foot-shocks in a confined arm of a Y-maze for a period of 3 minutes (training period). Control rats were also confined to the arm but received no foot-shocks. Rats were returned to the Y-maze a day later (trial 1) and 2 weeks subsequently (trial 2) to assess the level of avoidance learning. To evaluate the relative contribution of the NAS to avoidance learning, rats were lesioned electrolytically at the level of the NAS prior to training (post-operative training) and their behaviour compared with that of sham-operated controls and un-operated rats. Lesions to the NAS were not observed to produce ataxia or poverty in movement, but appeared to produce dishabituation in avoidance learning and an exacerbation in the 'freezing response' of the rats. Indications are that the NAS is necessary to modulate avoidance learning and to facilitate recovery from an aversive experience.....