In two experiments the involvement of the nucleus accumbens in instrumental conditioning was investigated using rats as subjects. In experiment 1, extensive bilateral cytotoxic lesions of the nucleus accumbens mildly suppressed instrumental responding reinforced with food, but had no detectable effect on the sensitivity of the rats' performance either to outcome devaluation or to degradation of the instrumental contingency. In experiment 2, restricted accumbens lesions reliably attenuated the excitatory effect of systemically administered d-amphetamine on lever pressing for a conditioned reinforcer, and completely abolished Pavlovian-instrumental transfer. Taken together these results give a picture of the involvement of the rat nucleus accumbens in instrumental conditioning. They support the widely held theory that the nucleus accumbens mediates the excitatory effects of appetitively conditioned Pavlovian signals on instrumental performance and refute the hypothesis that the nucleus accumbens is part of the neural circuitry by which incentive value is attached to the representations of instrumental outcomes.

[fre] L'application d'une méthode originale d'aide au développement d'une région rurale, l'approche système, a été lancée par le Sud-Est de la Belgique. L'approche globale (du point de vue d'une multiplicité d'acteurs) des situations ou problèmes, des objectifs et des programmes, permet d'arriver à des résultats opérationnels, rapidement, à des coûts peu élevés ; elle favorise le jeu de mécanismes de développement. [eng] An integrated development method, in a rural area : its application to South Eastern Belgium - The application of an original method of aid to the development of a rural region, the "approach system", has been introduced in South Eastern Belgium. The global approach (from the point of view of many protagonists) to situations or problems, to the aims and programmes, enables operational results to be reached quickly at little cost ; it facilitates the interplay of development processes.