Effects of limbic corticostriatal lesions on autoshaping performance in rats
B.J. Everitt^1*, J.A. Parkinson², G. Lachenal¹, K.M. Halkerston¹, N. Rudarakanchana¹, R.N. Cardinal¹, J. Hall¹, C.H. Morrison¹, J.W. Dalley¹, S.R. Howes¹, T.W. Robbins¹
1. Exp Psychol, 2. Anatomy, Univ Cambridge, Cambridge CB2 3EB, United Kingdom

It has previously been shown that acquisition of Pavlovian conditioned approach behaviour (autoshaping) in rats depends on a circuit involving the anterior cingulate cortex (Ant Cing), the nucleus accumbens core (AcbC), accumbens dopamine (DA) innervation, and the central nucleus of the amygdala (CeN). This study sought to determine which elements of this circuit are required for performance of the task in well-trained animals. Rats were first trained that one visual stimulus, the CS+, was always followed by food, while another, the CS–, never predicted food. As a consequence, they came to approach the CS+ selectively. Subjects that reached a performance criterion subsequently received excitotoxic lesions of the Ant Cing (lesion n = 10 / sham 6), AcbC (ns = 9 / 7), or CeN (8 / 7), or 6-OHDA-induced dopamine depletion of the entire nucleus accumbens (7 / 7). Subjects were then re-tested.
   Ant Cing lesions and AcbC lesions both impaired autoshaping performance. Acb DA depletion also impaired performance and the impairment was correlated with the degree of dopamine depletion, though the deficit was mild compared to that observed for the acquisition of autoshaping (Everitt et al. 1999). In contrast, rats with CeN lesions were unimpaired. These results support the view that the limbic corticostriatal circuit involving Ant Cing and AcbC is involved in the storage and/or expression of appetitive stimulus–reward associations, but suggest a critical role for CeN in early learning, which may reflect its role as a controller of attentional resources (Holland & Gallagher 1999).

Supported by: MRC (UK) & Wellcome Trust

Key words: nucleus accumbens core, anterior cingulate cortex, central nucleus of the amygdala, dopamine