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Effects of limbic corticostriatal lesions on autoshaping performance
in rats
B.J. Everitt1*, 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