A differential involvement of the shell and core subterritories of the nucleus accumbens of rats in attentional processes.
The nucleus accumbens comprises of two anatomically distinct subterritories: an inner core and an outer shell region. The distinct pattern of the core and shell input and output targets suggests that these two regions may mediate different behavioral processes. Using N-methyl-D-aspartate excitotoxic lesions in either the core or shell region, we investigated whether we can dissociate functionally these two subterritories. N-Methyl-D-aspartate-lesioned, sham-lesioned and non-operated animals were tested for locomotor activity in an open field and in two behavioral paradigms known to evaluate attentional deficits, namely the pre-pulse inhibition of the acoustic startle reflex and latent inhibition, measured in a two-way active avoidance paradigm. The shell-lesioned animals showed a small but significant hyperactivity in the open field when compared to the core-lesioned and to control animals. In the pre-pulse inhibition paradigm, core-lesioned animals demonstrated reduced pre-pulse inhibition to the two high pre-pulse intensities (80 dB[A], 84 dB[A]). In the active avoidance paradigm, whereas no lesion effects were detected in the non-pre-exposed groups, clear attenuation of latent inhibition was found in the shell-lesioned rats, in comparison to both core-lesioned and control rats, due to improved avoidance performance of the shell-pre-exposed group. From these results we suggest that the two subterritories of the nucleus accumbens are differentially involved in attention-related processes: the core lesion leads to significant disruption of pre-pulse inhibition while the shell lesion leads to heightened activity and significant attenuation of latent inhibition.
Jongen-Rêlo
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AL
Behavioral Neurobiology Laboratory, Swiss Federal Institute of Technology Zurich, Schorenstrasse 16, Postfach, CH-8603, Schwerzenbach, Switzerland. jongen@toxi.biol.ethz.ch
Kaufmann
S
S
Feldon
J
J
D000161:Acoustic Stimulation; D000818:Animals; D001288:Attention / Q000502:physiology*; D001362:Avoidance Learning / Q000502:physiology; D001522:Behavior, Animal / Q000187:drug effects; D001931:Brain Mapping; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D016202:N-Methylaspartate / Q000494:pharmacology; D009433:Neural Inhibition; D009714:Nucleus Accumbens / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D013216:Reflex, Startle / Q000502:physiology
D018690:Excitatory Amino Acid Agonists; D016202:N-Methylaspartate