Retrosplenial cortex lesion affected segregation of spatial information in place avoidance task in the rat

Abstract

Retrosplenial cortex (RSC) together with the hippocampus is a component of the spatial memory circuit. To elucidate the role of the RSC in spatial memory formation in the immediate presence of both relevant and irrelevant spatial stimuli, we used a new place avoidance task, in which rats learn to avoid shock in an unmarked place. In the present study, we manipulated the relevance of distal “Room” stimuli and local “Arena” stimuli for place avoidance. Rats with ibotenate lesions of RSC, control sham lesions (Csl) and intact control rats (Cint) initially learned the (Room&Arena)+ task variant in which both Room and Arena stimuli are relevant for defining the shock sector. Afterwards, different subsets of rats from each group were trained in the following task variants: (i) Room+Arena-, in which the arena continuously rotated so that Room stimuli were relevant and Arena stimuli were irrelevant for avoiding shock; (ii) Arena+, in which the arena and shock sector rotated in a dark room so that Arena stimuli were relevant and Room stimuli were irrelevant for avoiding shock; (iii) Room+, in which the arena was covered in shallow water so that only Room stimuli were relevant for avoiding the shock sector whether the arena was stationary or rotating. We found that damage of RSC impaired the Room+Arena- variant that required relevant and irrelevant stimuli to be segregated. Importantly, the same lesions spared task variants that did not require segregation. Our results suggest an involvement of retrosplenial cortex in the segregation of spatial information.