DIFFERENTIAL CORTICAL NETWORK DYNAMICS EVOKED BY DORSAL AND VENTRAL RETROSPLENIAL CORTEX STIMULATION

The retrosplenial cortex (RSC) plays a key role in spatial navigation and memory, but how its subregions influence frontal cortical activity remains unclear. In this study, we used high-resolution voltage-sensitive dye (VSD) imaging in rats to examine how the dorsal (RSCd) and ventral (RSCv) retrosplenial cortex differentially affect activity in the frontal cortex including the secondary motor cortex (M2). Stimulation of the RSCd rapidly evoked excitation in the visual cortex near the stimulation site and in the caudal M2 (cM2), followed by activation of the rostral M2 (rM2). Although RSCv stimulation also induced excitatory responses in these regions, responses in the rM2 were markedly weaker. To test whether RSCd-driven activation of the rM2 is mediated via the cM2, we locally applied the AMPA receptor antagonist CNQX to the cM2. Pharmacological inactivation of the cM2 markedly attenuated excitation in the rM2. These results indicate that activation of the cM2 is essential for RSCd-driven excitation of the rM2. Together, our findings highlight distinct functional roles of RSC subregions and reveal a hierarchical flow of information within the RSC–M2 network. This study provides functional anatomical insights into how frontal cortical networks contribute to spatial navigation.