5‐ Neurobiology

Differential activation of the subdivisions of retrosplenial cortex associatedto the retrieval of fear conditioned memory.

SigwaldE¹, Ponce N¹, Bignante A¹, Molina V²,de Olmos S¹, Lorenzo A¹.

¹Instituto de InvestigaciónMédica Mercedes y Martín Ferreyra, INIMEC, CONICET, Universidad Nacional deCórdoba. Friuli 2434, 5016-Córdoba, Argentina

²IFEC, CONICET,Universidad Nacional de Córdoba, Argentina

Introduction: The retrosplenial cortex (RSC) has been implicatedin complex cognitive functions such as learning, memory, spatial navigation andintrospection. Dysfunction of RSC is associated with diverse pathologicalconditions such as Alzheimer´s disease, autism or schizophrenia. Thus, addressingthe functional organization and activity of the subdivisions of RSC (areas A29and A30) during the execution of complex cognitive tasks might be relevant for understandingtheir physiological and pathological roles.

Material and Methods: Immunostaining was used for acomprehensive analysis of cFos and EGR-1 expression in RSC and related areas ofmale rats after acquisition and retrieval of contextual fear memory. The impactof MK801 treatment that selectively induces degeneration of layers IV-V neuronsof A29 (A29^MK801) was evaluated.

Results: Acquisition and evocation of fear memorypromoted the expression of cFos and EGR-1 in A30, dorsal hippocampus (DH),medial entorhinal cortex (MEnt) and basolateral amygdala (BLA) while EGR-1expression was down-regulated in A29 and caudomedial entorhinal cortex (CEnt). Afterfear conditioning, selective degeneration of A29^MK801 neurons impairedfear memory retrieval and prevented cFos and EGR-1 up-regulation in A30,without affecting their expression in DH, MEnt, BLA and CEnt.

Discussion: These observations indicated that RSC integrityis required for fear memory retrieval. The data also showed that fear memoryevocation elicits differential neuronal activation in RSC subdivisions, suggestingthat A30 activation depends on the functional integrity of A29^MK801neurons.