Pattern Separation performance and hippocampal neurogenesis in aged female rats

CANATELLI MALLAT M; GOYA RG; LEHMANN M; CHIAVELLINI P; MOREL GR

Conferencia; Neuromatch 3.0; 2020

Aging is associated with impaired performance in behavioral pattern separation (PS) tasks based on similarities in object features and in object location. Hippocampal dentate gyrus (DG) neurogenesis plays an important role in PS. In order to evaluate the effect of aging on discrimination of overlapping memories of object location or features, we assessed three groups of Sprague-Dawley rats: Young (Y, 4-5 mo., n=25), Middle-Aged (MA, 18 mo., n=32), and Senile (S, 28 mo., n=13). Spontaneous Location Recognition (SLR) and Spontaneous Object Recognition (SOR) were assessed in the three age groups. The testing chambers for SLR and SOR were black circular and white triangular arenas, respectively. Morphometric analysis revealed a significant age-related reduction in doublecortin (DCX) cell number and diameter in the DG. In the SLR, the discriminatory performance was markedly deteriorated in the MA and S rats as compared with Y rats. In the SOR, S rats presented deterioration in memory disambiguation but MA rats showed a preserved memory as compared with Y rats. Our findings reveal the existence of a significant vulnerability of DCX neurons to age in rats and deficient object location discrimination, likely related to deficient DG neurogenesis. Furthermore, the overlapping memories involving object location are more sensitive to age than overlapping memories involving features. A possible explanation for this observation is that the process of discriminating memories related to features is under the control of another pattern separator node, possibly the Prh, which is less affected by age. Our next goal is to study this region to evaluate the differences between the age groups in it.