Organizational Effects of Early Gonadal Secretions on Sexual Differentiation in Spatial Memory

Neonatally castrated (MNC) and control male rats (MC) and female rats treated neonatally with estradiol benzoate (FNE) and female controls (FC) were studied. In Exp. 1 spatial memory was assessed using a 12-arm radial maze. During acquisition, MC and FNE groups were more accurate in choice behavior than FC and MNC groups. In Exp. 2 the discriminative control exerted by different types of cues was evaluated. Alteration of the geometry of the room but not movable landmarks disrupted performance of MC and FNE groups. For the FC and MNC groups, alteration of either geometry or landmarks did not disrupt performance. In Exp. 3 the effect of a 15-min delay was determined. MC and FNE groups were more disrupted by a delay than MNC and FC groups. Together, these data suggest that early exposure to gonadal steroids (probably estradiol) improves acquisition of spatial tasks by reorganizing and simplifying associational-perceptual processes that guide spatial ability.