Dissociable onset of cognitive and motivational dysfunctions following neonatal lesions of the ventral hippocampus in rats

Abstract

This research examined cognitive and motivational processes at different developmental stages in rats with neonatal ventral hippocampus (VH) lesions, an approach used to model schizophrenia. In Experiment 1, performance in a T-maze alternation task was assessed on postnatal days (PNDs) 22 and 23. VH-lesioned rats displayed a severe deficit relative to controls. In Experiment 2, behaviorally naive rats were tested for spontaneous alternation at PND 29. Alternation was intact in VH-lesioned rats only when successive alternations were separated by >5 s. In Experiment 3, motivation was tested in a cost-benefit T-maze task and in a saccharine-water preference test. Between PNDs 22-37, behaviorally naive rats with neonatal VH lesions displayed weaker saccharine preference than controls, but the 2 groups did not differ on the cost-benefit task. At adulthood, between PNDs 56-72, the difference on saccharine preference persisted and an impairment on the cost-benefit task emerged. Overall, these results suggest that working memory deficits observed at the weaning stage were not secondary to spontaneous alternation or motivation dysfunctions.