Experience during suckling increases weight and volume of rat hippocampus.

Changes in brain anatomy resulting from early suckling experience were explored by measuring wet weight of whole brain, cortex, hippocampus and cerebellum in juvenile rats. Rats provided with ample opportunity to nipple-shift, a behavior associated with enhanced maze learning, had much larger hippocampal mass than rats whose nipple-shifting experience had been restricted. No differences were observed in the other areas measured. This effect of experience was confirmed by histological measurement of hippocampus volume following differential rearing.