Dimensions of the hippocampus, memory, and learning in the ontogenesis of rats.

Damage to the hippocampus in 20-, 50-, and 110-day-old rats impairs the processes of learning and short-term memory in them. In 50-day-old rats, hippocampectomy has less of an influence on the process of learning and memory than for 20- and 110-day-old animals. The anatomic and physiological characteristics of the hippocampus in 20-day-old rats may be evidence of a special importance of this formation at the early stages of ontogenesis, when the cerebral cortex is still insufficiently mature and its associations with other structures have not been entirely formed. The nonlinear nature of the dependence of the disruption of learning in rats of different ages after hippocampectomy suggests that the function of the rat hippocampus undergoes changes during the process of individual development of the animal.