Animal models of infantile amnesia, benign senescent forgetfulness, and senile dementia.

The Jacksonian principle of hierarchical development and dissolution of function was applied to infantile amnesia and memory loss in senescence. When the Jacksonian model is generalized to include life-span changes in memory it predicts a last-in, first-out appearance and disappearance of memory processes. Those memory capacities that are the last to appear in ontogeny should be the first to be compromised in aging. To evaluate this proposition in a specific context, the rodent literature on long-term memory in infant, adult, and aged animals was surveyed. Three types of memorial processes that emerged sequentially in development were identified and then examined in adult and aged rats. Although strong support of the Jacksonian principle did not emerge from this analysis, the data were sufficiently positive to suggest that the theory was still viable and even vigorous enough to guide future research on both the normal and pathological processes of development and aging.