Is Dendritic Proliferation of Surviving Neurons a Compensatory Response to Loss of Neighbors in the Aging Brain?

Abstract

The plastic capacities of the developing brain are well known, and it is the young brain that usually is emphasized when considering neuronal plasticity. The view taken here is that the plastic capacity of the developing brain does not suddenly cease as some developmental landmark is reached but that some degree of residual plasticity is maintained to the end of the developmental continuum (death). Functionally, this residual plasticity may be manifested in a variety of ways, including (1) recovery from strokes and lesions and (2) compensatory responses to the degenerative phenomena of the aging brain. We define neuronal “plasticity” as the adaptive response(s) of neurons to perturbations in their local environment. The perturbations may be in the chemical composition of the neuron’s immediate surround, its afferent supply, its targets, or in its neighboring neurons and glia. The plastic response(s) to such perturbations may include alteration in dendritic and/or axonal morphology, in synapses, receptors, metabolism, even in genetic expression (e.g., Black et al., 1984: Davis et al., 1986).