Dendritic spine plasticity in hippocampus.

Most excitatory input in the hippocampus and cerebral cortex impinges on dendritic spines. Alterations in dendritic spine density or shape are suspected to be morphological manifestations of changes in physiology or behavior. The links between spine plasticity and physiological responses have probably been best studied in the hippocampus in the context of changes in the circulating levels of steroid hormones or long-term potentiation. Here we review and present data which indicate that both the age of the preparation and the timing of the analysis can dramatically effect the results obtained. Collectively the data suggest that different cellular and morphological strategies may be utilized at different ages and under different circumstances to effect similar physiological responses or behaviors.