Abstract
Cognitive functioning is dependent on synapse density in the brain. Factors modulating synapse density might include the balance between synaptic pruning and sprouting. Loss of synapses during aging might explain cognitive decline and while previous reports have suggested a 10–15% synapse loss occurs during the normal aging process, more recent studies have found that decline in synaptic density only occurs after 65 years of age. In this context, the main objective of this manuscript is to discuss the findings of our 1993 study in light of more recent studies in aging, synapses and Alzheimer's disease.