Quantitative synaptic alterations in the human neocortex during normal aging

Neurology. 1993 Jan;43(1):192-7. doi: 10.1212/wnl.43.1_part_1.192.

Abstract

We quantified the synaptic population density in the frontal cortex of 25 individuals without dementia 16 to 98 years old, using sections double-immunolabeled for beta/A4 amyloid and for synaptophysin, and found a significant inverse correlation between the presynaptic terminal (PT) counts and age (r = -0.7, p < 0.001). Individuals older than 60 years had an average 20% decrease in PT density compared with individuals younger than 60 years. There were no significant correlations between the age and the number of beta/A4 amyloid-positive plaques or between synaptic density and the number of amyloid plaques. Further analysis of the digitized serial optical images showed focal areas of synapse loss and distended synaptophysin-containing boutons in the mature plaques of the normal aged cases. However, we found no microscopic changes in the synaptic content inside and outside the diffuse plaques. We suggest that a loss of synaptic input in the neocortex is an age-dependent factor that contributes to the overall synaptic loss in Alzheimer's disease, but that this might be largely independent of the beta/A4-amyloid deposition.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Aging / physiology*
  • Amyloid / analysis
  • Cerebral Cortex / cytology*
  • Humans
  • Image Processing, Computer-Assisted
  • Middle Aged
  • Reference Values
  • Synapses*

Substances

  • Amyloid