The effects of aging on layer 1 of primary visual cortex in the rhesus monkey.
The effect of age on layer 1 in primary visual cortex was determined in 19 rhesus monkeys of various ages. Twelve of the monkeys had been behaviorally tested. With age layer 1 becomes thinner and the glial limiting membrane becomes thicker. In the neuropil of layer 1 many of the dendrites in old monkeys appear to be degenerating and, as a consequence, electron micrographs from old monkeys display fewer dendritic and spine profiles per unit area than in young monkeys. As determined using both the disector and size-frequency methods, there is also a concomitant decrease in the numerical density of synapses with age. Although there is a significant correlation between the thinning of layer 1 in area 17 and age, there is no significant correlation between either the thinning of layer 1 or its loss of synapses and any of the behavioral measures of memory function obtained from the 12 behaviorally tested monkeys. Similar morphological changes with age occur in layer 1 of prefrontal cortex of these same monkeys, but in area 46 both the thinning of layer 1 and the loss of synapses show a significant correlation with behavioral measures of memory function. These differences between layer 1 in these two cortical areas presumably relate to the fact that prefrontal cortex has a greater role in subserving cognition than does primary visual cortex.
Peters
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A
Department of Anatomy and Neurobiology, Boston University School of Medicine, 715 Albany Street, Boston, MA 02118, USA.
Moss
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MB
Sethares
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C
D000375:Aging / Q000473:pathology*; D000818:Animals; D001522:Behavior, Animal; D003071:Cognition; D003712:Dendrites / Q000473:pathology; D005260:Female; D008253:Macaca mulatta; D008297:Male; D019581:Neuropil / Q000473:pathology; D011597:Psychomotor Performance; D013569:Synapses / Q000473:pathology; D014793:Visual Cortex / Q000473:pathology*