The Effects of Aging on Layer 1 of Primary Visual Cortex in the Rhesus Monkey

• Published in: Cerebral cortex (New York, N.Y. 1991) N.Y. 1991), 2001-02, Vol.11 (2), p.93-103
• Main Authors: Peters, Alan, Moss, Mark B., Sethares, Claire
• Format: Article
• Language: English
• Subjects: Aging - pathology; Animals; Behavior, Animal; Cognition; Dendrites - pathology; Female; Macaca mulatta; Male; Neuropil - pathology; Psychomotor Performance; Synapses - pathology; Visual Cortex - pathology
• ISSN: 1047-3211; 1460-2199; 1460-2199
• DOI: 10.1093/cercor/11.2.93

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.