What is it about?
Introduction: Normal aging is characterized by deterioration of visual abilities, affecting mainly visual acuity, contrast and wavelength sensitivity. In the present study we attempted to describe the morphological and morphometric alterations of the dendrites and the dendritic spines of the pyramidal cells of the visual cortex during normal aging, in order to approach the visual impairment of aged individuals from a neuropathological point of view. Material and methods: We studied the visual cortex in 20 brains using the Golgi technique. Results: In pyramidal cells, which represent the majority of cortical neurons, age-related pathology can be observed in cell somata as well as, most importantly, in dendrite number and morphology. The apical dendrites of some pyramidal cells are distorted and tortuous. Horizontal dendritic arborization is also severely decreased. These alterations were more prominent in the corticocortical pyramidal neurons of the 5th layer. Conclusions: The morphological and morphometric assessment of the dendrites and the dendritic spines in the visual cortex in normal aging revealed substantial alterations of the dendritic arborization and marked loss of the dendritic spines, which may be related to visual impairment even in normal aging.
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Why is it important?
In previous studies we have shown significant dendritic and spinal changes in the visual cortex during normal ageing and in Alzheimer’s disease . In the present study we attempted to describe the morphological and morphometric alterations of the dendrites and the dendritic spines of the pyramidal cells of the visual cortex during normal aging, in order to approach the visual impairment of aged individuals from a neuropathological point of view. Small pyramidal cells of layer V are mainly affected by age, while large pyramidal cells retain higher dendritic and spinal density. The statistical test performed for the comparison of the morphometric changes between the two subpopulations of pyramidal cells confirmed this hypothesis. The main differences between the subgroups are related to the size of the cell soma, the functionality and their afferent and efferent connections.
Perspectives
The present study points to the fact that brain aging is accompanied by rather subtle morphological and molecular changes at the level of single neuronal populations and different types of pyramidal cells of the human visual cortex are differently affected. The loss of dendrites and dendritic spines leads to a substantial decrease of the synaptic contacts of the cells of the visual cortex with the neurons of other cortical and subcortical areas implicated in the modulation of the visual information. These alterations seen in the thick sections of the silver-impregnated preparations, attributed to the degeneration of the dendritic spines, may explain the impaired central visual function during normal aging.
Professor Stavros J Baloyannis or Balogiannis or Balojannis or Baloyiannis or Mpalogiannis
Aristotle University of Thessaloniki
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This page is a summary of: Original article Age-related dendritic and spinal alterations of pyramidal cells of the human visual cortex, Folia Neuropathologica, January 2015, Termedia Sp. z.o.o.,
DOI: 10.5114/fn.2015.52406.
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