Abstract
We measured the length of the pyramidal neurons in the cortical layer III in four subregions of the planum temporale (transitions into superior temporal gyrus, Heschl's gyrus, insular cortex, and Sylvian fissure) in control group and Alzheimer disease patients. Our hypothesis was that overall length of the pyramidal neurons would be smaller in the Alzheimer disease group compared to controls and also there would be right-left asymmetry in both the control and Alzheimer disease groups. We found pyramidal neuron length asymmetry only in controls—in the transition into the Sylvian fissure—and the rest of the subregions in the control group and Alzheimer disease patients did not show size difference. However, control-Alzheimer disease group pyramidal neuron length comparison revealed (a) no length difference in superior temporal gyrus transition area, (b) reversal of asymmetry in the insular transition area with left insular transition significantly shorter in the Alzheimer disease group compared to the control group, (c) both right and left Heschl's gyrus transitions significantly shorter in the Alzheimer disease group compared to the control group, and (d) right Sylvian fissure transition significantly shorter in the Alzheimer disease group compared to the control group. This neuronal length measurement method could supplement already existing neuropathological criteria for postmortem Alzheimer disease diagnostics.
Highlights
Neurodegeneration in Alzheimer disease (AD) affects structures of the temporal lobe (MTA) and in particular the supratemporal plane of the temporal lobe—planum temporale (PT)
In all subregions (STG, I, Heschl’s gyri (HG), Sylvian fissure (SR)), length of pyramidal neurons was higher in the control group compared to the AD group
In terms of within groups asymmetry, we found significance only in the SR of the control group (R > L)
Summary
Neurodegeneration in Alzheimer disease (AD) affects structures of the temporal lobe (MTA) and in particular the supratemporal plane of the temporal lobe—planum temporale (PT) (for review see [1]). PT is mostly a heteromodal auditory association region whose asymmetry is established by 31 weeks of gestation. It is involved in auditory and spatial objects processing, auditory-motor integration, music pitch and tune recognition, and sound localization functions [2], and its structural and functional organization was recently revised. The posterior part is not part of the auditory cortex and it supports sensory-motor integration of the vocal tract actions [3]. Microanatomical changes were found in the cortex of the PT in patients with AD in the form of minicolumn thinning, this finding was not well correlated with decline in cognitive functions [5].
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