The cortex of the primary auditory area in Alzheimer's disease.

The cortex of the superior temporal gyrus has been examined in two brains with Alzheimer's disease. Numerous neurofibrillary tangles and neuritic plaques that are characteristic of the disease, were present in area 38 in the anterior part of the gyrus and in area 22 more posteriorly but the primary auditory cortex, area 41, was virtually unaffected by these pathological changes. This relatively minor involvement of the primary auditory cortex, like that of the primary somatic and visual areas, again emphasises the uniqueness of the olfactory system in being severely degenerate. The findings are considered to support the suggestion that the distribution of the pathological changes in Alzheimer's disease has an anatomical basis due to spread of the disease process along certain well-defined sets of cortical fibre connections.