Background: There are several cortical areas related to the limbic system that form the output
from the hippocampal formation whose cellular and morphological features are important for the onset
and progression of AD. We hypothesized that there would be a significant difference in the size of cortical
pyramidal neurons and that there would also be a hemispheric asymmetry between Alzheimer disease
patients and controls. These differences would potentially be accompanied by an increase in the
numbers of Fluoro-Jade B-positive degenerating cortical neurons and a corresponding decrease in the
numbers of DAPI-stained cortical neuronal nuclei in subjects with AD compared to controls. Such
changes could potentially be used as another marker in postmortem neuropathological diagnosis of AD.
Methods: We measured absolute numbers of DAPI and Fluoro-Jade B stained cells in five cortical areas
of the limbic system and four subareas of planum temporale in the post-mortem brains of subjects with
Alzheimer disease. We also measured the size of pyramidal neurons in layer III in the five cortical areas
of the limbic system in these subjects. All measurements were performed separately for the left and right
hemisphere in order to identify asymmetries between the two hemispheres.
Results: We observed a significant decrease in numbers of DAPI stained cells in layers IV-VI of the
anterior cingulate gyrus on the right side, in layers I-III of the posterior cingulate gyrus on the left side,
in layers IV-VI in the transition region from superior temporal gyrus into planum temporale on the right
and in layers IV-VI in the transition from planum temporale to insular cortex on the left. We also observed
a significant increase in the numbers of Fluoro-Jade stained cells in layers I-III of the anterior
cingulate gyrus and in layers I-III on the left and layers IV-VI of the right gyrus of Heschl. Shortening of
the size of layer III pyramidal neurons in subjects with Alzheimer´s disease was found in the anterior
cingulate gyrus on the right, in the posterior cingulate gyrus and entorhinal cortex on the left and on the
right in the parahippocampal gyrus.
Conclusion: Our study demonstrates asymmetries in different cortical regions of the temporal lobe that
can be used as another marker in the postmortem diagnosis of AD.