This is an immunohistochemical investigation of the indusium griseum (supracommissural hippocampus) of the brains of control subjects and patients with Alzheimer's disease (AD). Our assays revealed the presence of fine deposits of synaptophysin‐positive dots in the neuropil and around neurons in the indusium griseum of control subjects. By using an antibody to Alzheimer neurofibrillary tangles (NFT) we identified NFT and neuropil thread‐like structures in the indusium griseum of AD patients; no β‐amyloid protein‐containing senile plaques were seen. To our knowledge, this is the first documentation of the occurrence of NFT in the indusium griseum. We also performed immunohistochemical assays on anterior sagittal sulcal lesions of the corpus callosum (ASSLCC), also known as surface lesions of the corpus callosum. These studies revealed a uniformly increased expression of the 200 kDa phosphorylated neurofilament protein by the axons in the pale myelin areas around the zonal depressions caused by the mechanical pressure of the anterior pericallosal artery. By contrast, immunoreactivity with an antibody to glial fibrillary acidic protein was either unchanged or reduced in th