It was observed by Perry et al. that GAD activity was apparently reduced in post-mortem tissue homogenates (from all four cortical lobes) from patients with dementia (including AD and mixed-type dementias), but this was only observed at later stages of the disease, and was later shown by the same group to most likely have been the result of perimortem agonal state conditions (i.e., at or near the time of death) [205,206]. This evidence concerns the gene GAD1 and Alzheimer disease.