Sed tau (a component of the neurofibrillary tangle, a second AD neuropathological hallmark) have been proposed as sensitive and specific markers of AD in several studies [47,48]. It has also been found that changes in CSF Ab and tau are comparable to those observed in AD and HAD patients [49]. The pathogenic significance of these biomarkers is not well established but it has been hypothesized that
Amyloid plaque deposition [39,42-44]. Indeed, most forms of dementia are accompanied by a widespread degeneration in the cerebral cortex - such as the plaques in AD brain. AD is thus considered a "cortical dementia." HAD is also considered to be a cortical dementia however there is also targeted damage to regions lying under the cortex. Some authors consider HAD to be a subcortical dementia howeve