Cerebral blood flow changes in response to visual stimulation in demented patients

H.A. Buchtel, R.A. Koeppe, J. Mountz, N.L. Foster, S. Berent, B. Giordani and D.E. Kuhl.
VA Medical Center, Ann Arbor and University of Michigan Departments of Psychiatry, Internal Medicine, Division of Nuclear Medicine, Neurology, and Psychology.

The visual-spatial disorders that are commonly seen in dementia are usually attributed to a disturbance of higher-order mechanisms rather than to reduced responsiveness of the visual system. However, EEG evoked potentials are slowed or reduced in amplitude in patients with Alzheimer’s Disease (AD) and Parkinson’s Disease (PD) with dementia. To test the possibility that visual-spatial deficits seen in dementia may be secondary to reduced input to higher cortical centers, we carried out [O-15]-water activation PET scans with two groups of demented patients (PD with dementia, N=5; probable AD; N=5), and two control groups (normal control subjects, N=7; and cognitively intact patients with PD, N=4). Overall metabolic values were lower for the patient groups compared to normals, and stimulation effects were significantly lower in association cortices for the demented patients compared to the non-demented individuals. We are uncertain if the effect observed would entirely account for the behavioral findings in visual-spatial tasks, and plan to study these phenomena further. We do feel that responsiveness in the visual system should not be excluded as one of the factors contributing to cognitive deficits in demented patients.


Sponsored in part by NIH RO1 NS24896 to D.E. Kuhl