Figure 1.

rCBF responses in primary (striate) and association visual cortical areas, measured with PET and H₂¹⁵O during patterned flash stimulation at different frequencies, in control subjects and in Alzheimer's disease patients with mild dementia or moderate-severe dementia. Scaled increment in blood flow, ΔrCBF, corrects for global flow difference between groups. *, P < 0.05; **, P < 0.01, differs significantly from control mean. Coordinates (in millimeters) are in stereotactic (Talairach) space. Passive “parametric” stimulus paradigms such as this might be used to examine synaptic integrity in at-risk subjects, as well as drug effects on synaptic transmission in relation to dementia severity (see text). Modified from ref. 27. (The American Journal of Psychiatry 155, 785–794, 1998. Copyright 1998, the American Psychiatric Association. Reprinted by permission.)