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Abstract:
We previously reported that in Alzheimer patients,
cholinergic blockade with scopolamine decreases arousal and
interferes with visuospatial attention during visual search,
whereas cholinergic augmentation with physostigmine only slightly
increased arousal. We further examined our data to determine if
hemispatial asymmetries exist and if they are affected by
cholinergic manipulations. Eleven patients with probable
Alzheimer's disease and 11 elderly controls were tested. Valid
precues altered the aperture of spatial attention in visual search
for a target in an array of letters. Cue size was varied with
respect to spatial precision. Patients were slower responding to
targets presented in the left hemispace with scopolamine as
compared with physostigmine and with no-drug baseline. Patients
under the influence of scopolamine received less of a benefit from
the most spatially precise cue in comparison to controls with
scopolamine. These results suggest that our previously reported
scopolamine-induced reduction in the ability to scale the
attentional focus in Alzheimer's disease may be due to dysfunction
within the right hemisphere. Our findings in these patients are
consistent with a previous report of correlation between covert
shifts of attention and right parietal hypometabolism in
Alzheimer's disease.
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