Abstract
Blood flow velocities of the posterior cerebral arteries were obtained while healthy subjects were engaged in a visual spatial attention task. Experimental runs consisted of series of stimuli comprised of four elements (two left and two right of a central fixation point) presented briefly in blue against a purple screen. After a period of passive viewing a left or right pointing arrow indicated the visual half-field to be attended by the subjects in order to detect identical symbols on the attended side. Relative to the passive viewing condition a marked increase of flow was seen in both posterior cerebral arteries during the attention period. No differential increase of flow as a function of attended field was detected. These results are discussed in comparison with recent positron-emission tomography (PET) and electrophysiological data obtained with the same task.
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