Attentional deficits are thought to accompany damage to a number of different neural regions and are prominent in several neuropsychological syndromes (e.g., neglect). Yet only recently have studies begun to articulate specific attentional operations with different neural regions. The present proposal examines two types of attentional operations (voluntary and automatic shifting of spatial attention) and their role in perceptual processes that connect properties of objects together (i.e., perceptual integration). The first major question addressed by the proposed studies will be whether automatic and/or voluntary attentional shifts will be impaired in patients with unilateral lesions in parietal, temporal, or frontal regions. A voluntary shift of attention is one that is volitionally directed as when we shift our attention from one place to another to scan a complex scene. An automatic shift is one that is elicited without volition as when the sudden appearance of a stimulus attracts attention. Although a number of neuropsychological, neurophysiological, and electrophysiological investigations suggest that these two types of shifts involve different neural mechanisms, there is as yet little consensus. Different investigators have suggested that parietal, temporal, frontal or subcortical areas, as well as various combinations of these areas, might be differentially involved. By examining these two types of attentional shifts in different patient groups in the same study, we should be able to resolve at least part of this controversy. The second major purpose of the proposed studies is to examine the relation between automatic and/or voluntary attentional shifts and perceptual integration in the different patient groups. This issue is especially important since the PI and his colleagues have recently reported data from patients with lesions in the posterior superior temporal gyrus that could be interpreted as a deficit in automatic attentional shifts or as a deficit in perceptual integration. (The findings will be discussed at length in the body of the proposal). Procedures that have been thoroughly studied in normals and are believed to be sensitive to automatic versus voluntary shifts of attention on the one hand and feature integration on the other will be used. In this way, the proposed set of studies will not only clarify the relationship between different cortical regions and automatic and voluntary attentional shifts but will also help distinguish between deficits in attention and deficits in perceptual integration.
