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Steven S. Shimozaki, Miguel P. Eckstein, Bettina Olk, Alan Kingstone; Categorizing attentional loss in hemineglect with classification images. Journal of Vision 2004;4(8):453. doi: 10.1167/4.8.453.
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© ARVO (1962-2015); The Authors (2016-present)
Hemineglect describes patients with unilateral brain damage that tend to ignore the contralesional visual field. While neglect most commonly occurs with parietal lesions, damage to other areas may also cause neglect (see Karnath, Milner, & Vallar, 2002), possibly by different mechanisms. To identify potentially different causes of neglect, the perceptual templates in a cueing task were estimated for three normal observers and two male right-hemisphere lesioned patients (with previous histories of hemineglect) by correlating observers' responses with the image noise leading to those responses (‘classification images’). Observers performed a yes/no contrast discrimination of a signal appearing at one of two locations (2.5 deg left and right from center). Prior to the stimulus (140 ms), a peripheral precue (140 ms) indicated the signal location with 80% validity. The signal was a 3×3 ‘white X’ checkerboard (1.5 deg), with Gaussian image noise added to each of the 9 checkerboard squares. As expected, the cueing effects and classification images for the normal observers showed no hemispheric differences. As predicted from other studies of hemineglect (e.g., Posner, et al., 1984), the patients (CM, age 85; HL, age 69) had larger cueing effects with right-sided cues (contralesional invalid), compared to left-sided cues (contralesional valid). For CM, the contralesional classification images were positively correlated with the signal with contralesional cues, and negatively correlated with the signal with ipsilesional cues, indicating a severely suboptimal attentional system. For HL, the contralesional classification images were uncorrelated with the signal, regardless of the cue side. HL did not appear to utilize contralesional information, consistent with either a residual visual (hemianopia) or attentional sensitivity loss. In conclusion, classification images successfully distinguished between two different mechanisms of neglect within these two patients.
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