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Margarita Sarri, Jon Driver; Top-down attentional modulation of visual neglect in cancellation tasks. Journal of Vision 2007;7(9):433. doi: 10.1167/7.9.433.
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© ARVO (1962-2015); The Authors (2016-present)
Visual neglect following stroke does not invariably affect a fixed portion of space, but instead can be modulated by stimulation and task demands, including apparent attentional factors. Different versions of clinical cancellation tasks can reveal different degrees of neglect in the same patient, possibly due to variations in the attentional demands, although different versions typically vary in both top-down and bottom-up ways. Here we describe three cancellation experiments in which we manipulated solely ‘top-down’ attentional factors in different versions of a cancellation task, while always keeping visual displays identical across conditions. Our results show overall that top-down attentional demands can have a major impact on neglect performance in cancellation, with increasing demands on visual attention adversely affecting exploration towards the contralesional side. Specifically, we show that the level of difficulty for the required target discrimination (on the same stimulus displays) can dramatically modulate neglect performance. Further, that increasing discrimination difficulty for every item in the display can increase the number of contralesional omissions, even when no target selection process is required; but neglect can be more severe when attention has to be selectively directed to specific target among non-targets. We also investigate the possible effects of shifting attention from a more ‘global’ to a more ‘local’ level of discrimination, showing that while this may have some effect it is not a necessary condition for neglect to be exacerbated by discrimination difficulty.
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