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Nader Noori, Laurent Itti; Visuospatial attention shifts during non-visual mental tasks. Journal of Vision 2011;11(11):479. doi: 10.1167/11.11.479.
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We experimentally validate the hypothesis that seemingly irregular eye movements during mental tasks reflect shifts in spatial attention, in turn employed by executive attention to manage short-term memory through a spatial registry system. We build upon recent findings of neuroimaging (Knops, 2009) and patient studies (Koenigs, 2009) that suggest a crucial role for brain regions with visual-spatial characteristics in abstract mnemonic tasks that require memory manipulation. To validate our hypothesis, we recorded human gaze shifts during two mental tasks: either passively maintaining or sorting sequences of five random digits. We manipulated spatial binding of items to visual locations through different visual presentations of the stimuli; however, subjects were instructed and monitored for performing the tasks in memory and in front of a blank screen. In our first experiment we primed spatial binding of items along horizontal and vertical directions and saw when the task is sorting, the difference in normalized distribution of gaze-shift directions(GSD) along the horizontal direction, for horizontal relative to vertical priming, on average is +4.41% ± 1.51% (mean ± SE) which is significant (t-test, n = 9, p < 0.0192). However, when the task is passive maintaining the difference in GSDs along the on average is 1.3% ± 1.76% (mean ± SE), n.s. (t-test, n = 9, p > =0.9288). In our second experiment we showed that reversing the order of stimuli for mental sorting, leads to a horizontal symmetry in spatial distribution of gaze shifts amplitudes. We chose two categories of 5 digits, identified by these canonical strings:41230 and 03214. Exemplars for each category were generated by using different digit values while preserving relative ordering. Subtracting amplitude distributions of gaze-shifts leads to an antisymmetric distribution measured by linear correlation of data point of two sides of distributions (t(−0.78) = −4.318, df = 12, p < 0.0005).Our findings establish a functional relationship between presumably amodal mnemonic tasks and visual-spatial systems in human brain and might help explain the notable impact of executive memory tasks on visual processing.
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