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Matthias Niemeier, Ada Le, Boge Stojanoski; Contrast-specific neural responses underlying the perceptual bias. Journal of Vision 2008;8(6):995. doi: https://doi.org/10.1167/8.6.995.
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© ARVO (1962-2015); The Authors (2016-present)
Visuo-spatial and attentional functions are assumed to be predominantly represented in the right hemisphere because right-hemisphere lesions cause severe deficits such as spatial neglect. However, there is much debate about which neural mechanisms are affected, partially because in healthy people functional and behavioural right-dominant asymmetries are subtle and across participants inconsistent; e.g., most (though not all) people show a slight leftward bias in tasks that require perceptual comparisons of line length, numerosity, and luminance. Here we used a gratingscales task at different levels of pixel noise and event-related potentials to study biases in spatial frequency judgments. We found that leftward bias increased as contrast decreased with increasing pixel noise and that participants with reduced task sensitivity showed a stronger bias than sensitive participants. Also, task sensitivity was correlated with a more pronounced stimulus contrast-related negativity at posterior electrodes 100 ms after stimulus onset, and we observed a task-related component at about 200–300 ms that was modulated by sensitivity as well as contrast. While our data are consistent with a cognitive, possibly attentional account of perceptual bias, future research is required to unravel the complex interactions between attentional and ‘preattentional’ mechanisms of the right hemisphere.
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