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Jacob Jolij, Victor A. F. Lamme; Tms induced affective blindsight reverts to affective blindness when stimulus visibility is increased. Journal of Vision 2005;5(8):368. doi: 10.1167/5.8.368.
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© ARVO (1962-2015); The Authors (2016-present)
Some patients with a lesion to primary visual cortex (V1) show the remarkable capability of guessing correctly about stimulus attributes presented to the blind hemifield, a phenomenon called ‘blindsight’. Recently, blindsight has been demonstrated for the emotional expression of unseen faces. Here, we show that affective blindsight can also be induced in normal observers, where stimuli are rendered invisible through transcranial magnetic stimulation (TMS) of the striate cortex. Surprisingly, however, access to the emotional content of TMS-suppressed stimuli disappears when overall stimulus visibility is increased. We explain this paradoxical finding by taking into account two processing routes for affective information: a fast, but crude subcortical route, and a slower, but more accurate cortical route. We assert that under normal viewing conditions, human subjects primarily rely on cortically processed information. Only when visibility is low, and uncertainty increases, subcortical information is used, revealing the affective blindsight capability. We are only ‘blindly led by emotions’ when all else fails.
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