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Tony Ro, Stephenie Harrison, Jennifer Boyer, Kristen Greene; Unconscious orientation and color processing without primary visual cortex. Journal of Vision 2005;5(8):285. doi: 10.1167/5.8.285.
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In humans, the primary visual cortex (V1) is essential for subserving conscious vision. However, even without V1 and in the absence of awareness, some preserved ability to accurately respond to visual inputs has been demonstrated, a phenomenon referred to as blindsight. Here we used transcranial magnetic stimulation (TMS) to deactivate V1, producing transient blindness for visual targets presented in the foveal, TMS-induced scotoma. Despite complete unawareness of these targets, performance on forced choice discrimination tasks for orientation (Experiment 1) and color (Experiment 2) were both significantly above chance. In addition to demonstrating that TMS can be successfully used to induce blindsight within a normal population, these results suggest the existence of visual pathways that bypass V1 and can process orientation and color in the absence of awareness.
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