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Proc Natl Acad Sci U S A. 2005 Nov 15;102(46):16875-9. Epub 2005 Nov 1.

Unconscious processing of orientation and color without primary visual cortex.

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  • 1Department of Psychology, Rice University, Houston, TX 77005-1892, USA.


In humans, the primary visual cortex (V1) is essential for 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. We used transcranial magnetic stimulation (TMS) to deactivate V1, producing transient blindness for visual targets presented in a foveal, TMS-induced scotoma. Despite 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 a functioning geniculoextrastriate visual pathway that bypasses V1 and can process orientation and color in the absence of conscious awareness.

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