Nature 377, 336 - 338 (28 September 1995); doi:10.1038/377336a0

Blindsight in normal observers

F. Christopher Kolb & Jochen Braun

Computation and Neural Systems 139-74, California Institute of Technology, Pasadena, California 91125, USA

SOME patients with lesions in visual cortex lack conscious visual experience but, when tested, exhibit a significant ability, termed 'blindsight', to discriminate visual stimuli^1–3,27. Here we report two different visual displays that induce blindsight in normal observers. Using an objective measure, we show that conscious experience remains defective at presentation times much longer (1 s) than the onset of visual sensitivity (~60 ms). To obtain this effect, we generate a contrast between visual textures and then conceal the contrast by superimposing 'complementary' textures. Complementarity can involve either opposite motion or binocular rivalry and orthogonal orientation. In both cases, observers locate the texture contrast reliably but do not, by either subjective or objective measures, consciously experience it. Taken together with present knowledge of the visual cortical site(s) at which opposite motion and rivalrous orientation interact^4–7, this observation bears upon the functional anatomy of conscious visual experience.

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