Consciousness of the first order in blindsight

<p>At suprathreshold levels, detection and awareness of visual stimuliare typically synonymous in nonclinical populations. But followingpostgeniculate lesions, some patients may perform above chancein forced-choice detection paradigms, while reporting not to seethe visual events presented within their blind field. This phenomenon,termed “blindsight,” is intriguing because it demonstratesa dissociation between detection and perception. It is possible,however, for a blindsight patient to have some “feeling” of theoccurrence of an event without seeing per se. This is termed blindsighttype II to distinguish it from the type I, defined as discriminationcapability in the total absence of any acknowledgedawareness. Here we report on a well-studied patient, D.B., whoseblindsight capabilities have been previously documented. We havefound that D.B. is capable of detecting visual patterns defined bychanges in luminance (first-order gratings) and those definedby contrast modulation of textured patterns (textured gratings;second-order stimuli) while being aware of the former but reportingno awareness of the latter. We have systematically investigatedthe parameters that could lead to visual awareness of thepatterns and show that mechanisms underlying the subjective reportsof visual awareness rely primarily on low spatial frequency,first-order spatial components of the image.</p>