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. 2008 Aug 21;3(8):e3028.
doi: 10.1371/journal.pone.0003028.

Seeing without Seeing? Degraded Conscious Vision in a Blindsight Patient

Morten Overgaard  1 , Katrin Fehl, Kim Mouridsen, Bo Bergholt, Axel Cleeremans
Affiliations

Seeing without Seeing? Degraded Conscious Vision in a Blindsight Patient

Morten Overgaard et al. PLoS One. .

Abstract

Blindsight patients, whose primary visual cortex is lesioned, exhibit preserved ability to discriminate visual stimuli presented in their "blind" field, yet report no visual awareness hereof. Blindsight is generally studied in experimental investigations of single patients, as very few patients have been given this "diagnosis". In our single case study of patient GR, we ask whether blindsight is best described as unconscious vision, or rather as conscious, yet severely degraded vision. In experiment 1 and 2, we successfully replicate the typical findings of previous studies on blindsight. The third experiment, however, suggests that GR's ability to discriminate amongst visual stimuli does not reflect unconscious vision, but rather degraded, yet conscious vision. As our finding results from using a method for obtaining subjective reports that has not previously used in blindsight studies (but validated in studies of healthy subjects and other patients with brain injury), our results call for a reconsideration of blindsight, and, arguably also of many previous studies of unconscious perception in healthy subjects.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Experiment 1 reveals the size and location of GR's blind field.
This figure illustrates how the screen was divided into areas, where stimuli were presented. For each numbered area, 3 stimuli were presented in random order during the experiment. The colour code illustrates how many times she responded to stimuli flashed in the relevant part of the screen
Figure 2
Figure 2. A regression analysis illustrates the relationship between correctness and PAS.
The analysis reveals that the relationship between accuracy and awareness as assessed by PAS is the same in the intact and in the blind fields.
Figure 3
Figure 3. Probability of correctly identifying the stimulus given a “seen” vs. “unseen” report (Dichotomous Report) or given a “Clear Experience/Almost Clear Experience” vs. a “Weak Glimpse/Not seen” report (PAS report), plotted separately for the Intact and Blind fields".
See this image and copyright information in PMC

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