The continuum of detection and awareness of visual stimuli within the blind field: from blindsight to the sighted-sight

Arash Sahraie*, Ceri T. Trevethan, Mary J. MacLeod, Lawrence Weiskrantz, Amelia R. Hunt

*Corresponding author for this work

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

Purpose. We investigated systematically the effect of repeated exposure on detection and reported awareness of visual stimuli presented deep within the field defect of 5 hemianopic patients.

Methods. An objective measure of sensitivity (detection in a temporal two-alternative forced-choice paradigm) and subjective reports of awareness were recorded on trial by trial bases. Visual stimulus to be detected was a temporally modulated (10 Hz) circular patch (6° diameter) of vertical grating (1 c/°). Hemianopic patients took part in the study 8 to 15 months after injury, so that the findings could not be attributed to spontaneous recovery.

Results. Initially, high contrast (90%) target stimuli were detected at or near chance level with little reported awareness. In 4 of 5 cases, repeated stimulation led to improved sensitivity, indicated by increased detection scores and higher incidence of awareness. In a fifth case, there was no change in sensitivity despite extensive exposure (>22,000 trials).
Conclusions. At retinal locations deep within the field defect, repeated stimulation can lead to blindsight performance (type I detection without awareness), followed by detection with reported awareness (type II blindsight), and eventual reported visual experiences. The findings indicate that conscious awareness of stimuli lies on a continuous spectrum and repeated systematic training can lead to improved visual sensitivity.
Original languageEnglish
Pages (from-to)3579-3585
Number of pages6
JournalInvestigative Ophthalmology & Visual Science
Volume54
Issue number5
Early online date30 Apr 2013
DOIs
Publication statusPublished - 24 May 2013

Keywords

  • blindsight
  • hemianopia
  • rehabilitation

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