Unilateral neglect: the fate of the extinguished visual stimuli

: Recent neuropsychological literature has provided evidence for the phenomenon of perception without awareness, also referred to as covert (or implicit) knowledge or tacit awareness. Yet little is known to date about the fate of extinguished stimuli in patients with unilateral spatial neglect. Six right brain-damaged patients with USN and one control subject were presented with single lateralized visual stimuli and with pairs of same or different visual stimuli (one right, one left). A same/different judgement and a multiple choice recognition task were performed on overtly unidentified left-sided stimuli, to unveil possible phenomena of covert knowledge. Some evidence of covert knowledge was observed, and its relation to stimulus characteristics and task demands is discussed.