Simultanagnosia: A defect of sustained attention yields insights on visual information processing

Matthew Rizzo, Donald A. Robin

Research output: Contribution to journalArticlepeer-review

65 Scopus citations


Simultanagnosia, in which subjects report a piecemeal visual experience, offers an important probe of human attention. We studied 2 subjects with simultanagnosia following bilateral superior occipital strokes. Compared with controls, they could orient attention to spatial targets in visual, auditory, and mixed-modal conditions. A different task required immediate response to the appearance or disappearance at unpredictable intervals of any element in a random-dot CRT display. The subject tested could detect less than 50% of 1,600 events, and had increased “mirages” and prolonged reaction times. Undetected events occurred anywhere and formed temporal clusters. Application of signal-detection theory confirmed abnormal sensitivity and response bias (d' and beta). Yet performance improved when a valid cue introduced events in the random display. Our results suggest that simultanagnosia was related to an inability to sustain visuospatial attention across an array, corresponding to processing failure at a level of long-range (global) spatiotemporal interactions among converging inputs from early vision. The operations for orienting and sustaining attention may be dissociable at visual association cortex levels.

Original languageEnglish (US)
Pages (from-to)447-455
Number of pages9
Issue number3
StatePublished - Mar 1990
Externally publishedYes

ASJC Scopus subject areas

  • Clinical Neurology


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