Examining encoding imprecision in spatial working memory in schizophrenia.

Full Abstract

BACKGROUND: Visuospatial working memory is not a unitary sketch pad but comprises independent dimensions of target distance and direction and at least two levels of detail (fine-grained and category level). The aim of this study was to examine these multiple aspects of encoding in patients with schizophrenia using a modified delayed response task. METHOD: 42 patients with schizophrenia and 48 healthy controls pointed, as accurately as possible from a fixed starting position, to the visual location of target stimuli presented to a touch-sensitive screen. An adaptive staircase procedure was used to equate stimulus duration for each individual. Encoding accuracy and maintenance of distance (mm) and direction ( degrees ) information was examined following a 0-second (immediate) or 4-second (unfilled) delay. Analyses utilized both absolute (unsigned) and signed data. RESULTS: The results showed that the average duration required to detect a target was significantly longer in patients than controls. When stimulus duration was equated, (a) the absolute accuracy of distance and direction responses was not significantly different between groups at 0-second delay but was significantly reduced at 4-second delay in patients with schizophrenia, and (b) signed direction errors at 4-second delay were significantly different between groups at stimulus angles greater than 90 degrees . CONCLUSIONS: The findings challenge previous suggestions of deficits in fine-grained encoding of spatial information in schizophrenia but confirm a difficulty maintaining both direction and distance details in working memory. Imprecision in spatial memory in schizophrenia also introduced greater bias from category level (prior) representations, especially in left hemi-space.

Author information

Author/s: Badcock, Johanna C (JC); Badcock, David R (DR); Read, Christina (C); Jablensky, Assen (A);

Affiliation: Centre for Clinical Research in Neuropsychiatry/Graylands Hospital and School of Psychiatry and Clinical Neurosciences, University of Western Australia, John XXIII Avenue, Mt. Claremont, WA, 6010, Australia. jobad(-atsign-)cyllene.uwa.edu.au

Journal and publication information

Publication Type: Comparative Study; Journal Article; Research Support, Non-U.S. Gov't

Journal: Schizophrenia research (Schizophr Res), published in Netherlands. (Language: eng)

Reference: 2008-Mar; vol 100 (issue 1-3) : pp 144-52

Dates: Created 2008/03/10; Completed 2008/08/01;

PMID: 17804202, status: MEDLINE (last retrieval date: 2/18/2009, IMS Date: )

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