Visuospatial encoding deficits and compensatory strategies in schizophrenia revealed by eye movement analysis during a working memory task.
OBJECTIVE
To investigate scanpath abnormalities during the encoding of static stimuli in schizophrenia and their interaction with visuospatial working memory (VSWM) dysfunction.


METHODS
Outpatients with schizophrenia and control subjects were asked to encode a static pattern for subsequent recognition after a short delay. We measured the number of correct and incorrect choices. We also assessed the number and the distribution of fixations, the scanning time in specific regions of interest (ROIs) and the head movements during the encoding of the stimuli. The distributions of fixations and scanning time in definite ROIs during the discrimination of the correct pattern from the foils were also measured.


RESULTS
Patients recognised fewer correct patterns than controls. Correct trials in patients were characterised by a specific exploration of the central part of the stimulus during its presentation, whereas this feature was absent in incorrect trials. However, the scanning time and the numbers of fixations and head movements during encoding were similar in both groups and unrelated to recognition accuracy. In both groups, correct trials were associated with a selective exploration of the correct pattern amongst the six possibilities during recognition. Furthermore, patients gave more attention to incorrect patterns with a leftmost element identical to that of the correct response and also those approximating its global structure.


CONCLUSIONS
Patients showed a VSWM deficit independent of oculomotor dysfunctions and head movements during encoding. Patients' correct trials were related to specific scanning during encoding and discrimination phases. Analysis of these patterns suggests that patients try to compensate for reduced VSWM ability by using specific encoding strategies.
1Melbourne Neuropsychiatry Centre, University of Melbourne, c/o National Neuroscience Facility, Melbourne, Australia.
Luca
L
Cocchi
2Institute of Psychology, University of Lausanne, Switzerland.
Francesca
F
Bosisio
5Institute of Applied Mathematics (IMA), University of Lausanne, Switzerland.
André
A
Berchtold
6University Psychiatric Adult Department of Lausanne (DUPA), Centre Hospitalier Universitaire Vaudois and University of Lausanne, Lausanne, Switzerland.
Alina
A
Orita
7Service Médico-Pédagogique, University of Geneva School of Medicine, Geneva, Switzerland.
Martin
M
Debbané
1Melbourne Neuropsychiatry Centre, University of Melbourne, c/o National Neuroscience Facility, Melbourne, Australia.
Stephen J
SJ
Wood
2Institute of Psychology, University of Lausanne, Switzerland.
Françoise
F
Schenk