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Eye-movement patterns do not mediate size distortion effects in hemispatial neglect: looking without seeing
Monika Harvey1, Iain D Gilchrist, Bettina Olk
1Department of Psychology, University of Glasgow, Glasgow G12 8QB, Scotland, UK. m.harvey@psy.gla.ac.uk
Neuropsychologia
|April 2, 2003
Summary
Patients with hemispatial neglect may underestimate object size in their contralesional space. This study suggests this size distortion stems from representational failures, not hemianopia or eye movement issues.
Area of Science:
- Neuroscience
- Cognitive Psychology
- Clinical Neurology
Background:
- Studies indicate patients with hemispatial neglect may underestimate contralesional object size.
- Previous research suggested this effect might be due to hemianopia or a combination of neglect and hemianopia.
Purpose of the Study:
- To investigate the underlying mechanisms of size underestimation in hemispatial neglect.
- To differentiate between representational deficits, visual field impairments (hemianopia), and oculomotor control.
Main Methods:
- Right hemisphere lesioned patients (with and without neglect/hemianopia) and controls judged line sizes.
- Simultaneous presentation of horizontal or vertical lines in right and left hemispace.
- Oculomotor activity was monitored using eye movement tracking.
Main Results:
- Three of six patients exhibited size distortion for horizontal lines, underestimating left-sided objects.
- No evidence indicated eye movements mediated the size distortion effect.
- Hemianopia did not show a strong link to the observed size underestimation.
Conclusions:
- The findings suggest the size distortion effect in hemispatial neglect is not explained by hemianopia or eye movements.
- A representational or computational failure in processing horizontal extent is proposed as the cause.