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Hemispheric asymmetry in categorical versus coordinate visuospatial processing revealed by temporary cortical
S D Slotnick1, L R Moo, M A Tesoro
1Department of Psychology, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA. slotnick@jhu.edu
Journal of Cognitive Neuroscience
|January 11, 2002
Summary
This study tested hemispheric specialization for visuospatial processing. Findings suggest the left hemisphere excels at categorical tasks and the right at coordinate tasks, but only when tasks are sufficiently difficult.
Area of Science:
- Cognitive Neuroscience
- Neuropsychology
- Visuospatial Processing
Background:
- Kosslyn's 1987 hypothesis proposed distinct visuospatial processing roles for the left and right cerebral hemispheres.
- The left hemisphere was hypothesized to excel at categorical visuospatial tasks, while the right was hypothesized to excel at coordinate visuospatial tasks.
Purpose of the Study:
- To directly test Kosslyn's hypothesis on hemispheric specialization for visuospatial processing.
- To investigate the influence of task difficulty on observed hemispheric asymmetries.
Main Methods:
- Utilized the intracarotid sodium amobarbital procedure (Wada test) in 134 patients to temporarily deactivate one cerebral hemisphere.
- Administered a cognitive test battery including categorical and coordinate visuospatial tasks following hemisphere deactivation.
- Assessed processing capabilities of the intact hemisphere by analyzing performance on visuospatial tasks.
Main Results:
- Results supported Kosslyn's hypothesis when visuospatial tasks were of sufficiently high difficulty.
- A left hemispheric advantage was observed for both categorical and coordinate tasks under low difficulty conditions.
- Hemispheric asymmetry in visuospatial processing appears to be task-difficulty dependent.
Conclusions:
- The proposed hemispheric specialization for categorical and coordinate visuospatial processing is evident under demanding task conditions.
- The left hemisphere may exhibit a general processing advantage for simpler tasks, irrespective of visuospatial category.
- Task difficulty is a critical factor that may explain inconsistent findings regarding hemispheric asymmetry in visuospatial research.