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Hemispheric processing of spatial frequencies in two commissurotomy patients
1Department of Psychiatry, Dartmouth Medical College, Hanover, NH 03756.
Neuropsychologia
|January 1, 1990
Summary
This study investigated brain hemisphere specialization for spatial frequencies. Findings suggest that neither the left nor right brain hemisphere is specialized for processing high or low spatial frequencies, respectively.
Area of Science:
- Neuroscience
- Visual Perception
- Cognitive Psychology
Background:
- Theories propose hemispheric specialization in visual processing.
- Specifically, the left hemisphere may process high spatial frequencies, and the right, low spatial frequencies.
Purpose of the Study:
- To test the hypothesis of left hemisphere specialization for high spatial frequencies and right hemisphere specialization for low spatial frequencies in humans.
- To examine visual processing in commissurotomy patients and normal controls.
Main Methods:
- Presented pairs of sinusoidal gratings with varying spatial frequencies (1-8 cycles/degree) and orientations.
- Stimuli were shown in the left and right visual fields (LVF/RVF) for 167 msec.
- Two commissurotomy patients and twelve normal controls reported orientation differences.
Main Results:
- No evidence supported a high-frequency advantage in the right visual field (RVF) or low-frequency advantage in the left visual field (LVF).
- One patient showed a trend in the opposite direction; the other performed better with LVF stimuli across all frequencies.
- Normal controls did not exhibit a spatial frequency by visual field interaction.
Conclusions:
- Hemispheres do not appear specialized for specific spatial frequency ranges at the processing levels tested.
- The findings challenge existing hypotheses regarding hemispheric specialization for spatial frequency processing.