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Janine D. Mendola, Ian P. Conner; Does eye dominance predict fMRI signals in retinotopic cortex?. Journal of Vision 2005;5(8):284. doi: https://doi.org/10.1167/5.8.284.
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In studies of human amblyopia with fMRI techniques, we have considered the relationship between psychophysical measures of eye dominance and measured BOLD signals. To obtain comparable control data, eye dominance should be defined in normal subjects. There have been attempts to define eye dominance in normal subjects, although limited consensus exists. In this study, we consider two different definitions of eye dominance: one based on cognitive sighting preference, and the other based on superior resolution acuity. Sighting eye dominance was assessed with two standard tests, the Porta Test, and a ‘hole in hand’ variation of the Miles Test. We tested visual acuity with a Snellen eye chart as well as a computerized test of grating acuity, with greater expected sensitivity and selectivity. We found little correspondence between the dominance assignments made on the basis of sighting versus acuity. We next compared the fMRI signal magnitude generated by the dominant eye to that generated by non-dominant eye stimulation, according to either of the criteria, in 7 control subjects. Experiment 1 used a high contrast achromatic hemifield stimulus alternating with no stimulus in a blocked paradigm. Experiment 2 employed chromatic phase-encoded eccentricity and polar angle stimuli. The results from Experiment 2 provided a field-sign map for each subject that was used to define regions of interest (ROIs) corresponding to six visual areas (V1, V2, V3, VP, V4, V3A). We found that fMRI signals were significantly stronger in the dominant eye according to the acuity criterion. This consistent dominance effect was apparent for all retinotopic areas, especially those located in the ventral occipital territory (V1v, V2v, VP, V4). In contrast, using the cognitive criterion produced no significant interocular fMRI differences. We conclude that interocular BOLD differences in normal subjects are substantial, and may be predicted by acuity measures.
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