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Maro Machizawa, Crystal Goh, Jon Driver, Masud Husain; Hemispheric differences in visual working memory maintenance indexed by contralateral delay activity. Journal of Vision 2012;12(9):180. doi: 10.1167/12.9.180.
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© ARVO (1962-2015); The Authors (2016-present)
Investigations on patients with hemi-neglect or individuals with virtual lesions using transcranial magnetic stimulation (TMS) have suggested there might be hemispheric biases in visual processing, with possible right hemispheric dominance in visual attention and aspects of working memory. EEG studies of visual working memory in humans have until now treated both hemispheres equally, with the majority of the studies collapsing data across left- and right-attended conditions. Here, we examined whether a neural correlate of visual short-term memory maintenance, contralateral delay activity (CDA), reflects any hemispheric differences as a function of attended hemifield. We tested participants on visual working memory tasks. For each trial a brief sample display presented bilaterally either two or four items in each hemifield. One hemifield was made task-relevant by precuing for retention over 1,500ms. Color of samples (either red or green) indicated expected difficulty of probe (fine or coarse). The results revealed significant differences, with left-attend CDA activity maintained over time while right-attend activity decayed over the delay period. In addition, CDA amplitudes across all conditions within one hemifield correlated significantly with each other, while amplitudes between different hemifields did not. This was further confirmed by a principal component analysis on CDA amplitudes in all conditions that extracted two principal components: the first component loaded only with left-attend conditions while the second loaded only with all right-attended conditions. Voxel-based morphometry analysis (VBM) revealed significant associations between regions in posterior parietal and lateral occipital cortex and sustainability of the CDA component. These results suggest there are significant differences in CDA for left and right visual stimuli maintained in visual working memory, suggesting the nature of the CDA signal might be more complex than previously supposed.
Meeting abstract presented at VSS 2012
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