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Anastasia Flevaris, Shlomo Bentin, Lynn Robertson; Attentional selection of relative SF mediates global versus local processing: EEG evidence. Journal of Vision 2011;11(11):228. doi: 10.1167/11.11.228.
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© ARVO (1962-2015); The Authors (2016-present)
Previous research on functional hemispheric differences in visual processing has revealed a right hemisphere (RH) bias in global perception and a left hemisphere bias (LH) in local perception. Several theories of global versus local perception have proposed spatial frequency (SF) processing to underlie the hemispheric asymmetry. The Double Filtering by Frequency (DFF) theory proposed that visual attention selects and is directed to relatively low SFs by the RH and relatively high SFs by the LH, suggesting a direct causal relationship between SF selection and global versus local perception. We recently reported evidence in support of a flexible mechanism, based on relative SF, to underlie hemispheric asymmetry in global versus local perception (Flevaris, Bentin & Robertson, in press). However, the behavioral priming effects in the previous studies may have been observed due to a bi-directional additive model, in which the RH is biased towards relative LSFs and global objects whereas the LH is biased towards relative HSFs and local objects, rather than the DFF theory proposal, which is that selection of SF induces global/local processing. In the present experiment we examined the direction of modulation of responses in the two cerebral hemispheres by comparing activity in the EEG recorded at RH and LH sites while participants' attention was directed to global or local levels of processing after selection of relatively LSFs versus HSFs in a previous stimulus. Hemispheric asymmetry in the alpha band (8–12 Hz) during preparation for global versus local processing was modulated by selected SF. In contrast, preparatory activity associated with selection of SF was not modulated by previously attended level (global/local). These results support the DFF theory that top-down attentional selection of SF mediates global and local processing and is not simply a bottom-up residual.
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