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Lixia He, Zhentao Zuo, Lin Chen; Supramodal number-selective representation in human left parietal lobe at 7T. Journal of Vision 2013;13(9):883. doi: https://doi.org/10.1167/13.9.883.
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© ARVO (1962-2015); The Authors (2016-present)
The ability to apprehend the number of elements in a set is shared by humans (including infants) and other primates. This ability seems to be represented by specialist groups of neurons in bilateral IPS in both humans and monkeys. What remains controversial is whether these regions serve a unitary neuronal basis for all forms of numerical representations, i.e., independent of the sensory modality (e.g. visual and auditory numbers) present. To examine whether numbers are represented independently from different sensory modalities, we use fMRI adaptation paradigm and present the first ever study of cross-modal number processing where the brain is imaged at 7T to generate both higher resolution, higher signal-to-noise ratios and higher BOLD contrast sensitivity. The evidence we present indicates there are both common and distinct neural responses to visual and auditory numbers, depending on the hemisphere of human parietal lobes. Number-selective neurons represent numbers from visual and auditory modalities in a supramodal manner in the left IPS, while those neurons in the right IPS are more modality specific. Moreover, there exists an asymmetry in these supramodal responses for the order of the two consecutive crossmodal numbers present within a trial. A strong adaptation effect was observed for an auditory number following a visual number, but not vice versa. Further behavioral experiment using priming paradigm, with visual stimuli prior to auditory targets or auditory stimuli prior to visual targets, shows similar asymmetry as observed in fMRI studies. We infer that the asymmetry might be due to a dominant representation of visual numbers over that of auditory numbers.
Meeting abstract presented at VSS 2013
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