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Maryse Lassonde, Danielle Bastien, Anne Gallagher, Julie Tremblay, Phetsamone Vannasing, Franco Lepore; Specific functional asymmetries of the human visual cortex revealed by functional Near-Infrared Spectroscopy. Journal of Vision 2011;11(11):1068. doi: https://doi.org/10.1167/11.11.1068.
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© ARVO (1962-2015); The Authors (2016-present)
Over the past decades, the animal and human visual systems have been widely studied. Based on multiple invasive reports and neuroimaging studies, it is now well established that the cytoarchitecture of the visual cortex is related to its functional organization, which is the called retinotopic organization of the visual cortex. The present study aims to investigate retinotopic mapping as well as specific vertical and horizontal functional asymmetries within the human visual cortex using functional near-infrared spectroscopy (fNIRS). Black and white wedge checkerboard stimuli were randomly presented to the four visual fields (VF) quadrants of eight healthy adults in order to quantify and compare the localization and the amplitude of hemodynamic visual cortex responses to each stimulated VF quadrant. As expected, results showed a stronger visual cortical activation in the controlateral hemisphere and in the inverse upper/lower quadrant to the stimulation. We also measured significant stronger activations in the upper visual cortex when lower hemifield stimuli were presented compared to activations in the lower visual cortex when upper hemifield stimuli were showed. This confirms the vertical asymmetry of the visual cortex previously reported by neuroimaging and behavioural studies. The present work constitutes the first study showing functional asymmetries in the visual cortex using fNIRS and confirms the reliability of this non-invasive technique for functional mapping of the human brain.
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