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Edgar DeYoe, Jed Mathis, John Ulmer, Wade Mueller; Resting State Functional-Connectivity Mapping of Putative Visual Cortex in a Blind Patient. Journal of Vision 2012;12(9):1304. doi: 10.1167/12.9.1304.
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© ARVO (1962-2015); The Authors (2016-present)
fMRI signals in visual cortex of human subjects instructed to lie quietly with eyes open (or closed) contain spontaneous, low frequency, fluctuations that are temporally correlated within and across visual areas. Clinically, such functional connectivity MRI (fcMRI) could be particularly advantageous for pre-surgical mapping of viable cortex near a tumor site especially if conventional stimulus-driven mapping cannot be used. Here we report a unique case study of a 26 y/o female who suffered from a large intraventricular mass causing acquired functional blindness but with a preserved fcMRI map of visual cortex. Initially, the patient underwent conventional BOLD fMRI on a 3 Tesla MRI scanner with eyes open and directed toward a back-projection screen displaying a flashing, black and white checkerboard extending from the center of gaze to approximately 20 degrees eccentricity, alternating every 20 sec. with a uniform gray field. The patient could not fixate but was able to look in the direction of the screen so that at least the central portion of the retina was consistently exposed to the stimulus. Nevertheless, visually responsive voxels in the brain were absent. For fcMRI, the patient lay quietly with eyes open but directed toward the uniform gray screen which was on continuously during the 5 min scan. Independent component analysis using MELODIC (FSL) software revealed 3 components containing activation confined to portions of occipito-parietal cortex that, in healthy individuals, are associated with striate and extrastriate visual areas. Overall, the patient’s fcMRI patterns matched those of a healthy control imaged and analyzed in an identical manner and those of a cohort of 1414 individuals reported by Biswal et al., 2010 (IC’s 01-03). This case demonstrates that fcMRI patterns can remain at least qualitatively intact in the presence of pathology sufficient to block visually driven cortical activity and to cause functional blindness.
Meeting abstract presented at VSS 2012
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