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Giacinto Triolo, Sofia Crespi, Maria Concetta Morrone, Pier Girogio Gobbi, Andrea Falini, Francesco Bandello, Stefania Bianchi Marzoli; Multisensory Cortical Integration in patients with Hereditary Cone Dystrophy: An fMRI And DTI Study. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2983.
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To use functional Magnetic Resonance Imaging (fMRI) and diffusion tensor imaging (DTI) to: a) evaluate eteromodal versus unimodal recruitment of primary visual (V1) and auditory (A1) cortex in normal subjects; b) evaluate audio-visual integration in the portion of V1 corresponding to the visual field affected area in patients with hereditary cone dystrophy (HCD); c) quantify the integrity of optic radiations and connections between V1 and A1 in HCD patients.
Using a 3.0 Tesla scanner fMRI and DTI were acquired from 3 adults affected by HCD and 3 age-sex matched controls. Two paradigms of audio-visual stimulation were designed for fMRI acquisitions: 1) alternating monocular full visual field optic flow or auditory motion stimulation against a grey background and during blind folding; 2) visual and simultaneous audio-visual stimulation limited to central 10° of visual field. All subjects underwent complete neuro-ophthalmological examination, including standardized automated perimetry and fundus-related perimetry to test fixation stability and define the degrees of central scotoma in HCD patients. Brain Voyager QX 2.0 software was used for fMRI analysis and DTI studio 2.4.01 for DTI analysis.
fMRI data analysis showed a) statistically significant V1 cortical activation due to auditory stimulus in normal subjects also during blind foldin; b) V1 activations evoked by simultaneous audio-visual stimuli in HCD patients, but only in the portion of V1 unresponsive to visual stimulus. DTI analysis showed that mean Fractional Anisotropy was a) statistically significant higher in the inferior longitudinal fasciculus (ILF) connecting A1 with V1 in patients compared to controls; b) not statistically different in optic radiations between the two groups.
Our data suggest an eteromodal tuning of primary visual cortex in normal subjects and a multisensory audio-visual integration, through the ILF, in blind V1 of HCD patients, possibly due to cortical reorganization.
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