title: Correlation of vision loss with tactile-evoked V1 responses in retinitis pigmentosa.
abstract: Neuroimaging studies have shown that the visual cortex of visually impaired humans is active during tactile tasks. We sought to determine if this cross-modal activation in the primary visual cortex is correlated with vision loss in individuals with retinitis pigmentosa (RP), an inherited degenerative photoreceptor disease that progressively diminishes vision later in life. RP and sighted subjects completed three tactile tasks: a symmetry discrimination task, a Braille-dot counting task, and a sandpaper roughness discrimination task. We measured tactile-evoked blood oxygenation level dependent (BOLD) responses using functional magnetic resonance imaging (fMRI). For each subject, we quantified the cortical extent of the tactile-evoked response by the proportion of modulated voxels within the primary visual cortex (V1) and its strength by the mean absolute modulation amplitude of the modulated voxels. We characterized vision loss in terms of visual acuity and the areal proportion of V1 that corresponds to the preserved visual field. Visual acuity and proportion of the preserved visual field both had a highly significant effect on the cortical extent of the V1 BOLD response to tactile stimulation, while visual acuity also had a significant effect on the strength of the V1 response. These effects of vision loss on cross-modal responses were reliable despite high inter-subject variability. Controlling for task-evoked responses in the primary somatosensory cortex (S1) across subjects further strengthened the effects of vision loss on cross-model responses in V1. We propose that such cross-modal responses in V1 and other visual areas may be used as a cortically localized biomarker to account for individual differences in visual performance following sight recovery treatments.
authors.affiliation: Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90089, USA. Electronic address: samicunn@gmail.com.
authors.forename: Samantha I
authors.initials: SI
authors.lastname: Cunningham
authors.affiliation: Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90089, USA. Electronic address: jweiland@med.usc.edu.
authors.forename: James D
authors.initials: JD
authors.lastname: Weiland
authors.affiliation: Neuroscience Graduate Program, University of Southern California, Los Angeles, CA 90089, USA. Electronic address: plbao.usc@gmail.com.
authors.forename: Pinglei
authors.initials: P
authors.lastname: Bao
authors.affiliation: Department of Ophthalmology, University of Southern California, Los Angeles, CA 90089, USA. Electronic address: rlopezjaime@yahoo.com.mx.
authors.forename: Gilberto Raul
authors.initials: GR
authors.lastname: Lopez-Jaime
authors.affiliation: Neuroscience Graduate Program, University of Southern California, Los Angeles, CA 90089, USA; Department of Psychology, University of Southern California, Los Angeles, CA 90089, USA. Electronic address: btjan@usc.edu.
authors.forename: Bosco S
authors.initials: BS
authors.lastname: Tjan
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D001766:Blindness / Q000209:etiology / Q000503:physiopathology*; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009473:Neuronal Plasticity / Q000502:physiology; D012174:Retinitis Pigmentosa / Q000150:complications / Q000503:physiopathology*; D013003:Somatosensory Cortex / Q000502:physiology; D055698:Touch Perception / Q000502:physiology*; D014792:Visual Acuity / Q000502:physiology; D014793:Visual Cortex / Q000502:physiology*; D014794:Visual Fields / Q000502:physiology; D055815:Young Adult
keywords: Cross-modal plasticity; Primary somatosensory cortex; Primary visual cortex; Retinitis pigmentosa; Tactile-evoked response; fMRI