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Case Reports
. 2015 Mar 15;113(6):1727-42.
doi: 10.1152/jn.00420.2014. Epub 2014 Dec 17.

Tracking the Evolution of Crossmodal Plasticity and Visual Functions Before and After Sight Restoration

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Free PMC article
Case Reports

Tracking the Evolution of Crossmodal Plasticity and Visual Functions Before and After Sight Restoration

Giulia Dormal et al. J Neurophysiol. .
Free PMC article

Abstract

Visual deprivation leads to massive reorganization in both the structure and function of the occipital cortex, raising crucial challenges for sight restoration. We tracked the behavioral, structural, and neurofunctional changes occurring in an early and severely visually impaired patient before and 1.5 and 7 mo after sight restoration with magnetic resonance imaging. Robust presurgical auditory responses were found in occipital cortex despite residual preoperative vision. In primary visual cortex, crossmodal auditory responses overlapped with visual responses and remained elevated even 7 mo after surgery. However, these crossmodal responses decreased in extrastriate occipital regions after surgery, together with improved behavioral vision and with increases in both gray matter density and neural activation in low-level visual regions. Selective responses in high-level visual regions involved in motion and face processing were observable even before surgery and did not evolve after surgery. Taken together, these findings demonstrate that structural and functional reorganization of occipital regions are present in an individual with a long-standing history of severe visual impairment and that such reorganizations can be partially reversed by visual restoration in adulthood.

Keywords: blindness; crossmodal plasticity; sight recovery; ventral-dorsal pathways.

Figures

Fig. 1.
Fig. 1.
Behavioral performance in KL (at Pre, Post 1.5m, and Post 7m) and in sighted control subjects (SC). A: distance visual acuity measures expressed in Snellen decimal acuity obtained in the Landolt-C paradigm for binocular (OU) and right (operated) eye (OD). B: contrast sensitivity function (CSF). C: % coherence thresholds for radial and vertical global motion detection. D–F: % accuracy and ln-transformed correct response times (RTs) in the face categorization task (D) and the front-to-front (E) and front-to-profile (F) face individuation tasks, separately for upright and inverted faces. Bars represent SE from the mean.
Fig. 2.
Fig. 2.
Voxel-based morphometry (VBM) analyses and results. A and B: VBM analyses in KL. The smoothed gray matter tissue probability map (GM TPM) obtained at Pre was subtracted from the smoothed GM TPM obtained at Post 1.5m (A) and at Post 7m (B). Thresholds for significant differences were established based on the mean and SDs of the distribution of positive and negative differences observed in the differential image obtained in A and B. C: only voxels showing common between-session differences above or below 3 SDs from the mean of the distribution in A and B are reported, by overlapping the thresholded differential image on KL's native anatomical image.
Fig. 3.
Fig. 3.
fMRI activation maps of visual motion processing. A: between-session conjunction analysis highlighting regions showing consistent motion-specific responses [Motion > Static] across the 3 sessions in KL and associated beta parameter estimates in bilateral MT+/V5. B: brain regions showing larger motion-specific visual responses [Motion > Static] at Post 7m relative to Pre and associated beta parameter estimates. Results are displayed at a threshold of P < 0.05 familywise error (FWE) corrected over the whole brain on a 3D render of the brain and on transverse and sagittal slices of KL's structural image normalized to MNI space.
Fig. 4.
Fig. 4.
fMRI activation maps of face processing: brain regions responding more to Faces relative to both Cars and Scrambled Faces (ScrF) in all sessions in KL and associated beta parameter estimates. Results are displayed at a threshold of P < 0.001 uncorrected on a 3D render of the brain and on transverse slices of KL's structural image normalized to the Montreal Neurological Institute (MNI) space. ScrC, Scrambled Cars; OFA, occipital face area; FFA, fusiform face area.
Fig. 5.
Fig. 5.
fMRI activation maps of auditory processing. A and B: between-session conjunction analysis highlighting brain regions that are consistently activated during auditory stimulation across the 3 sessions in KL in auditory experiment 1 ([Motion + Voice Pre ∩ Post 1.5m ∩ Post 7m], A) and auditory experiment 2 ([Spatial + Pitch Pre ∩ Post 1.5m ∩ Post 7m], B). Corresponding t values are plotted along the calcarine sulcus from the most rostral pole (−60 in the y-axis) to the most caudal pole (−96 along the y-axis) for each session separately (Pre, Post 1.5m, and Post 7m) in gray and for the average of all sessions in black. C: beta parameter estimates are plotted for the main effect of sounds in an anatomical mask encompassing the pericalcarine region (primary visual cortex) in auditory experiment 1 for KL (at Pre, Post 1.5m, and Post 7m) and sighted control subjects (SC) and in auditory experiment 2 for KL (at Pre, Post 1.5m, and Post 7m), early blind (EB), late blind (LB), and sighted control (SC) subjects. Bars represent SE from the mean. D and E: brain regions showing larger recruitment during auditory stimulation at Pre relative to Post 7m in KL and associated beta parameter estimates in auditory experiment 1 ([Motion + Voice × Pre > Post 7m], D) and auditory experiment 2 ([Spatial + Pitch × Pre > Post 7m], E). Results are displayed at a threshold of P < 0.05 FWE corrected over the whole brain on sagittal, coronal, and transverse slices of KL's structural image normalized to MNI space.
Fig. 6.
Fig. 6.
Overlap between auditory and visual responses in KL's primary visual cortex in all sessions. Shown in blue is the between-session conjunction of the main effect of auditory conditions in auditory experiment 2 ([Spatial + Pitch Pre ∩ Post 1.5m ∩ Post 7m]). Shown in red is the between-session conjunction of the main effect of visual conditions in the Motion localizer ([Motion + Static Pre ∩ Post 1.5m ∩ Post 7m]). Shown in white is the overlap. Results are displayed at a threshold of P < 0.05 FWE corrected over the whole brain on sagittal and transverse slices of KL's structural image normalized to MNI space.
Fig. 7.
Fig. 7.
fMRI activation maps in control subjects. A and B: brain regions responding more to moving relative to stationary dots (A) and Faces relative to both Cars and Scrambled Faces (B) are shown in a representative subject from the sighted control group (right-handed woman, 32 yr old) and in KL before surgery. C: brain regions responding during global sound processing in auditory experiment 1 ([Motion + Voice]) are shown in a representative subject from the sighted control group (right-handed woman, 32 yr old) and KL before surgery. D: brain regions responding during global sound processing in auditory experiment 2 ([Spatial + Pitch]) are shown in a representative subject from the sighted control group (right-handed woman, 48 yr old), a representative subject from the early-blind group (right-handed woman, 56 yr old), a representative subject from the late-blind group (right-handed woman, 46 yr old), and KL before surgery. Results are displayed at a threshold P < 0.05 corrected (FWE) over the whole brain in A, C, and D and at a threshold of P < 0.001 uncorrected in B on transverse slices of each subject's structural image normalized to MNI space.

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