Abstract
Purpose :
Blindness induces cross-modal neuroplastic changes in the occipital cortex, however little is known about whether they persist after sight restoration. Here we report behavioural and neuroimaging results from visual, auditory, and tactile tasks from a patient who received osteo-odonto-keratoprosthesis (OOKP) sight-restoration surgery.
Methods :
The patient (F, 56y) had 20 years of poor vision/hearing and 1 year of blindness before receiving OOKP surgery. 9-months post-OOKP (Figure 1a), we assessed her ability to discriminate contrast (qCSF), colour (F-M test), motion (RDK), audiovisual integration (DFI), and tactile acuity (JVP Domes). Functional MRI was used to map brain activity using motion and ventral stream localisers (faces, places, tools, text), population receptive field analysis (pRF), as well as auditory and tactile stimulation. The patient’s perception was compared against control groups from prior studies, and neurological responses against a sighted-control matched for age, gender, and handedness.
Results :
While the patient reported high visual acuity (e.g. seeing “individual hair follicles”), qCSF results showed impaired contrast discrimination with a normal range of discriminable spatial frequencies, colour, motion and audiovisual integration (Table 1a). However, the patient had significantly superior tactile acuity to controls (p=.012). Functional MRI results showed expected visual responsivity, activating areas known to be sensitive to stimuli of faces, letters, objects, and motion (p<.001, uncorrected; not shown). Whole-brain pRF also showed a grossly intact retinotopic map in early visual areas (Figure 1b). The patient uniquely showed occipital activation to both auditory and tactile stimulation that extended to early visual regions (Table 1b).
Conclusions :
Despite good acuity, colour, and motion perception, contrast discrimination is uniquely impaired whereas tactile acuity remains superior after OOKP surgery. Whether the superior tactile acuity is a result of preserved cross-modal activity in the occipital cortex remains to be elucidated. Taken together, cross-modal multi-sensory neuroplastic changes resulting from blindness appear to persist alongside grossly preserved visual brain specialization and topology months after sight restoration.
This is a 2020 ARVO Annual Meeting abstract.