Affiliations: [a] Department of Psychiatry, Faculty of Medicine Universidad Complutense, Madrid, Spain
| [b] Department of Radiology, Gordon Center for Medical Imaging, Massachusetts General Hospital Harvard University, Boston, USA
| [c] Department of Biostatistics, Faculty of Medicine Universidad Complutense, Madrid, Spain
| [d] Department of Ear, Nose and Throat, Hospital Clínico Universitario San Carlos, Madrid, Spain
| [e] Department of Psychiatry and Neurology, Institute of Neuroscience, University of Texas Rio Grande Valley School of Medicine, Harlingen, USA
Correspondence:
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Corresponding author: Prof. Dr. Gabriel A. de Erausquin. Department of Psychiatry and Neurology. UTRGV School of Medicine. 2102 Treasure Hills Blvd. Harlingen, TX 78552, USA. E-mail: [email protected].
Abstract: Background:We previously demonstrated that using a sensory substitution device (SSD) for one week, tactile stimulation results in faster activation of lateral occipital complex in blind children than in seeing controls. Objective:We used long-term haptic tactile stimulation training with an SSD to test if it results in stable cross-modal reassignment of visual pathways after six months, to provide high level processing of tactile semantic content. Methods:We enrolled 12 blind and 12 sighted children. The SSD transforms images to a stimulation matrix in contact with the dominant hand. Subjects underwent twice-daily training sessions, 5 days/week for six months. Children were asked to describe line orientation, name letters, and read words. ERP sessions were performed at baseline and 6 months to analyze the N400 ERP component and reaction times (RT). N400 sources were estimated with Low Resolution Electromagnetic Tomography (LORETA). SPM8 was used to make population-level inferences. Results:We found no group differences in RTs, accuracy of identifications, N400 latencies or distributions with the line task at 1 week or at 6 months. RTs on the letter recognition task were also similar. After 6 months, behavioral training increased accurate letter identification in both seeing and blind children (Chi 2 = 11906.934, p = 0.000), but the increase was larger in blind children (Chi 2 = 8.272, p = 0.004). Behavioral training shifted peak N400 amplitude to left occipital and bilateral parietal cortices in blind children, but to left precentral and postcentral and bilateral occipital cortices in sighted controls. Conclusions:Blind children learn to recognize SSD-delivered letters better than seeing controls and had greater N400 amplitude in the occipital region. To the best of our knowledge, our results provide the first published example of standard letter recognition (not Braille) by children with blindness using a tactile delivery system.
