Recruitment of Visual Cortex for Sound Encoded Object Identification in the Blind

 Lotfi B. Merabet ¹, Lorella Battelli ¹, Souzana Obretenova ¹, Sara Maguire ¹, Peter Meijer ² and Alvaro Pascual-Leone ¹.

¹ Berenson-Allen Center for Noninvasive Brain Stimulation, Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Ave, Boston, Massachusetts 02115, USA.
² NXP Semiconductors, High Tech Campus 32, 5656 AE Eindhoven, The Netherlands.

Bar graph reporting the percent of correct responses as a function of site of stimulation (occipital cortex or vertex). Baseline (black bars) and post-rTMS performance (white bars) are reported. “*” = p<0.05 and “n.s.”= not significant.

Abstract

Individuals using a visual-to-auditory sensory substitution device (SSD) called "The vOICe" can identify objects in their environment through images encoded by sound. We have shown that identifying objects with this SSD is associated with activation of occipital visual areas. Here, we show that repetitive transcranial magnetic stimulation (rTMS) delivered to a specific area of occipital cortex (identified by functional MRI) profoundly impairs a blind user's ability to identify objects. rTMS delivered to the same site had no effect on a visual imagery task. The task and site-specific disruptive effect of rTMS in this individual suggests that the cross-modal recruitment of occipital visual areas is functional in nature and critical to the patient's ability to process and decode the image sounds using this SSD.