THE SOUND OF SCOTOMA: A multisensory integration approach for individuals with Macular Degeneration

Audio-spatial representation reorganizes in the absence of visual inputs, as in the case of blind individuals. However, it is not clear how this spatial reorganization works. Although blindness is an ideal condition to understand how other sensory modalities react in absence of vision, there are some limits in using it as a modal. The main limit is that blindness can be considered a stable model of cortical organization and it does not allow to understand the mechanisms which cause this reorganization. To understand this process, we have studied a unique group of individuals suffering from Macular Degeneration (MD) for whom loss of visual inputs due to a progressive scotoma is an ongoing process. In this dissertation I decided to focus on understanding auditory spatial representation in MD individuals and to develop technnological solutions for them incorporating multisensory integration. First, we developed a device called ARENA which is an audio-tactile matrix of speakers to study audio-spatial localization in MD individuals. Our findings show that visual loss brings an immediate change in the processing of audio-spatial percept by attracting the lateral sounds towards scotoma positions in the center, producing a strong auditory spatial perception bias. To recaliberate this audio-spatial bias and to give MD individuals an understanding of their own scotoma to develop an effective pseudo fovea, we have designed a rehabilitation protocol called Intelligent Audio Visual Thumble Training (IVATT). A multisensory feedback device Audio Visual Thumble (AVT) is developed for this training. Our findings show that this technique is effective to overcome the audio-spatial bias and can improve the precision towards visual stimuli in peripheral visual field. This work concludes that development of scotoma alters the audio-spatial representation and hence focus of rehabilitation techniques can be extended to bring-in multisensory modalities in order to utilize residual vision of MD individuals.