Sensory Substitution Devices for Blind Rehabilitation and Studying Crossmodal Plasticity
The VOICe Sensory Substitution Device
Over 300 million people are visually impaired worldwide, 45 million of whom are entirely blind. The majority of blind people acquire blindness late in life, but congenital blindness, or blindness inflicted at or near birth, still affects 1 out every 3,300 children in developed countries. While specialized therapies, surgeries, and medication make most blindness preventable, often blindness cannot be significantly ameliorated after the neural damage is complete. Therefore, several types of electronic prosthetic devices are being designed that take over the function of the damaged neural circuitry by stimulating still-functional visual neurons. However, these devices are invasive (often-requiring eye or brain surgery) and are still in development. An alternative approach is sensory substitution, which encodes visual information into a signal perceived by another still-functional sensory modality. Sensory modalities such as somatosensation of the skin and tongue have been utilized to transmit visual information by the Forehead Retina System and the BrainPort, respectively. Audition has been used by the vOICe device, which scans a video image and encodes vertical position as distinct frequencies, horizontal position as scan time (left to right), and the brightness of individual pixels as volume.
Expert users of the vOICe device claim that through extensive device usage they can learn to interpret the auditory signal effortlessly, and can perceive objects visually in a way that mimics visual awareness. In addition, the visual cortices of these users have been shown to be activated during vOICe device use. We are exploring systematically the extent to which the vOICe device generates “functional” vision. We also hope to clarify if and to what extent crossmodal plasticity restores visual function with vOICe device usage. In particular, we are interested in determining the properties of the vOICe user’s perception (such as novel illusions, and perceptual constancies) and using fMRI and psychophysics to determine the role that the device encoding and crossmodal plasticity play in generating these properties.
Professor Shinsuke Shimojo and Noelle Stiles are working on this project.