Blind persons may acquire their visual perception indirectly by sensory substitution devices such as the experimental BrainPort® vision device, in which an image from a video camera is converted to an electro-tactile display on the tongue. Recent evidence suggests that the visual cortex is activated in blind subjects during cross-modal interactions.
However, the underlying mechanisms of sensory substitution for visual perception in the brain remain largely undetermined. This hampers the development of effective rehabilitation protocols for vision restoration to individual patients.
Recently, researchers from the clinical faculty in the Sensory Substitution Lab, Department of Ophthalmology and UPMC Eye Center (Dr. Amy Nau and Dr. Joel S. Schuman), and the scientific faculty in the Neuroimaging Laboratory and the McGowan Institute for Regenerative Medicine (Dr. Kevin C. Chan and Dr. Seong-Gi Kim) at the University of Pittsburgh have launched a multidisciplinary project to identify the structural and functional connections that underlie the process of sensory substitution using advanced, non-invasive magnetic resonance imaging (MRI) techniques with the BrainPort.
Investigations at the UPMC Eye Center’s Sensory Substitution Lab, headed by Dr. Amy Nau, have shown that BrainPort enables perception of the immediate environment. Preliminary neuroimaging data also demonstrate significant differences in the brain architecture between early blind versus acquired blind or control subjects.
In addition, even in adults, there is increased activation of the deprived visual cortex when using the BrainPort® as a function of duration of blindness. This indicates that the brain is able to adapt to changing conditions beyond the traditional “critical period”. These findings may lead to new insights into the basic and clinical science of vision restoration.
Specifically, given that the deprived cortex appears to become less organized with duration of blindness, questions arise as to whether there is the timing of the use of sensory substitution becomes important. In addition, whether specific training protocols might enhance certain aspects of cross modal plasticity is unknown.
Sensory substitution devices such as the BrainPort®, combined with structural and functional magnetic resonance imaging studies, provide an ideal model system to non-invasively study the responses of the deprived visual cortex. This model may provide a direct method for predicting brain reorganization in individual subjects.
It may also lay a foundation for the neurophysiological bases of sensory substitution and improving rehabilitation protocols. The researchers believe that the collaborative project will be important for devising strategies to maximize the potentials for visual perception therapies to the blind.