Non-visual factors modulating 'visual' cortex

Amir Amedi ^1,2, William Stern ², Lotfi Merabet ², Ella Striem ¹, Peter Meijer ³, and Alvaro Pascual-Leone ².

¹ Department of Physiology and Program of Cognitive Science, Hebrew University, Jerusalem, Israel.
² Berenson-Allen Center for Noninvasive Brain Stimulation, Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, USA.
³ NXP Semiconductors, Eindhoven, The Netherlands.

Introduction: Restoration of sight in a blind person imposes great clinical and scientific challenges. Despite intensive efforts, recovery of vision using neuroprostheses has not been achieved. A major reason for this failure might be that the brain in the blind undergoes profound plastic changes and we do not know enough about vision and about how to communicate with this altered cortex to generate meaningful visual perception.

Methods: New findings regarding the nature of sensory representations and verbal memory information in sighted, blind and week long blindfolded subjects using functional Magnetic resonance imaging (fMRI) and Transcranial Magnetic Stimulation (TMS) will be presented. In addition I will present the use of sensory substitution devices (SSDs) in the context of blindness.

Results: In SSDs, visual information captured by an artificial receptor is delivered to the brain of a blind person using non-visual sensory information via a human-machine interface. Using an auditory-to-visual sensory substitution device called "The vOICe" we find that blind achieve successful performance on object recognition tasks, and specific recruitment of ventral and dorsal visual structures. Comparable recruitment of visual cortex was observed also in sighted users learning to use this device but not in sighted learning arbitrary associations between sounds and object identity.

Conclusions: Using fMRI and TMS we find that interactions between sensory modalities are critical to our understanding of sensory perception in the brain and that massive brain plasticity in the occipital cortex is possible during development but possible even in the adult visual cortex. The results using SSDs suggest "The vOICe" can be useful for blind individuals daily activities (e.g. object recognition and localization) but it also has a potential use to ‘guide’ the visual cortex to ‘read’ and interpret visual information arriving from a retinal prosthesis.