Exploring cortical connectivity of visual prosthesis users: A resting state study

Introduction: Electrophysiological studies of cortical activity have highlighted the organizational and functional differences in the cortex of blind subjects versus normal subjects. This reorganization is optimized by the nervous system to adapt to the new sensory modalities that subjects use in daily life. A cortical visual prosthesis is capable of restoring visual sensations to blind subjects based on phosphenes, which attempt to provide them with information about their surrounding environment. In this context, our study aims to characterize the cortical alterations resulting from the use of a vision neuroprosthesis.

Methods: In this preliminary approach, the blind subjects under study were temporary users (6 months) of a visual neuroprosthesis, which, through an array of microelectrodes implanted in the primary visual cortex, provided patterns of electrical stimulation that in turn evoked perceptions of phosphenes. To explore the cortical alterations resulting from the use of this neuroprosthesis, the cortical connectivity (spectral coherence, SC) of the users was analyzed in the resting state using electroencephalography techniques.

Results and Discussion: SC between all EEG channels revealed significant changes (p < 0.001) in 60% of the connections in the alpha band as a result of daily use of the neuroprosthesis (before implantation vs. after explantation). In other energy bands, connectivity was altered to a lesser extent (around 30% in the beta band). When comparing resting state activity with that of normal subjects, significant differences were observed in the beta band before the implant, whereas after the implant these differences tended to disappear.

Conclusions: These preliminary results revealed that cortical connectivity in the resting state significantly changes with the use of the vision neuroprosthesis, tending in some cases towards cortical patterns similar to those of non-blind individuals.