Creating virtual electrodes with 2D current steering.

Area of Science:

• Neuroscience
• Biomedical Engineering
• Ophthalmology

Background:

• Current steering techniques show promise for enhancing retinal prostheses by increasing the number of distinct percepts without additional electrodes.
• Virtual electrodes, created by stimulating electrode pairs, can generate unique cortical response patterns.

Purpose of the Study:

• To investigate the feasibility of creating virtual electrodes using 2D current steering.
• To determine if these virtual electrodes elicit cortical responses with predictable spatial characteristics.

Main Methods:

• Seven cats with suprachoroidal electrode arrays (42-channel) had neural activity recorded from the visual cortex.
• Stimuli were applied to physical electrodes and electrode groups (triangular, rectangular, hexagonal) to create virtual electrodes by varying charge proportions.
• Cortical response centroids from virtual and physical electrode stimulation were compared.

Main Results:

• Stimulating groups of up to six electrodes with equal charge produced cortical activation patterns similar to the central physical electrode.
• Current steering allowed directing the activation centroid towards specific electrodes within a group, though not significantly.

Conclusions:

• 2D current steering is feasible between at least six electrodes, potentially increasing percepts in retinal prostheses without more physical electrodes.
• The ability to reproduce spatial characteristics suggests current steering can compensate for faulty electrodes.