Filling in the Visual Gaps: Shifting Cortical Activity using Current Steering.

Area of Science:

• Neuroscience
• Biomedical Engineering
• Ophthalmology

Background:

• Cortical vision prostheses aim to restore sight in blind individuals by stimulating the visual cortex.
• Current electrode arrays face challenges in precise placement, leading to gaps in visual field representation.
• Gaps between implants can result in areas where no visual percepts are generated, limiting functional vision restoration.

Purpose of the Study:

• To introduce and evaluate current steering as a method to elicit neural responses between physical electrode locations in cortical vision prostheses.
• To investigate the feasibility of shifting the centroid of neural activity by manipulating stimulation parameters.
• To enhance visual field coverage and improve environmental perception for patients with cortical implants.

Main Methods:

• Dual-electrode stimulation was applied to the visual cortex of Sprague-Dawley rats.
• The centroid of neural activity was assessed to determine the location of evoked neural responses.
• The ratio of charge delivered to each electrode was systematically altered to modulate the centroid's position.

Main Results:

• The centroid of neural activity could be successfully shifted between physical electrode locations.
• Altering the charge ratio between dual electrodes precisely controlled the centroidal shift.
• This demonstrates the potential to fill gaps in visual percepts without increasing electrode density.

Conclusions:

• Current steering is a viable technique to modulate neural activation sites between implanted electrodes.
• This approach offers a solution to create a complete visual field representation in cortical vision prostheses.
• Improved environmental perception and functional vision restoration are potential benefits for patients with blindness.