Comparison of Physiological Brain Responses Evoked by Visual and Electrical Stimulation

Area of Science:

• Neuroscience
• Ophthalmology
• Biomedical Engineering

Background:

• Noninvasive current stimulation (nCS) is emerging for treating eye and brain disorders.
• Transcranial and transcorneal alternating current stimulation are common nCS methods for the visual system.
• The precise mechanisms of nCS neuromodulation via eye stimulation remain unclear.

Purpose of the Study:

• To investigate the activation patterns elicited by nCS in the rat visual system.
• To compare responses from electrical stimulation versus visual stimulus (VS).
• To evaluate the impact of different electrode placements (eyeball-eyeball, eyeball-neck) on evoked responses.

Main Methods:

• Electrical impulses were delivered to rat eyes, alternating with VS.
• Neuronal responses were recorded in the superior colliculus and primary visual cortex.
• Two electrode configurations were tested: eyeball-eyeball and eyeball-neck.

Main Results:

• nCS and VS produced distinct activation patterns.
• Electrically evoked potentials showed shorter latency and different shapes compared to VS.
• Transcorneal alternating current stimulation (tACS) resulted in shorter sinks and sources than VS, indicating different current flow patterns.

Conclusions:

• The eyeball-eyeball nCS paradigm yielded responses more similar to VS.
• Individual transcorneal electrical impulses consistently activate visual system neurons.
• nCS effectively activates visual circuits, offering potential for vision restoration therapies despite delivery variations.