Intracortical bipolar stimulation allows selective activation of neuronal populations in the cortex
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Background
Intracortical electrical stimulation has emerged as a promising approach for sensory restoration, such as a cortical visual prosthesis, yet its effectiveness is limited by current spread and electrode density constraints.
Objective
To determine whether intracortical bipolar current steering—via modulation of the return electrode position—can enhance neural activation selectivity compared to traditional monopolar stimulation, with the aim of improving spatial precision in sensory restoration.
Methods
We applied intracortical stimulation and used two-photon calcium imaging on acute brain slices to directly visualize neural responses to bipolar stimulation. Biophysical computational modeling was used to complement the experimental results. The analysis included both cellular and population-level assessments to evaluate the impact of several stimulation patterns, such as current direction, electrode spacing and current amplitude, on recruitment patterns.
Results
Bipolar stimulation selectively activated distinct neural populations based on the direction of the current flow. This approach decreased the overlap between activated groups and increased the number of independently addressable neural clusters by up to 9-fold relative to monopolar stimulation. Moreover, the electrode configuration and spacing critically influenced the spatial spread of activation.
Conclusions
Intracortical bipolar current steering enhances neural activation selectivity by engaging independent neural populations through current directionality. These findings suggest that this strategy may improve the spatial precision of neural prosthetics and sensory restoration without the need for an increased electrode density.
