Adaptive Charge Modulation Enables Focal, Selective Spinal Cord Stimulation.

Area of Science:

• Neuroscience
• Biomedical Engineering

Background:

• Clinical neuromodulation typically uses low-frequency electrical stimulation for localized neuron activation.
• Current methods struggle to precisely target deep neural tissues distant from stimulating electrodes.

Purpose of the Study:

• Introduce Adaptive Charge Modulation (ACM), a novel spatiotemporal stimulation strategy.
• Demonstrate ACM's ability to focus neural activation at deep tissue sites, particularly in the spinal cord.
• Enhance the precision and reach of neuromodulation and neural interfaces.

Main Methods:

• ACM employs multipolar, biphasic rectangular pulses for charge-balanced stimulation.
• Applied epidural spinal cord stimulation in rat models.
• Utilized high spatiotemporal resolution, 2,112-channel brain-spine recordings to analyze neural responses.
• Evaluated chronic stability over 68 days in freely behaving animals.

Main Results:

• ACM achieved single-muscle selectivity in spinal cord stimulation with minimal co-activation.
• Characterized response latencies and pathways consistent with focal deep neural recruitment.
• Demonstrated chronic stability of electrodes and ACM over 68 days.
• Observed reduced surface activation compared to conventional methods.

Conclusions:

• ACM enables focal activation of deep neural targets using epidural surface electrodes.
• This strategy potentially overcomes limitations of traditional low-frequency stimulation (LFS).
• ACM offers expanded reach and precision for neuromodulation and neural interface applications.