Microelectrode array recordings from the ventral roots in chronically implanted cats.

Area of Science:

• Neuroscience
• Biomedical Engineering
• Neural Engineering

Background:

• Ventral spinal roots exclusively contain motoneuron axons, offering a unique site for motor neural recording in the peripheral nervous system.
• Current methods for peripheral nerve recording often lack specificity for motor signals.

Purpose of the Study:

• To demonstrate the feasibility of recording single unit motor activity from ventral spinal roots using chronic implants.
• To evaluate the performance of floating microelectrode arrays (FMAs) for ventral root recordings.
• To investigate the impact of electrode size on signal quality and long-term stability.

Main Methods:

• Chronic implantation of 32-channel FMAs in the L6 and L7 ventral spinal roots of nine cats.
• Recording single unit activity for up to 12 weeks post-implantation.
• Systematic variation of electrode site sizes (25-160 μm) to assess signal-to-noise ratio (SNR) and unit yield.

Main Results:

• Feasible chronic recording of single unit activity from ventral spinal roots was demonstrated.
• No significant difference in unit yield or SNR was observed across tested electrode sizes.
• Both SNR and unit yield showed decay over time, but functional recording (SNR >2) persisted up to 12 weeks.

Conclusions:

• Penetrating microelectrode arrays can successfully record activity from multiple isolated motor units chronically implanted in ventral spinal roots.
• This technique holds promise for developing spinal nerve interfaces for advanced neural prostheses.
• Findings will inform the design of improved microelectrodes for chronic ventral spinal root neural recording.