HermesB: a continuous neural recording system for freely behaving primates.

Area of Science:

• Neuroscience
• Biomedical Engineering
• Implantable Devices

Background:

• Chronically implanted electrode arrays are crucial for electrophysiology and neural prosthetics.
• Current experimental methods often require subject restraint, limiting data collection duration and scope.
• Developing systems for freely behaving subjects is key to advancing neural prosthetics.

Purpose of the Study:

• To introduce HermesB, a dual-channel, battery-powered neural recording system with an integrated accelerometer.
• To enable long-duration, continuous neural and acceleration data acquisition in freely behaving primates.
• To investigate neural signal variability and behavioral contexts in unrestrained subjects.

Main Methods:

• Developed HermesB: a self-contained, programmable system recording broadband neural data (30 kS/s) and acceleration.
• Utilized a removable compact flash card for data storage up to 48 hours.
• Collected long-duration data from an adult macaque monkey.

Main Results:

• Observed significant variations in action potential shape and noise over time (up to 24 hours).
• Action potential voltage varied by up to 30%, with step changes up to 25% correlated with head acceleration.
• Reduced 5-25 Hz local field potential (LFP) power and increased firing rate variability during active periods.
• Successfully classified 93% of recording blocks as active/inactive using LFP power thresholds.

Conclusions:

• Neural signals are not stable over long durations and require adaptive processing for spike sorting.
• HermesB provides insights into neural dynamics during natural behaviors, inaccessible with traditional methods.
• The system is valuable for advancing neural prosthetics and electrophysiological research by capturing behavioral context.