Repeatable, low-drift recordings in behaving non-human primates using flexible microelectrodes.

Area of Science:

• Neuroscience
• Biomedical Engineering
• Materials Science

Background:

• Traditional rigid microelectrode arrays in non-human primates (NHPs) cause tissue damage and signal instability due to mechanical mismatch.
• Brain micromotion leads to neuron drift, compromising single-unit tracking in chronic and acute recordings.
• Delivering flexible electrodes through the dura mater in NHPs presents significant technical challenges.

Purpose of the Study:

• To develop and validate a flexible microelectrode array system for acute, repeated neurophysiological recordings in awake, behaving NHPs.
• To overcome the technical barriers of inserting ultra-thin flexible electrodes into the NHP brain.
• To demonstrate the efficacy of flexible electrodes in reducing single-unit drift compared to rigid probes.

Main Methods:

• Fabrication of a 32-site, 7 μm-thick Parylene-C flexible microelectrode array.
• Development of a novel "telescopic" insertion method using concentric guide tubes and a microwire shuttle.
• Acute, repeated penetrations through intact dura in awake rhesus macaques performing a delayed response task.

Main Results:

• Achieved an 80% single-unit recording success rate in awake NHPs.
• Recorded stable, task-responsive neuronal activity from prefrontal and posterior parietal cortex over 1-2 hour sessions.
• Demonstrated a significant reduction in single-unit drift (hundreds to tens of microns) using flexible electrodes compared to rigid probes.

Conclusions:

• Flexible microelectrode arrays provide a practical and dependable solution for NHP neuroscience.
• The developed insertion technique enables repeated, stable recordings without new craniotomies.
• This technology advances the potential for ultra-stable, long-term neurophysiology in large animal models.