High channel count single-unit recordings from nonhuman primate frontal cortex.

Background: Single unit recording in behaving nonhuman primates is widely used to study the primate central nervous system. However, certain questions cannot be addressed without recording large numbers of neurons simultaneously. Multiple 96-electrode probes can be implanted at one time, but certain problems must be overcome to make this approach practical.

New Method: We describe a series of innovations and practical guidance for implanting and recording from 8 arrays of 96 electrodes (768 electrodes) in the frontal cortex of Macaca mulatta. The methods include an individualized 3D-printed connector mounting platform, sequencing of assembly and surgical steps to minimize surgery time, and interventions to protect electrical connections of the implant.

Results: The methodology is robust and was successful in our hands on the first attempt. On average, we were able to isolate hundreds (535.7 and 806.9 in two animals) of high quality units in each session during one month of recording.

Comparison With Existing Methods: To the best of our knowledge, this technique at least doubles the number of Blackrock arrays that have been successfully implanted in single animals. Although each technological component was pre-existing at the time we developed these methods, their amalgamation to solve the problem of high channel count recording is novel.

Conclusions: The implantation of large numbers of electrodes opens new research possibilities. Refinements could lead to even greater capacity.