Aseptic, semi-sealed cranial chamber implants for chronic multi-channel neurochemical and electrophysiological neural recording in nonhuman primates

Abstract

Background: Invasive electrophysiological recordings in subcortical structures of nonhuman primates typically involve implanting electrodes into the brain through a skull-mounted chamber. These electrodes may be attached to the chamber temporarily for hours of neural recording, or permanently for long-term studies. Current challenges involve maintaining asepsis and integrating dual-modality monitoring of both electrical and chemical neural activity.

New method: We developed an implantable neural interface that provides such dual-modality monitoring in monkeys, while maintaining aseptic conditions for year-long periods. We leveraged osseointegrating materials and hermetic sealing strategies to prevent the transmission of pathogenic species, while preserving the modular functionality of chamber systems, such as sensor depth adjustability. The system also features an aspirating port for culturing chamber fluid to ensure continued asepsis.

Results: Our chamber system was shown to provide successful recordings of dopamine and electrical neural activity in two monkeys while maintaining negative bacteria culture results for over a year post-implantation.

Comparison with existing methods: Sealed chamber systems prevent contamination and reduce the risk of compromising animal health by minimizing the accumulation of pathogenic organisms. Such sealed chambers also eliminate the need for frequent cleaning. However, neurochemical measurements require specialized electrodes with fragile carbon fiber tips and are not compatible with recently developed, sealed chamber systems.

Conclusion: This advanced chamber design builds upon traditional chamber protocols to enable chronic measurements of chemical and electrical neural activity. This approach facilitates novel ways to study the brain in behaving primates while prioritizing the long-term health and welfare of the animals.

Keywords: Chronic neural implants; Multichannel; Neural recording; Neurochemical recording; Primate cephalic chamber.