Basic neuroscienceA multi-site array for combined local electrochemistry and electrophysiology in the non-human primate brain

- We present a novel multi-contact recording array and supporting headstage.
- The system allows concurrent in vivo electrochemistry and electrophysiology.
- The system is validated using measures of arousal in an awake macaque monkey.
- A detailed protocol for device fabrication by photolithography is provided.

BackgroundCurrently, the primary technique employed in circuit-level study of the brain is electrophysiology, recording local field or action potentials (LFPs or APs). However most communication between neurons is chemical and the relationship between electrical activity within neurons and chemical signaling between them is not well understood in vivo, particularly for molecules that signal at least in part by non-synaptic transmission.New methodWe describe a multi-contact array and accompanying head stage circuit that together enable concurrent electrophysiological and electrochemical recording. The array is small (<200 μm) and can be assembled into a device of arbitrary length. It is therefore well-suited for use in all major in vivo model systems in neuroscience, including non-human primates where the large brain and need for daily insertion and removal of recording devices places particularly strict demands on design.ResultsWe present a protocol for array fabrication. We then show that a device built in the manner described can record LFPs and perform enzyme-based amperometric detection of choline in the awake macaque monkey.Comparison with existing methods Existing methods allow single mode (electrophysiology or electrochemistry) recording. This system is designed for concurrent, dual-mode recording. It is also the only system designed explicitly to meet the challenges of recording in non-human primates.ConclusionsOur system offers the possibility for conducting in vivo studies in a range of species that examine the relationship between the electrical activity of neurons and their chemical environment, with exquisite spatial and temporal precision.