Epi-Intra neural probes with glassy carbon microelectrodes help elucidate neural coding and stimulus encoding in 3D volume of tissue

Abstract

Objective. In this study, we demonstrate practical applications of a novel 3-dimensional neural probe for simultaneous electrophysiological recordings from the surface of the brain as well as deep intra-cortical tissue. We used this 3D probe to investigate signal propagation mechanisms between neuronal cells and their responses to stimuli in a 3D fashion. Approach. This novel probe leverage 2D thin-film microfabrication technique to combine an epi-cortical (surface) and an intra-cortical (depth) microelectrode arrays (Epi-Intra), that unfold into an origami 3D-like probe during brain implantation. The flexible epi-cortical component conforms to the brain surface while the intra-cortical array is reinforced with stiffer durimide polymer layer for ease of tissue penetration. The microelectrodes are made of glassy carbon material that is biocompatible and has low electrochemical impedance that is important for high fidelity neuronal recordings. These recordings were performed on the auditory region of anesthetized European starling songbirds during playback of conspecific songs as auditory stimuli. Main results. The Epi-Intra probe recorded broadband activity including local field potentials (LFPs) signals as well as single-unit activity and multi-unit activity from both surface and deep brain. The majority of recorded cellular activities were stimulus-locked and exhibited low noise. Notably, while LFPs recorded on surface and depth electrodes did not exhibit strong correlation, composite receptive fields (CRFs)—extracted from individual neuron cells through a non-linear model and that are cell-dependent—were correlated. Significance. These findings demonstrate that CRFs extracted from Epi-Intra recordings are excellent candidates for neural coding and for understanding the relationship between sensory neuronal responses and their stimuli (stimulus encoding). Beyond CRFs, this novel neural probe may enable new spatiotemporal 3D volumetric mapping to address, with cellular resolution, how the brain coordinates function.

Electrode Materials for Chronic Electrical Microstimulation

“…[ 92 ] As previously mentioned, GC shows outperforming properties compared with Pt microelectrodes of similar geometry in terms of electrochemical stability. [ 166 ] The GC microelectrodes have been recently miniaturized and GC MEA intracortical probes demonstrated the capability to record high quality single‐unit neural activity and to detect low dopamine concentrations in vitro and in vivo, [ 18,203,204,205 ] offering great promise for multimodal interaction with the brain. Besides glassy carbon, porous graphene electrodes obtained by laser pyrolysis and subsequent doping with nitric acid exhibited a CIL of 3.1 mC cm −2 and very low impedance (519 Ω at 1 kHz for 250 µm diameter electrodes), which remained relatively stable in PBS solution over 28 days, and showing no physical degradation after 1 million cycles.…”

Advances in Carbon-Based Microfiber Electrodes for Neural Interfacing

“…With proper surface modifications, many of these microfiber electrodes can enable closed-loop function as they exhibit appropriate properties for high precision neural recording and stimulation. They have also been demonstrated with better stability when used for neural interfacing (Vomero et al, 2017;Nimbalkar et al, 2018;Vahidi et al, 2020). Among them, CF microelectrodes with small cross sections have been used for detection of neurotransmitters such as dopamine and serotine for over three decades in the brain using fast-scan cyclic voltammetry (Robinson et al, 2003;Dankoski and Wightman, 2013;Taylor et al, 2015;Castagnola et al, 2020).…”

Closed-loop neuromodulation will increase the utility of mouse models in Bioelectronic Medicine

“…Neural stimulation and recording electronics have shrunk to nearly the size of individual neurons (Muller et al, 2015 ). In fact, the same advances from the semiconductor industry have resulted in microfabricated electrodes that are on par with the scale of individual neurons (Vahidi et al, 2020 ). Using these fabrication techniques, electrodes and electronics can be co-located (Datta-Chaudhuri et al, 2016 ; Datta-Chaudhuri et al, 2014a ; Datta-Chaudhuri et al, 2014b ), but these approaches are generally not appropriate for chronic implantation as they lack robust barrier layers.…”