Selective Formation of Porous Pt Nanorods for Highly Electrochemically Efficient Neural Electrode Interfaces.

The enhanced electrochemical activity of nanostructured materials is readily exploited in energy devices, but their utility in scalable and human-compatible implantable neural interfaces can significantly advance the performance of clinical and research electrodes. We utilize low-temperature selective dealloying to develop scalable and biocompatible one-dimensional platinum nanorod (PtNR) arrays that exhibit superb electrochemical properties at various length scales, stability, and biocompatibility for high performance neurotechnologies. PtNR arrays record brain activity with cellular resolution from the cortical surfaces in birds and nonhuman primates. Significantly, strong modulation of surface recorded single unit activity by auditory stimuli is demonstrated in European Starling birds as well as the modulation of local field potentials in the visual cortex by light stimuli in a nonhuman primate and responses to electrical stimulation in mice. PtNRs record behaviorally and physiologically relevant neuronal dynamics from the surface of the brain with high spatiotemporal resolution, which paves the way for less invasive brain-machine interfaces.

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

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.