Multichannel Silicon Probes for Awake Hippocampal Recordings in Large Animals.

Alexandra V Ulyanova,D Kacy Cullen,H Isaac Chen,Carlo Cottone,Brian G Jamieson,Victoria E Johnson,Christopher D Adam,John A Wolf,Tahl Holtzman,Kimberly G Gagnon,Paul F Koch

doi:10.3389/fnins.2019.00397

Abstract

Decoding laminar information across deep brain structures and cortical regions is necessary in order to understand the neuronal ensembles that represent cognition and memory. Large animal models are essential for translational research due to their gyrencephalic neuroanatomy and significant white matter composition. A lack of long-length probes with appropriate stiffness allowing penetration to deeper structures with minimal damage to the neural interface is one of the major technical limitations to applying the approaches currently utilized in lower order animals to large animals. We therefore tested the performance of multichannel silicon probes of various solutions and designs that were developed specifically for large animal electrophysiology. Neurophysiological signals from dorsal hippocampus were recorded in chronically implanted awake behaving Yucatan pigs. Single units and local field potentials were analyzed to evaluate performance of given silicon probes over time. EDGE-style probes had the highest yields during intra-hippocampal recordings in pigs, making them the most suitable for chronic implantations and awake behavioral experimentation. In addition, the cross-sectional area of silicon probes was found to be a crucial determinant of silicon probe performance over time, potentially due to reduction of damage to the neural interface. Novel 64-channel EDGE-style probes tested acutely produced an optimal single unit separation and a denser sampling of the laminar structure, identifying these research silicon probes as potential candidates for chronic implantations. This study provides an analysis of multichannel silicon probes designed for large animal electrophysiology of deep laminar brain structures, and suggests that current designs are reaching the physical thresholds necessary for long-term (∼1 month) recordings with single-unit resolution.

Highlights

Spatiotemporal neuronal ensembles distributed throughout laminar structures in the brain such as the cortex and hippocampus are presumed to be the substrate for cognition and memory
Multichannel Silicon Probes Designed for Chronic Implantation in Large Animal
Multichannel silicon probes designed for large animal electrophysiology were evaluated for their ability to continuously record neurophysiological signals in awake behaving pigs, and for neuropathological changes induced by their placement in the porcine hippocampus over time

Summary

Introduction

Spatiotemporal neuronal ensembles distributed throughout laminar structures in the brain such as the cortex and hippocampus are presumed to be the substrate for cognition and memory. For spikefield entrainment analyses as well as for neuromodulationbased approaches, it is important to know where inputs that drive the cells originate and how they interact locally. We must decode laminar information across different structures to understand the spatiotemporal ensembles that represent cognition and memory. Measuring the coordination of spiking activity of large numbers of neurons, and those thought to give rise to distributed functional networks, is critical for understanding neural information processing underlying cognition and behavior (Lewis et al, 2015)

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