Acute Neuropixels recordings in the marmoset monkey.

Abstract

High-density linear probes, like Neuropixels, provide an unprecedented opportunity to understand how neural populations within specific laminar compartments contribute to behavior. Marmoset monkeys, unlike macaque monkeys, have a lissencephalic (smooth) cortex that enables recording perpendicular to the cortical surface, thus making them an ideal animal model for studying laminar computations. Here we present a method for acute Neuropixels recordings in the common marmoset (Callithrix jacchus). The approach replaces the native dura with an artificial silicon-based dura that grants visual access to the cortical surface, which is helpful in avoiding blood vessels, ensures perpendicular penetrations, and could be used in conjunction with optical imaging or optogenetic techniques. The chamber housing the artificial dura is simple to maintain with minimal risk of infection and could be combined with semi-chronic microdrives and wireless recording hardware. This technique enables repeated acute penetrations over a period of several months. With occasional removal of tissue growth on the pial surface, recordings can be performed for a year or more. The approach is fully compatible with Neuropixels probes, enabling the recording of hundreds of single neurons distributed throughout the cortical column.Significance statement The cerebral cortex of the macaque monkey is extensively folded, which poses a major problem for studying laminar computations in many cortical areas. Marmosets, however, have a smooth brain that allows for simultaneous recordings from all layers of the cortex in areas that are buried deep in sulci in the macaque. In this manuscript, we describe an artificial dura system that utilizes the state-of-the-art in high-density probes, Neuropixels. This system enables us to easily insert multiple Neuropixels into the marmoset cortex normal to the cortical surface permitting repeated laminar recordings for up to a year or more.