High-density, Identified Cell Recordings from Motor Cortex of Awake Behaving Macaques using Multiple 1024-channel...

Recording bioelectric signals from large populations of single neurons in the primate brain remains challenging. Chronic implants offer limited coverage (∼100 channels) and sample fixed cortical regions, while acutely inserted electrodes allow broader access via multiple daily penetrations. We aimed to develop a CMOS-based probe with high electrode-channel density, and optimized procedures for acute large-scale single-unit recordings in behaving monkeys.

We designed a novel single-shank SiNAPS CMOS probe for acute recordings in monkeys with additional integrated multiplexing circuits to reduce output lines. A multi-probe system enables synchronous sampling at 20 kHz/channel from two SINAPS-NHP probes during repeated insertions into the motor cortex of behaving macaques. We developed methods to identify neurons via antidromic activation.

The probe (10.7 mm × 158 μm × 50 μm) samples neural activity from 1,024 electrodes (14 × 14 μm², 30 μm pitch) arranged in four columns and reaches an electrode-channel density of 304.4 channels/mm2. A pilot hole facilitates dural penetration, and optimized insertion procedures allow recordings from diverse cortical sites. Some neurons were identified as pyramidal tract cells projecting to the spinal cord.

Each probe enables monitoring of intracortical areas of 7.75 × 0.1 mm², detecting hundreds of single neurons per session, and reaches deep regions such as the anterior bank of the central sulcus, rich in corticospinal cells.

This technology and methods unlock routine acute recordings from 2,048 channels with single-neuron resolution and cell-type identification, advancing the neurophysiological toolkit for primate research.