Spinal cord neural interfacing in common marmosets (Callithrix jacchus)

Abstract

Objective: Spinal cord injury (SCI) remains an ailment with no comprehensive cure, and affected patients suffer from a greatly diminished quality of life. This large population could significantly benefit from prosthetic technologies to replace missing limbs, reanimate nonfunctional limbs, and enable new modes of technologies to restore muscle control and function. While cortically driven brain machine interfaces (BMIs) have achieved great success in interfacing with an external device to restore lost functions, interfacing with the spinal cord can provide an additional site to record motor control signals, which can have its own advantages, albeit challenges from using a smaller non-human primate (NHP) model. The goal of this study is to develop such a spinal cord neural interface to record motor signals from the high cervical levels of the spinal cord in a common marmoset (Callithrix jacchus) model. Approach and MainResults: Detailed methods are discussed for this smaller NHP model that includes behavioral training, surgical methods for electrode placement, connector placement and wire handling, electrode specifications and modifications for accessing high cervical level interneurons and motorneurons. The study also discusses the methods and challenges involved in behavioral multi-channel extracellular recording from the marmoset spinal cord, including the major recording failure mechanisms encountered during the study.Significance: Marmosets provide a good step between rodent and larger NHP models due to their small size, ease of handling, cognitive abilities, and similarities to other primate motor systems. The study shows the feasibility of recording spinal cord signals and using marmosets as a smaller NHP model in behavioral neuroscience studies. Interfacing with the spinal cord in chronically implanted animals can provide useful information about how motor control signals within the spinal cord are transformed to cause limb movements.

A Hyperflexible Electrode Array for Long‐Term Recording and Decoding of Intraspinal Neuronal Activity

“…First, the acquisition bandwidth, which is limited by the channel count, remains rather too low to take advantage of potential spatial resolution for singleunit recording. [12,14] Second, fracturing of the electrode due to its mechanical stiffness causes instability of electrical interfacing during long-term recording, [15,16] particularly due to frequent relative movements of SC tissues. [17] Furthermore, electrode implants are often significantly more rigid than the SC tissue, causing disparate displacement of the electrode and targeted neurons, causing local tissue damage.…”

“…[17] Furthermore, electrode implants are often significantly more rigid than the SC tissue, causing disparate displacement of the electrode and targeted neurons, causing local tissue damage. [16] The mechanical mismatch is known to induce elevated inflammatory responses near the electrodes, leading to glial scar formation, neuron degeneration, and signal degradation at the interface. [16,18] Using state-of-art nanofabrication technologies, we developed a multichannel SC hyperflexible electrode array (SHEA) for chronic recording and decoding of SC signals.…”

“…[16] The mechanical mismatch is known to induce elevated inflammatory responses near the electrodes, leading to glial scar formation, neuron degeneration, and signal degradation at the interface. [16,18] Using state-of-art nanofabrication technologies, we developed a multichannel SC hyperflexible electrode array (SHEA) for chronic recording and decoding of SC signals. This technology enables the fabrication of a dense 128-channel electrode array with a spatial resolution of cellular dimensions and a hyperflexible array structure with an electrode bending force comparable to the cellular traction force.…”

“…[ 16 ] The mechanical mismatch is known to induce elevated inflammatory responses near the electrodes, leading to glial scar formation, neuron degeneration, and signal degradation at the interface. [ 16,18 ]…”

Multisite Simultaneous Neural Recording of Motor Pathway in Free-Moving Rats

“…For instance, Stephanie Lacour at EPFL invented an e-Dura implant that is capable of long-term recording, stimulating, and drug delivery of spinal cord [ 41 , 42 ]. Regardless of which technique is applied, it is optimal to connect the electrode or electrode array to the connector and fix it on the skull [ 43 ], if it is not wireless.…”