Decoding Bilateral Hindlimb Kinematics From Cat Spinal Signals Using Three-Dimensional Convolutional Neural Network

Abstract

To date, decoding limb kinematic information mostly relies on neural signals recorded from the peripheral nerve, dorsal root ganglia (DRG), ventral roots, spinal cord gray matter, and the sensorimotor cortex. In the current study, we demonstrated that the neural signals recorded from the lateral and dorsal columns within the spinal cord have the potential to decode hindlimb kinematics during locomotion. Experiments were conducted using intact cats. The cats were trained to walk on a moving belt in a hindlimb-only condition, while their forelimbs were kept on the front body of the treadmill. The bilateral hindlimb joint angles were decoded using local field potential signals recorded using a microelectrode array implanted in the dorsal and lateral columns of both the left and right sides of the cat spinal cord. The results show that contralateral hindlimb kinematics can be decoded as accurately as ipsilateral kinematics. Interestingly, hindlimb kinematics of both legs can be accurately decoded from the lateral columns within one side of the spinal cord during hindlimb-only locomotion. The results indicated that there was no significant difference between the decoding performances obtained using neural signals recorded from the dorsal and lateral columns. The results of the time-frequency analysis show that event-related synchronization (ERS) and event-related desynchronization (ERD) patterns in all frequency bands could reveal the dynamics of the neural signals during movement. The onset and offset of the movement can be clearly identified by the ERD/ERS patterns. The results of the mutual information (MI) analysis showed that the theta frequency band contained significantly more limb kinematics information than the other frequency bands. Moreover, the theta power increased with a higher locomotion speed.

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

“…[33] Previous studies have shown that intraspinal signals can be used to extract motor intent. [34][35][36] Motor neurons in the ventral horn are involved in precise locomotor encoding compared to white matter and dorsal root ganglia. However, so far as we know, there are no electrodes that have been used to decode neurons in the ventral horn, which may be due to its low accessibility caused by its deep location.…”

Electrospinography for non-invasively recording spinal sensorimotor networks in humans

“…For example, it has been demonstrated that there is a decrease in 8-30 Hz activity recorded from the epidural space in the skull before and during forelimb movement in rats [39]. Another study recording activity from the lumbar spinal cord using micro wires found low frequencies (0.5-30 Hz) and high frequencies (100 Hz) conveyed more information about hind limb movement in cats [40]. Additionally, gPDC analysis suggests that the ESG recordings are bidirectional, which further reduces the likelihood that the data are from some other physiological source such as EMG which should cause mono-directional changes in gPDC (i.e.…”