Jul 2026· Research Square· 0 citations· 48 references
Medicine
TL;DR
This work demonstrates for the first time in humans that clinical-grade lumbosacral epidural paddle arrays capture sufficient fine-scale spatiotemporal structure to decode these overlapping inputs from highly overlapping, volume-conducted epidural fields.
Abstract
Restoration of dynamic motor function following neurological injury increasingly relies on adaptive neuroprostheses, which require real-time sensory feedback to continuously adjust to a user’s physical state. However, it remains unknown whether distinct afferent activity can even be decoded from highly overlapping, volume-conducted epidural fields. This challenge is particularly pronounced in the lumbosacral enlargement, where common fibular (CFN) and tibial nerve (TN) afferents converge extensively, producing highly similar cord dorsum potential (CDP) topographies. Here, we demonstrate for the first time in humans that clinical-grade lumbosacral epidural paddle arrays capture sufficient fine-scale spatiotemporal structure to decode these overlapping inputs. Using a 32-contact array and peripheral nerve stimulation, we constructed a 42-dimensional feature space capturing distributed amplitudes, field geometry, and waveform morphology. A support vector machine decoded four distinct afferent classes (left and right CFN and TN) with a median accuracy of 90.9% ± 0.3%. Shapley Additive Explanations revealed decoding was driven by contact-level voltage patterns and temporal waveform complexity, while the geometric features contributed minimally. These afferent-specific signatures persisted even at sub-motor threshold stimulation intensities. By utilizing standard clinical arrays, this approach provides a pathway toward rapid deployment of interpretable closed-loop neuromodulation, avoiding the surgical risks of penetrating or peripheral interfaces.
It is demonstrated that a single ultrathin circumferential intradural electrode array can decode motor intent, classify sensory inputs, and discriminate visceral afferent signals across rodent and porcine models.
S. El Hadwe, Rubén Ruiz-Mateos Serrano, George Psaltakis et al.· Nature Communications· 0 citations
These findings demonstrate that STN motor representations are context-dependent, anatomically organized, and temporally distinct, reinforcing the STN's dynamic engagement during motor execution.
E. Radcliffe, Morgan K Hampton, H. Granberg et al.· Journal of Neural Engineerin...· 0 citations
Activity in WDR neurons is established as a core component of the N1 potential, supporting the use of spinal SEPs as a translational biomarker of analgesic target engagement within the dorsal horn of anaesthetised Wistar rats.
Kenneth A J Steel, Tony Blockeel, E. Ajay et al.· bioRxiv· 0 citations
The spinal cord serves as a crucial relay for motor commands, yet the role of its local circuitry in sensorimotor integration remains poorly understood. Most non-invasive cortical stimulation studies, rely on electrophysiological readouts or inferred spinal function from corticospinal anatomy, leaving the downstream impact of cortical stimulation on spinal circuitry largely uncharted in vivo. Advances in spinal cord functional MRI (SC-fMRI) now enable spatially resolved imaging of segmental gray and white matter and their interactions with descending cortical inputs. Here, we introduce a multimodal framework that combines single-pulse transcranial magnetic stimulation (TMS) of the primary motor cortex with SC-fMRI to probe TMS-evoked spinal activity in humans. Using graded TMS intensities, we examined blood oxygenation level-dependent (BOLD) responses in the cervical spinal cord and asked how spinal activation depends on effective engagement of the descending motor system. Our findings reveal robust, intensity-dependent spinal BOLD responses aligned with descending pathways, with activation concentrated in expected territories such as the lateral corticospinal tract and ventral horn at segments innervating the stimulated hand muscle. By linking peripheral output to segment- and pathway-resolved spinal signals, these results demonstrate that concurrent TMS–SCfMRI can capture, in vivo, how cortical drive is expressed within human spinal circuitry and provide a new framework to measure spinal contributions to sensorimotor control with spatial specificity beyond traditional peripheral readouts. Graphical Abstract
E. Sareen, Rebecca Jones, E. Raffin et al.· bioRxiv· 0 citations
Humans perform a variety of complex hand movements to manipulate objects, requiring precise control of changing forces. Understanding the role of sensorimotor cortex and the cortical dynamics underlying these actions is crucial for developing interventions that restore dexterous hand function after injury or disease. In this study, two male individuals with tetraplegia resulting from cervical spinal cord injury attempted a series of isometric grasps. Neural activity was recorded from the motor and somatosensory cortices using intracortical microelectrode arrays while participants attempted to exert a static or ramping force up and down. Despite their inability to execute movement and limited afferent input, the spiking activity in motor and somatosensory cortex was modulated with the task. Within the neural response we identified independent neural modes - distinct patterns of population-level neural activity that were informative about both the timing and magnitude of the attempted force. Moreover, distinct neural modes were observed during static and dynamic grasping conditions, suggesting independent control schemes for maintaining and changing forces. These modes were related to phases of the task, including the onset, offset, holding periods, as well as increasing and decreasing attempted forces. These results will inform the design of intracortical brain-computer interface (iBCI) systems that can leverage the patterns of grasp and force control evident in sensorimotor cortex during attempted movement to restore dexterous hand function.Significance Statement Restoring dexterous hand function after injury remains a major challenge, partly due to an incomplete understanding of the cortical dynamics underlying grasping and force control. In this study, we investigated neural activity within the motor and somatosensory cortices of individuals with tetraplegia attempting to perform grasps to different target forces with varying temporal profiles. We identified distinct neural modes modulated during specific phases of grasp that encode attempted force information throughout the task. These findings suggest that brain-computer interfaces could leverage these neural modes to restore grasping and force modulation.
G. Blumenthal, B. Dekleva, C. Gontier et al.· Journal of Neuroscience· 0 citations
Upper limb prostheses fail to deliver complete tactile sensation, so most users depend on visual guidance and excessively adjust their grasping movements. The core research focus has shifted from integrating sensory feedback to selecting optimal stimulation strategies for generating tactile perception that is functional, anatomically consistent and neurophysiologically natural. This paper presents a PRISMA-informed scoping review of recent tactile feedback published from January 1, 2020, to May 31, 2026, then integrates classic anatomy and neuroprosthetic papers to build a compact evaluation framework. The initial search retrieved 136 records from PubMed. After removing 4 duplicate entries, 132 unique articles were screened by title and abstract. A total of 20 full-text articles were evaluated, among which 16 studies were finally included. Another eight landmark studies were manually retrieved from Google Scholar, Web of Science and IEEE Xplore to supplement the analysis of cortical mapping, mechanoreceptors, proprioception, motor unit recruitment and interface evolution. The synthesis shows that the strongest studies do not optimize stimulus intensity alone. They align stimulation site, encoding rule, and evaluation metrics with the upper limb afferent route from cutaneous receptors to somatotopic hand area (S1) and with the motor route that stabilizes grasp through corticospinal drive and residual muscle recruitment. On the basis of the synthesis, this work proposes a neuroanatomical mechanism diagram and a three-part evaluation criterion covering perceptual realism, functional utility, and neural congruence. The proposed framework provides a practical evaluation scaffold for selecting tactile feedback strategies in future bionic limb studies.
Xinbi Luo· Theoretical and Natural Scie...· 0 citations