1
|
McPherson JG, Bandres MF. Neural population dynamics reveal that motor-targeted intraspinal microstimulation preferentially depresses nociceptive transmission in spinal cord injury-related neuropathic pain. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.27.550880. [PMID: 37546721 PMCID: PMC10402167 DOI: 10.1101/2023.07.27.550880] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/08/2023]
Abstract
The purpose of this study is to determine whether intraspinal microstimulation (ISMS) intended to enhance voluntary motor output after spinal cord injury (SCI) modulates neural population-level spinal responsiveness to nociceptive sensory feedback. The study was conducted in vivo in three cohorts of rats: neurologically intact, chronic SCI without behavioral signs of neuropathic pain, and chronic SCI with SCI-related neuropathic pain (SCI-NP). Nociceptive sensory feedback was induced by application of graded mechanical pressure to the plantar surface of the hindpaw before, during, and after periods of sub-motor threshold ISMS delivered within the motor pools of the L5 spinal segment. Neural population-level responsiveness to nociceptive feedback was recorded throughout the dorso-ventral extent of the L5 spinal segment using dense multi-channel microelectrode arrays. Whereas motor-targeted ISMS reduced nociceptive transmission across electrodes in neurologically intact animals both during and following stimulation, it was not associated with altered nociceptive transmission in rats with SCI that lacked behavioral signs of neuropathic pain. Surprisingly, nociceptive transmission was reduced both during and following motor-targeted ISMS in rats with SCI-NP, and to an extent comparable to that of neurologically intact animals. The mechanisms underlying the differential anti-nociceptive effects of motor-targeted ISMS are unclear, although they may be related to differences in the intrinsic active membrane properties of spinal neurons across the cohorts. Nevertheless, the results of this study support the notion that it may be possible to purposefully engineer spinal stimulation-based therapies that afford multi-modal rehabilitation benefits, and specifically that it may be possible to do so for the individuals most in need - i.e., those with SCI-related movement impairments and SCI-NP.
Collapse
Affiliation(s)
- Jacob G. McPherson
- Program in Physical Therapy, Washington University School of Medicine
- Department of Anesthesiology, Washington University School of Medicine
- Washington University Pain Center, Washington University School of Medicine
- Program in Neurosciences; Washington University School of Medicine
- Department of Biomedical Engineering; Washington University in St. Louis
| | - Maria F. Bandres
- Program in Physical Therapy, Washington University School of Medicine
- Department of Biomedical Engineering; Washington University in St. Louis
| |
Collapse
|
2
|
Kaptan M, Horn U, Vannesjo SJ, Mildner T, Weiskopf N, Finsterbusch J, Brooks JCW, Eippert F. Reliability of resting-state functional connectivity in the human spinal cord: assessing the impact of distinct noise sources. Neuroimage 2023; 275:120152. [PMID: 37142169 DOI: 10.1016/j.neuroimage.2023.120152] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2023] [Revised: 04/20/2023] [Accepted: 05/01/2023] [Indexed: 05/06/2023] Open
Abstract
The investigation of spontaneous fluctuations of the blood-oxygen-level-dependent (BOLD) signal has recently been extended from the brain to the spinal cord, where it has stimulated interest from a clinical perspective. A number of resting-state functional magnetic resonance imaging (fMRI) studies have demonstrated robust functional connectivity between the time series of BOLD fluctuations in bilateral dorsal horns and between those in bilateral ventral horns, in line with the functional neuroanatomy of the spinal cord. A necessary step prior to extension to clinical studies is assessing the reliability of such resting-state signals, which we aimed to do here in a group of 45 healthy young adults at the clinically prevalent field strength of 3T. When investigating connectivity in the entire cervical spinal cord, we observed fair to good reliability for dorsal-dorsal and ventral-ventral connectivity, whereas reliability was poor for within- and between-hemicord dorsal-ventral connectivity. Considering how prone spinal cord fMRI is to noise, we extensively investigated the impact of distinct noise sources and made two crucial observations: removal of physiological noise led to a reduction in functional connectivity strength and reliability - due to the removal of stable and participant-specific noise patterns - whereas removal of thermal noise considerably increased the detectability of functional connectivity without a clear influence on reliability. Finally, we also assessed connectivity within spinal cord segments and observed that while the pattern of connectivity was similar to that of whole cervical cord, reliability at the level of single segments was consistently poor. Taken together, our results demonstrate the presence of reliable resting-state functional connectivity in the human spinal cord even after thoroughly accounting for physiological and thermal noise, but at the same time urge caution if focal changes in connectivity (e.g. due to segmental lesions) are to be studied, especially in a longitudinal manner.
Collapse
Affiliation(s)
- Merve Kaptan
- Max Planck Research Group Pain Perception, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany.
| | - Ulrike Horn
- Max Planck Research Group Pain Perception, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - S Johanna Vannesjo
- Department of Physics, Norwegian University of Science and Technology, Trondheim, Norway
| | - Toralf Mildner
- Methods & Development Group Nuclear Magnetic Resonance, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Nikolaus Weiskopf
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany; Felix Bloch Institute for Solid State Physics, Faculty of Physics and Earth Sciences, University of Leipzig, Leipzig, Germany
| | - Jürgen Finsterbusch
- Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Jonathan C W Brooks
- School of Psychology, University of East Anglia Wellcome Wolfson Brain Imaging Centre (UWWBIC), Norwich, United Kingdom
| | - Falk Eippert
- Max Planck Research Group Pain Perception, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany.
| |
Collapse
|
3
|
Bandres MF, Gomes JL, Moreno Romero GN, Twyman AR, McPherson JG. Precision neuromodulation: Promises and challenges of spinal stimulation for multi-modal rehabilitation. FRONTIERS IN REHABILITATION SCIENCES 2023; 4:1135593. [PMID: 37152244 PMCID: PMC10154513 DOI: 10.3389/fresc.2023.1135593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/01/2023] [Accepted: 03/24/2023] [Indexed: 05/09/2023]
Abstract
Spinal cord injury results in multiple, simultaneous sensorimotor deficits. These include, but are not limited to, full or partial paralysis of muscles below the lesion, muscle spasms, spasticity, and neuropathic pain. Bowel, bladder, and sexual dysfunction are also prevalent. Yet, the majority of emerging spinal stimulation-based therapies focus on a single issue: locomotor rehabilitation. Despite the enormous potential of these translational advances to transform the lives of people living with spinal cord injury, meaningful recovery in other domains deemed critical priorities remains lacking. Here, we highlight the importance of considering the diverse patterns of neural transmission that underlie clinically similar presentations when developing spinal stimulation-based therapies. We also motivate advancement of multi-modal rehabilitation paradigms, which leverage the dense interconnectivity of sensorimotor spinal networks and the unique ability of electrical stimulation to modulate these networks to facilitate and guide simultaneous rehabilitation across domains.
Collapse
Affiliation(s)
- Maria F. Bandres
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, United States
- Program in Physical Therapy, Washington University School of Medicine in St. Louis, St. Louis, MO, United States
| | - Jefferson L. Gomes
- Program in Physical Therapy, Washington University School of Medicine in St. Louis, St. Louis, MO, United States
| | - Gerson N. Moreno Romero
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, United States
| | - Avery R. Twyman
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, United States
| | - Jacob Graves McPherson
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, United States
- Program in Physical Therapy, Washington University School of Medicine in St. Louis, St. Louis, MO, United States
- Department of Anesthesiology, Washington University School of Medicine in St. Louis, St. Louis, MO, United States
- Washington University Pain Center, Washington University School of Medicine in St. Louis, St. Louis, MO, United States
- Washington University Program in Neurosciences, Washington University in St. Louis, St. Louis, MO, United States
| |
Collapse
|
4
|
Bandres MF, Gomes JL, McPherson JG. Spinal stimulation for motor rehabilitation immediately modulates nociceptive transmission. J Neural Eng 2022; 19:10.1088/1741-2552/ac9a00. [PMID: 36228593 PMCID: PMC9797038 DOI: 10.1088/1741-2552/ac9a00] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 10/13/2022] [Indexed: 12/31/2022]
Abstract
Objective. Spinal cord injury (SCI) often results in debilitating movement impairments and neuropathic pain. Electrical stimulation of spinal neurons holds considerable promise both for enhancing neural transmission in weakened motor pathways and for reducing neural transmission in overactive nociceptive pathways. However, spinal stimulation paradigms currently under development for individuals living with SCI continue overwhelmingly to be developed in the context of motor rehabilitation alone. The objective of this study is to test the hypothesis that motor-targeted spinal stimulation simultaneously modulates spinal nociceptive transmission.Approach. We characterized the neuromodulatory actions of motor-targeted intraspinal microstimulation (ISMS) on the firing dynamics of large populations of discrete nociceptive specific and wide dynamic range (WDR) neurons. Neurons were accessed via dense microelectrode arrays implantedin vivointo lumbar enlargement of rats. Nociceptive and non-nociceptive cutaneous transmission was induced before, during, and after ISMS by mechanically probing the L5 dermatome.Main results. Our primary findings are that (a) sub-motor threshold ISMS delivered to spinal motor pools immediately modulates concurrent nociceptive transmission; (b) the magnitude of anti-nociceptive effects increases with longer durations of ISMS, including robust carryover effects; (c) the majority of all identified nociceptive-specific and WDR neurons exhibit firing rate reductions after only 10 min of ISMS; and (d) ISMS does not increase spinal responsiveness to non-nociceptive cutaneous transmission. These results lead to the conclusion that ISMS parameterized to enhance motor output results in an overall net decrease n spinal nociceptive transmission.Significance. These results suggest that ISMS may hold translational potential for neuropathic pain-related applications and that it may be uniquely suited to delivering multi-modal therapeutic benefits for individuals living with SCI.
Collapse
Affiliation(s)
- Maria F. Bandres
- Program in Physical Therapy, Washington University School of Medicine in St. Louis
- Department of Biomedical Engineering; Washington University in St. Louis
| | - Jefferson L. Gomes
- Program in Physical Therapy, Washington University School of Medicine in St. Louis
| | - Jacob G. McPherson
- Program in Physical Therapy, Washington University School of Medicine in St. Louis
- Department of Anesthesiology, Washington University School of Medicine in St. Louis
- Washington University Pain Center, Washington University School of Medicine in St. Louis
- Program in Neuroscience; Washington University School of Medicine in St. Louis
- Department of Biomedical Engineering; Washington University in St. Louis
| |
Collapse
|
5
|
Zaback M, Tiwari E, Krupka AJ, Marchionne F, Negro F, Lemay MA, Thompson CK. Toward Assessing the Functional Connectivity of Spinal Neurons. Front Neural Circuits 2022; 16:839521. [PMID: 35310548 PMCID: PMC8927546 DOI: 10.3389/fncir.2022.839521] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Accepted: 01/28/2022] [Indexed: 12/14/2022] Open
Abstract
Spinal interneurons play a critical role in motor output. A given interneuron may receive convergent input from several different sensory modalities and descending centers and relay this information to just as many targets. Therefore, there is a critical need to quantify populations of spinal interneurons simultaneously. Here, we quantify the functional connectivity of spinal neurons through the concurrent recording of populations of lumbar interneurons and hindlimb motor units in the in vivo cat model during activation of either the ipsilateral sural nerve or contralateral tibial nerve. Two microelectrode arrays were placed into lamina VII, one at L3 and a second at L6/7, while an electrode array was placed on the surface of the exposed muscle. Stimulation of tibial and sural nerves elicited similar changes in the discharge rate of both interneurons and motor units. However, these same neurons showed highly significant differences in prevalence and magnitude of correlated activity underlying these two forms of afferent drive. Activation of the ipsilateral sural nerve resulted in highly correlated activity, particularly at the caudal array. In contrast, the contralateral tibial nerve resulted in less, but more widespread correlated activity at both arrays. These data suggest that the ipsilateral sural nerve has dense projections onto caudal lumbar spinal neurons, while contralateral tibial nerve has a sparse pattern of projections.
Collapse
Affiliation(s)
- Martin Zaback
- Department of Health and Rehabilitation Sciences, College of Public Health, Temple University, Philadelphia, PA, United States,Department of Bioengineering, College of Engineering, Temple University, Philadelphia, PA, United States
| | - Ekta Tiwari
- Department of Bioengineering, College of Engineering, Temple University, Philadelphia, PA, United States,School of Engineering, Brown University, Providence, RI, United States
| | - Alexander J. Krupka
- Department of Bioengineering, College of Engineering, Temple University, Philadelphia, PA, United States,Department of Biology, DeSales University, Center Valley, PA, United States
| | - Francesca Marchionne
- Department of Bioengineering, College of Engineering, Temple University, Philadelphia, PA, United States
| | - Francesco Negro
- Department of Clinical and Experimental Sciences, Universita degli Studi di Brescia, Brescia, Italy
| | - Michel A. Lemay
- Department of Bioengineering, College of Engineering, Temple University, Philadelphia, PA, United States
| | - Christopher K. Thompson
- Department of Health and Rehabilitation Sciences, College of Public Health, Temple University, Philadelphia, PA, United States,Shriner’s Hospital for Children, Philadelphia, PA, United States,*Correspondence: Christopher K. Thompson,
| |
Collapse
|