Journal of Neurophysiology

Aging, Force, and Feedback: Rethinking Proprioception Through Motor Unit Insights

In this episode, coauthor Mélanie Henry highlights the findings of the newly published study, “Influence of Age and Feedback Modality on the Proprioceptive Sense of Force: Insights from Motor Unit Recordings.”  She discusses how different types of feedback—auditory vs. visual—affect force-reproduction accuracy across age groups. Surprisingly, middle-aged and older adults performed better with auditory feedback, an improvement linked to increased motor unit coherence in the beta band. Tune in to explore how aging influences proprioception, how the brain adapts to different sensory inputs, and what this means for motor control and rehabilitation strategies.

 

Influence of age and feedback modality on the proprioceptive sense of force: insights from motor unit recordings

Mélanie Henry, Abdulkerim Darendeli, Taylor Tvrdy, Sajjad Daneshgar, and Roger M. Enoka

Journal of Neurophysiology 2025 133:4, 1103-1115

Unlocking the Spine: Exploring the Neurophysiology of Dry Needling

In this episode, coauthor Gretchen Seif discusses her recently published study, “Neurophysiological Effects of Latent Trigger Point Dry Needling on Spinal Reflexes.” Dive into the fascinating world of deep dry needling (DDN) as she highlights its impact on spinal reflexes in the triceps surae. Dr. Seif breaks down the study's key findings—including unchanged H reflex responses and increased soleus inhibition immediately and 72 hours post-DDN—along with the observed gains in ankle range of motion. Learn how these differential effects on excitatory and inhibitory reflexes reveal the complex spinal-level mechanisms of DDN and what it could mean for clinical practice.

 

Neurophysiological effects of latent trigger point dry needling on spinal reflexes

Gretchen Seif, Alan M. Phipps, Joseph M. Donnelly, Blair H. S. Dellenbach, and Aiko K. Thompson

Journal of Neurophysiology 2025 133:1, 288-298

JNP Podcasts: Unlocking Insulin's Mechanism: Activation of Parasympathetic Hepatic Neurons via mTOR Signaling

In this episode, coauthor Karoline Martins dos Santos discusses the recently published research, "Insulin activates parasympathetic hepatic-related neurons of the paraventricular nucleus of the hypothalamus through mTOR signaling." The study investigates the complex role of insulin in regulating hepatic glucose production, focusing on how insulin influences specific brain regions. While it's known that insulin reduces liver glucose production, the precise mechanisms and brain areas involved have remained unclear. Dr. Martins dos Santos explains how insulin activates parasympathetic hepatic-related neurons in the paraventricular nucleus (PVNhepatic) and how this process relies on mTOR signaling. 

 

Insulin activates parasympathetic hepatic-related neurons of the paraventricular nucleus of the hypothalamus through mTOR signaling

Karoline Martins dos Santos, Sandy E. Saunders, Vagner R. Antunes, and Carie R. Boychuk

Journal of Neurophysiology 2025 133:1, 320-332

JNP Podcasts: Decoding Motor Control - Estimating Descending Activation in Fast and Slow Movements

In this episode, coauthor Lei Zhang explores the research titled "Estimating descending activation patterns from EMG in fast and slow movements using a model of the stretch reflex." Lei introduces a novel method that directly estimates descending activation from electromyographic (EMG) signals and arm kinematics by inverting a model of the spinal stretch reflex—without relying on muscle models or an arm dynamics model. This innovative approach uncovers how movement speed influences the time structure of descending activation, while also highlighting the crucial role of the spinal stretch reflex in movement generation.

 

Estimating descending activation patterns from EMG in fast and slow movements using a model of the stretch reflex

Lei Zhang and Gregor Schöner

Journal of Neurophysiology 2025 133:1, 162-176

JNP Podcasts: The Power of Light Touch: How Fingertip Contact Modulates Balance and Vestibular Responses

In this episode, coauthor Megan Goar discusses the recently published research titled "Light touch alters vestibular-evoked balance responses: insights into dynamics of sensorimotor reweighting." The research uncovers how minimal fingertip contact (light touch) during balance tasks can reduce the impact of electrical vestibular stimulation (EVS) on body sway. Not only does this touch alter sway magnitude, but it also reveals a high-frequency center of pressure element, tied to vestibular inputs, that is typically unseen in free-standing postures. Ms. Goar explains how these findings highlight the central nervous system’s remarkable ability to adaptively reweight sensorimotor processes to optimize balance control.

 

Light touch alters vestibular-evoked balance responses: insights into dynamics of sensorimotor reweighting

Megan H. Goar, Michael Barnett-Cowan, and Brian C. Horslen

Journal of Neurophysiology 2025 133:1, 142-161

JNP Podcasts: Improving localization and measurements of M-waves using high-density surface electromyography

In this episode, coauthor Ernesto Bedoy discusses their recently published research, "Improving Localization and Measurements of M-Waves Using High-Density Surface Electromyography." The study presents an innovative approach to enhancing the measurement of evoked potentials through high-density surface electromyography (HD-sEMG). By incorporating spatial filters and ultrasound imaging, the research significantly improves the precision and localization of evoked potentials, providing a more accurate method for assessing motor pathway integrity. These advancements hold promise for developing better tools to detect and treat neurological deficits, offering a significant contribution to the field of neurophysiological research.

 

Improving localization and measurements of M-waves using high-density surface electromyography

Ernesto H. Bedoy, Efrain A. Guirola Diaz, Ashley N. Dalrymple, Isaiah Levy, Thomas Hyatt, Darcy M. Griffin, George F. Wittenberg, and Douglas J. Weber

Journal of Neurophysiology 2025 133:1, 299-309

JNP Podcasts: Hypercapnia elicits changes in diaphragm neuromotor control

In this episode, coauthor Obaid U. Khurram discusses their recently published research, "Hypercapnia Impacts Neural Drive and Timing of Diaphragm Neuromotor Control." The study explores the complex neuromotor control of the diaphragm muscle (DIAm) under hypercapnic conditions, an area that has not been fully understood. Dr. Khurram explains how hypercapnia increases motor unit recruitment and discharge rates, indicating an enhanced respiratory drive. The research also reveals how hypercapnia affects the postinspiratory (descending) ramp of diaphragm EMG activity, shortening it to facilitate faster respiratory rates. Tune in for valuable insights into the physiological mechanisms of diaphragm function and adaptation in response to elevated carbon dioxide levels.

 

Hypercapnia impacts neural drive and timing of diaphragm neuromotor control

Obaid U. Khurram, Maximilian J. Kantor-Gerber, Carlos B. Mantilla, and Gary C. Sieck

Journal of Neurophysiology 2024 132:6, 1966-1976

JNP Micro Podcasts: Flexion reflexes during transspinal stimulation

In this episode, coauthors Maria Knikou and Abdullah M. Sayed Ahmad discuss their research on "Transspinal stimulation downregulates flexion reflex pathways during walking in healthy humans." The study investigates how transspinal stimulation over the thoracolumbar region affects reflex pathways during walking, revealing its ability to suppress the tibialis anterior flexion reflex at varying frequencies (15, 30, and 50 Hz).

Transspinal stimulation downregulates flexion reflex pathways during walking in healthy humans

Maria Knikou and Abdullah M. Sayed Ahmad

Journal of Neurophysiology 2025 133:2, 530-538

JNP Micro Podcasts: Impact of glucagon-like peptide-1 receptor agonists on axonal function in diabetic peripheral neuropathy

In this episode, coauthor Arun V. Krishnan highlights the article titled "Impact of glucagon-like peptide-1 receptor agonists on axonal function in diabetic peripheral neuropathy." Diabetic peripheral neuropathy is known to be relentlessly progressive and irreversible. Prospective studies in 24 participants with diabetic peripheral neuropathy (DPN) treated with glucagon-like peptide-1 receptor agonists (GLP-1RA) demonstrated improvements in clinical neuropathy scores, nerve conduction studies, and axonal excitability recordings. Analysis of axonal excitability recordings revealed the mechanism for GLP-1RA improvement in DPN were changed consistent with improvements in Na⁺/K⁺–ATPase pump function, and this was supported by mathematical modeling.

 

Impact of glucagon-like peptide-1 receptor agonists on axonal function in diabetic peripheral neuropathy

Roshan Dhanapalaratnam, Tushar Issar, Ann M. Poynten, Kerry-Lee Milner, Natalie C. G. Kwai, and Arun V. Krishnan

Journal of Neurophysiology 2025 133:1, 14-21

JNP Micro Podcasts: Uncovering Balance Control from Foot Force

Join coauthors Rika Dimitrova and Kaymie Shiozawa in this podcast where they dive deep into their research on human balance control. In this episode, they explore the insights of three papers: "Frequency-domain patterns in foot-force line-of-action: an emergent property of standing balance control," "Human foot force suggests different balance control between younger and older adults," and "Human foot force informs balance control strategies when standing on a narrow beam."

Their work uncovers a novel, closed-form analytical result that links the frequency-domain patterns of foot force to the body’s neuromotor control during quiet standing. The podcast delves into the complexities of balance control in different age groups, demonstrating how older adults adapt their balance strategies to compensate for muscle weakness, relying more on neural feedback. With a focus on foot-ground force interactions, the duo breaks down how these findings can provide a new balance assessment tool, highlighting its significance in both research and real-world applications.

Additionally, Dr. Sugimoto-Dimitrova and Dr. Shiozawa discuss the challenges of maintaining balance in more demanding conditions—such as standing on a narrow beam—and explore how biomechanics and neural control work together to stabilize the body.

 

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Frequency-domain patterns in foot-force line-of-action: an emergent property of standing balance control

Rika Sugimoto-Dimitrova, Kaymie Shiozawa, Kreg G. Gruben, and Neville Hogan

Journal of Neurophysiology 2024 132:5, 1445-1456

 

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Human foot force suggests different balance control between younger and older adults

Kaymie Shiozawa, Rika Sugimoto-Dimitrova, Kreg G. Gruben, and Neville Hogan

Journal of Neurophysiology 2024 132:5, 1457-1469

 

Human foot force informs balance control strategies when standing on a narrow beam

Kaymie Shiozawa, Marta Russo, Jongwoo Lee, Neville Hogan, and Dagmar Sternad

Journal of Neurophysiology 2024 132:4, 1302-1314