Journal of neurophysiology最新文献

{"title":"Role of voltage-gated Ca²⁺ channel dysfunction in gastric vagal afferent neuropathy following spinal cord injury.","authors":"Hannah J Goudsward, Victor Ruiz-Velasco, Salvatore L Stella, Gregory M Holmes","doi":"10.1152/jn.00230.2025","DOIUrl":"10.1152/jn.00230.2025","url":null,"abstract":"<p><p>Upper gastrointestinal dysfunction is one of the most common comorbidities of spinal cord injury (SCI) and significantly impairs overall health and quality of life. Despite the need for targeted treatment options, the causal mechanisms underlying upper gastrointestinal dysfunction after injury remains unknown. Previous studies have demonstrated gastric vagal afferents are less sensitive to stimuli after SCI, which may be due to changes in voltage-gated Ca²⁺ (Ca_V) channels in gastric-projecting nodose ganglia (NG) neurons, as they contribute to action potential initiation along vagal afferents and neurotransmitter release at central synapses. Therefore, the purpose of this study was to investigate whether altered function of Ca_V channels in gastric NG neurons develops after upper thoracic SCI using whole cell patch-clamp electrophysiology. Although no change in the biophysical properties of Ca_V channels were observed 3-days postinjury, there was a significant (<i>P</i> = 0.0006) reduction in the Ca²⁺ current density in gastric NG neurons isolated from 3-wk SCI animals as compared with controls (16.41 ± 2.41 pA/pF vs. 39.92 ± 5.63 pA/pF). When evaluating the Ca_V channel expression profile, we found the Ca_V2.2 blocker ω-conotoxin produced the largest Ca²⁺ current inhibition in the 3-day SCI (60.0 ± 6.6%, <i>n</i> = 13), 3-wk SCI (59.4 ± 6.7%, <i>n</i> = 15), and control groups (3-day: 67.4 ± 8.1%, <i>n</i> = 11; 3-wk: 58.3 ± 5.0%). However, the effect of ω-agatoxin was significantly (<i>P</i> = 0.0225) higher in the 3-wk SCI group compared with the 3-day SCI group. These findings suggest Ca_V channel currents are reduced following 3-wk SCI in gastric NG neurons, offering necessary insights into the cellular mechanisms underlying vagal afferent hyposensitivity postinjury.<b>NEW & NOTEWORTHY</b> This study demonstrated that voltage-gated Ca²⁺ channel currents are diminished in gastric vagal afferent neurons 3 wk following experimental spinal cord injury. In addition, there is an increased contribution of P/Q-type channels 3-wk postinjury, though N-type channels still provide the majority of Ca²⁺ currents. These results provide necessary insight into the cellular mechanism underlying the pathophysiological reduction of gastric vagal afferent sensitivity after injury, which may benefit future studies investigating therapeutic interventions for the neurogenic gut.</p>","PeriodicalId":16563,"journal":{"name":"Journal of neurophysiology","volume":" ","pages":"875-886"},"PeriodicalIF":2.1,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12416546/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144789341","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Differences in Hebbian stimulation effects between biceps and triceps brachii in humans.","authors":"Carley L P Butler, Minkyu Lee, Monica A Perez","doi":"10.1152/jn.00168.2025","DOIUrl":"10.1152/jn.00168.2025","url":null,"abstract":"<p><p>Animal and human studies indicate that monosynaptic corticospinal connections are more prevalent in biceps than triceps brachii motoneurons. Based on this evidence, we hypothesized that Hebbian stimulation, which targets corticospinal-motoneuronal connections, would enhance corticospinal excitability more in the biceps than the triceps brachii. To test this hypothesis, we assessed motor-evoked potential (MEP) size using transcranial magnetic stimulation (TMS) at resting motor threshold (MEP-RMT) and maximum stimulator output (MEP-100%) immediately and up to 30 min poststimulation. During Hebbian stimulation, 180 paired pulses were delivered, with corticospinal volleys evoked by TMS arriving at corticospinal-motoneuronal synapses 1-2 ms before antidromic potentials from brachial plexus electrical stimulation. Central and peripheral conduction times were similar between muscles. We found that both MEP-RMT and MEP-100% increase in the biceps and triceps immediately and up to 30 min poststimulation. The increase in MEP-RMT was greater in the biceps compared with the triceps, whereas MEP-100% changes did not differ between muscles. Since the maximum MEP size was larger in the biceps than in the triceps, we conducted a control experiment testing responses at an intermediate size between MEP-RMT and MEP-100% (MEP-Control), ensuring similar baseline sizes between muscles. Notably, Hebbian stimulation continued to produce a greater increase in MEP-Control in the biceps than in the triceps. These findings suggest that Hebbian plasticity enhances corticospinal excitability more in the elbow flexor than extensor muscles, emphasizing the need to consider muscle-specific innervation patterns when future studies assess the therapeutic effect of this technique in individuals with motor impairment.<b>NEW & NOTEWORTHY</b> Differences in corticospinal projections to elbow flexor and extensor motoneurons are well established. Our findings demonstrate that Hebbian stimulation, based on spike-timing-dependent plasticity, enhances corticospinal excitability more in the biceps brachii than in the triceps brachii. These results highlight the importance of incorporating muscle-specific innervation patterns when designing plasticity-driven therapeutic strategies.</p>","PeriodicalId":16563,"journal":{"name":"Journal of neurophysiology","volume":" ","pages":"887-895"},"PeriodicalIF":2.1,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144682708","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Compression of motor unit recruitment threshold patterns is present in the subacute phase poststroke.","authors":"Mio Ito, Takanori Ito, Hayase Funakoshi, Kei Takahata, Nina L Suresh, Takanori Kokubun","doi":"10.1152/jn.00179.2025","DOIUrl":"10.1152/jn.00179.2025","url":null,"abstract":"<p><p>Voluntary contraction anomalies of poststroke survivors progress from flaccid paralysis to recovery of upper extremity motor function in the subacute phase. However, muscle weakness often persists, and it is unclear what changes or aberrations persist in neuromuscular function, particularly in motor unit behavior. Our objective was to characterize motor unit discharge behavior in patients with hemiplegic stroke in the subacute phase. We tested seven patients with subacute stroke at two timepoints (timepoints 1 and 2), a minimum of 2 wk apart during the subacute phase. We used wireless surface electromyography to detect motor unit activities on both sides of our tested participants. Participants carried out two types of target force-tracking tasks with isometric elbow flexion. We performed a two-way ANOVA between the timepoint and test side. The recruitment threshold force (RTF) of the ramp task exhibited a significant interaction between the timepoint and test side (<i>P</i> < 0.00). The post hoc test showed the RTF of the affected side was not significantly lower than the contralateral side (<i>P</i> = 0.99) at timepoint 1. On the contrary, the affected side at timepoint 2 was significantly lower than the contralateral side (<i>P</i> < 0.00). The low recruitment threshold on the affected side may be more exacerbated than the contralateral side chronologically during the subacute phase of stroke. Our results suggest that the assessment of motor units in the subacute phase of stroke can contribute to the early detection of abnormal neuromuscular activity and, thereby, the establishment of effective rehabilitation.<b>NEW & NOTEWORTHY</b> This study clarified altered chronological motor unit recruitment patterns in the subacute stroke. We revealed that the neuromuscular physiological abnormalities on the affected side may persist from the subacute period to the chronic stage. To maximize recovery of motor function in patients with prolonged stroke symptoms, it is necessary to detect neuromuscular dysfunction in the subacute phase and establish early prevention. This study provided fundamental knowledge on the preventive rehabilitation of persistent paresis during the subacute phase.</p>","PeriodicalId":16563,"journal":{"name":"Journal of neurophysiology","volume":" ","pages":"896-903"},"PeriodicalIF":2.1,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144835392","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Changes in heartbeat-evoked potentials reflect changes in blood pressure.","authors":"Arthur Plantard, Romain Séry, Vincent Pichot, Florian Chouchou","doi":"10.1152/jn.00118.2025","DOIUrl":"10.1152/jn.00118.2025","url":null,"abstract":"<p><p>The heartbeat-evoked potential (HEP) is a growingly used electrophysiological method to study cardiac interoception; however, cardiovascular influences on these responses are not fully understood. In the present study, we studied the effect of changes in blood pressure through positional modifications and slow-paced breathing on HEP. Eighteen volunteers (22 ± 1.79 yr old) underwent 5-min tasks in upright and supine positions, with spontaneous and slow-paced breathing at 6 cycles/min. We continuously recorded blood pressure, electrocardiography, and high-density (128 electrodes) electroencephalography (EEG). We observed an increase in early (around 200 ms) and late (around 400 ms) HEP components in the supine position (<i>P</i> < 0.001) and more pronounced with slow-paced breathing (<i>P</i> < 0.001). HEP exhibited a frontocentral topography, and source modeling indicated mainly insular and cingulate cortex of the early component, which extended to frontal regions during the late component (<i>P</i> < 0.05). Diastolic (DBP) and pulse (PBP) blood pressure increased in an upright position (<i>P</i> < 0.05), whereas baroreflex sensitivity (BRS) increased in the supine position (<i>P</i> < 0.001). Changes in early and late HEP were mainly correlated to changes in PBP (<i>r</i> = 0.55; <i>r</i> = 0.49, respectively, <i>P</i> < 0.001), DBP (<i>r</i> = -0.35; <i>r</i> = -0.35, <i>P</i> < 0.010), and BRS (<i>r</i> = 0.61; <i>r</i> = 0.47, <i>P</i> < 0.001). The present study demonstrated modulations of HEP according to cardiovascular activities, suggesting a heightened integration of baroreflex afferents by positional modulations and to a lesser extent by respiratory modulations. These changes should be considered in assessments of interoception in clinical populations.<b>NEW & NOTEWORTHY</b> Heartbeat-evoked potentials (HEPs) allow to explore the interaction between cardiovascular and central nervous systems, showing that interoceptive processing may influence cognitive, emotional, and sensorimotor functions. However, the extent to which cardiovascular dynamics modulate HEPs remains unclear. Here, we demonstrate that cardiovascular changes alter both early and late cortical responses, indicating that HEPs are strongly influenced by the cardiovascular system.</p>","PeriodicalId":16563,"journal":{"name":"Journal of neurophysiology","volume":" ","pages":"830-842"},"PeriodicalIF":2.1,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144682691","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Resting-state brain dynamics are associated with cardiovascular and metabolic profiles in healthy adults.","authors":"Mariya Patel, Joe Braun, Charlotte Keatch, Tatiana Kameneva, Will Woods, Elisabeth Lambert","doi":"10.1152/jn.00114.2025","DOIUrl":"10.1152/jn.00114.2025","url":null,"abstract":"<p><p>Cardiovascular and metabolic dysfunction plays a significant role in the onset and progression of inflammation and cerebrovascular diseases, often leading to cognitive impairment. Although growing evidence highlights the link between activity in key brain regions and cardiovascular disease events, the relationship between brain dynamics and cardiovascular or metabolic profiles in healthy individuals remains largely unexplored. We performed magnetoencephalography in 29 healthy participants (12 males and 17 females; aged 19-72 yr). Brain activity, calculated as neural activity index (NAI), was determined in 15 regions of interest in each participant. Brachial and central blood pressure (BP), arterial stiffness, and metabolic profile were assessed. Brachial diastolic BP correlated positively with NAI in the right parahippocampal gyrus, insula, and amygdala (across several frequency bands), whereas both central systolic and diastolic BP correlated positively with NAI in the left orbitofrontal cortex (θ and α bands). Arterial stiffness measured via augmentation index correlated negatively with NAI in the left and right medial prefrontal cortex (δ and high-γ bands), whereas pulse wave velocity correlated positively with the left caudate (θ and α bands). NAI in several brain regions showed associations with metabolic parameters (lipid levels, kidney function, and liver proteins), including the middle frontal gyrus, anterior cingulate gyrus, lateral occipital cortex, precuneus, insula, parahippocampal gyrus, hippocampus, amygdala, putamen, and thalamus (across several frequency bands). We have shown that activity in key brain regions correlated with cardiovascular and metabolic profiles in healthy individuals, suggesting that regions involved in cognitive and emotional processing may be influenced by or contribute to cardiovascular and metabolic health.<b>NEW & NOTEWORTHY</b> Using magnetoencephalography, we have shown for the first time, a non-task-related association of resting-state brain dynamics with cardiovascular and metabolic profiles in a group of healthy individuals. These findings are important in understanding that even in healthy individuals, early associations between brain function and cardiovascular-metabolic health can be detected before the development of any disease states.</p>","PeriodicalId":16563,"journal":{"name":"Journal of neurophysiology","volume":" ","pages":"1020-1031"},"PeriodicalIF":2.1,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144957691","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Early onset of hyperexcitability of medial mammillary body neurons in 5XFAD⁺ mice-an early target of Alzheimer's disease.","authors":"Todd L Stincic, Jian Qiu, Cole Martinson, Martin J Kelly, Oline K Ronnekleiv","doi":"10.1152/jn.00310.2025","DOIUrl":"10.1152/jn.00310.2025","url":null,"abstract":"<p><p>There are over seven million people in the United States living with Alzheimer's disease (AD), and two-thirds of these patients are postmenopausal women. In addition to neurodegenerative changes within the cortex and hippocampus, there are pronounced pathological changes in the mammillary bodies (MBs), which are thought to play a role in the development of AD. Currently, we documented in 5XFAD⁺ female mice that there was an early onset of Aβ immunostaining extracellularly that coincided with increased staining of vesicular glutamate transporter2 (vGlut2) intracellularly in medial MB neurons. We saw these changes at as early as 2 mo of age that reached a maximum by 3-4 mo. Using whole-cell current clamp and voltage clamp recordings from medial MB neurons of 4-mo-old females, we discovered that in 5XFAD⁺ ovariectomized females, the medial MB neurons were significantly depolarized and were hyperexcited based on their decreased rheobase and higher firing frequency (<i>F</i>-<i>I</i> curve) than their littermate controls. There was an increase in the persistent sodium current and the T-type calcium current that contributed to the pronounced increase in the excitability. Although medial MB neurons from 4-mo-old 5XFAD⁺ male mice did not show differences in their cellular properties, they did exhibit a pronounced increase in excitability (<i>F</i>-<i>I</i> curve) versus their littermate controls. Therefore, the hyperexcitability of medial MB neurons, which correlated with the high expression of vGlut2, could affect downstream targets in the anterior thalamic nuclei and beyond (e.g., entorhinal cortex), causing a clear cascading effect on the Papez circuitry excitability.<b>NEW & NOTEWORTHY</b> This study reveals early pathological changes in the medial mammillary bodies of female 5XFAD⁺ mice, an Alzheimer's disease model, with increased Aβ and vGlut2 expression beginning at 2 mo. Electrophysiological recordings show that female MB neurons are in a hyperexcitable state, driven by enhanced persistent sodium and T-type calcium currents. These changes suggest that MB dysfunction may contribute to Papez circuit hyperexcitability in AD, highlighting a previously underexplored site of pathology in postmenopausal females.</p>","PeriodicalId":16563,"journal":{"name":"Journal of neurophysiology","volume":" ","pages":"928-939"},"PeriodicalIF":2.1,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12453389/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144789340","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A complex social-acoustical environment supports development and maintenance in the zebra finch auditory pallium.","authors":"Samantha M Moseley, C Daniel Meliza","doi":"10.1152/jn.00247.2025","DOIUrl":"10.1152/jn.00247.2025","url":null,"abstract":"<p><p>Postnatal experience is critical to auditory development in vertebrates. The Australian zebra finch (<i>Taeniopygia castanotis</i>) provides a valuable model for understanding how complex social-acoustical environments influence the development of the neural circuits that support the perception of vocal communication signals. We previously showed that zebra finches raised by their parents in a breeding colony [colony-reared (CR)] perform twice as well in a song discrimination task as birds raised with only their families [pair-reared (PR)], and we identified functional differences within the auditory pallium of PR birds that could explain this behavioral effect. Here, using single-unit extracellular recordings from the L3 subdivision of field L and caudomedial nidopallium (NCM) at three developmental timepoints (18-20, 30-35, and 90-110 days post hatch), we tracked how experience affects the emergence of these functional properties. Although CR birds showed stable single-unit response properties from fledging to adulthood alongside improvements in population-level encoding, PR birds exhibited changes in neural function that began emerging at 18 days for population metrics and by 30 days for single-unit properties, progressing into adulthood. These included altered spike waveforms, reduced firing rates, lower selectivity, lower discriminability, lower coding efficiency, and lower noise invariance. Notably, these functional changes occurred despite PR birds receiving normal exposure to the song of a male tutor, suggesting that plasticity supporting song memorization is dissociable from plasticity that supports recognition of conspecifics' songs. Our findings demonstrate that a complex social-acoustical environment is necessary for the development and maintenance of the cortical-level auditory circuits that decode conspecific vocalizations.<b>NEW & NOTEWORTHY</b> Young zebra finches need to hear songs and calls from many birds to maintain and develop normal auditory brain circuits. When birds are raised in impoverished social-acoustical environments, the functional properties of auditory neurons change from fledging through adulthood, losing the ability to discriminate and encode vocal signals effectively. Remarkably, these deficits occur despite normal exposure to tutor song, suggesting that song memorization and auditory perception rely on different developmental mechanisms with distinct experience requirements.</p>","PeriodicalId":16563,"journal":{"name":"Journal of neurophysiology","volume":" ","pages":"1032-1046"},"PeriodicalIF":2.1,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12452028/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144957567","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Analysis of shared synaptic inputs to different motor unit subgroups in triceps surae during a postural standing task.","authors":"Joshua W Cohen, Taian Vieira, Tanya D Ivanova, S Jayne Garland","doi":"10.1152/jn.00508.2024","DOIUrl":"10.1152/jn.00508.2024","url":null,"abstract":"<p><p>Previously, we have observed differential firing behaviors and recruitment locations of distinct motor unit (MU) subgroups within the same muscles. This study examined the amount of shared synaptic inputs to these MU subgroups. Twenty-four participants (10 healthy young adults: 5 females, 5 males; means ± SD: age 27 ± 2.5 yr and 14 healthy older adults: 6 males and 8 females; means ± SD: age 74.8 ± 5.3 yr) stood on a force platform and leaned in five directions maintaining their center of pressure for 35 s per direction. High-density surface electromyography recordings from the medial gastrocnemius, lateral gastrocnemius, and soleus were decomposed into single MU action potentials. MU tracking classified MUs as \"common\" or \"unique\" across leaning directions. Synaptic input was estimated using a coherence analysis (proportion of common input; PCI). Three PCI analyses (common, unique, and between the MU subgroups) quantified neural connectivity. MU subgroup significantly affected PCI (<i>F</i> = 25.92, <i>P</i> < 0.0001), with common MUs exhibiting higher PCI than unique (MD = 0.08, CI [0.07, 0.09], <i>P</i> < 0.0001) and between-subgroup MUs (MD = 0.04, CI [0.03, 0.05], <i>P</i> = 0.0058). Unique MUs had significantly lower PCI than between-subgroup MUs (MD = 0.04, CI [0.03, 0.06], <i>P</i> = 0.048). Taken together, both subgroups receive shared neural inputs for task-specific force production, more so in the common motor units. Importantly, a main effect of age (<i>F</i> = 4.56, <i>P</i> = 0.04) was observed, with older adults exhibiting higher PCI, though post hoc analyses did not reveal significant differences (<i>P</i> = 0.45-0.67).<b>NEW & NOTEWORTHY</b> Our study reveals differing amounts of shared neural inputs to MU subgroups within the same muscle during standing balance. The proportion of common input (PCI) varies with leaning direction, indicating task dependency and different descending and proprioceptive inputs. Surprisingly, age did not significantly affect PCI values in any MU subgroup or the entire muscle, suggesting that age-related differences in recruitment and firing patterns are more related to factors such as proprioceptive feedback than a common input.</p>","PeriodicalId":16563,"journal":{"name":"Journal of neurophysiology","volume":" ","pages":"1007-1019"},"PeriodicalIF":2.1,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144883053","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Short-latency afferent inhibition on cortical motor representation in healthy humans.","authors":"Akiko Yuasa, Shintaro Uehara, Boqun Liu, Yohei Otaka","doi":"10.1152/jn.00064.2025","DOIUrl":"10.1152/jn.00064.2025","url":null,"abstract":"<p><p>The motor system continuously receives sensory inputs and uses this information to perform purposeful movements in a process known as sensorimotor integration. As a biomarker of sensorimotor integration efficacy, short-latency afferent inhibition (SAI), the phenomenon whereby afferent sensory inputs inhibit cortical motor outputs in a given muscle, has been widely studied in humans. However, it remains unclear how the (sensory) nerve-muscle relationship, that is, anatomical proximity and homotopy (nerve supply to muscles), affects SAI magnitude. To address this question, we assessed SAI magnitudes in cortical motor excitability by examining the size of the motor representations of two intrinsic hand muscles when afferent inputs were provided to the nerves either innervating or noninnervating the muscles. In 16 healthy adults, we measured the effect of conditioning electrical stimuli to the median nerve (MN) or ulnar nerve (UN) at the wrist on motor evoked potentials induced by transcranial magnetic stimulation in the first dorsal interosseous (innervated by UN) and abductor pollicis brevis (innervated by MN) muscles, both of which are anatomically located closer to MN than to UN. Conditioning MN stimulation resulted in a significant SAI in both muscles, with no significant difference in SAI between the muscles. No clear SAI was found in either muscle with the UN stimulation. These results suggest that SAI magnitude may depend on anatomical proximity rather than on homotopy. Given the inhibition of the motor representation size of both muscles, the specific nature of such SAI may contribute to the synergistic coordination between muscles.<b>NEW & NOTEWORTHY</b> We found the significant SAI in both cortical broad (motor map) and local (hotspot) areas of the FDI and APB hand muscles only when a conditioning stimulus was delivered to the MN not to the UN. These results suggest that the SAI magnitude may depend on anatomical proximity rather than homotopic interactions between the nerve-muscle relationship, which may contribute to the synergistic coordination of muscles in response to afferent sensory inputs.</p>","PeriodicalId":16563,"journal":{"name":"Journal of neurophysiology","volume":" ","pages":"866-874"},"PeriodicalIF":2.1,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144784499","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Central and peripheral fatigue indices following resistance exercise with and without blood flow restriction among people with multiple sclerosis.","authors":"Ethan C Hill, Christopher E Proppe, Sean M Lubiak, Mason A Howard, Anuj J Prajapati, Niriham M Shah, Nihar N Patel, Paola M Rivera, Roksana B Zak, Jeffrey T Schmidt, Michael A Trevino","doi":"10.1152/jn.00197.2025","DOIUrl":"10.1152/jn.00197.2025","url":null,"abstract":"<p><p>Muscle fatigue is a prevalent and challenging symptom in people with multiple sclerosis (PwMS), typically involving pronounced central (e.g., reduced corticospinal excitability) and relatively lower peripheral contributions (e.g., metabolic stress) compared with healthy controls. Blood flow restriction (BFR) applied during resistance exercise is an innovative approach to facilitate exercise benefits among PwMS. Therefore, the purpose of this investigation was to examine how distinct resistance exercise approaches including low-load (LL), LL with blood flow restriction (LLBFR), and high-load (HL) affect central and peripheral fatigue when applied in a clinically relevant, real-world context. Twelve females (42 ± 12 yr) and three males (41 ± 10 yr) with MS performed unilateral leg extensions with a HL [3 × 12 at 70% of one repetition maximum (1RM)], LL (1 × 30, 3 × 15 at 30% 1RM), and LLBFR (LL with 60% limb occlusion pressure). Prior to and immediately after each exercise bout, maximal voluntary isometric contraction (MVIC) torque and indices of central [surface electromyographic (sEMG) amplitude, superimposed twitch torque (STT), V_WAVE/M_WAVE] and peripheral [potentiated twitch torque (PTT)] fatigue were assessed. There were similar acute decreases in MVIC torque (-21.0% relative to baseline; <i>P</i> < 0.001, <i>g</i> = 1.486), but exercise-specific decreases in PTT between LLBFR (-37.1%; <i>P</i> < 0.001, <i>g</i> = 1.135) and HL (-14.2%; <i>P</i> = 0.093, <i>g</i> = 0.440). STT increased (+24.5%, <i>P</i> = 0.018, <i>g</i> = 0.650), whereas there were decreases in sEMG amplitude (-9.7%; <i>P</i> = 0.004, <i>g</i> = 0.852) and V_WAVE/M_WAVE (-7.9%; <i>P</i> < 0.001, <i>g</i> = 1.037) that were not different among conditions. LLBFR may represent a more effective resistance exercise strategy for PwMS due to its ability to induce greater peripheral fatigue, a proxy for metabolic stress.<b>NEW & NOTEWORTHY</b> Low-load resistance exercise with blood flow restriction (LLBFR) uniquely elevates peripheral fatigue in people with multiple sclerosis (PwMS), a population which typically experiences increased central fatigue mechanisms. Although high- and low-load protocols evoked mixed central and peripheral fatigue, LLBFR was distinctly associated with peripheral fatigue potentially reflecting the metabolite trapping provoked by the occlusive stimulus. These findings suggest that low-load resistance exercise, particularly LLBFR, may provide innovative strategies to enhance exercise efficacy in PwMS.</p>","PeriodicalId":16563,"journal":{"name":"Journal of neurophysiology","volume":" ","pages":"843-855"},"PeriodicalIF":2.1,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144784498","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}