Journal of neurophysiology最新文献

{"title":"Hypertonic saline-evoked muscle pain in the quadriceps reduces neuromuscular performance and alters corticospinal excitability.","authors":"Gabriella Elder, Samuel A Smith, Alexis R Mauger, Ryan Norbury","doi":"10.1152/jn.00087.2025","DOIUrl":"10.1152/jn.00087.2025","url":null,"abstract":"<p><p>Muscle pain can alter corticospinal function, but the specific excitatory/inhibitory effects on the quadriceps across different levels of corticospinal neuron recruitment remain unclear. Furthermore, maximal force production is reduced with muscle pain, but how the rate of force development, a key component of neuromuscular function, remains less known. To investigate this, healthy participants completed an isometric maximal voluntary contraction (MVC) followed by submaximal, intermittent contractions after receiving a hypertonic saline injection into the vastus lateralis to cause quadriceps pain (HYP), or isotonic saline, a nonpainful control (ISO). Peripheral nerve stimulation was delivered during and after MVCs to determine neuromuscular function. Transcranial magnetic stimulation (TMS) was delivered at 120% and 150% of active motor threshold during submaximal contractions to determine corticospinal excitability/inhibition, along with paired-pulse TMS to determine short-interval intracortical inhibition (SICI). Results revealed a moderate effect size (ES) reduction in MVC force (ES = -0.68, <i>P</i> = 0.020), early-phase rate of force development (ES = -0.57, <i>P</i> = 0.029), and voluntary activation (ES = -0.66, <i>P</i> = 0.008) in HYP compared with ISO. Corticospinal excitability increased in HYP compared with ISO (ES = 0.60, <i>P</i> = 0.023), whereas corticospinal inhibition decreased in HYP at higher stimulation intensities only (ES = 0.63, <i>P</i> = 0.017). Conversely, SICI increased in HYP compared with ISO (ES = 0.58, <i>P</i> = 0.035). Our findings indicate that muscle pain induced by a hypertonic saline injection reduced quadriceps neuromuscular function due to centrally mediated mechanisms, potentially involving both excitatory and inhibitory effects on the corticospinal tract.<b>NEW & NOTEWORTHY</b> Hypertonic saline-induced quadriceps muscle pain reduced knee-extensor maximal voluntary force, rate of force development, and voluntary activation, without altering peripheral muscle function, suggesting a centrally mediated impairment of neuromuscular performance in healthy individuals. Alongside these changes was an increase in corticospinal excitability at both low and high stimulation intensities, whereas pain decreased corticospinal inhibition at high stimulation intensities only. Furthermore, hypertonic saline-induced pain increased intracortical inhibition, suggesting nonuniform effects of pain on the corticospinal tract.</p>","PeriodicalId":16563,"journal":{"name":"Journal of neurophysiology","volume":" ","pages":"715-727"},"PeriodicalIF":2.1,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144698817","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":"Impairment of the blood-brain barrier accelerates a negative ultraslow potential in the locust CNS.","authors":"R Meldrum Robertson, Andrew Donini, Yuyang Wang","doi":"10.1152/jn.00191.2025","DOIUrl":"10.1152/jn.00191.2025","url":null,"abstract":"<p><p>Insects provide useful models for investigating evolutionarily conserved mechanisms underlying electrical events associated with brain injury and death. Spreading depolarizations (SD) are transient events that propagate through neuropil whereas the negative ultraslow potential (NUP) is sustained and reflects accumulating damage in the tissue. We used the locust, <i>Locusta migratoria</i>, to investigate ion homeostasis at the blood-brain barrier (BBB) during SD and NUP induced by treatment with the Na⁺/K⁺-ATPase inhibitor, ouabain. We found that sustained SD caused by the metabolic inhibitor, sodium azide, was associated with a large reduction of K⁺ efflux from the BBB at ganglia (= gray matter) but not at connectives (= white matter). This was accompanied by a large increase in tissue resistivity but no conductance changes of identified motoneuron dendrites in the neuropil. Males recovered more slowly from ouabain-induced SD, as previously described for anoxic SD. Impairment of barrier functions of the BBB pharmacologically with cyclosporin A or 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), or by cutting nerve roots, accelerated the NUP, thus promoting earlier and more frequent SD, but had no effect on the temporal parameters of SD. We conclude that the mechanisms underlying onset and recovery of SD are minimally affected by the damage associated with the NUP. We suggest that future research using tissue-specific genetic approaches in <i>Drosophila</i> to target identified molecular structures of the BBB are likely to be fruitful.<b>NEW & NOTEWORTHY</b> Inhibition of the sodium pump in the locust central nervous system (CNS) causes repetitive spreading depolarization (SD) and a negative ultraslow potential (NUP) providing a model for investigation of phenomena relevant to human health. We show that impairment of the blood-brain barrier accelerates the NUP but has no impact on the trajectory of SD events. Hence, rapid mechanisms of onset and recovery of ion homeostasis occur against a background of slowly increasing neural damage.</p>","PeriodicalId":16563,"journal":{"name":"Journal of neurophysiology","volume":" ","pages":"471-485"},"PeriodicalIF":2.1,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144584202","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":"Is the degree of postactivation depression similar between soleus responses evoked by transcutaneous spinal cord and peripheral nerve stimulation?","authors":"Julia Sordet, Alain Martin, Thomas Lapole, Ioannis Amiridis, Jean-Pierre Quenot, Maria Papaiordanidou","doi":"10.1152/jn.00137.2025","DOIUrl":"10.1152/jn.00137.2025","url":null,"abstract":"<p><p>Transcutaneous spinal cord stimulation (tSCS) evokes responses in multiple lower limb muscles, referred to as transspinal-evoked potentials (TEPs). In certain conditions, these responses can result primarily from the activation of Ia afferents at the dorsal roots of the spinal cord and share similarities with the H-reflex elicited by peripheral nerve stimulation (PNS). The aim of this study was to compare these two responses with regard to the postactivation depression mechanism. Volunteers participated in two experimental sessions, in which tSCS was applied at the L1-L2 level (<i>n</i> = 20, main experiment) or at the T10-T11 level (<i>n</i> = 10, additional experiment). Recruitment curves in 1-s paired-pulse stimulations were constructed for the two types of stimulation. The amplitude of soleus H-reflex and TEP was matched (∼85% of maximal H-reflex), and postactivation depression was tested by conditioning the H-reflex (H_COND) or the TEP (TEP_COND) using either PNS (H_TEST) or tSCS (TEP_TEST). The results of the main experiment demonstrated no significant difference in the conditioning ratios (<i>P</i> = 0.99). However, in the additional experiment, the degree of postactivation depression was found to be higher when a TEP was conditioned using tSCS compared with the other conditioning ratios obtained in the two experiments (for all, <i>P</i> < 0.03). Although both responses evoked in soleus muscle seem to be similarly sensitive to the postactivation depression phenomenon when low-stimulation intensities are used, the electrode placement seems to exert an influence on the degree of depression induced on tSCS-evoked responses.<b>NEW & NOTEWORTHY</b> Although responses evoked by both tSCS and peripheral nerve stimulation are known to exhibit postactivation depression, a hallmark of Ia afferent activation, this study identifies specific methodological conditions under which tSCS can elicit a soleus muscle response equivalent to the classical H-reflex. When electrode placement minimizes the recruitment of Ia afferents from the vastus lateralis and low-stimulation intensities are applied, the tSCS response appears to engage the same neural pathways as peripheral nerve stimulation.</p>","PeriodicalId":16563,"journal":{"name":"Journal of neurophysiology","volume":" ","pages":"529-542"},"PeriodicalIF":2.1,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144626595","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":"<i>N</i>-Methyl d-aspartate receptor hypofunction reduces steady-state visual-evoked potentials.","authors":"Alexander Schielke, Bart Krekelberg","doi":"10.1152/jn.00296.2024","DOIUrl":"10.1152/jn.00296.2024","url":null,"abstract":"<p><p>The dynamic coordination of neural activity across populations of neurons is impaired in neuropsychiatric disorders. Here, we focused on the large-scale rhythmic responses induced by flickering light. These so-called steady-state visual-evoked potentials (SSVEPs) are reduced in people with schizophrenia (Sz). A large body of work has identified hypofunction of the <i>N</i>-methyl d-aspartate receptor (NMDAR) as a potential contributor to the symptoms of Sz. Here, we tested the hypothesis that NMDAR hypofunction can account for a reduced ability to generate the coordinated activity reflected in SSVEPs. We recorded SSVEPs using multielectrode arrays permanently implanted in the primary visual cortex of nonhuman primates. In separate sessions, animals were injected with saline (control) or a subanesthetic dose of ketamine (an NMDAR antagonist) to induce an NMDAR hypofunction state. SSVEPs generated during NMDAR hypofunction were substantially reduced and, consistent with findings in Sz, this reduction was found across a range of frequencies from 5 to 40 Hz. These findings provide novel insight into the role of NMDAR hypofunction in the generation of altered coordinated activity and provide experimental support for the hypothesis that NMDAR hypofunction underlies some of the symptoms of schizophrenia.<b>NEW & NOTEWORTHY</b> It has been hypothesized that <i>N</i>-methyl d-aspartate receptor (NMDAR) hypofunction causes symptoms of schizophrenia, including impairments in coordinated neuronal activity. Our findings support this hypothesis by showing that a drug (ketamine) that impairs NMDAR function reduces coordinated neural activity in response to flickering light, matching deficits found in schizophrenia. Developing experimental models and testing hypotheses that describe altered cortical processing is key to understanding the underlying neural deficits and developing treatments for neuropsychiatric diseases.</p>","PeriodicalId":16563,"journal":{"name":"Journal of neurophysiology","volume":" ","pages":"591-601"},"PeriodicalIF":2.1,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12446419/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144626596","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":"Flexible tapping synchronization in macaques: dynamic switching of timing strategies within rhythmic sequences.","authors":"Ameyaltzin Castillo-Almazán, Oswaldo Pérez, Luis Prado, Nori Jacoby, Hugo Merchant","doi":"10.1152/jn.00158.2025","DOIUrl":"10.1152/jn.00158.2025","url":null,"abstract":"<p><p>The ability to synchronize bodily movements with regular auditory rhythm across a broad range of tempos underlies humans' capacity for playing music and dancing. This capability is prevalent across human cultures but relatively uncommon among nonhuman species. Recent research indicates that monkeys can predictively synchronize to regular, isochronous metronomes, exhibiting a preference for visual rather than auditory sequences. In this study, we trained macaques to perform a visual synchronization tapping task, testing their synchronization abilities over a wide tempo range and characterizing their precision and accuracy in timing intervals throughout rhythmic sequences. In addition, we investigated whether the macaques used priors or error correction strategies to maintain synchrony with the metronome. Our findings demonstrate that, following sufficient training, macaques exhibit a remarkable capability to synchronize across diverse tempos. Through an inference model analysis, we identified two distinct timing control strategies used by the macaques: an initial strong regression-to-the-mean effect transitioning dynamically into a more precise error correction approach at their preferred tempo. These results provide compelling evidence that primates possess sophisticated rhythmic timing mechanisms, effectively leveraging internal and external cues to regulate their tapping behavior according to task demands.<b>NEW & NOTEWORTHY</b> We trained macaques in a visual synchronization tapping task and using an inference model, we found that they are highly precise and accurate in their rhythmic performance. The model also captured a dynamic switch in behavior. At the beginning of the task, the monkeys used their prior knowledge about the interval statistics and then switched to an error correction mechanism to generate intervals depending on the previously produced duration.</p>","PeriodicalId":16563,"journal":{"name":"Journal of neurophysiology","volume":" ","pages":"580-590"},"PeriodicalIF":2.1,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144258294","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":"Anisotropic object-based shifts of attention arise from unequal influences of visual field meridians on neural attention gradients.","authors":"David H Hughes, Adam J Barnas, Adam S Greenberg","doi":"10.1152/jn.00554.2024","DOIUrl":"10.1152/jn.00554.2024","url":null,"abstract":"<p><p>Object-based attention prioritizes the processing of information appearing within a selected object. We previously showed an object-based shift direction anisotropy (SDA) whereby horizontal shifts are more efficient than vertical shifts (Barnas AJ, Greenberg AS. <i>Atten Percept Psychophys</i> 78: 1985-1997, 2016; Barnas AJ, Greenberg AS. <i>Vis Cogn</i> 27: 768-791, 2019), an effect modulated by the visual field meridians (Barnas AJ, Greenberg AS. <i>Q J Exp Psychol (Hove)</i> 77: 2516-2532, 2024). Our present aim was to understand how the functional brain mechanisms of attention give rise to the SDA. We hypothesized that the SDA arises from attentional resources being partitioned differently by horizontal and vertical meridians. To test this, we used fMRI of the visual cortex while subjects shifted attention horizontally and vertically within a single, L-shaped object. An SDA was observed when targets crossed the visual field meridians, and the object vertex was positioned in the upper-left corner. However, no SDA was observed when the object vertex was positioned in the lower-right corner. Cue-related activations revealed that attention spreads throughout the vertical component of each object (even to locations where the target never appeared). In addition, the vertical meridian seemed to impede the spread of attention for the upper-left object's horizontal component. However, for the lower-right object, the horizontal component showed a similar attentional modulation to its vertical component, commensurate with behavioral performance in response to that object. These results suggest the efficiency of horizontal shifts crossing the vertical meridian is enhanced by the support of attentional resources from both hemispheres. As such, we offer a refinement of how the visual field meridians may influence the spread of object-based attention via an anisotropic attention gradient.<b>NEW & NOTEWORTHY</b> Our previous behavioral work suggests that inconsistent object-based attention effects (measured as the same-object advantage) arise from differences in shift direction efficiency (a shift direction anisotropy) across the visual field meridians, such that shifts are faster horizontally than vertically. Using fMRI, we present neurobiological evidence that the meridians may cause an unequal allocation of object-based attentional resources. These results necessitate updating theories of object-based attentional selection to account for the effects of visual field meridians.</p>","PeriodicalId":16563,"journal":{"name":"Journal of neurophysiology","volume":" ","pages":"504-516"},"PeriodicalIF":2.1,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144540584","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":"Impact of upper cervical spinal cord hemisection on diaphragm neuromotor control.","authors":"Obaid U Khurram, Maximilian J Kantor-Gerber, Carlos B Mantilla, Gary C Sieck","doi":"10.1152/jn.00279.2025","DOIUrl":"10.1152/jn.00279.2025","url":null,"abstract":"<p><p>Neural drive to the diaphragm muscle (DIAm) for breathing is generated in the medulla and descends primarily ipsilaterally to phrenic motor neurons (PhMNs) in the cervical spinal cord. Neuromotor control of the DIAm during breathing involves motor unit (MU) recruitment, sustained activity, and derecruitment, which may be differentially altered on ipsilateral and contralateral sides after C₂ spinal hemisection (C₂SH). In awake rats, bilateral DIAm electromyographic (EMG) activity was recorded via chronically implanted electrodes during eupnea in nine Sprague-Dawley rats before and 14 days (<i>day 14</i>) after C₂SH. The durations of MU recruitment and derecruitment were estimated by evaluating EMG signal stationarity, i.e., changes in the mean square average of onset- and offset-aligned 10-ms bins within a longer (e.g., 80 ms) sampling period reflect changes in EMG due to MU recruitment. The amplitudes of DIAm EMG at the end of the recruitment and beginning of the derecruitment phase were measured. On the ipsilateral side, C₂SH decreased DIAm EMG recruitment amplitude by ∼30% and peak amplitude by ∼35% by <i>day 14</i>, likely reflecting a decrease in the number of MUs recruited. On the contralateral side, C₂SH increased recruitment amplitude by ∼70% and peak amplitude by ∼80% by <i>day 14</i>, likely reflecting an increase in the number of MUs recruited. The derecruitment amplitude decreased ipsilaterally and increased contralaterally, consistent with the recruitment of higher threshold MUs contralaterally. The present study reveals that the impact of C₂SH on ipsilateral and contralateral DIAm neuromotor control varies depending on the loss of ipsilateral neural drive.<b>NEW & NOTEWORTHY</b> Neuromotor control of the diaphragm muscle (DIAm) after C₂ spinal hemisection (C₂SH) is impacted differentially between ipsilateral and contralateral sides. We show neural drive to ipsilateral phrenic motor neurons decreases after C₂SH, leading to a reduction in the number of DIAm motor units (MUs) recruited. Contralateral neural drive increases after C₂SH, leading to an increase in the number of MU recruited. These results provide novel information about the impact of C₂SH on DIAm neuromotor control.</p>","PeriodicalId":16563,"journal":{"name":"Journal of neurophysiology","volume":" ","pages":"698-714"},"PeriodicalIF":2.1,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12376190/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144731771","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":"Ipsilateral motor cortex regulates distinctly via interhemispheric inhibition force production versus force control in isometric unimanual contraction.","authors":"Zhongfei Bai, Feifei Zhu, Jack Jiaqi Zhang, Dan Yu, Jing Zhang, Shan Liang, Yefang Yang, Lingling Zhong, Jiani Lu, Ulf Ziemann, Lingjing Jin","doi":"10.1152/jn.00261.2025","DOIUrl":"10.1152/jn.00261.2025","url":null,"abstract":"<p><p>Ipsilateral primary motor cortex (M1) contributions to force production are recognized, whereas conflicting evidence persists regarding movement-modulated short-interval interhemispheric inhibition (SIHI) dynamics and their role in force control precision. This study systematically investigates how ipsilateral M1 regulates unimanual force production through SIHI, focusing on its dual role in force production and force control precision. <i>Experiment 1</i> used short trains of 10-Hz transcranial magnetic stimulation (TMS) to evaluate the effects of disruption on the ongoing activity of ipsilateral M1 on force-tracking variability during 20% and 50% maximal voluntary contraction (MVC). <i>Experiment 2</i> used dual-coil TMS to quantify SIHI dynamics during sustained isometric contractions. Behavioral performance was assessed using the coefficient of variation (CV). Disruptive repetitive TMS of the ipsilateral M1 significantly increased force-tracking CV at both 20% (<i>P</i> = 0.002) and 50% MVC (<i>P</i> < 0.001), confirming its facilitatory role. Sustained contractions reduced ipsilateral-to-active SIHI (<i>P</i> < 0.001), whereas persistent SIHI during isometric contraction positively correlated with force control precision at both 20% (<i>r</i> = 0.41, <i>P</i> = 0.045) and 50% MVC (<i>r</i> = 0.59, <i>P</i> = 0.003). This study demonstrates that ipsilateral M1 regulates unilateral hand force production and precision through dynamic bidirectional modulation of SIHI, highlighting its dual role in isometric unimanual contraction and potential implications for poststroke rehabilitation.<b>NEW & NOTEWORTHY</b> This study reveals a dual regulatory mechanism by which the ipsilateral M1 optimizes unimanual force production and control through dynamic modulation of SIHI. We demonstrate that ipsilateral M1 facilitates force generation by attenuating SIHI, whereas persistent SIHI during isometric contraction correlates with precision during sustained contractions.</p>","PeriodicalId":16563,"journal":{"name":"Journal of neurophysiology","volume":" ","pages":"667-676"},"PeriodicalIF":2.1,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144731772","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":"Aging alters face expressions processing and recognition: insights on possible neural mechanisms.","authors":"Francesca Ginatempo, Nicola Loi, Mohammed Zeroual, Marinella Cadoni, Mauro Fadda, Andrea Lagorio, Franca Deriu","doi":"10.1152/jn.00237.2024","DOIUrl":"10.1152/jn.00237.2024","url":null,"abstract":"<p><p>The present work investigated how aging influences the different stages of face expression processing: fixation patterns, early perception, face motor response, and recognition. Thirty-four participants (17 young, 17 senior) were subjected to <i>1</i>) recording of fixation patterns, <i>2</i>) recording of the P100 and the N170 components of event-related potentials, <i>3</i>) excitability of short intracortical inhibition (SICI) and intracortical facilitation (ICF) of the face primary motor cortex (face M1), and <i>4</i>) recognition task during the passive viewing of neutral, happy, and sad faces expressions. Senior subjects mostly looked at the mouth, had reduced pupil size, and delayed N170 latency, regardless of expression, compared with young subjects, and a reduced P100 amplitude when viewing sad faces. Senior subjects' excitability of face M1 was enhanced compared to the young group; both groups had a reduced SICI when viewing happy faces, but only senior subjects exhibited reduced SICI for sad faces. Young subjects had better recognition accuracy and response times than senior ones, particularly for sad expressions. When viewing sad expressions, SICI was negatively correlated with recognition accuracy. Data suggested that aging reduces visual attention for sad faces, which appears to be connected to an increased excitability of face M1, which in turn is linked to their impaired recognition skills, especially when processing negative face expressions. These findings provide new insights into the comprehension of how aging affects cognitive functions and the process of face expression recognition.<b>NEW & NOTEWORTHY</b> The study of the face expression processing in young and senior subjects evidenced that aging alters the fixation pattern for face expressions by reducing the visual attention toward sad faces. This alteration is associated with a reduced intracortical inhibition in face primary motor cortex, which correlates with compromised recognition abilities for sad face expressions.</p>","PeriodicalId":16563,"journal":{"name":"Journal of neurophysiology","volume":" ","pages":"543-558"},"PeriodicalIF":2.1,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144540583","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":"Influence of sustained cognitive loading on finger circulatory and thermoperceptual responsiveness to localized cooling.","authors":"Maaike I Moes, Antonis Elia, Ola Eiken, Michail E Keramidas","doi":"10.1152/jn.00090.2025","DOIUrl":"10.1152/jn.00090.2025","url":null,"abstract":"<p><p>We examined whether finger vasomotor and thermoperceptual responses to local cooling would be modulated by sustained cognitive loading. Finger temperature, circulatory [i.e., cutaneous vascular conductance (CVC)] and perceptual responses were monitored, in 12 healthy men, during and after a 30-min hand-immersion in 8°C-water, performed either immediately after a 60-min continual execution of a cognitive task (cognitive→cold trial), or during the simultaneous performance of the cognitive task (cognitive + cold trial). Subjects' responses were compared with those obtained in a control cold-provocation trial, wherein they watched an emotionally neutral documentary. The cognitive task temporarily enhanced the perceived levels of mental effort and fatigue in both intervention trials. During cooling in the cognitive→cold trial, the area under the curve (AUC) for finger CVC was enhanced [49 (23) PU·mmHg^-1·min vs. control: 36 (22) PU·mmHg^-1·min], the cold-induced increase in mean arterial pressure was blunted [2 (4) mmHg vs. control: 8 (4) mmHg] (<i>P</i> < 0.01), and the thermal discomfort was alleviated [2.2 (0.5) vs. control: 2.5 (0.7); <i>P</i> = 0.05]. In the cognitive + cold trial, no intertrial differences were noted during the cold-water immersion (<i>P</i> ≥ 0.28), but AUC for finger CVC was augmented during the last part of the rewarming [29 (12) PU·mmHg^-1·min vs. control: 24 (11) PU·mmHg^-1·min; <i>P</i> = 0.05]. Present findings demonstrate that <i>1</i>) in moderately mentally fatigued individuals, finger cold-induced vasoconstriction is transiently attenuated, and thermal discomfort is mitigated, and <i>2</i>) superimposition of cognitive loading on cold stress does not alter finger vasoreactivity or thermosensitivity during cooling, but facilitates reperfusion following cooling.<b>NEW & NOTEWORTHY</b> The study examined whether finger vasoreactivity and thermosensitivity to local cooling would be modulated by two different paradigms of enhanced cognitive strain evoked by the prolonged execution of a mentally demanding task. When localized cold stress was applied in moderately mentally fatigued individuals, finger cold-induced vasoconstriction was temporarily attenuated, and thermal discomfort was mitigated. The simultaneous application of cognitive loading and local cooling did not potentiate finger vasoconstriction during cooling but facilitated digit reperfusion following cooling.</p>","PeriodicalId":16563,"journal":{"name":"Journal of neurophysiology","volume":" ","pages":"445-457"},"PeriodicalIF":2.1,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144584203","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}