Experimental Brain Research最新文献

{"title":"Effects of first-step constraints on multi-muscle synergies and early postural adjustments during step initiation.","authors":"Mateus Santos-Dias, Paulo B de Freitas, Sandra M S F Freitas, Mark L Latash","doi":"10.1007/s00221-026-07412-9","DOIUrl":"10.1007/s00221-026-07412-9","url":null,"abstract":"<p><p>Step initiation requires the coordinated preparation of posture and movement, yet how first step constraints influence multi-muscle synergies stabilizing the center of pressure (COP), anticipatory synergy adjustments (ASAs), and early postural adjustments (EPAs) remains poorly understood. This study examined the effects of stepping surface height and step length on these outcomes in healthy young adults. Sixteen participants initiated a step under five conditions: level, step-up, step-down, short-step, and long-step. Surface electromyography was recorded from 16 leg and trunk muscles bilaterally, and COP coordinates were obtained from a force platform. The uncontrolled manifold approach was used to quantify multi-muscle synergies and ASAs stabilizing COP in the anteroposterior (AP) and mediolateral (ML) directions during steady-steady and around the foot lift-off {-25:+25 ms}. Multi-muscle synergies stabilizing COP-AP were present across all conditions, and their index did not differ significantly across stepping conditions, supporting the view that steady-state synergic organization reflects the demands of upright stance rather than anticipation of the upcoming step. Synergies stabilizing COP-ML were absent in all conditions. ASAs were not detected in any condition or direction, suggesting that step initiation relies more on EPA-based rather than synergy-level anticipatory mechanisms. Stepping surface height significantly influenced EPA onset timing and COP displacement magnitude in both directions, with the step-down condition producing earlier EPA onset and smaller displacements than the step-up condition. Step length did not significantly affect EPAs. These findings reveal a dissociation between synergic muscle organization and COP trajectory control and highlight the asymmetric postural demands of descending versus ascending steps during step initiation.</p>","PeriodicalId":12268,"journal":{"name":"Experimental Brain Research","volume":"244 12","pages":""},"PeriodicalIF":2.1,"publicationDate":"2026-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149227386","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comment on \"High-intensity interval training modulates APP expression and reduces neuronal apoptosis in a β-amyloid-induced model of Alzheimer's disease: hippocampal evidence\".","authors":"Stephany Mello, Ifza Zia","doi":"10.1007/s00221-026-07413-8","DOIUrl":"https://doi.org/10.1007/s00221-026-07413-8","url":null,"abstract":"<p><p>Godinho et al. reported that high-intensity interval training (HIIT) modulated molecular and cellular markers associated with neuroprotection in a β-amyloid-induced model of Alzheimer's disease. However, the causal relationship between reduced APP expression and neuronal apoptosis, the translation of molecular adaptations into cognitive outcomes, and the discrepancy between FNDC5 mRNA and protein expression remain unclear. This Letter highlights these three considerations and discusses potential mechanisms that warrant further investigation.</p>","PeriodicalId":12268,"journal":{"name":"Experimental Brain Research","volume":"244 12","pages":""},"PeriodicalIF":2.1,"publicationDate":"2026-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149227408","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A multimodal framework to assess differences in dynamic visual acuity between athletes with and without recent sport-related concussion.","authors":"Katelyn M Mitchell, Kristine N Dalton, Michael E Cinelli","doi":"10.1007/s00221-026-07409-4","DOIUrl":"https://doi.org/10.1007/s00221-026-07409-4","url":null,"abstract":"<p><p>Sport-related concussions (SRC) commonly affect vision and cognition, but there is limited understanding of how concurrent balance and exertion demands may affect visual-cognitive performance beyond symptom resolution.Purpose To determine if a dynamic visual acuity (DVA) task performed during standing and walking could differentiate performance between athletes with and without concussion history.Methods Interuniversity athletes (N = 30, age = 20.9 years ± 1.4) with SRC history who were asymptomatic (SRC = 14; females = 6) were compared to athletes without SRC (CONTROL = 16; female = 7). A DVA task was completed while seated, standing, and during low- and moderate-intensity treadmill walking. A Tumbling 'E' target was presented randomly in either random walk (R) or horizontal (H) motion (2.31 m/s), in one of four orientations; responses were selected using a handheld keypad. Performance was characterized as a change in DVA score from Seated (logMAR) and response time (RT, ms). A linear mixed-effects model was fitted for DVA change scores and a generalized mixed effects model for median RT.Results The SRC group exhibited worse DVA change scores during standing and walking compared to CONTROL (p < .05) during R-motion only. Whereas both groups responded faster during treadmill walking for both R- and H-motion (p < .001). Only two athletes (14%) in the SRC group experienced mild symptoms that did not affect performance during the protocol.Conclusion A multimodal DVA assessment, including standing and walking conditions, may be a feasible approach to detect differences in visual-cognitive performance for athletes following clinical recovery of concussion.</p>","PeriodicalId":12268,"journal":{"name":"Experimental Brain Research","volume":"244 12","pages":""},"PeriodicalIF":2.1,"publicationDate":"2026-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149206775","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cortical and subcortical correlates of perceptual responses during sinusoidal galvanic vestibular stimulation: a BOLD fMRI study.","authors":"Brendan McCarthy, Donggyu Rim, Gianni Sesa-Ashton, Lewis S Crawford, Luke A Henderson, Vaughan G Macefield","doi":"10.1007/s00221-026-07411-w","DOIUrl":"10.1007/s00221-026-07411-w","url":null,"abstract":"<p><p>The cortical and subcortical circuitry underpinning motion sickness is poorly understood. However, certain regions - including the nucleus of the solitary tract (NTS) and the parieto-insular vestibular cortex (PIVC) - are known to be involved in the generation of nausea. The PIVC, in particular, is believed to serve an important role in the processing of vestibular inputs. We have previously used low-frequency sinusoidal galvanic vestibular stimulation (sGVS) to induce perceptions of side-to-side motion, which also induces nausea in ~ 40% of people. While sGVS has been previously used with brain imaging to investigate vestibular pathways, those studies used shorter bouts of stimulation (~ 30 s) which did not induce nausea. Here, we have used functional magnetic resonance imaging (fMRI) to record blood-oxygen-level-dependent (BOLD) signal-intensity changes at baseline (5 min), during low-frequency sGVS for a sustained period of time (± 2 mA, 0.08 Hz, 100 cycles; ~21 min) and during a recovery period (9 min) in 17 participants. Surprisingly, however, only four participants reported incipient or overt nausea during stimulation. Nevertheless, two regions displayed BOLD signal-intensity changes associated with the long-form (as opposed to previously used short-form) stimulation: the nucleus accumbens and locus coeruleus. Though sensations of nausea were not as apparent as expected (perhaps due to the necessity of participants adopting a supine position with their heads fixed in place), these regions would appear to be more associated with a longer period of vestibular stimulation, perhaps required to evoke sensations of nausea.</p>","PeriodicalId":12268,"journal":{"name":"Experimental Brain Research","volume":"244 12","pages":""},"PeriodicalIF":2.1,"publicationDate":"2026-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13672383/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149192209","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Acute unilateral DBS of the basolateral amygdala does not affect motricity, anxiety-like behavior, or fear memory consolidation in rats.","authors":"Douglas Affonso Formolo, Nicholas Roberto Drabowski, Hiago Murilo Mello, Alexandre Ademar Hoeller, Cristiane Ribeiro de Carvalho, Alexandre Trofino Neto, Roger Walz","doi":"10.1007/s00221-026-07408-5","DOIUrl":"10.1007/s00221-026-07408-5","url":null,"abstract":"<p><p>Deep brain stimulation (DBS) is an alternative to ablative functional neurosurgeries. The basolateral amygdala (BLA) is a potential DBS target for treating psychiatric disorders. However, understanding the associated behavioral and cognitive effects is necessary for safety and tolerability concerns. Therefore, we investigated potential acute effects of unilateral BLA DBS. Adult male Wistar rats were implanted with monopolar electrodes in the right BLA. In Experiment 1, different groups of animals were stimulated for 10 min with either high-frequency (HFS, 130 Hz) or low-frequency (LFS, 20 Hz) stimulation using different stimulation intensities (0 [Control], 10, 50, or 100 µA). Immediately after stimulation, animals were tested in the elevated plus-maze (EPM) and subsequently in the open field test (OFT). In Experiment 2, two groups of animals were subjected to a fear-conditioning protocol and stimulated with HFS or LFS (50 µA) immediately after conditioning. Animals were then tested for short- (2 h) and long-term (24 h) fear memory consolidation. BLA DBS showed no significant effects on: (i) anxiety-like behavior expression for HFS (p = 0.46) or LFS (p = 0.37); (ii) locomotor activity (HFS, p = 0.12; LFS, p = 0.60), in terms of distance traveled in the OFT, or (iii) fear memory consolidation (HFS, p = 0.31; LFS, p = 0.68). Under the stimulation parameters and experimental conditions tested, acute unilateral BLA DBS did not significantly affect spontaneous locomotor activity, anxiety-like behavior, or fear memory consolidation in rats. These results provide information relevant to the tolerability and safety of amygdala DBS.</p>","PeriodicalId":12268,"journal":{"name":"Experimental Brain Research","volume":"244 11","pages":""},"PeriodicalIF":2.1,"publicationDate":"2026-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13658534/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149165108","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modulation of human primary motor cortex plasticity during proactive and retroactive interference between motor practice and paired associative stimulation.","authors":"Haijiang Meng, Qian Zhao, Linfeng Jiang, Wenming Lu, Jian Zhang","doi":"10.1007/s00221-026-07407-6","DOIUrl":"10.1007/s00221-026-07407-6","url":null,"abstract":"<p><p>Proactive and retroactive interference have been widely demonstrated behaviorally, but their neurophysiological effects have rarely been compared within the same experimental framework. This study compared the primary motor cortex (M1) plasticity responses when motor practice (MP) was performed before or after paired associative stimulation (PAS25) and explored whether these responses were accompanied by changes in intracortical inhibition. A within-subject design was employed. A right-hand precision grip task with real-time electromyographic feedback was used to examine practice-related refinement of feedback-guided motor control, and PAS25 was used to induce long-term potentiation-like plasticity in M1. Two combined intervention protocols were examined: MP followed by PAS25 (MP→PAS25) and PAS25 followed by MP (PAS25→MP), with PAS25 alone serving as the reference condition. Motor-evoked potentials (MEPs), short-interval intracortical inhibition, and long-interval intracortical inhibition were assessed before and immediately after each intervention protocol. MEP amplitude increased significantly following PAS25 alone, whereas significant pre-post reductions were observed across both the MP→PAS25 and PAS25→MP combined protocols. Post-intervention MEP amplitudes were significantly lower in both combined conditions than in the PAS25-alone condition, with no significant difference between the two combined conditions. No significant time × condition interactions were detected for short-interval intracortical inhibition or long-interval intracortical inhibition. Combining MP with PAS25 produced MEP responses that differed from PAS25 alone, while the two intervention orders showed similar post-intervention responses despite their opposite temporal order. These neurophysiological effects were not accompanied by detectable changes in the specific short-interval intracortical inhibition and long-interval intracortical inhibition measures assessed in the present study. The physiological processes underlying these effects remain to be determined.</p>","PeriodicalId":12268,"journal":{"name":"Experimental Brain Research","volume":"244 11","pages":""},"PeriodicalIF":2.1,"publicationDate":"2026-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149105877","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effective connectivity in the active encoding of facial emotions: a dynamic causal modeling study.","authors":"Wang Guodong, Weng Saizheng, Ji Jiawu, Xu Yuanyuan, Yang Zirong, Nie Lili","doi":"10.1007/s00221-026-07406-7","DOIUrl":"10.1007/s00221-026-07406-7","url":null,"abstract":"<p><p>Previous studies have identified brain regions involved in the active encoding of emotional content of facial expressions (ECFEs); however, little is known about how these regions interact within a functional network. Electroencephalography data were recorded from 62 healthy university students performing a delayed match-to-sample task in which facial expressions served as both encoding and interfering stimuli. Dynamic causal modeling was applied to examine encoding-related modulations of effective connectivity among six nodes in bilateral inferior occipital, inferior temporal, and inferior frontal gyri. During the early time window (1-200 ms), encoding modulated almost all the connectivities including reduced bottom-up excitatory and strengthened top-down inhibitory visual-temporal connectivities, strengthened bidirectional visual-frontal connectivities, and reduced bidirectional temporal-frontal connectivities. During the later window (200-400 ms), only a subset of connectivities was modulated, marked by strengthened top-down excitatory and inhibitory connectivities from frontal and temporal regions to visual areas. Modulation strength was not reliably associated with behavioral performance. Exploratory Bayesian model selection within a restricted model space showed a numerical advantage for a bottom-up excitatory model during encoding and a top-down excitatory model during interference suppression under fixed-effects modeling; however, random-effects analysis indicated that this preference was modest and not uniform across participants. These findings suggest that the active encoding of ECFEs is supported, but not determined, by directional interactions among brain modules, implicating strengthened high-order top-down control over posterior sensory areas, together with functional decoupling of face-sensitive areas from ongoing visual input.</p>","PeriodicalId":12268,"journal":{"name":"Experimental Brain Research","volume":"244 11","pages":""},"PeriodicalIF":2.1,"publicationDate":"2026-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149105808","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Same geometry, different dynamics: what uncontrolled manifold (UCM) analysis misses about motor control.","authors":"Madhur Mangalam, Nick Stergiou","doi":"10.1007/s00221-026-07404-9","DOIUrl":"https://doi.org/10.1007/s00221-026-07404-9","url":null,"abstract":"<p><p>Uncontrolled Manifold (UCM) analysis separates the variability of multi-joint motion into a part that affects the task goal (task-relevant) and a part that does not (task-irrelevant), using the geometric relationship-the task Jacobian-between joint motion and task outcome. The resulting partition has been interpreted as evidence of neural control strategies that stabilize task goals while permitting flexibility in execution. UCM is conventionally reported as time-averaged variance indices, and this time-averaging step discards the temporal structure of movement variability. Using a three-joint planar reaching model, we generate variability with three temporal structures (periodic oscillation, white noise, and pink noise) matched in spatial covariance, and find that the time-averaged geometric indices-the ratio [Formula: see text] and the [Formula: see text]-transformed synergy index [Formula: see text]-remain statistically indistinguishable for white and pink noise, whereas temporal indices computed on the same trials (lag-1 autocorrelation, detrended-fluctuation scaling, spectral slope) show large effect sizes. This double dissociation confirms that time-averaged summaries remain blind to temporal correlations. The projection operation retains temporal information in the single-trial and time-resolved components, yet the meaning of that information for motor control remains open: the mapping from a temporal property of a projected series to a specific control process is itself unestablished, so applying time-series methods to the projections opens a fresh interpretive problem. UCM therefore identifies whether coordination is structured by task constraints while leaving the generating processes undetermined. Establishing this boundary is the contribution of the present work: geometric partitioning yields a spatial account of coordination whose temporal origins lie beyond the method and call for a dedicated dynamical theory.</p>","PeriodicalId":12268,"journal":{"name":"Experimental Brain Research","volume":"244 11","pages":""},"PeriodicalIF":2.1,"publicationDate":"2026-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13627172/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149105823","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Two-digit grasp as pointing movements by the opposing digits: evidence based on the uncontrolled manifold analysis.","authors":"Makoto Iwasa, Saya Iwasa, Mark L Latash","doi":"10.1007/s00221-026-07400-z","DOIUrl":"10.1007/s00221-026-07400-z","url":null,"abstract":"<p><p>We used the concept of performance-stabilizing synergies to test predictions of two hypotheses on the organization of reach-to-grasp movements, one assuming separate control of the transport and aperture, and the other assuming that such actions represent pointing movements by the opposing digits. Healthy participants performed series of reach-to-grasp movements to a cylindrical object with and without targets on the object surface with the dominant and non-dominant hands. Joint motion was captured by a motion analysis system. Inter-trial variance in the joint configuration space was analyzed within the framework of the uncontrolled manifold (UCM) hypothesis, and synergy indices were computed for the thumb and index finger tips, hand, and aperture trajectories. The synergy index was higher for both digit-tip trajectories and the hand compared to the synergy index for the aperture during the first half of the movement. Analysis of the variance components showed that, compared to the values computed for the aperture, there was lower variance affecting the trajectories of each of the two digits (orthogonal to the UCM), while variance that did not affect those trajectories (within the UCM) was higher for the index finger and lower for the thumb. We interpret these findings as supporting the two-digit pointing hypothesis. They illustrate the power of the UCM-based method to distinguish between competing motor control hypotheses.</p>","PeriodicalId":12268,"journal":{"name":"Experimental Brain Research","volume":"244 11","pages":""},"PeriodicalIF":2.1,"publicationDate":"2026-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149074211","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The effects of increasing and decreasing dopamine on inhibition of return: a psychopharmacological investigation.","authors":"Grace A Whitaker, Ellen Poliakoff, Sarah L Martin, Joanna C Neill, Monty Silverdale, Christopher Kobylecki, Wael El-Deredy","doi":"10.1007/s00221-026-07355-1","DOIUrl":"10.1007/s00221-026-07355-1","url":null,"abstract":"<p><p>Inhibition of Return (IOR) is the phenomenon of being slower to re-attend to previously attended locations, and is thought to improve the efficiency of attention. Previous studies of dopaminergic disorders indicate that excessive or insufficient dopamine signaling in the striatum of the brain reduces IOR magnitude. However, there have been no studies of the direct effects of dopamine depletion on IOR in healthy individuals, or that have compared the effect of dopamine increases and decreases within the same population. Therefore, in the present study, we administered a selective dopamine-2 receptor (D2R) agonist and antagonist to the same healthy participants (cabergoline and amisulpride, respectively) and measured IOR. We further investigated the effects of dopamine manipulation on the underlying cognitive processes of IOR using event-related potentials. Both manipulations reduced the IOR effect relative to placebo, consistent with a non-linear relationship between dopamine and IOR. Given the D2R selectivity of both drugs and the accompanying changes in eye-blink rate, these effects are likely driven by primarily striatal dopamine, potentially reflecting frontostriatal modulation of the balance between attentional flexibility and stability.</p>","PeriodicalId":12268,"journal":{"name":"Experimental Brain Research","volume":"244 11","pages":""},"PeriodicalIF":2.1,"publicationDate":"2026-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13616838/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149069373","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}