Somatosensory feedback provides ongoing representation of the body’s movements and interaction with the environment that is important for postural control. Altered somatosensory feedback may require compensation to maintain balance, which could include greater attentional resources or increased reliance on other sensory modalities to maintain posture through sensory reweighting. The prefrontal cortex (PFC) has been implicated in allocating attentional resources to maintain postural control, which may be associated with reweighting among sensory modalities. It is unknown whether increased PFC activity will compensate for altered sensory feedback and will be associated with sensory reweighting, demonstrated by changes in visual and somatosensory cortical activity. Therefore, the purpose of this study was to evaluate the contribution of attentional resources and sensory reweighting to postural control, assessed by changes in cortical activity and body sway under conditions of altered sensory feedback during standing. Fifteen healthy, neurotypical participants (ages 21–58) completed somatosensory testing and the Modified Clinical Test of Sensory Interaction in Balance whilst activity in the PFC, somatosensory, visual and motor cortices was measured using functional near-infrared spectroscopy, and an inertial sensor tracked postural sway. Increased postural sway and PFC activity were evident with vision occluded and unstable surface. Somatosensory, visual and motor cortices demonstrated chromophore and side-specific differences that may reflect the range of age and somatosensory function among the sample cohort and suggest that a threshold of sensory challenge may be necessary to evoke cortical changes. However, increased PFC activity supports increased reliance on attentional resources to maintain balance in response to sensory challenge.
We explored the relations between unintentional finger force production (enslaving) and multi-finger force-stabilizing synergies using the framework of the uncontrolled manifold (UCM) hypothesis. In particular, we formulated three mutually exclusive hypotheses on the relations between the synergy indices for the force produced by the instructed finger, enslaved fingers, and all the fingers. The subjects performed accurate force production task with two fingers of a hand (index and ring) while the visual feedback showed the force produced by all the fingers (unknown to the subjects). Synergy index reflecting inter-trial variance analysis confirmed strongest synergies stabilizing the total force and weakest synergies stabilizing the force by the enslaved fingers. Analysis of 60-s trials with and without continuous visual feedback on total force demonstrated an increase in the enslaving index. Analysis of the diffusion plots (Hurst index) confirmed larger stability along the UCM for the enslaved finger force. Overall, our results show that the traditional view on enslaving as a robust phenomenon ensuring linear relations between the intended and unintended finger forces is likely wrong: Enslaving increases with time as reflected in the smaller indices of force-stabilizing synergies. These findings also suggest that enslaving is defined predominantly by neural factors.
Hypoxic-ischemic brain injury (HIBI) is characterized by complex pathological processes that contribute to acute neuronal damage. Photobiomodulation (PBM) and hydrogen inhalation have each demonstrated neuroprotective effects in ischemic and hypoxic models; however, the effects of their combined application in acute HIBI have not been directly evaluated. In this study, HIBI was induced in mice, followed by treatment with PBM alone, hydrogen inhalation alone, or their combination. Behavioral performance, physiological parameters, and molecular markers of neuronal survival, glial activation, neuroinflammation, apoptosis, and hypoxia signaling were evaluated at 24 h after injury. While PBM or hydrogen alone partially attenuated HIBI-induced alterations, combined treatment more effectively preserved locomotor activity, stabilized physiological parameters, and reduced neuronal loss. These effects were accompanied by decreased glial activation and inflammatory signaling, suppression of apoptotic pathways, and improved regulation of hypoxia-related signaling. Collectively, these findings demonstrate that combined PBM and hydrogen inhalation confers enhanced neuroprotection compared with monotherapies by modulating multiple pathological mechanisms in acute HIBI.
The latest hypothesis regarding the source of enhanced neural activation from resistance training is the reticulospinal rather than the corticospinal tract, based on invasive animal and emerging human data. The present study employed a six-week isometric resistance training intervention in a randomized controlled design to address this knowledge gap. Thirty-nine healthy, untrained males (age 23 y, sustained contraction group n = 13, explosive contraction group n = 9, control group n = 17) underwent neuromuscular and electrophysiological testing and completed all study requirements. Maximal isometric torque (MVC) and rate of torque development (RTD) were measured during a familiarization session as well as before and after the six-week period. Transcranial magnetic stimulation was used to assess motor-evoked potential (MEP) area and silent period duration while subjects contracted to 10
This study investigated how gravity affects upper limb movements and the perception of them by evaluating and comparing objectively measured temporal properties of vertical pointing movements with subjectively perceived ones. Sixteen participants performed vertical pointing movements toward upward or downward targets at various distances (simple movement task). Subsequently, participants judged and chose which target could be reached temporally earlier, rather than at a higher movement speed, from upward and downward targets presented simultaneously at various combinations of distances by responding via pointing movements (choice movement task) or by pressing a button without pointing (choice reaction task). The results of the simple movement task showed that the movement times were longer for pointing toward downward targets than those toward upward targets when those distances were equal. In contrast, in both the choice movement and choice reaction tasks under the target conditions with the equivalent distances, participants were likely to judge the downward target as being reachable earlier than the upward one. These findings suggest a discrepancy between the objectively observed effects of gravity on pointing movements and subjectively estimated effects of gravity.
Binaural beat stimulation (BBS) has been shown to activate the cerebral cortex and promote physical and mental relaxation. This study investigated the immediate effects of theta-frequency BBS following cycling exercise on prefrontal cortical activation in healthy adults. Sixty healthy adults were recruited from the community using convenient sampling. Each participant completed a 20-min cycling exercise on two consecutive days. In a randomized order, one day was followed by a 20-min wide-band theta-frequency (5.5–8.5 Hz) BBS combined with pink noise and the other day by a sham BBS intervention. An eight-channel dry-electrode electroencephalography system was used to record the changes of prefrontal cortical activation at six time points before and after the cycling exercise. A total of 52 participants completed the study. Compared to the sham stimulus, the theta-frequency BBS combined with pink noise significantly enhanced the theta and alpha wave powers. Power changes in the left and right prefrontal cortices and the frontal midline regions (r=0.28–0.51, p<0.05) across multiple time points indicated an immediate enhancement of prefrontal cortical activation. This preliminary study suggests that receiving wide-band theta-frequency BBS after20 minutes of cycling exercise may modulate prefrontal cortex activity. Given its non-invasive and simple nature, BBS warrants further exploratory research to determine its potential role as a supplementary tool in post-exercise recovery strategies.
Tool embodiment refers to the integration of external objects into action-related body representations. Although vision is often assumed to support this process, it remains unclear how tool use under short-term visual deprivation affects explicit ownership and agency across the adult lifespan. This study examined whether blindfolded cane use elicits subjective ownership and agency in younger and older adults, and whether these experiences are associated with forearm tactile distance perception and perceived reaching distance. Forty-three healthy right-handed adults completed two blindfolded cane-use conditions: object search training and navigation training. Tactile Distance Judgment and Reaching Distance Estimation tasks were administered before and after cane use, and participants rated ownership and agency after each condition. Across age groups and conditions, agency ratings were consistently stronger than ownership ratings. Regression analyses indicated that behavioral recalibration measures, especially Reaching Distance Estimation Error, were more consistently associated with agency than ownership, with the clearest joint-model effect observed for agency during navigation. Age Group also contributed to agency during navigation, although age-dependent interaction effects did not reach statistical significance. These findings suggest that short-term blindfolded cane use can support explicit action-based control over a tool without necessarily producing a strong conscious feeling that the tool belongs to the body. The results highlight a dissociation between explicit ownership, agency, and behavioral indices of tool-related sensorimotor updating under blindfolded tool use.
Corpus callosotomy is a palliative procedure for drug-resistant generalized epilepsy. Posterior callosotomy (PC) may preserve prefrontal fibres while offering seizure control comparable to total callosotomy (TC), but experimental comparisons are scarce. This pilot evaluated the acute behavioural effects of PC versus TC in a pentylenetetrazole (PTZ) kindling rat model. Fourteen adult male Wistar rats (500–700 g) underwent PTZ kindling (37.5 mg/kg, i.p.; seven sessions in two blocks with a 22-day drug-free interval); the eleven survivors were randomized to PC (n = 5) or TC (n = 6). Seizures were graded with the revised Racine scale. One week after surgery, a PTZ rechallenge was performed. Within- and between-group comparisons used t-tests or non-parametric equivalents (α = 0.05); callosal sectioning was verified histologically post-mortem. No significant within- or between-group differences in seizure duration were found for any Racine category (all p > 0.05; between-group p 0.174–0.486); a post-hoc analysis indicated only very large effects (Cohen’s d ≈ 1.9) were detectable at 80
This study examined how three-dimensional upper-limb movement trajectories are modulated by changes in gravitational load. We hypothesized that individuals adopt a trajectory elevation strategy in reach-to-grasp movements performed on a desk to compensate for increased movement variability arising from motor noise. To increase motor demands and create conditions under which trial-related fatigue effects could emerge, we manipulated arm weight and used an extended repeated-trial protocol. Participants completed 400 reach-to-grasp trials under three weight conditions (0 g, 200 g, and 400 g), with weights applied to the forearm during the middle 300 trials in the 200 g and 400 g conditions. From the first weighted block—when substantial muscle fatigue was unlikely to have developed—maximum trajectory height was greater in the weighted conditions than in the 0 g condition. Across trials, trajectory height gradually decreased in the 0 g and 200 g conditions, whereas a slight increase was observed in the 400 g condition. In the 400 g condition, trajectory elevation across trials was positively correlated with trajectory variability in later trials. These findings are consistent with the hypothesis that trajectory elevation may serve as a strategy to mitigate detrimental effects on task performance caused by fluctuations in motor output, whether arising from added weight or trial-related fatigue effects. Additionally, exploratory analyses examined the effects of within-day repeated practice on aperture control during reach-to-grasp movements.
Temporal judgments depend on sequence regularity and on the sensory modality in which events occur. We asked whether modality-specific sequence history and across-trial modality context make distinct contributions to temporal sensitivity and perceived timing in isochrony judgments. Participants judged whether the sixth event in a six-item sequence occurred earlier or later than expected. The first five events were auditory or visual; the final event either matched this modality or switched modality. The four sequence types were presented either in separate blocks or randomly interleaved across trials; this manipulation is referred to as presentation mode. Temporal sensitivity, indexed by the just noticeable difference (JND), was better for auditory than for visual sequences and better for modality-consistent than for modality-inconsistent sequences. Effects involving presentation mode were treated as descriptive because this factor was between participants and confounded with hardware settings. Perceived timing, indexed by the point of subjective equality (PSE), showed large shifts for modality-switch endings in the interleaved group. The results support a dissociation between sequence-related effects on temporal sensitivity and context-dependent biases in perceived timing.
Cybersickness is a common sensation when using Virtual Reality (VR) technologies resulting in nausea, headache, eyestrain, and disorientation. Here, we investigated whether providing vibration cues to the user’s torso can provide a multisensory VR experience that increases the sense of presence in VR while also mitigating cybersickness in younger and older adults. A total of N = 111 healthy volunteers (62 younger, 49 older) participated in this study. Participants were engaged in a VR game that passively moved them through a virtual scene. During the VR task, participants were equipped with a vibration vest including 40 actuators and were randomly assigned to one of three experimental conditions: vibration matching the visual scene (directed vibration), vibration not matching the visual scene (undirected vibration), or no vibration at all (control group). Cybersickness was measured using the SSQ and the FMS. Overall, younger adults reported significantly more cybersickness compared to older adults. With regards to vibration, the results differed between age groups. While no differences between the vibration conditions were found for older adults, directed vibration resulted in lower cybersickness scores compared to undirected vibration in younger adults. No relationship between presence and cybersickness was found. Our results suggest that vibration cues may have a beneficial effect on cybersickness for younger adults, and it is worth further exploring how vibration may be optimized to further reduce cybersickness in VR users.
Conventional band-power analysis conflates the periodic and aperiodic components of neural activity. The present study applied spectral parameterization to separate these two components in order to characterize the neural activity of the shooting preparation phase and of the pre- and post-task resting states. A total of 28 proficient shooters were ultimately included and completed shooting tasks under three conditions-Hostage-Rescue, Long-Range, and Close-Range. EEG signals were recorded during the preparation phase of each condition and during the eyes-closed resting states before and after the task. Spectral parameterization was employed to extract the aperiodic exponent, the aperiodic offset, and the periodic oscillatory power within the theta, alpha, and beta bands, as well as their summed power. Exploratory analyses were subsequently conducted from three perspectives: the shooting preparation phase across different conditions, comparisons between high- and low-performance groups, and pre- versus post-task resting states, with resting-state functional connectivity additionally examined. The spectral-parameterization metrics revealed no significant differences among the three conditions at the whole-brain or electrode level. After grouping trials by shooting performance metrics, differences that were condition-dependent and metric-specific emerged. Compared with the pre-task resting-state, the aperiodic exponent of the post-task resting state was significantly lower, whereas the periodic oscillatory power of the theta band was significantly higher. Spectral parameterization can separate the periodic and aperiodic components of shooting EEG. In this study, no significant neural differences were detected among the preparation phases of the three conditions, and the differences obtained by grouping trials according to performance were condition-dependent and metric-specific, remaining exploratory findings that await validation. Changes in the post-task resting-state EEG suggest that brain activity did not recover immediately, possibly in relation to post-task changes in excitatory dominance and mental fatigue.
This study investigated whether haptic contact modulates vestibular-induced self-motion perception and reduces perceptual errors caused by asymmetric vestibular stimulation. Fifteen healthy right-handed participants underwent asymmetric sinusoidal whole-body rotations about the vertical axis in darkness, consisting of half-cycles with equal amplitudes but different velocities, a paradigm known to induce errors in the localization of a previously memorized visual target. This error, quantified as the final position error (FPE), mainly results from reduced self-motion perception during the slower half-cycle. Under vestibular-only conditions, a large FPE was observed after four cycles. To investigate the influence of haptic input, participants touched a spatially fixed object with either the right or the left hand during asymmetric rotation The object was placed either at the body midline or in the right or left hemispace. Haptic contact significantly reduced the vestibular induced FPE, by enhancing perception of the slow self-motion, likely through proprioceptive input from the upper limb. The strongest improvement was observed when participants used the right hand to contact an object in the right hemispace, with smaller reductions occurring with right-hand contact at the midline or in the left hemispace. The effect was less pronounced with left-hand contact. Importantly, although haptic contact markedly reduced vestibular-induced perceptual errors, it did not abolish the underlying vestibular adaptive process responsible for the FPE. In conclusion, haptic contact significantly mitigates vestibular-induced self-motion misperception, with effects depending on both hand laterality and contact location.
To examine dimensional associations between anxiety- and depression-related symptom severity, pain catastrophizing, and resting-state EEG features in patients with knee osteoarthritis (KOA). Resting-state EEG spectral power (delta, theta, alpha, beta) was analysed in 62 KOA patients from the DEFINE cohort. Emotional symptoms were assessed with the Hospital Anxiety and Depression Scale (HADS), along with the Pain Catastrophizing Scale (PCS) and clinical–demographic variables. Multivariate regression analyses identified significant predictors, while linear and tree-based machine learning models were used post hoc to explore whether multivariate and non-linear approaches converged with the regression findings. Catastrophizing was independently and significantly associated with both anxiety and depression symptom scores across regression and exploratory machine learning models. For depression, a multifactorial pattern was additionally observed: higher bilateral parietal delta power, greater catastrophizing, lower education, and greater body weight showed independent associations with more severe symptom scores. Machine learning analyses indicated that EEG features were weak standalone correlates but showed modest complementary associations when combined with clinical variables. Pain catastrophizing was consistently associated with both anxiety and depression symptom scores, and resting-state EEG features showed limited but complementary associations with depressive symptom scores in KOA. Importantly, these associations were observed within a sample presenting predominantly subclinical HADS scores, and findings should be interpreted as reflecting dimensional associations within a rehabilitation cohort rather than clinical anxiety or depressive disorder.
The ego-centred straight-ahead (SA) and gravity-centred visual vertical (VV) constitute important reference frames for perception and action. Clinical studies have shown a strong association between SA and VV representational biases following right hemispheric stroke, suggesting that the brain builds 3D representations referenced to the body in the horizontal plane and to gravity in the frontal plane. Here, we tackled this hypothesis in 37 right-handed healthy individuals (median age 20 years; 23 [62
Standing balance is maintained through the integration of signals from the proprioceptive, visual, and vestibular systems. Galvanic vestibular stimulation (GVS) delivered through head-worn electrodes is increasingly used in clinical vestibular rehabilitation and immersive entertainment interfaces, but it is known to impact on-feet postural stability. Prior studies assessing balance and postural effects have predominantly focused on bilateral mastoid-based uniaxial GVS paradigms. Limited research has characterized balance metrics under multiaxial GVS configurations using four-electrode montages generating multiple directional stimulation paradigms. Standing balance was assessed in healthy participants with eyes closed using a dual force-plate system to record center-of-pressure (COP) dynamics. Participants were exposed to six randomized GVS stimulation conditions across four electrodes placed on the left and right mastoids, center forehead, and nape of the neck, while static, dynamic sway, and velocity-based COP features were extracted to characterize postural responses. GVS significantly altered static, dynamic sway, and velocity-based balance measures compared with the Null condition across six stimulation paradigms. All GVS stimulations increased COP displacement, sway length, sway area, and peak velocities, while reducing sway density metrics across mediolateral (ML) and anteroposterior (AP) axes. These findings provide an early quantitative characterization of postural responses to an unconventional GVS montage and create a foundation for predicting body motion during multiaxial vestibular stimulations. Such insights are important for the safe application of GVS in standing and ambulatory contexts, including clinical vestibular rehabilitation and immersive simulation environments.
Whether the cognitive benefits of athletic training transfer to specific academic domains, such as arithmetic, remains poorly understood. This study investigated the behavioral and electrophysiological (ERP) correlates of multiplication verification in 19 high school cycling athletes and 19 matched controls. Behaviorally, athletes exhibited significantly lower baseline mathematical proficiency (SATM scores), lower accuracy, slower reaction times and poorer processing efficiency. Electrophysiologically, athletes initially demonstrated significantly larger posterior P300 amplitudes than controls. Crucially, these group differences were substantially attenuated after statistically controlling for baseline mathematical proficiency using analysis of covariance (ANCOVA). The findings suggest that arithmetic-related neural processing differences in athletes may be associated with variability in mathematical proficiency rather than reflecting a generalized neurocognitive disadvantage. More broadly, the results support the view that cognitive adaptations associated with athletic expertise may be relatively domain-specific and may not automatically generalize to highly practiced academic skills such as arithmetic verification.
We tested one of the central assumptions of the uncontrolled manifold (UCM) hypothesis, that stability within and orthogonal to the UCM differs in a task-specific way. This was done by exploring the effects of visual feedback on the fast random walk (RW) and slow drifts during multi-finger force production. Healthy participants used the index and middle fingers of both hands to produce an accurate total force magnitude with different initial sharing of the force between the hands. After 5 s, visual feedback was manipulated—kept for both force and sharing, for only one of those variables, or turned off. The subjects tried to keep their performance unchanged for 55 s. Trajectories both along and orthogonal to the UCM for total force showed fast RW and slow drifts. The diffusion plots confirmed persistent RW within the first 0.2 s and anti-persistent RW after 0.5 s. Persistent RW was similar across visual feedback conditions and larger orthogonal to the UCM. Its Hurst index correlated between the UCM and orthogonal to the UCM direction across participants. Anti-persistent RW depended strongly on visual feedback. Drift magnitude and characteristic time depended strongly on visual feedback, being similar along and orthogonal to the UCM. We conclude that RW destabilizes the state of the system, thus encouraging exploration of nearby states over short time intervals, and contributes to its stability over larger time intervals. Visual feedback plays a more important role in structuring the stability of performance compared to the explicit task formulation. RW and drift exploration promise new insights into the organization of stability in abundant systems and a potential biomarker for clinical studies.
