Experimental Brain Research最新文献

This study investigates how the combination of robot-mediated haptic interaction and cerebellar neuromodulation can improve task performance and promote motor skill development in healthy individuals using a robotic exoskeleton worn on the index finger. The authors propose a leader-follower type of mirror game where participants can follow a leader in a two-dimensional virtual reality environment while the exoskeleton tracks the index finger motion using an admittance filter. The game requires two primary learning phases: the initial phase focuses on mastering the pinching interface, while the second phase centers on predicting the leader's movements. Cerebral transcranial direct current stimulation (tDCS) with anodal polarity is applied to the subjects during the game. It is shown that the subjects' performance improves as they play the game. The combination of tDCS with finger exoskeleton significantly enhances task performance. Our research indicates that modulation of the cerebellum during the mirror game improves the motor skills of healthy individuals. The results also indicate potential uses for motor neurorehabilitation in hemiplegia patients.

Suffering an acute asymmetry in vestibular function (i.e., vestibular neuritis) causes increased sway. Non-causal studies report associations between lateral semicircular canal function and balance ability, but direct links remain controversial. We investigate the immediate effect on body sway after unilateral vestibulo-ocular reflex (VOR) gain down adaptation simulating acute peripheral vestibular hypofunction. Eighteen healthy adults, mean age 27.4 (± 12.4), stood wearing an inertial measurement device with their eyes closed on foam before and after incremental VOR gain down adaptation to simulate mild unilateral vestibular neuritis. Active head impulse VOR gain was measured before and after the adaptation to ensure VOR gain adaptation. Percentage change for VOR gain was determined. Sway area was compared before and after VOR adaptation. VOR gain decreased unilaterally exceeding meaningful change values. Sway area was significantly greater immediately after VOR gain down adaptation, but quickly returned to baseline. In a subset of subjects VOR gain was re-assessed and found to remain adapted despite sway normalization. These results indicate that oculomotor adaptation targeting the lateral semicircular canal VOR pathway has an immediate, albeit transient increase in body sway. Rapid return of body sway to baseline levels suggests dynamic sensory reweighting between vestibular and somatosensory inputs to resolve the undesirable increased body sway.

This study aims to assess fixational eye movements (FEMs) obtained under binocular and monocular viewing in normal individuals across different age groups. We recruited 68 healthy participants divided into Group 1 (children, 3-9 years, n = 20), Group 2 (adolescents, 10-19 years, n = 26), and Group 3 (adults, 20-73 years, n = 22). FEMs were collected using a high-resolution video-based tracker under 3 viewing conditions: binocular viewing (BV), monocular viewing right eye (MV_RE), and monocular viewing left eye (MV_LE). We quantified fixation stability, the frequency, amplitude, and disconjugacy of fixational saccades, and inter-saccadic drift velocity in BV, MV_RE, and MV_LE. We also computed inter-ocular fixation stability under binocular viewing and monocular viewing in the 3 groups. Fixation instability (FI) and fixational saccade amplitudes were higher in Group 1 than in Group 3 whereas inter-saccadic drifts were increased in Group 3. Vergence stability was greater in binocular viewing than in monocular viewing likely due to binocular summation in all groups. However, the fixational saccade amplitude and drift velocity of the right and left eye did not significantly differ across different viewing conditions within each group. Interestingly, the inter-ocular fixation stability ratio and vergence stability showed no significant differences between the groups. In conclusion, FEMs differ across age groups but inter-ocular FEMs are immune to the effects of age and can be a valuable parameter while evaluating FEM abnormalities in diseases like amblyopia.

Motor skill learning and performance are improved when successful actions are paired with extrinsic rewards, such as money. Positive feedback indicating successful task performance is thought to induce intrinsic reward associated with goal attainment, evidenced by increases in positive affect that correlate with neural reward signaling. However, it is not clear whether the subjective, internal reward processes elicited by positive feedback promote motor learning and performance.Here, we tested the hypothesis that intrinsic reward elicited by positive feedback promotes motor learning and performance. Participants practiced a visuomotor interception task using a joystick, and received feedback during practice indicating success or failure depending on their accuracy. During practice, the accuracy demands were adapted to control and vary the frequency of positive feedback across randomly ordered blocks of practice at either 50%, 70%, or 90%. Performance was measured for each condition as the average accuracy during practice. Learning was estimated by measuring the accuracy pre and post practice in the absence of feedback. We queried participants periodically on their enjoyment of the task to index affective responses to performance feedback.The intrinsic reward elicited by positive feedback, operationalized by the increase in enjoyment immediately following positive versus negative feedback, was positively correlated with learning from pre to post practice. However, increasing the overall amount of positive feedback by lower accuracy demands did not improve performance. These results suggest that experiencing intrinsic reward due to positive feedback benefits motor learning only when it is contingent on good performance.

Paradoxically visual dependence is reported to increase with age, contributing to falls risk, whereas visual function typically declines. This study assesses the relationship between age, objective and subjective measures of visual function and visual dependence, in healthy young and older adults. Forty-four healthy Young (YA; n = 32; 18 males, aged 26.2 ± 5.3 yrs.) and Older (OA; n = 12; 3 males, aged 62.4 ± 6.7 yrs.) adults were assessed for objective (visual acuity, contrast sensitivity, depth perception, and lower peripheral vision), and subjective visual function (VFQ-25) along with motion sickness susceptibility. Subjective Visual Vertical (SVV) and induced nausea and vection were assessed using the Rod and Disc Test (RDT). Groups were compared using Mann-Whitney U, whilst determinants of SVV variability were evaluated using Multiple regression modelling. Visual acuity (p < 0.01) and contrast sensitivity (p = 0.04) were lower in OA. Visual dependence (SVV tilt errors) was not associated with ageing (p = 0.46). YA experienced greater RDT-induced vection (p = 0.03). Visual acuity and contrast sensitivity accounted for modest proportions of variance in SVV tilt errors (VA; R² = 0.14, F(1,42) = 8.00, p < 0.01; β = 6.37) and (CS; R² = 0.06, F(1,42) = 3.93, p = 0.05; β = -4.97), respectively. Our findings suggest that subclinical differences in visual acuity and contrast sensitivity contribute to SVV tilt error variability, among both healthy young and older adults. Further studies are needed to define the inter-relationship between age-related visual function, non-visual factors (including vestibular and somatosensory fidelity, activity levels, fear of falling and cognitive function) and visual dependence.

Many athletes with recurrent ankle sprains complain of neurophysiological deficits related to chronic ankle instability (CAI). However, it remains unclear how changes in the corticospinal pathway affect the potential risk of subsequent ankle sprains. The purpose of this study was to investigate whether the corticospinal excitability (input-output properties) and silent period (SP) could be related to the risk of subsequent ankle sprains among athletes. Forty-three male collegiate basketball athletes were enrolled, and 82 ankles were finally sorted into four ankle groups based on symptoms (CAI, sub-CAI, copers, and normal). The neurophysiological data was recorded in both ankles using transcranial magnetic stimulation (TMS) as baseline assessments. Subsequently, we prospectively followed the occurrence of subsequent ankle sprain injuries for 24 months (SG, subsequent ankle sprain group; NSG, non-sprain group). In the baseline assessment, we confirmed that the threshold of the input-output properties in the CAI group was higher than those in the normal group. After the follow-up, 22 ankles sustained subsequent ankle sprains (SGs). We also found that SGs exhibited a significantly longer SP at the middle and high stimulus intensities of TMS compared to NSGs (60 ankles) (middle: p = 0.012, Cohen's d = 0.644, and high: p = 0.020, Cohen's d = 0.590). These findings suggest that a prolonged SP could be a crucial factor affecting subsequent ankle sprains in athletes. To prevent further recurrent sports injuries, neurophysiologic probes, particularly a longer SP, might be a potential assessment tool to return to the field.

To investigate differences in proprioception using four proprioceptive tests in children with and without hypermobility. Additionally, it was tested if the results on one proprioceptive test predict the results on the other tests. Of the children (8-11years), 100 were classified as normal mobile (Beighton score 0-4) and 50 as hypermobile (Beighton score 5-9). To test proprioception, in the upper extremity the unilateral and bilateral joint position reproduction tasks were used and for the lower extremity the loaded and unloaded wedges task. No differences were found in any of the proprioception tests between the two groups. Estimating the height of the wedges was easier in the loaded position (mean penalty in standing and sitting position, 4.78 and 6.19, respectively). Recalling the elbow position in the same arm resulted in smaller errors compared to tasks reproducing the position with the contralateral arm. Of the four angles used (110°, 90°, 70°, 50°), the position recall in the 90° angle had the smallest position error (1.8°). Correlations between the proprioception tests were weak (Loaded and Unloaded (r 0. 28); Uni and Bilateral (r 0.39), Upper and Lower extremity not significant). No indication of poorer proprioception was found in children with hypermobile joints compared to their normal mobile peers. Loading gives extra information that leads to fewer errors in the wedges task performed while standing, but this effect is independent of joint mobility. Proprioception test outcomes are dependent on the test used; upper extremity results do not predict lower extremity outcomes or vice versa.

Ischemic Conditioning (IC) is a procedure involving brief periods of occlusion followed by reperfusion in stationary limbs. Blood Flow Restriction with Exercise (BFR-E) is a technique comprising blood flow restriction during aerobic or resistance exercise. Both IC and BFR-E are Blood Flow Modulation (BFM) strategies that have shown promise across various health domains and are clinically relevant for stroke rehabilitation. Despite their potential benefits, our knowledge on the application and efficacy of either intervention in stroke is limited. This scoping review aims to synthesize the existing literature on the impact of IC and BFR-E on motor and neurophysiological outcomes in individuals post-stroke. Evidence from five studies displayed enhancements in paretic leg strength, gait speed, and paretic leg fatiguability after IC. Additionally, BFR-E led to improvements in clinical performance, gait parameters, and serum lactate levels. While trends toward motor function improvement were observed post-intervention, statistically significant differences were limited. Neurophysiological changes showed inconclusive results. Our review suggests that IC and BFR-E are promising clinical approaches in stroke, however high-quality studies focusing on neurophysiological mechanisms are required to establish the efficacy and underlying mechanisms of both in stroke. Recommendations regarding future directions and clinical utility are provided.

In psychophysiological research, the use of Virtual Reality (VR) for stimulus presentation allows for the investigation of how perceptual processing adapts to varying degrees of realism. Previous time-domain studies have shown that perceptual processing involves modality-specific neural mechanisms, as evidenced by distinct stimulus-locked components. Analyzing induced oscillations across different frequency bands can provide further insights into neural processes that are not strictly phase-locked to stimulus onset. This study uses a simple perceptual paradigm presenting images of faces and cars on both a standard 2D monitor and in an immersive VR environment. To investigate potential modality-dependent differences in attention, cognitive load, and task-related post-movement processing, the induced alpha, theta and beta band responses are compared between the two modalities. No evidence was found for differences in stimulus-dependent attention or task-related post-movement processing between the 2D conditions and the realistic virtual conditions in electrode space, as posterior alpha suppression and re-synchronization of centro-parietal beta did not differ between conditions. However, source analysis revealed differences in the attention networks engaged during 2D and 3D perception. Midfrontal theta was significantly stronger in laboratory conditions, indicating higher cognitive load than in the VR environment. Exploratory analysis of posterior theta showed stronger responses in VR, possibly reflecting the processing of depth information provided only by the 3D material. In addition, the theta response seems to be generated by distinct neuronal sources under realistic virtual conditions indicating enhanced involvement of semantic information processing and social cognition.

Rhythmic auditory cueing (RAC) using an isochronous metronome is an effective approach to immediately enhance spatiotemporal aspects of gait for people with Parkinson disease (PwPD). Whereas entraining to RAC typically occurs subconsciously via cerebellar pathways, the use of metronome frequencies that deviate from one's typical cadence, such as those used in rehabilitation, may require conscious awareness. This heightened awareness may increase cognitive load and limit the persistence of gait training gains. Here, we explore the immediate effects of incorporating an implicit motor learning approach (i.e., error-based recalibration) to gait training with RAC. Twenty older adults (10 with PD and 10 controls) were asked to match their footfalls to both isochronous and subtly varying metronomes while walking on a treadmill and overground. Our findings revealed intriguing differences between treadmill and overground walking. During treadmill walking to a slower metronome frequency, both groups reduced their cadence and increased step lengths, but did not make the necessary adjustments to match the subtly varying metronome. During overground walking, both groups modified their cadence in response to a 3-4% change in metronome frequency (p < 0.05). Both metronomes yielded evidence of implicit and explicit retention during overground and treadmill walking. Furthermore, during overground walking the PD group showed greater implicit retention of cadence changes following the varying metronome, compared to the isochronous metronome. Our results suggest that incorporating implicit motor learning approaches to gait training during a single session of overground walking may enhance short term implicit retention of gait behaviors for PwPD.