Experimental Brain Research最新文献

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.

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.

Interlimb differences in reach control could impact the learning of a motor sequence that requires whole-arm movements. The purpose of this study was to investigate the learning of an implicit, 3-dimensional whole-arm sequence task with the non-dominant left arm compared to the dominant right arm. Thirty-one right-hand dominant adults completed two consecutive days of practice of a motor sequence task presented in a virtual environment with either their dominant right or non-dominant left arm. Targets were presented one-at-a-time alternating between Random and Repeated sequences. Task performance was indicated by the time to complete the sequence (response time), and kinematic measures (hand path distance, peak velocity) were used to examine how movements changed over time. While the Left Arm group was slower than the Right Arm group at baseline, both groups significantly improved response time with practice with the Left Arm group demonstrating greater gains. The Left Arm group improved performance by decreasing hand path distance (straighter path to targets) while the Right Arm group improved performance through a smaller decrease in hand path distance combined with increasing peak velocity. Gains made during practice on Day 1 were retained on Day 2 for both groups. Overall, individuals reaching with the non-dominant left arm learned the whole-arm motor sequence task but did so through a different strategy than individuals reaching with the dominant right arm. The strategy adopted for the learning of movement sequences that require whole-arm movements may be impacted by differences in reach control between the nondominant and dominant arms.

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.

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.

Fibromyalgia syndrome (FMS) is a chronic disorder characterized commonly by widespread musculoskeletal pain and fatigue, predominantly affecting women, with its complexity often leading to underdiagnosis and complicating treatment effectiveness. Transcranial magnetic stimulation (TMS) metrics are potential markers to optimize FMS treatments; however, evidence is limited. Our study aimed to explore the relationship between cortical excitability and inhibition, assessed through TMS markers, and clinical characteristics in patients with FMS. This presented cross-sectional study employed baseline data from a clinical trial with 108 FMS patients, mostly female (88.8%), and mean age of 47.3 years old (SD = 12.06). Our analysis showed that decreased short-intracortical inhibition (SICI) was associated with gabapentinoids use, nicotine history, and increased fatigue levels, suggesting its connection with compensatory mechanisms for non-painful FMS features. Increased motor intracortical facilitation (ICF) was linked with greater pain severity and shorter FMS duration, implying its relationship with a reorganization of sensorimotor pathways due to chronic pain. Additionally, higher resting motor threshold (rMT) was associated with less effective pain modulation (lower conditioned pain modulation [CPM]), indicating a disruption of pain compensatory mechanism. Given the role of SICI in indexing homeostatic brain mechanisms and its association with fatigue, a hallmark characteristic of FMS-induced behavioral changes, these results suggest that FMS likely has a deleterious effect on brain inhibitory function, thus providing a potential novel insight for FMS mechanisms. In addition, it seems that this compensatory mechanism's disruption is enhanced by pharmacological agents such as gabapentioids and nicotine.

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.

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.

The changes in brain function in response to mild head injury are usually subtle and go undetected. Physiological biomarkers would aid in the early diagnosis of mild head injury. In this study we used hypercapnia to follow changes in cerebral vascular reactivity after repetitive mild head injury. We hypothesized head injury would reduce vascular reactivity. Rats were maintained on a reverse light-dark cycle and head impacted daily at 24 h intervals over three days. All head impacts were delivered while rats were fully awake under red light illumination. There was no neuroradiological evidence of brain damage. After the 3rd impact rats were exposed to 5% CO₂ and imaged for changes in BOLD signal. All imaging was done while rats were awake without the confound of anesthesia. The data were registered to a 3D MRI rat atlas with 171 segmented brain areas providing site specific information on vascular reactivity. The changes in vascular reactivity were not uniform across the brain. The prefrontal cortex, somatosensory cortex and basal ganglia showed the hypothesized decrease in vascular reactivity while the cerebellum, thalamus, brainstem, and olfactory system showed an increase in BOLD signal to hypercapnia.

Plantarflexors provide propulsion during walking and receive input from both corticospinal and corticoreticulospinal tracts, which exhibit some frequency-specificity that allows potential differentiation of each tract's descending drive. Given that stroke may differentially affect each tract and impair the function of plantarflexors during walking; here, we examined this frequency-specificity and its relation to walking-specific measures during post-stroke walking. Fourteen individuals with chronic stroke walked on an instrumented treadmill at self-selected and fast walking speed (SSWS and FWS, respectively) while surface electromyography (sEMG) from soleus (SOL), lateral gastrocnemius (LG), and medial gastrocnemius (MG) and ground reaction forces (GRF) were collected. We calculated the intermuscular coherences (IMC; alpha, beta, and low-gamma bands between SOL-LG, SOL-MG, LG-MG) and propulsive impulse using sEMG and GRF, respectively. We examined the interlimb and intralimb IMC comparisons and their relationships with propulsive impulse and walking speed. Interlimb IMC comparisons revealed that beta LG-MG (SSWS) and low-gamma SOL-LG (FWS) IMCs were degraded on the paretic side. Intralimb IMC comparisons revealed that only alpha IMCs (both speeds) exhibited a statistically significant difference to random coherence. Further, alpha LG-MG IMC was positively correlated with propulsive impulse in the paretic limb (SSWS). Alpha and beta/low-gamma bands may have a differential functional role, which may be related to the frequency-specificity of the underlying descending drives. The persistence of alpha band in plantarflexors and its strong positive relationship with propulsive impulse suggests relative alteration of corticoreticulospinal tract after stroke. These findings imply the presence of frequency-specific descending drives to walking-specific muscles in chronic stroke.