Mobile Electroencephalography Reveals Differences in Cortical Processing During Exercises With Lower and Higher Cognitive Demands in Preadolescent Children.

PURPOSE: The aim of this study was to examine whether cortical activity changes during exercise with increasing cognitive demands in preadolescent children. METHOD: Twenty healthy children (8.75 [0.91] y) performed one movement game, which was conducted with lower and higher cognitive demands. During a baseline measurement and both exercise conditions, cortical activity was recorded using a 64-channel electroencephalographic system, and heart rate was assessed. Ratings of perceived excertion and perceived cognitive engagement were examined after each condition. To analyze power spectral density in the theta, alpha-1, and alpha-2 frequency bands, an adaptive mixture independent component analysis was used to determine the spatiotemporal sources of cortical activity, and brain components were clustered to identify spatial clusters. RESULTS: One-way repeated-measures analyses of variance revealed significant main effects for condition on theta in the prefrontal cluster, on alpha-1 in the prefrontal, central, bilateral motor, bilateral parieto-occipital, and occipital clusters, and on alpha-2 in the left motor, central, and left parieto-occipital clusters. Compared with the lower cognitive demand exercise, cortical activity was significantly higher in theta power in the prefrontal cluster and in alpha-1 power in the occipital cluster during the higher cognitive demand exercise. CONCLUSION: The present study shows that exercise complexity seems to influence cortical processing as it increased with increasing cognitive demands.

Ecological validity in exercise neuroscience research: A systematic investigation.

The contribution of cortical processes to adaptive motor behaviour is of great interest in the field of exercise neuroscience. Next to established criteria of objectivity, reliability and validity, ecological validity refers to the concerns of whether measurements and behaviour in research settings are representative of the real world. Because exercise neuroscience investigations using mobile electroencephalography are oftentimes conducted in laboratory settings under controlled environments, methodological approaches may interfere with the idea of ecological validity. This review utilizes an original ecological validity tool to assess the degree of ecological validity in current exercise neuroscience research. A systematic literature search was conducted to identify articles investigating cortical dynamics during goal-directed sports movement. To assess ecological validity, five elements (environment, stimulus, response, body and mind) were assessed on a continuum of artificiality-naturality and simplicity-complexity. Forty-seven studies were included in the present review. Results indicate lowest average ratings for the element of environment. The elements stimulus, body and mind had mediocre ratings, and the element of response had the highest overall ratings. In terms of the type of sport, studies that assessed closed-skill indoor sports had the highest ratings, whereas closed-skill outdoor sports had the lowest overall rating. Our findings identify specific elements that are lacking in ecological validity and areas of improvement in current exercise neuroscience literature. Future studies may potentially increase ecological validity by moving from reductionist, artificial environments towards complex, natural environments and incorporating real-world sport elements such as adaptive responses and competition.

Somatosensory perturbations influence cortical activity associated with single-limb balance performance.

To determine the association between cortical activity and postural control performance changes with differing somatosensory perturbations. Healthy individuals (n = 15) performed a single-limb balance task under four conditions: baseline, unstable surface (foam), transcutaneous electrical nerve stimulation (TENS) applied to the stance-limb knee, and combined foam + TENS. Cortical activity was recorded with electroencephalography (EEG) and postural sway via triaxial force plate. EEG signals were decomposed, localized, and clustered to generate power spectral density in theta (4-7 Hz) and alpha-2 (10-12 Hz) frequency bands in anatomical clusters. Postural sway signals were analyzed with center of pressure (COP) sway metrics (e.g., area, distance, velocity). Foam increased theta power in the frontal and central clusters (d = 0.77 to 1.16), decreased alpha-2 power in bilateral motor, right parietal, and occipital clusters (d = - 0.89 to - 2.35) and increased sway area, distance, and velocity (d = 1.09-2.57) relative to baseline. Conversely, TENS decreased central theta power (d = - 0.60), but increased bilateral motor, left parietal, and occipital alpha-2 power (d = 0.51-1.40), with similar to baseline balance performance. In combination, foam + TENS attenuated sway velocity detriments and cortical activity caused by the foam condition alone. There were weak and moderate associations between percent increased central theta and occipital activity and increased sway velocity. Somatosensory perturbations changed patterns of cortical activity during a single-limb balance task in a manner suggestive of sensory re-weighting to pertinent sensory feedback. Across conditions decreased cortical activity in pre-motor and visual regions were associated with reduced sway velocity.

Stance leg and surface stability modulate cortical activity during human single leg stance.

Mobile Electroencephalography (EEG) provides insights into cortical contributions to postural control. Although changes in theta (4-8 Hz) and alpha frequency power (8-12 Hz) were shown to reflect attentional and sensorimotor processing during balance tasks, information about the effect of stance leg on cortical processing related to postural control is lacking. Therefore, the aim was to examine patterns of cortical activity during single-leg stance with varying surface stability. EEG and force plate data from 21 healthy males (22.43 ± 2.23 years) was recorded during unipedal stance (left/right) on a stable and unstable surface. Using source-space analysis, power spectral density was analyzed in the theta, alpha-1 (8-10 Hz) and alpha-2 (10-12 Hz) frequency bands. Repeated measures ANOVA with the factors leg and surface stability revealed significant interaction effects in the left (p = 0.045, ηp2 = 0.13) and right motor clusters (F = 16.156; p = 0.001, ηp2 = 0.41). Furthermore, significant main effects for surface stability were observed for the fronto-central cluster (theta), left and right motor (alpha-1), as well as for the right parieto-occipital cluster (alpha-1/alpha-2). Leg dependent changes in alpha-2 power may indicate lateralized patterns of cortical processing in motor areas during single-leg stance. Future studies may therefore consider lateralized patterns of cortical activity for the interpretation of postural deficiencies in unilateral lower limb injuries.

Balance task difficulty affects postural sway and cortical activity in healthy adolescents.

Electroencephalographic (EEG) research indicates changes in adults' low frequency bands of frontoparietal brain areas executing different balance tasks with increasing postural demands. However, this issue is unsolved for adolescents when performing the same balance task with increasing difficulty. Therefore, we examined the effects of a progressively increasing balance task difficulty on balance performance and brain activity in adolescents. Thirteen healthy adolescents aged 16-17 year performed tests in bipedal upright stance on a balance board with six progressively increasing levels of task difficulty. Postural sway and cortical activity were recorded simultaneously using a pressure sensitive measuring system and EEG. The power spectrum was analyzed for theta (4-7 Hz) and alpha-2 (10-12 Hz) frequency bands in pre-defined frontal, central, and parietal clusters of electrocortical sources. Repeated measures analysis of variance (rmANOVA) showed a significant main effect of task difficulty for postural sway (p < 0.001; d = 6.36). Concomitantly, the power spectrum changed in frontal, bilateral central, and bilateral parietal clusters. RmANOVAs revealed significant main effects of task difficulty for theta band power in the frontal (p < 0.001, d = 1.80) and both central clusters (left: p < 0.001, d = 1.49; right: p < 0.001, d = 1.42) as well as for alpha-2 band power in both parietal clusters (left: p < 0.001, d = 1.39; right: p < 0.001, d = 1.05) and in the central right cluster (p = 0.005, d = 0.92). Increases in theta band power (frontal, central) and decreases in alpha-2 power (central, parietal) with increasing balance task difficulty may reflect increased attentional processes and/or error monitoring as well as increased sensory information processing due to increasing postural demands. In general, our findings are mostly in agreement with studies conducted in adults. Similar to adult studies, our data with adolescents indicated the involvement of frontoparietal brain areas in the regulation of postural control. In addition, we detected that activity of selected brain areas (e.g., bilateral central) changed with increasing postural demands.

Neuroplastic changes in anterior cruciate ligament reconstruction patients from neuromechanical decoupling.

The purpose of this study was to identify how the brain simultaneously perceives proprioceptive input during joint loading in anterior cruciate ligament reconstruction (ACLR) patients, when compared to healthy controls. Seventeen ACLR patients (ACLR) and seventeen controls (CONT) were tested for the somatosensory cortical activation using electroencephalography (EEG) while measuring knee laxity using a knee arthrometer. The relationship between cortical activation and joint laxity within group was also examined. The ACLR patients had increased cortical activation (36.4% ± 11.5%) in the somatosensory cortex during early loading (ERD1) to the injured limb compared to the CONT's matched limb (25.3% ± 13.2%, P = 0.013) as well as compared to the noninjured limb (25.1% ± 14.2%, P = 0.001). Higher somatosensory cortical activity during midloading (ERD2) to the ACLR knee positively correlated with knee laxity (mm) during early loading (LAX1, r = 0.530), midloading (LAX2, r = 0.506), total anterior loading (LAXA, r = 0.543), and total antero-posterior loading (LAXT, r = 0.501), while the noninjured limb revealed negative correlations between ERD1 and LAXA (r = -0.534) as well as between ERD2 and LAX2 (r = -0.565). ACLR patients demonstrate greater brain activation during joint loading in the injured knees when compared to healthy controls' matched knees as well as contralateral healthy knees, while the CONT group shows similar brain activation patterns during joint loading between limbs. These different neural activation strategies may indicate neuromechanical decoupling following an ACL reconstruction and evidence of altered sensorimotor perception and control of the knee (neuroplasticity), which may be critical to address after surgery for optimal neuromuscular control and patients' outcomes.

Effects of Acute Physical Exercise With Low and High Cognitive Demands on Executive Functions in Children: A Systematic Review.

PURPOSE: Whereas many studies addressed the relation between acute physical exercise and executive functions (EF) in children, the effects of various modalities of acute exercise on EF still remain unclear. This systematic review investigated the effects of exercise with low and high cognitive demands on speed of processing and accuracy of performance in tasks examining inhibition, working memory, and cognitive flexibility in children. METHOD: A systematic literature research in electronic databases was performed. Controlled trials assessing the effects of acute exercise on EF in a pre-post design were included. RESULTS: Ten studies involving a total of 890 participants revealed positive effects in working memory performance in speed of processing after acute exercises with low cognitive demands compared with seated rest, mixed results for inhibition after exercises with low and high cognitive demands, and mixed results for cognitive flexibility with low cognitive demands. Concerning accuracy, only mixed results were found for inhibition after exercises with low and high cognitive demands. CONCLUSION: The differentiated effects of acute exercises with low and high cognitive demands led to more positive effects in speed of processing compared with accuracy of performance. Further investigations including assessment of neurophysiological parameters of EF are needed.

Behavioral and cortical dynamics underlying superior accuracy in short-distance passes.

Improved pass accuracy is a prominent determinant of success in football. It demands an effective interaction of complex behavioral and cortical dynamics. Exploring differences in the ability to sustain an accurate pass behavior in a stable setting and the associated cortical dynamics at different expertise levels may provide an insight into skilled strategies contributing to superior accuracy in football. The aim of this study is to compare trial-to-trial variability of pass biomechanics and the corresponding cortical dynamics during short-distance passes between novices and experienced football players. Thirty participants (15 novices, 15 football players) performed 90 short-distance passes. The intertrial variability of pass biomechanics (foot acceleration, range of hip flexion, knee flexion and foot rotation) was assessed by means of multiscale entropy. The task-related cortical dynamics were analyzed via source-derived event-related spectral perturbations. Experienced players demonstrated higher accuracy and overall lower entropy values across multiple time scales which was significant for hip flexion. The electroencephalography data revealed group differences in parieto-occipital alpha desynchronization and frontal theta synchronization in successive phases of passes. The current findings suggest that experienced football players may show a skilled ability to recruit and retain pass biomechanics promoting higher accuracy, whereas novices may show an explorative behavior with higher spatial variability. This difference may be associated with distinctive visuospatial and attentional strategies acquired with expertise in football. Our study provides an insight into expertise-specific behavioral and cortical dynamics of superior accuracy in football and a basis for its prospective investigation in enriched contexts.

The Mode of Endurance Exercise Influences Changes in EEG Resting-State Graphs among High-Level Cross-Country Skiers.

PURPOSE: Acute bouts of exercise influence the communication and organization of brain networks, with exercise intensity and volume regarded as key moderators. However, differences in coordination demands and limb involvement between exercise modes may also affect the communication and organization of brain networks after exercise and should be considered additionally. This study aimed to investigate the effect of mode on exercise-induced changes in electroencephalogaphy (EEG) resting-state networks comparing running (RUN) and cross-country skating (XC). METHODS: Fifteen male, highly trained participants were tested for peak oxygen uptake (V̇O 2peak ) during RUN (65.3 mL·min -1 ·kg -1 ) and XC (63.5 mL·min -1 ·kg -1 ) followed by incremental protocols at 50%, 70%, and 90% of speed at V̇O 2peak in both modes on the treadmill. After each exercise bout, 5-min resting-state EEG assessments using 64 channels were performed. Upon graph theory, small world index (SWI), clustering coefficient (CC), and path length (PL) were assessed in theta, alpha-1 and alpha-2 frequency bands. Repeated-measures ANOVA was applied to analyze the influence of exercise intensity and mode on modulations in brain network efficiency. RESULTS: Main effects of mode on SWI ( P = 0.047), CC ( P < 0.001), and PL ( P = 0.031) in the alpha-2 network indicated stronger modulations in network efficiency after XC. Main effects of exercise intensity in the theta network indicated modulated SWI ( P < 0.001), CC ( P < 0.001), and PL ( P = 0.003) after exercise at 90% of V̇O 2peak speed. Physiological outcomes (heart rate, blood lactate concentration, and rating of perceived exertion) were influenced by intensity solely. CONCLUSIONS: The present study demonstrates that an acute bout of coordinatively challenging endurance exercise may affect brain networks differently compared with running. Future studies may consider exercise mode as a potential moderator in the acute interaction between exercise and the brain.

EEG-derived brain graphs are reliable measures for exploring exercise-induced changes in brain networks.

The interaction of acute exercise and the central nervous system evokes increasing interest in interdisciplinary research fields of neuroscience. Novel approaches allow to monitor large-scale brain networks from mobile electroencephalography (EEG) applying graph theory, but it is yet uncertain whether brain graphs extracted after exercise are reliable. We therefore aimed to investigate brain graph reliability extracted from resting state EEG data before and after submaximal exercise twice within one week in male participants. To obtain graph measures, we extracted global small-world-index (SWI), clustering coefficient (CC) and characteristic path length (PL) based on weighted phase leg index (wPLI) and spectral coherence (Coh) calculation. For reliability analysis, Intraclass-Correlation-Coefficient (ICC) and Coefficient of Variation (CoV) were computed for graph measures before (REST) and after POST) exercise. Overall results revealed poor to excellent measures at PRE and good to excellent ICCs at POST in the theta, alpha-1 and alpha-2, beta-1 and beta-2 frequency band. Based on bootstrap-analysis, a positive effect of exercise on reliability of wPLI based measures was observed, while exercise induced a negative effect on reliability of Coh-based graph measures. Findings indicate that brain graphs are a reliable tool to analyze brain networks in exercise contexts, which might be related to the neuroregulating effect of exercise inducing functional connections within the connectome. Relative and absolute reliability demonstrated good to excellent reliability after exercise. Chosen graph measures may not only allow analysis of acute, but also longitudinal studies in exercise-scientific contexts.

External Focus of Attention Influences Cortical Activity Associated With Single Limb Balance Performance.

OBJECTIVE: External focus (EF) of attention leads to improved balance performance. Consideration of the neuromodulatory effects of EF may inform its clinical utility in addressing neuroplastic impairments after musculoskeletal injuries. This study aimed to determine whether electrocortical activity and balance performance changed with attentional foci that prioritized differing sensory feedback and whether changes in electrocortical activity and balance were associated. METHODS: Individuals who were healthy (n = 15) performed a single-limb balance task under 3 conditions: internal focus (IF), somatosensory focus (EF with a baton [EF-baton]), and visual focus (EF with a laser [EF-laser]). Electrocortical activity and postural sway were recorded concurrently using electroencephalography and a triaxial force plate. Electroencephalographic signals were decomposed, localized, and clustered to generate power spectral density in θ and α-2 frequency bands. Postural sway signals were analyzed with center-of-pressure sway metrics (eg, area, distance, velocity) and knee angle. The relationship between percent change in clustered brain activity and task performance metrics was assessed. RESULTS: Both EF conditions resulted in increased cortical activity and improved balance performance compared with IF. EF-laser had the largest effect, demonstrating increased frontal θ power (d = 0.64), decreased central θ power (d = -0.30), and decreased bilateral motor, bilateral parietal, and occipital α-2 power (d = -1.38 to -4.27) as well as a shorter path distance (d = -0.94) and a deeper (d = 0.70) and less variable (d = -1.15) knee angle than IF. Weak to moderate associations exist between increases in cortical activity and improved balance performance (ρ = 0.405-0.584). CONCLUSION: EF resulted in increased cortical activity associated with cognitive, motor, somatosensory, and visual processing. EF-laser, which prioritized visual feedback, had the largest and broadest effects. Changes in cortical activity resulting from EF were independently associated with improved balance performance. IMPACT: This study demonstrates that goal-oriented attention results in functional increases in brain activity compared with internally directed self-focus. These results suggest EF may target neurophysiologic impairments and improve balance in clinical populations.

Functional Cortical Connectivity Related to Postural Control in Patients Six Weeks After Anterior Cruciate Ligament Reconstruction.

Whereas initial findings have already identified cortical patterns accompanying proprioceptive deficiencies in patients after anterior cruciate ligament reconstruction (ACLR), little is known about compensatory sensorimotor mechanisms for re-establishing postural control. Therefore, the aim of the present study was to explore leg dependent patterns of cortical contributions to postural control in patients 6 weeks following ACLR. A total of 12 patients after ACLR (25.1 ± 3.2 years, 178.1 ± 9.7 cm, 77.5 ± 14.4 kg) and another 12 gender, age, and activity matched healthy controls participated in this study. All subjects performed 10 × 30 s. single leg stances on each leg, equipped with 64-channel mobile electroencephalography (EEG). Postural stability was quantified by area of sway and sway velocity. Estimations of the weighted phase lag index were conducted as a cortical measure of functional connectivity. The findings showed significant group × leg interactions for increased functional connectivity in the anterior cruciate ligament (ACL) injured leg, predominantly including fronto-parietal [F (1, 22) = 8.41, p ≤ 0.008, η2 = 0.28], fronto-occipital [F (1, 22) = 4.43, p ≤ 0.047, η2 = 0.17], parieto-motor [F (1, 22) = 10.30, p ≤ 0.004, η2 = 0.32], occipito-motor [F (1, 22) = 5.21, p ≤ 0.032, η2 = 0.19], and occipito-parietal [F (1, 22) = 4.60, p ≤ 0.043, η2 = 0.17] intra-hemispherical connections in the contralateral hemisphere and occipito-motor [F (1, 22) = 7.33, p ≤ 0.013, η2 = 0.25] on the ipsilateral hemisphere to the injured leg. Higher functional connectivity in patients after ACLR, attained by increased emphasis of functional connections incorporating the somatosensory and visual areas, may serve as a compensatory mechanism to control postural stability of the injured leg in the early phase of rehabilitation. These preliminary results may help to develop new neurophysiological assessments for detecting functional deficiencies after ACLR in the future.

Modulations of Inter-Hemispherical Phase Coupling in Human Single Leg Stance.

INTRODUCTION: Recent findings from neuroimaging studies provided initial insights into cortical contributions to postural control. These studies observed enhanced cortical activation and connectivity when task-difficulty and postural instability increased. However, little attention has been paid to the allocation of cortical networks appearing with a decreasing base of support from bipedal to single leg stance. Therefore, the aim of the present study was to investigate modulations of functional connectivity from bipedal to single leg stance. EXPERIMENTAL PROCEDURES: Cortical activity during bipedal and single leg stance (left) was investigated in 15 male subjects using 128 channel mobile electroencephalography (EEG), while standing on a triaxial force plate. Power spectral density was calculated for theta (4-7 Hz), alpha-1 (8-10 Hz) and alpha-2 (10-12 Hz) frequency bands. Estimations of the phase lag index (PLI) were conducted as a measure of functional connectivity. Moreover, postural control was analyzed by the area of sway and sway velocity. RESULTS: The results demonstrated a significantly increased area of sway and decreased alpha-2 power in single leg compared to bipedal stance. Furthermore, PLIs within the alpha-2 frequency band showed significantly decreased inter-hemispherical phase coupling in single leg stance, associated with connections involving the left motor region. DISCUSSION: Altogether, the present findings may indicate modulations of cortical contributions in single leg compared to bipedal stance. The present data suggest that decreased inter-hemispherical functional connectivity, in conjunction with a global increase in cortical excitability, may indicate enhanced alertness and task-specific selective inhibition of motor networks in favor of postural control.

Exergames Inherently Contain Cognitive Elements as Indicated by Cortical Processing.

Exergames are increasingly used to train both physical and cognitive functioning, but direct evidence whether and how exergames affect cortical activity is lacking. Although portable electroencephalography (EEG) can be used while exergaming, it is unknown whether brain activity will be obscured by movement artifacts. The aims of this study were to assess whether electrophysiological measurements during exergaming are feasible and if so, whether cortical activity changes with additional cognitive elements. Twenty-four young adults performed self-paced sideways leaning movements, followed by two blocks of exergaming in which participants completed a puzzle by leaning left or right to select the correct piece. At the easy level, only the correct piece was shown, while two pieces were presented at the choice level. Brain activity was recorded using a 64-channel passive EEG system. After filtering, an adaptive mixture independent component analysis identified the spatio-temporal sources of brain activity. Results showed that it is feasible to record brain activity in young adults while playing exergames. Furthermore, five spatially different clusters were identified located frontal, bilateral central, and bilateral parietal. The frontal cluster had significantly higher theta power in the exergaming condition with choice compared to self-paced leaning movements and exergaming without choice, while both central clusters showed a significant increase in absolute alpha-2 power in the exergaming conditions compared to the self-paced movements. This is the first study to show that it is feasible to record brain activity while exergaming. Furthermore, results indicated that even a simple exergame without explicit cognitive demands inherently requires cognitive processing. These results pave the way for studying brain activity during various exergames in different populations to help improve their effective use in rehabilitation settings.

Distribution of insulin-like growth factors in condylar hyperplasia.

Condylar hyperplasia (CH) is a local overgrowth of the condylar process of the temporomandibular joint (TMJ) of unknown etiology. Probably, growth factors like the insulin-like growth factors (IGFs) are involved in its pathogenesis. Specimens from 12 patients were investigated histologically and immunohistochemically to obtain the distribution of the IGFs-I and -II and the IGF1 receptor. The results revealed juvenile and adult subtypes. While generally IGF-II could only be detected weakly, in the juvenile cases strong immunostaining for IGF-I in cartilage and bone supposes an influence on pathological growth processes.

Single-Leg Assessment of Postural Stability After Anterior Cruciate Ligament Injury: a Systematic Review and Meta-Analysis.

BACKGROUND: Previous reports of single-leg assessment demonstrated functional deficits in postural stability following anterior cruciate ligament (ACL) injury. However, quantified measures describing postural stability vary among investigations and results seem not to be clear. The first aim of this systematic review was to quantify postural deficits in eyes open single-leg stance in patients after ACL injury. Moreover, the second aim was to examine the potential of traditional center of pressure (CoP) measures in order to distinguish postural stability between ACL patients and healthy controls. METHODS: A systematic literature search in the databases PubMed and Scopus was conducted from their inception to December 2016 to identify relevant articles. Eligibility criteria were limited to controlled trials of eyes open static single-leg stance on a force or pressure plate recording CoP measures in patients after ACL injury. RESULTS: Eleven studies were included, involving a total of 329 ACL-injured and 265 control subjects. Random-effects meta-analysis showed significantly increased sway magnitudes (SMDwm = 0.94, p = 0.003) and velocities (SMDwm = 0.66, p = 0.0002) in the ACL group compared to the healthy controls. Sway magnitude in anteroposterior (SMDwm = 0.58, p = 0.02) and mediolateral (SMDwm = 1.15, p = 0.02) direction were significantly increased in ACL patients. No differences were found for the non-injured side. Similarly, no differences have been observed among ACL patients between the injured and non-injured side for sway velocity, while sway magnitude significantly differed (SMDwm = 0.58, p = 0.05). CONCLUSIONS: The findings of this systematic review and meta-analysis demonstrated decreased postural stability in individuals with ACL injury. Sway magnitude and velocity were significantly increased in the ACL group compared to the healthy controls. Although the included research still exhibited considerable heterogeneity, it may be proposed that fundamental CoP measures are suitable to differentiate patients after ACL injury and healthy controls with respect to postural stability in eyes open single-leg stance.