Interhemispheric transfer time correlates with white matter integrity of the corpus callosum in healthy older adults.

The corpus callosum (CC) has been identified as an important structure in the context of cognitive aging (Fling et al., 2011). Interhemispheric transfer time (IHTT) is regularly used in order to estimate interhemispheric integration enabled by the CC (Marzi, 2010; Nowicka and Tacikowski, 2011). However, only little is known with regards to the relationship between IHTT and the structural properties of the CC with only few studies with specific samples and methods available (Whitford et al., 2011). Thus, the present study aimed at investigating this relationship applying an event-related potentials (ERP) based approach of estimating IHTT as well as diffusion weighted imaging (DWI) with fractional anisotropy (FA) as an indicator of white matter integrity (WMI) of the genu, corpus and splenium of the CC. 56 healthy older adults performed a Dimond Task while ERPs were recorded and underwent DWI scanning. IHTT derived from posterior electrode sites correlated significantly with FA of the splenium (r = -0.286*, p = .03) but not the corpus (r = -0.187, p = .08) or genu (r = -0.189, p = .18). The present results support the notion that IHTT is related to WMI of the posterior CC. It may be concluded that ERP based IHTT is a suitable indicator of CC structure and function, however, likely specific to the interhemispheric transfer of visual information. Future studies may wish to confirm these findings in a more divers sample further exploring the precise interrelation between IHTT and structural or functional properties of the CC.

Stroboscopic Eyewear Applied During Warm-Up Does Not Provide Additional Benefits to the Sport-Specific Reaction Speed in Highly Trained Table Tennis Athletes.

PURPOSE: While long-term training with stroboscopic eyewear suggests performance-enhancing effects on visuomotor abilities, it remains unclear whether a short-term application, for example, during a warm-up, results in immediate performance gains. This study evaluated potential performance-enhancing effects of stroboscopic eyewear applied during warm-up on reaction speed that may provide athletes an edge in visuomotor-demanding sports. METHODS: Twenty-eight international-level table tennis athletes participated in this study. Participants performed their individual 10-minute table-tennis-specific warm-up under normal visual conditions and with stroboscopic eyewear. Prior to and after the warm-up, visuomotor reaction time was assessed in a sport-specific reaction test where athletes had to return 30 table tennis balls played by a ball machine at high speed to their backhand side. Reaction time was determined as the interval between ball output and movement onset as triggered by a mechanical switch. Furthermore, the time between ball-table contact and ball-racket contact (hit time) was analyzed as an indicator of how early the athletes intercepted the ball. RESULTS: Reaction time significantly improved following the warm-up (P < .001, ηp2=.393). However, there was no additional benefit of the stroboscopic eyewear (P = .338, ηp2=.034). No changes after the warm-up were observed for hit time (P = .246, ηp2=.055). CONCLUSIONS: The results indicate that warm-up facilitated visuomotor reaction speed; however, stroboscopic eyewear did not provide additional positive effects when compared to a warm-up under normal visual conditions. While shutter glasses may be useful for training over longer periods, short-term positive effects were not supported in this study.

The relationship between interhemispheric transfer time and physical activity as well as cardiorespiratory fitness in healthy older adults.

The structural and functional degradation of the corpus callosum (CC) has been shown to play an important role in the context of cognitive aging (Reuter-Lorenz and Stanczak, 2000). This is also reflected by findings of elongated interhemispheric transfer time (IHTT) in older adults (Riedel et al., 2022). At the same time, a protective effect of physical activity (PA) and cardiorespiratory fitness (CRF) on brain health including the CC is widely accepted (Hillman et al., 2008; Loprinzi et al., 2020). Based on this idea, the present study investigated the relationship between IHTT and PA/CRF in 107 healthy older adults (m: 64, f: 43) aged 67.69 ± 5.18. IHTT was calculated detecting event-related potentials (ERPs) using an established Dimond-Task. PA was evaluated using accelerometry resulting in estimates of overall bodily motion and time spent at higher intensity PA. CRF was estimated using graded exercise testing, approximating running speed at 4 mmol/l blood lactate concentration. The results showed a negative correlation between IHTTright→left and PA overall as well as in the male subgroup and between IHTTleft→right and CRF in women. This indicates a potential relationship between IHTT and PA/CRF. While the present investigation is only the first to hint at such a relationship taking into account the differential effects with regards to sex, mode of PA/CRF and IHTT direction, it is in line with previous findings and theoretical suggestions linking brain health to PA/CRF in the context of aging. Further research is needed in order to increase our understanding of the underlying mechanisms and of the influence of sex, PA intensity, degree of CRF and significance of IHTT direction.

Stroboscopic vision prolongs visual motion perception in the central nervous system.

Stroboscopic training has repeatedly been shown to improve visual and visuomotor performance in sports. Although recent research suggests that stroboscopic vision puts a training stimulus to the central nervous system, the underlying mechanism how it affects motion perception and processing in the brain is still unknown. Twenty-six participants performed a computer-based simple reaction test in response to a visual motion stimulus under normal (baseline) and stroboscopic conditions (5 Hz frequency, 40% duty cycle) (stroboscopic). A third condition under normal vision intermittently stopped the motion stimulus at the same frequency and duty cycle as in the stroboscopic condition. This condition controlled for the amount of visual motion information independent of the shutter glasses (screen shutter) and provided information about the effect of luminance changes induced by the stroboscopic eyewear. A 64-channel EEG was recorded to determine the amplitude and latency of the N2 component as a correlate of visual motion perception in the motion-sensitive visual area MT. Reaction time under stroboscopic conditions was significantly delayed when compared to both the baseline (p < 0.001) and screen shutter (p < 0.001) conditions. This was accompanied by a significantly prolonged N2 latency (p < 0.001) and lower N2 amplitude (p < 0.001) with the shutter glasses. There was no difference in reaction time or N2 amplitude/latency between the baseline and screen shutter condition (p ≥ 0.176). Stroboscopic eyewear delays the speed of visual motion perception and processing in the central nervous system and reduces the visuomotor reaction speed. This may form the neurophysiological basis for performance gains following stroboscopic training.

The impact of aging on interhemispheric transfer time and respective sex differences.

Age-related cognitive decline has been attributed to degeneration of the corpus callosum (CC), which allows for interhemispheric integration and information processing [22,69]. Along with decreased structural integrity, altered functional properties of the CC may cause impaired cognitive performance in older adults, yet this aspect of age-related decline remains insufficiently researched [59]. In this context, potential sex-related differences have been proposed [31,58]. A promising parameter, which has been suggested to estimate functional properties of the CC is the interhemispheric transfer time (IHTT), which is ideally obtained from event-related potentials (ERP) evoked by lateralized stimuli [45]. To examine the possible functional consequences of aging with regards to the CC, the present study investigated the IHTT of 107 older (67.69 ±â€¯5.18y) as well as of 23 younger participants (25.09 ±â€¯2.59y). IHTT was obtained using an established letter matching task and targeting early N170 ERP components at posterior electrode sites. The results revealed significantly elongated IHTT in older compared to younger participants, but no significant sex differences. Furthermore, there was a significant positive correlation between IHTT and age, predominantly driven by the female participants. The present findings add support to the notion, that IHTT is subject to age-related elongation reflecting impaired interhemispheric transmission. Age-related decline in women appears to occur at a different age range compared to men.

Auditory Information Accelerates the Visuomotor Reaction Speed of Elite Badminton Players in Multisensory Environments.

Although vision is the dominating sensory system in sports, many situations require multisensory integration. Faster processing of auditory information in the brain may facilitate time-critical abilities such as reaction speed however previous research was limited by generic auditory and visual stimuli that did not consider audio-visual characteristics in ecologically valid environments. This study investigated the reaction speed in response to sport-specific monosensory (visual and auditory) and multisensory (audio-visual) stimulation. Neurophysiological analyses identified the neural processes contributing to differences in reaction speed. Nineteen elite badminton players participated in this study. In a first recording phase, the sound profile and shuttle speed of smash and drop strokes were identified on a badminton court using high-speed video cameras and binaural recordings. The speed and sound characteristics were transferred into auditory and visual stimuli and presented in a lab-based experiment, where participants reacted in response to sport-specific monosensory or multisensory stimulation. Auditory signal presentation was delayed by 26 ms to account for realistic audio-visual signal interaction on the court. N1 and N2 event-related potentials as indicators of auditory and visual information perception/processing, respectively were identified using a 64-channel EEG. Despite the 26 ms delay, auditory reactions were significantly faster than visual reactions (236.6 ms vs. 287.7 ms, p < 0.001) but still slower when compared to multisensory stimulation (224.4 ms, p = 0.002). Across conditions response times to smashes were faster when compared to drops (233.2 ms, 265.9 ms, p < 0.001). Faster reactions were paralleled by a lower latency and higher amplitude of the auditory N1 and visual N2 potentials. The results emphasize the potential of auditory information to accelerate the reaction time in sport-specific multisensory situations. This highlights auditory processes as a promising target for training interventions in racquet sports.

Visual Perception and Visuomotor Reaction Speed Are Independent of the Individual Alpha Frequency.

While the resting-state individual alpha frequency (IAF) is related to the cognitive performance and temporal resolution of visual perception, it remains unclear how it affects the neural correlates of visual perception and reaction processes. This study aimed to unravel the relation between IAF, visual perception, and visuomotor reaction time. One hundred forty-eight (148) participants (28 non-athletes, 39 table tennis players, and 81 badminton players) investigated in three previous studies were considered. During a visuomotor reaction task, the visuomotor reaction time (VMRT) and EMG onset were determined. In addition, a 64-channel EEG system identified the N2, N2-r, and BA6 negativity potentials representing the visual and motor processes related to visuomotor reactions. Resting-state individual alpha frequency (IAF) in visual and motor regions was compared based on sport experience (athletes vs. non-athletes), discipline (badminton vs. table tennis), and reaction performance (fast vs. medium vs. slow reaction time). Further, the differences in the IAF were determined in relation to the speed of neural visual (high vs. medium vs. low N2/N2-r latency) and motor (high vs. medium vs. low BA6 negativity latency). Group comparisons did not reveal any difference in the IAF between athletes and non-athletes (p = 0.352, η p 2 = 0.02) or badminton and table tennis players (p = 0.221, η p 2 = 0.02). Similarly, classification based on the behavioral or neural performance indicators did not reveal any effects on the IAF (p ≥ 0.158, η p 2 ≤ 0.027). IAF was not correlated to any of the behavioral or neural parameters (r ≤ 0.10, p ≥ 0.221). In contrast to behavioral results on cognitive performance and visual temporal resolution, the resting state IAF seemed unrelated to the visual perception and visuomotor reaction speed in simple reaction tasks. Considering the previous results on the correlations between the IAF, cognitive abilities, and temporal sampling of visual information, the results suggest that a higher IAF may facilitate the amount and frequency but not the speed of information transfer.

Dorsolateral Prefrontal Functional Connectivity Predicts Working Memory Training Gains.

Background: Normal aging is associated with working memory decline. A decrease in working memory performance is associated with age-related changes in functional activation patterns in the dorsolateral prefrontal cortex (DLPFC). Cognitive training can improve cognitive performance in healthy older adults. We implemented a cognitive training study to assess determinants of generalization of training gains to untrained tasks, a key indicator for the effectiveness of cognitive training. We aimed to investigate the association of resting-state functional connectivity (FC) of DLPFC with working memory performance improvement and cognitive gains after the training. Method: A sample of 60 healthy older adults (mean age: 68 years) underwent a 4-week neuropsychological training, entailing a working memory task. Baseline resting-state functional MRI (rs-fMRI) images were acquired in order to investigate the FC of DLPFC. To evaluate training effects, participants underwent a neuropsychological assessment before and after the training. A second follow-up assessment was applied 12 weeks after the training. We used cognitive scores of digit span backward and visual block span backward tasks representing working memory function. The training group was divided into subjects who had and who did not have training gains, which was defined as a higher improvement in working memory tasks than the control group (N = 19). Results: A high FC of DLPFC of the right hemisphere was significantly associated with training gains and performance improvement in the visuospatial task. The maintenance of cognitive gains was restricted to the time period directly after the training. The training group showed performance improvement in the digit span backward task. Conclusion: Functional activation patterns of the DLPFC were associated with the degree of working memory training gains and visuospatial performance improvement. Although improvement through cognitive training and acquisition of training gains are possible in aging, they remain limited.

Short- and Long-Term Stroboscopic Training Effects on Visuomotor Performance in Elite Youth Sports. Part 1: Reaction and Behavior.

PURPOSE: Recent research suggests that stroboscopic training is an effective tool to improve visual and visuomotor performance. However, many studies were limited by small samples, short training interventions, inexperienced athletes, and an exclusive focus on short-term effects. This first part of the study evaluates the short- and long-term effects of stroboscopic training on visuomotor reaction speed in elite athletes. METHODS: Forty-five young elite badminton athletes participated in this study, of which 32 (13.7 yr) were included in the final data analysis. Participants were assigned to an intervention (stroboscopic vision) or control group (normal vision). Both groups performed identical badminton-specific training drills implemented into the regular training schedule. Before and after a 10-wk training period and after a 6-wk retention interval, athletes performed a laboratory reaction test to determine EMG onset and visuomotor reaction time (VMRT). In addition, a field test investigated stroboscopic training effects on the quality of ball-racquet contact and net drop performance. RESULTS: VMRT decreased immediately after stroboscopic training (pre, 251 ms; post, 238 ms; P = 0.005, d = 0.63), and reactions remained significantly faster after the retention interval (retention, 241 ms; P = 0.041, d = 0.50). Analyses on EMG onset data suggested these adaptations were attributable to the premotor rather than the motor time. VMRT remained unchanged in the control group (pre, 252 ms; post, 256; retention, 253 ms; P > 0.99). Field test performance improvements were observed for the quality of ball-racquet contact and net drop performance; however, changes were not different between groups. CONCLUSIONS: Stroboscopic training induced short- and long-term accelerations of visuomotor reaction speed in elite badminton players. Stroboscopic eyewear may be an effective training tool to accelerate visuomotor reactions in highly skilled athletes.

Short- and Long-Term Stroboscopic Training Effects on Visuomotor Performance in Elite Youth Sports. Part 2: Brain-Behavior Mechanisms.

PURPOSE: Stroboscopic training has repeatedly been shown to improve visuomotor abilities. However, although performance improvements were attributed to visual processes, information on the neurophysiological mechanisms is missing. Part 2 of this study investigated the effects of stroboscopic training on neural visual and motor functions and its contribution to training-induced changes in visuomotor reaction time. METHODS: Forty-five young elite badminton athletes participated in this study, of which 32 (age, 13.7 yr) were included in the final data analysis. Participants were assigned to an intervention (stroboscopic vision) or control group (normal vision). Before and after a 10-wk training and after a 6-wk retention period, participants performed visual perception and reaction tasks in response to visual motion stimuli. The N2 and N2-r motion onset visual-evoked potentials, its linear combination (Vlc), and the BA6 negativity potential were determined using a 64-channel EEG. RESULTS: A significant TIME-GROUP effect was observed for the Vlc score (P = 0.019, ηp2 = 0.18), indicating a lower Vlc in the intervention group. However, post hoc tests did not reach significance. Within-subject correlation analyses revealed that changes in reaction speed were related to latency changes in N2 (r = 0.59, P < 0.001), N2-r (r = -0.64, P < 0.001), and the combined Vlc (r = 0.68, P < 0.001). Regression analyses across participants including multiple (N2/N2-r) or single (Vlc) predictors provided an explained variance of >60% (N2/N2-r, r2 = 0.62; Vlc, r2 = 0.64). No training effects or correlations were observed for the BA6 negativity. CONCLUSIONS: The results indicate that faster visuomotor reactions after stroboscopic training are accompanied by accelerated visual perception and processing, whereas motor processes seemed to be unaffected. Stroboscopic training may be promising to specifically address the visual system in visuomotor-demanding sports.

The Impact of Age on the Association Between Physical Activity and White Matter Integrity in Cognitively Healthy Older Adults.

Cognition emerges from coordinated processing among distributed cortical brain regions, enabled through interconnected white matter networks. Cortical disconnection caused by age-related decline in white matter integrity (WMI) is likely to contribute to age-related cognitive decline. Physical activity (PA) has been suggested to have beneficial effects on white matter structure. However, its potential to counteract age-related decline in WMI is not yet well established. The present explorative study analyzed if PA was associated with WMI in cognitively healthy older adults and if this association was modulated by age. Forty-four cognitively healthy older individuals (aged 60-88 years) with diffusion-tensor imaging (DTI) and PA measurements were included from the AgeGain study. Voxelwise analysis using Tract-Based Spatial Statistics (TBSS) demonstrated that PA was associated with WMI in older adults. However, results emphasized that this association was restricted to high age. The association between PA and WMI was found in widespread white matter regions suggesting a global rather than a regional effect. Supplementary analyses demonstrated an association between the integrity of these regions and the performance in memory [verbal learning and memory test (VLMT)] and executive functioning (Tower of London).Results of the present explorative study support the assumption that PA is associated with WMI in older adults. However, results emphasize that this association is restricted to high age. Since cognitive decline in the elderly is typically most pronounced in later stages of aging, PA qualifies as a promising tool to foster resilience against age-related cognitive decline, via the preservation of the integrity of the brains WM.

Motion-Onset Visual Potentials Evoked in a Sport-Specific Visuomotor Reaction Task.

Although neural visual processes play a crucial role in sport, experiments have been restricted to laboratory conditions lacking ecological validity. Therefore, this study examined the feasibility of measuring visual evoked potentials in a sport-specific visuomotor task. A total of 18 international elite young table tennis athletes (mean age 12.5 years) performed a computer-based and a sport-specific visuomotor reaction task in response to radial motion-onset stimuli on a computer screen and table tennis balls played by a ball machine, respectively. A 64-channel electroencephalography system identified the N2 and N2-r motion-onset visual evoked potentials in the motion-sensitive midtemporal visual area. Visual evoked potential amplitudes were highly correlated between conditions (N2 r = .72, N2-r r = .74) although significantly lower in the sport-specific task than in the lab-based task (N2 p < .001, N2-r p < .001). The results suggest that sport-specific visual stimulation is feasible to evoke visual potentials. This emphasizes the investigation of visual processes under more ecologically valid conditions in sport and exercise science.

Effects of Endurance Exercise Bouts in Hypoxia, Hyperoxia, and Normoxia on mTOR-Related Protein Signaling in Human Skeletal Muscle.

Przyklenk, A, Aussieker, T, Gutmann, B, Schiffer, T, Brinkmann, C, Strüder, HK, Bloch, W, Mierau, A, and Gehlert, S. Effects of endurance exercise bouts in hypoxia, hyperoxia, and normoxia on mTOR-related protein signaling in human skeletal muscle. J Strength Cond Res 34(8): 2276-2284, 2020-This study investigated the effects of short-term hypoxia (HY), hyperoxia (PER), and normoxia on anabolic signaling proteins in response to an acute bout of moderate endurance exercise (EEX) before and after an endurance exercise training intervention. Eleven healthy male subjects conducted one-legged cycling endurance exercise (3 × 30 min·wk for 4 weeks). One leg was trained under hypoxic (12% O2) or hyperoxic conditions (in a randomized cross-over design), and the other leg was trained in normoxia (20.9% O2) at the same relative workload. Musculus vastus lateralis biopsies were taken at baseline (T0) as well as immediately after the first (T1) and last (T2) training session to analyze anabolic signaling proteins and the myofiber cross-sectional area (FCSA). No significant differences were detected for FCSA between T0 and T2 under all oxygen conditions (p > 0.05). No significant differences (p > 0.05) were observed for BNIP3, phosphorylated RSK1, ERK1/2, FoxO3a, mTOR, and S6K1 between all conditions and time points. Phosphorylated Akt/PKB decreased significantly (p < 0.05) at T1 in PER and at T2 in HY and PER. Phosphorylated rpS6 decreased significantly (p < 0.05) at T1 only in PER, whereas nonsignificant increases were shown in HY at T2 (p = 0.10). Despite no significant regulations, considerable reductions in eEF2 phosphorylation were detected in HY at T1 and T2 (p = 0.11 and p = 0.12, respectively). Short-term hypoxia in combination with moderate EEX induces favorable acute anabolic signaling responses in human skeletal muscle.

The Speed of Neural Visual Motion Perception and Processing Determines the Visuomotor Reaction Time of Young Elite Table Tennis Athletes.

Purpose: Recent research in adult badminton athletes has shown the visuomotor reaction time (VMRT) is strongly dependent on the speed of visual signal perception and processing in the brain's visual motion system. However, it remains unclear if this relation can be confirmed for other visuomotor demanding disciplines as well as different age groups. This study aimed to validate previous findings in international elite youth table tennis players to shed light on the generalizability of neural performance determinants across different visuomotor demanding sports and age groups. Methods: Thirty-seven young elite international table tennis players (18 male, 19 female, mean age: 13.5 years) from 23 nations participated in this study. Participants performed a visuomotor reaction task in response to visual motion stimuli presented at two different motion velocity conditions. Visuomotor performance was evaluated by measuring the electromyographic (EMG) onset as well as the VMRT. In addition, a 64-channel electroencephalography (EEG) system was used to investigate the stimulus and response-locked event-related potentials (ERPs) in the brain's visual motion sensitive area MT as well as the pre- and supplementary motor cortex indicating the speed of cortical visual and motor information processing, respectively. Correlation and multiple regression analyses identified the neural processes determining visuomotor performance. Results: The VMRT (232 vs. 258 ms, P < 0.001, d = -2.33) and EMG onset (181 vs. 206 ms, P < 0.001, d = -2.14) were accelerated in the fast motion velocity condition which was accompanied by an earlier stimulus-locked N2 (187 vs. 193 ms, P < 0.001, d = -0.80) and later response-locked N2-r (17 vs. -0.1 ms, P < 0.001, d = 1.04). The N2 and N2-r latencies were correlated with EMG onset and VMRT in both velocity conditions and explained between 80% and 90% of the variance in visuomotor reaction speed. Neural processes in BA6 did not differ between stimulus velocity conditions and did not contribute to the regression model. Conclusion: The results validate our previous findings and support the importance of neural visual processes for the visuomotor reaction speed across different visuomotor demanding sports and age groups. This suggests the visual system might be a promising target for specific visual diagnostics and training interventions.

The Effect of 4-Week Stroboscopic Training on Visual Function and Sport-Specific Visuomotor Performance in Top-Level Badminton Players.

PURPOSE: Stroboscopic training is suggested to improve visuomotor abilities in sports. However, previous research has primarily focused on untrained participants and only considered behavioral data. Because visuomotor performance is substantially determined by neural visual processes, this study aimed to examine the effects of stroboscopic training on visuomotor performance and neural visual function of athletes. METHODS: A total of 10 German top-level badminton players (intervention: n = 5 and control: n = 5) participated in this study. Over a 4-week training period, athletes performed badminton-specific visuomotor tasks either wearing shutter glasses (intervention) or under normal visual conditions (control). Prior to and after the training period, behavioral smash-defense tests and neurophysiologic investigations of the N2 motion onset visual evoked potential were used to identify modulations in the athletes' visuomotor performance and visual perception speed, respectively. RESULTS: Badminton training improved visuomotor performance in both groups; however, stroboscopic training resulted in superior posttraining performance compared with normal visual conditions (P = .007). Training-induced modulations in N2 latency did not reach significance, although a strong relationship was observed between changes in N2 latency and changes in visuomotor performance (r = -.55), indicating that higher performance gains following training were associated with a stronger reduction in N2 latency. CONCLUSIONS: The results indicate that stroboscopic training may be more effective than conventional visuomotor training for improving visuomotor abilities even in athletes performing at high skill levels. Furthermore, visuomotor performance gains could potentially be mediated by neural adaptations in the visual motion system. These findings should be confirmed for athletes from different disciplines.

The pre-stimulus oscillatory alpha phase affects neural correlates of early visual perception.

A growing number of studies suggest the phase of ongoing alpha oscillations in the brain influences visual perception. However, it remained largely unconsidered if this is associated with a phase dependence of neurophysiological processes especially in the visual cortex. Therefore, this study investigated the link between the pre-stimulus oscillatory alpha phase and neural correlates of early visual perception. In 64 subjects a 64-channel EEG system was used to examine the phase dependence of pattern-reversal visual evoked potentials (VEP) in a visual perception experiment. The pre-stimulus oscillatory phase over the primary visual cortex was determined for the individual alpha peak frequency (iAPF) as well as the frequency of maximal phase locking (PLFfmax). The phase dependence of VEP latency was determined using single-trial phase sorting. The results indicate a significantly shorter latency for the N75 and P100 components of the VEP between 40°-100° (p < 0.05) and 90°-120° (p < 0.05), respectively when trials were phase-sorted based on the iAPF. In contrast, the PLFfmax phase did not affect the N75 or P100 latency. The study indicates a link between the pre-stimulus alpha phase and neural correlates of early visual perception. These results extend previous behavioral findings to the neurophysiological level and support current models suggesting visual perception is modulated by ongoing alpha oscillations.

Mechanisms and modulators of cognitive training gain transfer in cognitively healthy aging: study protocol of the AgeGain study.

BACKGROUND: Cognitively healthy older people can increase their performance in cognitive tasks through training. However, training effects are mostly limited to the trained task; thus, training effects only poorly transfer to untrained tasks or other contexts, which contributes to reduced adaptation abilities in aging. Stabilizing transfer capabilities in aging would increase the chance of persistent high performance in activities of daily living including longer independency, and prolonged active participation in social life. The trial AgeGain aims at elaborating the physiological brain mechanisms of transfer in aging and supposed major modulators of transfer capability, especially physical activity, cerebral vascular lesions, and amyloid burden. METHODS: This 4-year interventional, multicenter, phase 2a cognitive and physical training study will enroll 237 cognitively healthy older subjects in four recruiting centers. The primary endpoint of this trial is the prediction of transfer of cognitive training gains. Secondary endpoints are the structural connectivity of the corpus callosum, Default Mode Network activity, brain-derived neurotrophic factors, motor fitness, and maximal oxygen uptake. DISCUSSION: Cognitive transfer allows making use of cognitive training gains in everyday life. Thus, maintenance of transfer capability with aging increases the chance of persistent self-guidance and prolonged active participation in social life, which may support a good quality of life. The AgeGain study aims at identifying older people who will most benefit from cognitive training. It will increase the understanding of the neurobiological mechanisms of transfer in aging and will help in determining the impact of physical activity and sport as well as pathologic factors (such as cerebrovascular disease and amyloid load) on transfer capability. TRIAL REGISTRATION: German Clinical Trials Register (DRKS), ID: DRKS00013077 . Registered on 19 November 2017.

The athletes' visuomotor system - Cortical processes contributing to faster visuomotor reactions.

Many sports require athletes to rapidly transform visual information into a targeted motor response, a process referred to as visuomotor reaction. On the behavioural level, athletes have long been established to achieve faster simple visuomotor reaction times when compared to non-athletes. However, although the superior performance in athletes has been attributed to the central nervous system, the underlying neural mechanisms remained poorly studied. More recently, a growing number of neurophysiological and neuroimaging studies systematically addressed the functional and structural modulations in the athletes' visual and motor systems as well as their contribution to visuomotor performance. This article reviews current research on structural and functional characteristics of the athletes' cortical visuomotor system associated with simple visuomotor reactions, sports-specific visuomotor performance and visuomotor training. The primary objective is to shed light on the neural mechanisms potentially contributing to superior visuomotor reaction performance in athletes participating in visuomotor demanding disciplines. A more comprehensive understanding of performance-determining neural functions could provide great potential for diagnostics and training to improve athletic performance.

Effects of triceps surae muscle strength and tendon stiffness on the reactive dynamic stability and adaptability of older female adults during perturbed walking.

This study aimed to examine whether the triceps surae (TS) muscle-tendon unit (MTU) mechanical properties affect gait stability and its reactive adaptation potential to repeated perturbation exposure in older adults. Thirty-four older adults each experienced eight separate unexpected perturbations during treadmill walking, while a motion capture system was used to determine the margin of stability (MoS) and base of support (BoS). Ankle plantar flexor muscle strength and Achilles tendon (AT) stiffness were analyzed using ultrasonography and dynamometry. A median split and separation boundaries classified the subjects into two groups with GroupStrong ( n = 10) showing higher ankle plantar flexor muscle strength (2.26 ± 0.17 vs. 1.47 ± 0.20 N·m/kg, means ± SD; P < 0.001) and AT stiffness (544 ± 75 vs. 429 ± 86 N/mm; P = 0.004) than GroupWeak ( n = 12). The first perturbation caused a negative ΔMoS (MoS in relation to unperturbed baseline walking) at touchdown of perturbed step (PertR), indicating an unstable position. GroupStrong required four recovery steps to return to ΔMoS zero level, whereas GroupWeak was unable to return to baseline within the analyzed steps. However, after repeated perturbations, both groups increased ΔMoS at touchdown of PertR with a similar magnitude. Significant correlations between ΔBoS and ΔMoS at touchdown of the first recovery step and TS MTU capacities (0.41 < r < 0.57; 0.006 < P < 0.048) were found. We conclude that older adults with TS muscle weakness have a diminished ability to control gait stability during unexpected perturbations, increasing their fall risk, but that degeneration in muscle strength and tendon stiffness may not inhibit the ability of the locomotor system to adapt the reactive motor response to repeated perturbations. NEW & NOTEWORTHY Triceps surae muscle weakness and a more compliant Achilles tendon partly limit older adults' ability to effectively enlarge the base of support and recover dynamic stability after an unexpected perturbation during walking, increasing their fall risk. However, the degeneration in muscle strength and tendon stiffness may not inhibit the ability of the locomotor system to adapt the reactive motor response to repeated perturbations.

Tracking the Reorganization of Module Structure in Time-Varying Weighted Brain Functional Connectivity Networks.

Identification of module structure in brain functional networks is a promising way to obtain novel insights into neural information processing, as modules correspond to delineated brain regions in which interactions are strongly increased. Tracking of network modules in time-varying brain functional networks is not yet commonly considered in neuroscience despite its potential for gaining an understanding of the time evolution of functional interaction patterns and associated changing degrees of functional segregation and integration. We introduce a general computational framework for extracting consensus partitions from defined time windows in sequences of weighted directed edge-complete networks and show how the temporal reorganization of the module structure can be tracked and visualized. Part of the framework is a new approach for computing edge weight thresholds for individual networks based on multiobjective optimization of module structure quality criteria as well as an approach for matching modules across time steps. By testing our framework using synthetic network sequences and applying it to brain functional networks computed from electroencephalographic recordings of healthy subjects that were exposed to a major balance perturbation, we demonstrate the framework's potential for gaining meaningful insights into dynamic brain function in the form of evolving network modules. The precise chronology of the neural processing inferred with our framework and its interpretation helps to improve the currently incomplete understanding of the cortical contribution for the compensation of such balance perturbations.