Somatosensory evoked potentials and high-frequency oscillations in athletes

Somatosensory-Evoked Potentials as a Marker of Functional Neuroplasticity in Athletes: A Systematic Review

Background

Somatosensory-evoked potentials (SEP) represent a non-invasive tool to assess neural responses elicited by somatosensory stimuli acquired via electrophysiological recordings. To date, there is no comprehensive evaluation of SEPs for the diagnostic investigation of exercise-induced functional neuroplasticity. This systematic review aims at highlighting the potential of SEP measurements as a diagnostic tool to investigate exercise-induced functional neuroplasticity of the sensorimotor system by reviewing studies comparing SEP parameters between athletes and healthy controls who are not involved in organized sports as well as between athlete cohorts of different sport disciplines.

Methods

A systematic literature search was conducted across three electronic databases (PubMed, Web of Science, and SPORTDiscus) by two independent researchers. Three hundred and ninety-seven records were identified, of which 10 cross-sectional studies were considered eligible.

Results

Differences in SEP amplitudes and latencies between athletes and healthy controls or between athletes of different cohorts as well as associations between SEP parameters and demographic/behavioral variables (years of training, hours of training per week & reaction time) were observed in seven out of 10 included studies. In particular, several studies highlight differences in short- and long-latency SEP parameters, as well as high-frequency oscillations (HFO) when comparing athletes and healthy controls. Neuroplastic differences in athletes appear to be modality-specific as well as dependent on training regimens and sport-specific requirements. This is exemplified by differences in SEP parameters of various athlete populations after stimulation of their primarily trained limb.

Conclusion

Taken together, the existing literature suggests that athletes show specific functional neuroplasticity in the somatosensory system. Therefore, this systematic review highlights the potential of SEP measurements as an easy-to-use and inexpensive diagnostic tool to investigate functional neuroplasticity in the sensorimotor system of athletes. However, there are limitations regarding the small sample sizes and inconsistent methodology of SEP measurements in the studies reviewed. Therefore, future intervention studies are needed to verify and extend the conclusions drawn here.

Specialized Somatosensory-Motor Integration Functions in Musicians

Somatosensory signals play roles in the fine control of dexterous movements through a somatosensory-motor integration mechanism. While skilled individuals are typically characterized by fine-tuned somatosensory functions and dexterous motor skills, it remains unknown whether and in what manner their bridging mechanism, the tactile-motor and proprioceptive-motor integration functions, plastically changes through extensive sensorimotor experiences. Here, we addressed this issue by comparing physiological indices of these functions between pianists and nonmusicians. Both tactile and proprioceptive stimuli to the right index finger inhibited corticospinal excitability measured by a transcranial magnetic stimulation method. However, the tactile and proprioceptive stimuli exerted weaker and stronger inhibitory effects, respectively, on corticospinal excitability in pianists than in nonmusicians. The results of the electroencephalogram measurements revealed no significant group difference in the amplitude of cortical responses to the somatosensory stimuli around the motor and somatosensory cortices, suggesting that the group difference in the inhibitory effects reflects neuroplastic adaptation of the somatosensory-motor integration functions in pianists. Penalized regression analyses further revealed an association between these integration functions and motor performance in the pianists, suggesting that extensive piano practice reorganizes somatosensory-motor integration functions so as to enable fine control of dexterous finger movements during piano performances.

A Biomarker for Benign Adult Familial Myoclonus Epilepsy: High-Frequency Activities in Giant Somatosensory Evoked Potentials

BACKGROUND

Benign adult familial myoclonus epilepsy (BAFME) is one of the diseases that cause cortical myoclonus (CM) with giant somatosensory evoked potentials (SEPs). There are no useful diagnostic biomarkers differentiating BAFME from other CM diseases.

OBJECTIVE

To establish reliable biomarkers including high-frequency oscillations (HFOs) with giant SEPs for the diagnosis of BAFME.

METHODS

This retrospective case study included 49 consecutive CM patients (16 BAFME and 33 other CM patients) who exhibited giant P25 or N35 SEPs. SEPs were processed by a band-pass filter of 400-1000 Hz to analyze HFOs. Clinical and SEP findings were compared between (1) BAFME and other CM groups and (2) patients with presence and absence of P25-HFOs (HFOs superimposed on giant P25). The diagnostic power of each factor for BAFME was calculated.

RESULTS

All 16 BAFME patients showed SEP P25-HFOs with significantly higher occurrence (P < 0.0001) compared with that of other CM groups. The presence of P25-HFOs significantly correlated with a BAFME diagnosis (P < 0.0001) and high SEP P25 and N35 amplitudes (P = 0.01 and P < 0.0001, respectively). BAFME was reliably diagnosed using P25-HFOs with high sensitivity (100%), specificity (87.9%), positive predictive value (80%), and negative predictive value (100%), demonstrating its superiority as a diagnostic factor compared to other factors.

CONCLUSIONS

P25-HFOs with giant SEPs is a potential biomarker for BAFME diagnosis. P25-HFOs may reflect cortical hyperexcitability partly due to paroxysmal depolarizing shifts in epileptic neuronal activities and higher degrees of rhythmic tremulousness than those in ordinary CM. © 2021 International Parkinson and Movement Disorder Society.

Association of short- and long-latency afferent inhibition with human behavior

Transcranial magnetic stimulation (TMS) paired with nerve stimulation evokes short-latency afferent inhibition (SAI) and long-latency afferent inhibition (LAI), which are non-invasive assessments of the excitability of the sensorimotor system. SAI and LAI are abnormally reduced in various special populations in comparison to healthy controls. However, the relationship between afferent inhibition and human behavior remains unclear. The purpose of this review is to survey the current literature and synthesize observations and patterns that affect the interpretation of SAI and LAI in the context of human behavior. We discuss human behaviour across the motor and cognitive domains, and in special and control populations. Further, we discuss future considerations for research in this field and the potential for clinical applications. By understanding how human behavior is mediated by changes in SAI and LAI, this can allow us to better understand the neurophysiological underpinnings of human motor control.

Modality-specific improvements in sensory processing among baseball players

Long-term skills training is known to induce neuroplastic alterations, but it is still debated whether these changes are always modality-specific or can be supramodal components. To address this issue, we compared finger-targeted somatosensory-evoked and auditory-evoked potentials under both Go (response) and Nogo (response inhibition) conditions between 10 baseball players, who require fine hand/digit skills and response inhibition, to 12 matched track and field (T&F) athletes. Electroencephalograms were obtained at nine cortical electrode positions. Go potentials, Nogo potentials, and Go/Nogo reaction time (Go/Nogo RT) were measured during equiprobable somatosensory and auditory Go/Nogo paradigms. Nogo potentials were obtained by subtracting Go trial from Nogo trial responses. Somatosensory Go P100 latency and Go/Nogo RT were significantly shorter in the baseball group than the T&F group, while auditory Go N100 latency and Go/Nogo RT did not differ between groups. Additionally, somatosensory subtracted Nogo N2 latency was significantly shorter in the baseball group than the T&F group. Furthermore, there were significant positive correlations between somatosensory Go/Nogo RT and both Go P100 latency and subtracted Nogo N2 latency, but no significant correlations among auditory responses. We speculate that long-term skills training induce predominantly modality-specific neuroplastic changes that can improve both execution and response inhibition.

Pitfalls in Scalp High-Frequency Oscillation Detection From Long-Term EEG Monitoring

Aims: Intracranially recorded high-frequency oscillations (>80 Hz) are considered a candidate epilepsy biomarker. Recent studies claimed their detectability on the scalp surface. We aimed to investigate the applicability of high-frequency oscillation analysis to routine surface EEG obtained at an epilepsy monitoring unit. Methods: We retrospectively analyzed surface EEGs of 18 patients with focal epilepsy and six controls, recorded during sleep under maximal medication withdrawal. As a proof of principle, the occurrence of motor task-related events during wakefulness was analyzed in a subsample of six patients with seizure- or syncope-related motor symptoms. Ripples (80-250 Hz) and fast ripples (>250 Hz) were identified by semi-automatic detection. Using semi-parametric statistics, differences in spontaneous and task-related occurrence rates were examined within subjects and between diagnostic groups considering the factors diagnosis, brain region, ripple type, and task condition. Results: We detected high-frequency oscillations in 17 out of 18 patients and in four out of six controls. Results did not show statistically significant differences in the mean rates of event occurrences, neither regarding the laterality of the epileptic focus, nor with respect to active and inactive task conditions, or the moving hand laterality. Significant differences in general spontaneous incidence [WTS(1) = 9.594; p = 0.005] that indicated higher rates of fast ripples compared to ripples, notably in patients with epilepsy compared to the control group, may be explained by variations in data quality. Conclusion: The current analysis methods are prone to biases. A common agreement on a standard operating procedure is needed to ensure reliable and economic detection of high-frequency oscillations.

The Effects of Filter's Class, Cutoff Frequencies, and Independent Component Analysis on the Amplitude of Somatosensory Evoked Potentials Recorded from Healthy Volunteers

Objective: The aim of this study was to investigate the effects of different preprocessing parameters on the amplitude of median nerve somatosensory evoked potentials (SEPs). Methods: Different combinations of two classes of filters (Finite Impulse Response (FIR) and Infinite Impulse Response (IIR)), three cutoff frequency bands (0.5–1000 Hz, 3–1000 Hz, and 30–1000 Hz), and independent component analysis (ICA) were used to preprocess SEPs recorded from 17 healthy volunteers who participated in two sessions of 1000 stimulations of the right median nerve. N30 amplitude was calculated from frontally placed electrode (F3). Results: The epochs classified as artifacts from SEPs filtered with FIR compared to those filtered with IIR were 1% more using automatic and 140% more using semi-automatic methods (both p < 0.001). There were no differences in N30 amplitudes between FIR and IIR filtered SEPs. The N30 amplitude was significantly lower for SEPs filtered with 30–1000 Hz compared to the bandpass frequencies 0.5–1000 Hz and 3–1000 Hz. The N30 amplitude was significantly reduced when SEPs were cleaned with ICA compared to the SEPs from which non-brain components were not removed using ICA. Conclusion: This study suggests that the preprocessing of SEPs should be done carefully and the neuroscience community should come to a consensus regarding SEP preprocessing guidelines, as the preprocessing parameters can affect the outcomes that may influence the interpretations of results, replicability, and comparison of different studies.

Football Players Do Not Show "Neural Efficiency" in Cortical Activity Related to Visuospatial Information Processing During Football Scenes: An EEG Mapping Study

This study tested the hypothesis of cortical neural efficiency (i.e., reduced brain activation in experts) in the visuospatial information processing related to football (soccer) scenes in football players. Electroencephalographic data were recorded from 56 scalp electrodes in 13 football players and eight matched non-players during the observation of 70 videos with football actions lasting 2.5 s each. During these videos, the central fixation target changed color from red to blue or vice versa. The videos were watched two times. One time, the subjects were asked to estimate the distance between players during each action (FOOTBALL condition, visuospatial). Another time, they had to estimate if the fixation target was colored for a longer time in red or blue color (CONTROL condition, non-visuospatial). The order of the two conditions was pseudo-randomized across the subjects. Cortical activity was estimated as the percent reduction in power of scalp alpha rhythms (about 8-12 Hz) during the videos compared with a pre-video baseline (event-related desynchronization, ERD). In the FOOTBALL condition, a prominent and bilateral parietal alpha ERD (i.e., cortical activation) was greater in the football players than non-players (p < 0.05) in contrast with the neural efficiency hypothesis. In the CONTROL condition, no significant alpha ERD difference was observed. No difference in behavioral response time and accuracy was found between the two groups in any condition. In conclusion, a prominent parietal cortical activity related to visuospatial processes during football scenes was greater in the football players over controls in contrast with the neural efficiency hypothesis.

THE CORRELATIVE ANALYSIS OF AMPLITUDE-TEMPORAL CHARACTERISTICS OF EVOKED POTENTIALS OF BRAIN CORTEX IN SPORTSMEN

The article considers the correlative analysis of amplitude-temporal characteristics of evoked potentials of brain cortex in sportsmen of playing kinds of sport and athletes at perception and processing of significant information “What” and “Where” in the brain cortex. The method of electroencephalography (Р300 methodology) was used to study the evoked potentials of the brain cortex. The statistical processing of data was realized using the statistical package MedStat. Kendall coefficient of correlation was used depending on data distribution, different from the normal values distribution. In the result of research there were revealed the high interconnections of latency of later components in sportsmen of both groups of examined persons at observation of significant stimuli “What” and “Where”. There was revealed the intensification of correlations of latency in frontal, central and temporal parts of the brain cortex. The correlations of amplitude of late components of biopotentials of the brain cortex were characterized with mean coefficients of interconnection mainly in sagittal central frontal and also parietal parts of cortex.

Skill-Specific Changes in Somatosensory Nogo Potentials in Baseball Players

Athletic training is known to induce neuroplastic alterations in specific somatosensory circuits, which are reflected by changes in somatosensory evoked potentials and event-related potentials. The aim of this study was to clarify whether specific athletic training also affects somatosensory Nogo potentials related to the inhibition of movements. The Nogo potentials were recorded at nine cortical electrode positions (Fz, Cz, Pz, F3, F4, C3, C4, P3 and P4) in 12 baseball players (baseball group) and in 12 athletes in sports, such as track and field events and swimming, that do not require response inhibition, such as batting for training or performance (sports group). The Nogo potentials and Go/Nogo reaction times (Go/Nogo RTs) were measured under a somatosensory Go/Nogo paradigm in which subjects were instructed to rapidly push a button in response to stimulus presentation. The Nogo potentials were obtained by subtracting the Go trial from the Nogo trial. The peak Nogo-N2 was significantly shorter in the baseball group than that in the sports group. In addition, the amplitude of Nogo-N2 in the frontal area was significantly larger in the baseball group than that in the sports group. There was a significant positive correlation between the latency of Nogo-N2 and Go/Nogo RT. Moreover, there were significant correlations between the Go/Nogo RT and both the amplitude of Nogo-N2 and Nogo-P3 (i.e., amplitude of the Nogo-potentials increases with shorter RT). Specific athletic training regimens may induce neuroplastic alterations in sensorimotor inhibitory processes.

Use-dependent cortical processing from fingertips in touchscreen phone users

Cortical activity allotted to the tactile receptors on fingertips conforms to skilful use of the hand. For instance, in string instrument players, the somatosensory cortical activity in response to touch on the little fingertip is larger than that in control subjects. Such plasticity of the fingertip sensory representation is not limited to extraordinary skills and occurs in monkeys trained to repetitively grasp and release a handle as well. Touchscreen phones also require repetitive finger movements, but whether and how the cortex conforms to this is unknown. By using electroencephalography (EEG), we measured the cortical potentials in response to mechanical touch on the thumb, index, and middle fingertips of touchscreen phone users and nonusers (owning only old-technology mobile phones). Although the thumb interacted predominantly with the screen, the potentials associated with the three fingertips were enhanced in touchscreen users compared to nonusers. Within the touchscreen users, the cortical potentials from the thumb and index fingertips were directly proportional to the intensity of use quantified with built-in battery logs. Remarkably, the thumb tip was sensitive to the day-to-day fluctuations in phone use: the shorter the time elapsed from an episode of intense phone use, the larger the cortical potential associated with it. Our results suggest that repetitive movements on the smooth touchscreen reshaped sensory processing from the hand and that the thumb representation was updated daily depending on its use. We propose that cortical sensory processing in the contemporary brain is continuously shaped by the use of personal digital technology.

Human proprioceptive adaptations during states of height-induced fear and anxiety

Clinical and experimental research has demonstrated that the emotional experience of fear and anxiety impairs postural stability in humans. The current study investigated whether changes in fear and anxiety can also modulate spinal stretch reflexes and the gain of afferent inputs to the primary somatosensory cortex. To do so, two separate experiments were performed on two separate groups of participants while they stood under conditions of low and high postural threat. In experiment 1, the proprioceptive system was probed using phasic mechanical stimulation of the Achilles tendon while simultaneously recording the ensuing tendon reflexes in the soleus muscle and cortical-evoked potentials over the somatosensory cortex during low and high threat conditions. In experiment 2, phasic electrical stimulation of the tibial nerve was used to examine the effect of postural threat on somatosensory evoked potentials. Results from experiment 1 demonstrated that soleus tendon reflex excitability was facilitated during states of height-induced fear and anxiety while the magnitude of the tendon-tap-evoked cortical potential was not significantly different between threat conditions. Results from experiment 2 demonstrated that the amplitudes of somatosensory-evoked potentials were also unchanged between threat conditions. The results support the hypothesis that muscle spindle sensitivity in the triceps surae muscles may be facilitated when humans stand under conditions of elevated postural threat, although the presumed increase in spindle sensitivity does not result in higher afferent feedback gain at the level of the somatosensory cortex.

Reactivity of alpha rhythms to eyes opening is lower in athletes than non-athletes: a high-resolution EEG study

In the present study, we tested the hypothesis that compared with non-athletes, elite athletes are characterized by a reduction of reactivity of electroencephalographic (EEG) alpha rhythms (about 8-12 Hz) to eyes opening in the condition of resting state, as a possible index of spatially selective cortical activation (i.e. "neural efficiency"). EEG data (56 channels; Eb-Neuro©) were recorded in 18 elite karate athletes and 28 non-athletes during resting state eyes-closed and eyes-open conditions. The EEG data were spatially enhanced by surface Laplacian estimation. Cortical activity was indexed by task-related power decrease (TRPD), namely the alpha power during the eyes-open referenced to the eyes-closed resting condition. Low-frequency alpha TRPD (about 8-10 Hz) was lower in the elite karate athletes than in the non-athletes in frontal (p<0.00002), central (p<0.008) and right occipital (p<0.02) areas. Similarly, high-frequency alpha TRPD (about 10-12 Hz) was lower in the elite karate athletes than in the non-athletes in frontal (p<0.00009) and central (p<0.01) areas. These results suggest that athletes' brain is characterized by reduced cortical reactivity to eyes opening in the condition of resting state, in line with the "neural efficiency" hypothesis. The present study motivates future research evaluating the extent to which this general functional brain feature is related to heritable trait or intensive visuo-motor training of elite athletes.

Benefits of sports participation for executive function in disabled athletes

We investigated the effect of sports activity on physically-disabled individuals using behavioral and electrophysiological techniques. Visual go/no-go discriminative and simple response tasks were used. Participants included 17 disabled athletes, 9 from open-skill (wheelchair basketball) and eight from closed-skill (swimming) sports, and 18 healthy non-athletes. Reaction times of the disabled athletes were slower than those of healthy non-athletes on both tasks (7% and 13% difference, respectively). Intra-individual variations in reaction times, switch cost, and number of false alarms, were higher in the swimmers, but comparable to healthy non-athletes, in the basketball group. Event-related potentials (ERPs) early components P1, N1, and P2 had longer latencies in the disabled athletes. The late P3 component had longer latency and smaller amplitude in the disabled athletes only in the discriminative response task. The N2 component, which reflected inhibition/execution processing in the discriminative response task, was delayed and reduced in the swimmer group, but was comparable to healthy subjects in the basketball group. Our results show that (1) the ERP components related to perceptual processing, and late components related to executive processing, were impaired in disabled subjects; and (2) open-skill sports such as basketball may partially compensate for executive control impairment by fostering the stability of motor responses and favoring response flexibility.