Neurophysiological aspects of speech perception and production in stuttering

Stuttering is a speech disorder in which the smooth succession of speech sounds is interrupted by frequent blocks, prolongations and/or repetitions of sounds or syllables. When stuttering manifests itself for the first time during childhood, it is called developmental stuttering. When stuttering is of non-developmental origin, it is referred to as acquired stuttering. Acquired stuttering mostly derives from damage to the central nervous system which is called neurogenic stuttering. Neurologically, stuttering is characterized by alterations in cortical and subcortical brain regions related to speech motor planning, initiation, execution and monitoring. Neurological research in stuttering contains a plethora of spatial neuroimaging studies (e.g. fMRI) but a dearth of neurophysiological studies, especially when it comes to speech motor control. However, fluent speech does not only require the appropriate amount of (de)activation of specific brain regions, it also needs a timely and precise coordination of these brain regions. Therefore, the present thesis aimed to identify neurophysiological characteristics of speech motor control in stuttering by the use of electro-encephalography. First, temporal coordination of motor related activity during a visual word recognition task was assessed. Time points of motor related activity during hand action and non-action verb processing were compared in a group of fluent speakers and a group of adults with developmental stuttering. Secondly, speech motor preparatory activity preceding single word production was measured in real time by evoking a contingent negative variation (CNV) during a picture naming task. The CNV is an event-related potential reflecting motor preparatory activity in the basal ganglia-thalamo-cortical – loop. Speech motor preparation was compared between fluent speakers, and both fluent and stuttered words of stuttering speakers. Thirdly, although developmental and neurogenic stuttering are suggested to share common neural substrates, both types of stuttering were compared to assess whether this also accounts for speech motor preparatory activity. To that purpose, the same CNV picture naming task was performed in a case of neurogenic stuttering. Timing of motor related activation was considerable altered in the stuttering group, even during a silent reading task without (speech) movement requirements. The time point of maximal motor difference between both verb types was delayed with 100 ms and showed a reversed activation pattern compared to that of fluent speakers. This reversal is hypothesized to encompass two different motor abnormalities: a general motor hyperactivation, presenting during non-action verb processing, and a specific hand motor deficit, causing decreased excitability of this region during hand action verb processing. These findings confirm that temporal alterations in neural motor activations in stuttering are not restricted to overt speech production. Secondly, speech motor preparatory activity generated by the basal ganglia-thalamo-cortical – loop was found to have a crucial role in stuttering. Not only has its amount of activation a determining role in the actual moment of a stutter, its activation seems also related to the underlying stuttering pathology. An important divergence between left and right hemisphere is seen in this respect. When motor preparatory activity in right basal ganglia-thalamo-cortical – loop is markedly increased, no stutter will occur. The more frequent and/or the more severe a person stutters, the higher this increase is or must be to enable fluent speech production. The lower the motor preparatory activity preceding a stutter in the left basal ganglia-thalamo-cortical – network, the more this person will stutter in general. As such, left basal ganglia-thalamo-cortical – loop is suggested to have a link with the stuttering pathology. These findings concur with a growing amount of studies stating that right hemisphere alterations are related to (successful) compensation strategies, while the left hemisphere would contain the primary cause of stuttering. Thirdly, important differences emerged when comparing the findings concerning speech motor preparatory activity of the developmental stuttering group and the case with neurogenic stuttering. Roughly speaking, an increase in stuttering frequency was associated with an increase in CNV slope in the developmental stuttering group and a decrease in CNV in the case of neurogenic stuttering. Although neurogenic and developmental stuttering are believed to share common neural characteristics, these may be restricted to neuroanatomical findings. Both types of stuttering may show considerable variation in neurophysiological functioning, probably related to a difference in lesion localisation. Finally, when findings of the present studies are placed within a broader framework, the importance of the motor loop of feedforward processing in stuttering is highlighted. All observed motor alterations presented without simultaneous deficits in feedback processing or without obvious inferences of language impairments. Overall, the present thesis evidences that neurophysiology is able to discover interesting and intriguing neural findings that may aid in unravelling the enigma of stuttering

Inter and intra individual variability of the gait fundamental parameters on healthy children : definition of the clinically relevant normative data

The aim of this study was to determine the norm of the gait fundamental biomechanical parameters for the healthy pediatric population and associated measurement error, for this laboratory. Twenty-seven children cleared for neurological and musculoskeletal impairments, from a nearby school, aged between 7 and 9 joined this study. Kinematics, Kinetics, Electromyography and Anthropometrics were collected. Children were prepared with 53 passive markers (according to CAST) and instructed to walk through a walkway. Six muscles were bilaterally analyzed, Gluteus Medius, Adductor Longus, Rectus Femoris, Semitendinosus, Tibialis Anterior, and Gastrocnemius. Eleven children were re-evaluated within a 7 days time window to determine the measurement error (intra-observer). The analysis of Joint Angular Displacement, Moments, Powers, GRF and EMG revealed a good overlapping of the left and right side curves, with wave patterns in accordance to the literature. Clinical Measurements variables were within published healthy ranges, as were the Gait Parameters variables. Eight variables revealed SEM values between 2º and 5º, while all others were below 2º. Higher SEM was found for the variables Cadence (3.64 steps/min), Mean Value of Pelvic Tilt (2.48º), Maximum Hip Angle (2.56º), Minimum Hip angle (4.94º), Knee Angle at Initial Contact (2.40º), and TT ROM (2.79º)

Biofeedback's effect on sports performance: a meta-analysis and analysis of moderators

Thesis (Ed.D.)--Boston UniversitySince the late 1970s, research and applied work has focused on the use of biofeedback as a technique to assist in the development of sports performance through different means, including improvement of sports skills, reduction of injuries, and improvement of muscle strength, among others. However, there is no scientific work statistically comparing these implementations using biofeedback. A meta-analysis was designed towards this gap in the literature; 33 investigations were gathered and statistically compared. Dependent variables, (e.g. the type of biofeedback, and the number of biofeedback sessions) were treated as moderators and their effect on the overall analysis were calculated. A random effect model was used due to the presence of heterogeneity across studies (I^2 = 54.95 (p<0.001, 95% CI), that included variations on the studies' compared outcomes. The meta-analysis' overall result showed a significant effect of biofeedback interventions on sports performance through a strong effect size, d = 0.72, with a high significance Z= 6.77, p<0.001, (95% confidence interval (CI) 0.51 - 0.93). Significant moderators' effects were found indicating that studies using EMG modality (d= 0.891, 95% CI 0.60 -1.18,p < 0.001, Z= 6.05), studies with the number of sessions higher than 8 (d = 0.84, 95% CI 0.40 -1.27, p<0.001, Z= 3.77), studies targeting outcomes indirectly linked to sports performance (d = 0.91, 95% CI 0.59- 1.22, p<0.001, Z = 5.64), and studies using biofeedback along with other interventions (d = 0.90, 95% CI 0.48 -1.32, p<0.001, Z= 4.18) had higher effect on the overall analysis. The meta-analysis findings are an important reference for researchers and practitioners using biofeedback, because they indicate that biofeedback interventions have a positive effect on sports performance. Moreover, the meta-analysis point to methodological factors playing an important role on interventions using biofeedback, as studies that had a greater effect were those with methods using EMG biofeedback modality, studies with more than eight biofeedback sessions, studies focusing on outcome measures indirectly related to sports performance, and studies that included biofeedback interventions along with other interventions

Optimization of near-infrared spectroscopy-based neurofeedback for use in the treatment of attention-deficit hyperactivity disorder

Die Aufmerksamkeitsdefizit-Hyperaktivitätsstörung (ADHS) zählt zu den am häufigsten vorkommenden psychischen Störungen im Kindes- und Jugend-, aber auch im Erwachsenenalter, ca. 2,5-5% der Weltbevölkerung sind davon betroffen. Die Erkrankung wirkt sich in drei Kernbereichen aus: Hyperaktivität, Impulsivität und Unaufmerksamkeit, mit tiefgreifenden Beeinträchtigungen in verschiedenen Bereichen des Lebens, am deutlichsten in der Schule, bei der Arbeit und in interpersonellen Beziehungen. Es existieren verschiedene Behandlungsansätze, welche die vielseitige Symptomatologie der ADHS anzugehen versuchen. Die Medikation stellt dabei die gängigste Behandlungsmethode dar, ist jedoch nicht selten mit Nebenwirkungen verbunden. Die Methode des Neurofeedbacks (NF) ist zwar unlängst kein neuartiges Verfahren mehr, ist aber eine Behandlungsmethode, welche, aufgrund der fraglichen Wirksamkeit, in den letzten Jahren viele Diskussionen anregt hat. Da die Methode jedoch an der Schnittstelle zur Verhaltenstherapie und der neusten neurophysiologischen Forschung liegt, bietet sie die Möglichkeit fortwährend um die aktuellsten wissenschaftlichen Erkenntnisse erweitert zu werden. Die vorliegende Dissertation strebt die Optimierung des NIRS-basierten NF Paradigmas zur Behandlung von ADHS durch die Untersuchung folgender Punkte an: 1) Wie können NIRS-basierte Paradigmen in VR implementiert werden? 2) Welche sind die zugrundeliegenden Mechanismen, die für einen erfolgreichen NF Trial und Paradigma verantwortlich sind? 3) Wie können Methoden kombiniert werden um NF Paradigmen weiter zu entwickeln? Die Dissertation umfasst vier Studien. In Studie 1 untersuchten wir die Effektivität eines Nahinfrarotspektroskopie-(NIRS)-basierten NF Paradigmas, realisiert im virtuellen Klassenzimmer, zur Behandlung hoch-impulsiver Universitätsstudenten. In Studie 2 wurde ein ’Standard’- NIRS-basiertes NF Paradigma für ADHS in seinen Einzelteilen überprüft und Empfehlungen für die Weiterentwicklung eines NF Studiendesigns diskutiert sowie Netzwerke, welche mit Erfolg und Misserfolg bei NF Trials assoziiert sind, untersucht. In Studie 3 untersuchten wir das post-Fehlerverhalten bei ADHS-Patienten im Vergleich zu gesunden Kontrollpersonen (healthy controls, HC). Im Einzelnen betrachteten wir die ’P300-informed’ NIRS-Analyse um die Unterschiede zwischen ADHS-Patienten und HC genauer zu untersuchen. Zusätzlich wurde die Studie konzipiert um die Effektivität von EEG/NIRS für den zukünftigen Einsatz in einem multimodalen NF Studiendesign für ADHS zu überprüfen. In Studie 4 wird das Studiendesign für eine großangelegte und momentan laufende Studie mit Schulkindern mit ADHS beschrieben, in welcher das Paradigma aus Studie 1 zum Einsatz kommt. Dies liefert eine erste Zusammenfassung über die umfangreiche Datenerhebung, welche zu neuen Erkenntnissen bei NIRS-NF bei ADHS führen soll

Noncontact injuries in Scottish hockey: A study of epidemiology, current practice and a preventative measure

Introduction: There is limited evidence on noncontact injury epidemiology, current warm-up practice and exercise interventions used to reduce injuries in hockey. Therefore, the aims of this thesis are to investigate (1) noncontact injuries, (2) current warm-up practice and (3) the effects of a novel warm-up on female sub-elite hockey players in Scotland. Methodology: Study 1 was an online injury survey on 317 hockey players focussing on noncontact injuries. Study 2 was an observational study that investigated the current warm-up practices of 17 hockey teams. Study 3 was a controlled study that used 40 female hockey players and explored the effects of an 8-week hockey-specific neuromuscular training programme (NMTP) on electromyography, kinematics and kinetics during a sagittal plane hop, hop and twist and unanticipated sidecut. Results: Study 1 showed that the most common injuries were affecting the knee and hamstrings (0.89 and 0.69/1000 hours respectively) with no timeloss (31.4%) or mild to moderate injuries (30.3%) and usually occurred during sidecutting, sudden acceleration and landing (19.6%, 13.8% and 12.9% respectively). The injuries were more frequently occurring to females than males 4.73 vs 3.47/1000 hours. Study 2 revealed a warm-up time of 20 minutes including pulse raiser, activate and mobilise and potentiate elements. The occurrence of static stretching was greater (41.2%) than neuromuscular training (11.7%). Study 3 showed some significant increases in muscle activation for Gastrocnemius, Quadriceps and Gluteals both pre-and post-landing, with greater increases in the intervention group. There were significant reductions in maximum knee abduction, excursion and the rate of force development following 8-weeks of neuromuscular training. There were no significant differences in performance. Conclusion: Noncontact hockey injury epidemiology requires further research and the current provision of warm-ups should be evidence-based. A novel hockey-specific NMTP can elicit some significant changes in muscle activity, kinematics and kinetics that may reduce the risk of noncontact injuries