Older adults exhibit a more pronounced modulation of beta oscillations when performing sustained and dynamic handgrips

Muscle contractions are associated with a decrease in beta oscillatory activity, known as movement-related beta desynchronization (MRBD). Older adults exhibit a MRBD of greater amplitude compared to their younger counterparts, even though their beta power remains higher both at rest and during muscle contractions. Further, a modulation in MRBD has been observed during sustained and dynamic pinch contractions, whereby beta activity during periods of steady contraction following a dynamic contraction is elevated. However, how the modulation of MRBD is affected by aging has remained an open question. In the present work, we investigated the effect of aging on the modulation of beta oscillations and their putative link with motor performance. We collected magnetoencephalography (MEG) data from younger and older adults during a resting-state period and motor handgrip paradigms, which included sustained and dynamic contractions, to quantify spontaneous and motor-related beta oscillatory activity. Beta power at rest was found to be significantly increased in the motor cortex of older adults. During dynamic hand contractions, MRBD was more pronounced in older participants in frontal, premotor and motor brain regions. These brain areas also exhibited age-related decreases in cortical thickness; however, the magnitude of MRBD and cortical thickness were not found to be associated after controlling for age. During sustained hand contractions, MRBD exhibited a decrease in magnitude compared to dynamic contraction periods in both groups and did not show age-related differences. This suggests that the amplitude change in MRBD between dynamic and sustained contractions is larger in older compared to younger adults. We further probed for a relationship between beta oscillations and motor behaviour and found that greater MRBD in primary motor cortices was related to degraded motor performance beyond age, but our results suggested that age-related differences in beta oscillations were not predictive of motor performance

Bilateral upper-limb coordination in aging and stroke

Bilateral upper-limb coordination is an important ability for our living independency, since most of our daily tasks, such as lifting a box or using knife and fork, require the simultaneous use of both arms (Waller et al., 2006). However, bilateral coordination decline has been observed in both healthy aging and neurological groups (Pollock et al., 2014; Maes et al., 2017) , which often results in decreased quality of life (Broeks et al., 1999; Franceschini et al., 2010). Therefore, this dissertation sought to understand the characteristics and mechanisms of bilateral coordination and its impairments. The two fundamental bilateral movements in human upper limbs, i.e., in-phase (homologous muscles from bilateral arms activate simultaneously) and anti-phase (different muscle groups from bilateral arms activate simultaneously) movements, have been found to show different characteristics in behavioral and neural measurements (Swinnen and Wenderoth, 2004). Behaviorally, anti-phase movements are found to be performed with lower movement accuracy and higher phase variability between hands compared to in-phase movements (Wuyts et al., 1996; Byblow et al., 2000; Pollok et al., 2007). On the neural level, fMRI studies demonstrated that the left hemisphere shows larger task-related BOLD signal changes compared to the right hemisphere during in-phase movements (Aramaki et al., 2006), while the BOLD signal changes between the two hemispheres are similar during anti-phase movements (Walsh et al., 2008). These results suggest a left-dominated control of in-phase movements. However, a critical limitation in the literature is the lack of causal evidence supporting hemispherical specialization in bilateral coordination. Therefore, it is unclear whether the observed behavioral differences between anti-phase and in-phase movements were truly due to distinct hemispheric control. Another limitation of the literature is the design of existing paradigms. While most of our daily activities involve movements engaging multiple joints at the same time (Keenan et al., 2006; Murphy et al., 2006), previous studies mostly investigated single joint movements (e.g. index finger tapping, forearm pronation-supination). Contrary to single joint movements, bilateral movements engaging multiple joints require not only inter-limb coordination, but also additional intra-limb coordination. Therefore, it is unclear whether the previous findings from single joint movements could be directly applied to multiple joint movements. In this dissertation, we used a bilateral coordination paradigm involving both shoulder and elbow joints to investigate the neural mechanisms behind bilateral coordination and its decline. We designed three studies focusing on 1) the differences between bilateral in-phase and anti-phase movements from a human motion perspective, 2) how aging affects different bilateral coordination patterns and its neural correlates, as well as 3) how lesioned hemisphere affects bilateral coordination impairments and whether distinct rehabilitation treatments are needed after a left or right hemispheric stroke. In Study 1, we examined the two basic bilateral coordination modes, in-phase and anti-phase movements, in healthy young right-handed participants. We used a bilateral circle drawing task involving both shoulder and elbow joints. During the movements, we measured participants’ hand positions with high temporal and spatial precision, and developed intra-limb and inter-limb measures to differentiate movement characteristics during the two basic movement modes. For intra-limb coordination, we quantified trajectory variability of each hand during the movements. For inter-limb coordination, we computed the phase synchronization between hands. We found that intra-limb coordination was worse in the non-dominant hand during anti-phase compared to in-phase movements. In contrast, intra-limb coordination in the dominant hand did not differ between anti-phase and in-phase movements. Second, participants showed worse inter-limb synchronization during anti-phase compared to in-phase movements. Moreover, we examined the hand acceleration profile of both hands, and found that participants’ bilateral hands accelerated and decelerated in an in-phase manner during in-phase movements. In contrast, the acceleration and deceleration of the two hands were unrelated during anti-phase movements. These inter-limb acceleration profiles support the idea of differential neural mechanisms behind bilateral anti-phase and in-phase movements: during in-phase movements, the hands are governed by a common neural generator, while during anti-phase movements, the two hands are controlled by both hemispheres more independently. Taken together, Study 1 showed that the current experimental setup is able to differentiate the performance between bilateral in-phase and anti-phase movements engaging multiple joints. Therefore, we used the same paradigm combined with electroencephalography (EEG) to examine the presumed decline of bilateral coordination in aging. In Study 2, we investigated the effect of aging on the two basic bilateral movement modes. We used intra- and inter-limb measures as the behavioral measures, and EEG as a neural measure. Behaviorally, we found that older adults only showed significant impairments in anti-phase movements, but not in-phase movements, compared to young adults. On the neural level, we found that older adults showed different neural responses during anti-phase and in-phase movements compared to young adults. Specifically, during in-phase movements, young adults showed a more pronounced decrease of alpha power (8-12 Hz) over the left compared to the right hemisphere, while older adults showed similar levels of alpha power decrease over both hemispheres. Furthermore, in the older adults, we found a marginal correlation between the change in alpha power over the right hemisphere and the behavioral performance, which indicated a compensatory brain response. As for the anti-phase movements, we found that participants with stronger directional inter-hemispheric connectivity in the beta band (15-25 Hz) showed worse behavioral performance, and this effect was more pronounced in the older adults. This result implies that a balanced inter-hemispheric contribution is essential for executing a successful anti-phase movement. Our findings therefore show that the two hemispheres are differentially involved in the two basic bilateral coordination modes. These different neural characteristics may explain the distinct decline patterns of in-phase and anti-phase movements in older adults. However, causal evidence to support hemispherical specialization is needed to confirm our findings. Therefore, we conducted Study 3, where we used stroke as a lesion model to examine the influence of the lesioned hemisphere on bilateral coordination. In Study 3, we examined the bilateral coordination ability in patients with left (LHS) and right hemispheric stroke (RHS), as well as healthy controls. Given that healthy young participants show a left-dominant control in in-phase movements in Study 2 and in the previous literature (Aramaki et al., 2006; Maki et al., 2008), we expected that LHS patients would display a more pronounced impairment of in-phase movements compared to RHS patients. In contrast, since anti-phase movements require a more balanced inter-hemispheric contribution as shown in Study 2, and RHS patients show larger inter-hemispheric inhibition compared to healthy participants and LHS patients (Lewis and Perreault, 2007b), we expected that RHS patients would show more impairment in anti-phase movements compared to LHS patients. As predicted, we found that patients with RHS patients exhibited greater impairment during anti-phase movements (both intra- and inter-limb parameters) and LHS patients showed greater impairment during in-phase movements (intra-limb parameters only). Though LHS patients did not show greater impairment in inter-limb coordination during in-phase movements compared to RHS patients, our regression analysis revealed that only LHS patients swapped hand dominance during the task. We interpreted this result as a compensatory mechanism whereby bilateral in-phase movements in the LHS group switched from a left-dominated cortical control to a right-dominated cortical control. Our findings not only provide causal evidence for hemispheric specialization in bilateral movement coordination, but also characterize the differential impairments in bilateral coordination after a left or right hemispheric stroke. Taken together, this dissertation highlighted differential neural control processes involved in bilateral in-phase and anti-phase movements, and demonstrated how these distinct mechanisms lead to impaired bilateral coordination in aging and stroke. The present results could therefore advance the development of therapeutic strategies that seek to counteract bilateral coordination decline, such as differential treatment for patients with left and right hemispheric lesions, or the use of noninvasive brain stimulation at a target hemisphere.:List of abbreviations List of figures List of tables Chapter 1. General introduction 1.1. Introduction 1.2. Bilateral coordination in human upper extremities 1.3. Age-related motor decline 1.4. Stroke-induced motor impairments Chapter 2. Rationale of the Dissertation Chapter 3. Study I: Human motion characteristics during bilateral in-phase and anti-phase movements 3.1. Introduction 3.2. Materials and methods 3.3. Results 3.4. Discussion 3.5. Conclusion Chapter 4. Study II: The effect of aging on bilateral coordination 49 4.1. Introduction 4.2. Materials and methods 4.3. Results 4.4. Discussion 4.5. Conclusion Chapter 5. Study III: Effects of lesioned side on bilateral coordination after strokes 5.1. Introduction 5.2. Materials and methods 5.3. Results 5.4. Discussion 5.5. Conclusion Chapter 6. General discussion 6.1. Summary of research 6.2. Contributions and clinical implications 6.3. Outlook for future research Chapter 7. Summary of the dissertation References Appendix Appendix 1. Supplementary information for study 1 Appendix 2. Supplementary information for study 2 Appendix 3. Supplementary information for study 3 Appendix 4. Declaration of authenticit

Estimating brain age from structural MRI and MEG data: insights from dimensionality reduction techniques

Brain age prediction studies aim at reliably estimating the difference between the chronological age of an individual and their predicted age based on neuroimaging data, which has been proposed as an informative measure of disease and cognitive decline. As most previous studies relied exclusively on magnetic resonance imaging (MRI) data, we hereby investigate whether combining structural MRI with functional magnetoencephalography (MEG) information improves age prediction using a large cohort of healthy subjects (N = 613, age 18–88 years) from the Cam-CAN repository. To this end, we examined the performance of dimensionality reduction and multivariate associative techniques, namely Principal Component Analysis (PCA) and Canonical Correlation Analysis (CCA), to tackle the high dimensionality of neuroimaging data. Using MEG features (mean absolute error (MAE) of 9.60 years) yielded worse performance when compared to using MRI features (MAE of 5.33 years), but a stacking model combining both feature sets improved age prediction performance (MAE of 4.88 years). Furthermore, we found that PCA resulted in inferior performance, whereas CCA in conjunction with Gaussian process regression models yielded the best prediction performance. Notably, CCA allowed us to visualize the features that significantly contributed to brain age prediction. We found that MRI features from subcortical structures were more reliable age predictors than cortical features, and that spectral MEG measures were more reliable than connectivity metrics. Our results provide an insight into the underlying processes that are reflective of brain aging, yielding promise for the identification of reliable biomarkers of neurodegenerative diseases that emerge later during the lifespan

Neuroprotective Effects of Long-term Endurance Training on the Cortical Autonomic Network in the Aging Brain

This study tested whether long-term endurance training in older adults (ET; n = 15, 55 ± 4 years, relative VO2max = 50 ± 8 ml/kg/min) would alter cardiovagal control and preserve the cortical autonomic network compared to age-matched controls (CON; n = 15, 56 ± 4 years, relative VO2max = 37 ± 9 ml/kg/min). The hypothesis predicts 1) altered deactivation patterns of the ventral medial prefrontal cortex (vMPFC) in response to isometric hand grip (IHG) and 2) greater indices of cardiovagal control; a) increased baroreflex sensitivity at rest, b) greater heart rate change (ΔHR) and c) reductions in high frequency heart rate variability (ΔHF HRV) in the ET group. Functional magnetic resonance imaging was utilized to observe BOLD signal changes. There was no difference in measured indices of cardiovagal control between groups and both exhibited vMPFC deactivation with IHG. Overall, ET does not preserve cortical functional patterns in the older brain or enhance cardiovagal control compared to age-matched controls

Biomechanical Spectrum of Human Sport Performance

Writing or managing a scientific book, as it is known today, depends on a series of major activities, such as regrouping researchers, reviewing chapters, informing and exchanging with contributors, and at the very least, motivating them to achieve the objective of publication. The idea of this book arose from many years of work in biomechanics, health disease, and rehabilitation. Through exchanges with authors from several countries, we learned much from each other, and we decided with the publisher to transfer this knowledge to readers interested in the current understanding of the impact of biomechanics in the analysis of movement and its optimization. The main objective is to provide some interesting articles that show the scope of biomechanical analysis and technologies in human behavior tasks. Engineers, researchers, and students from biomedical engineering and health sciences, as well as industrial professionals, can benefit from this compendium of knowledge about biomechanics applied to the human body

The neuropsychological measure (EEG) of flow under conditions of peak performance

Flow is a mental state characterised by a feeling of energised focus, complete involvement and success when fully immersed in an activity. The dimensions of and the conditions required for flow to occur have been explored in a broad spectrum of situational contexts. The close relationship between flow and peak performance sparked an interest in ways to induce flow. However, any process of flow induction requires a measure to trace the degree to which flow is in fact occurring. Self-reports of the flow experience are subjective and provide ad hoc information. Psycho-physiological measures, such as EEG, can provide objective and continuous indications of the degree to which flow is occurring. Unfortunately few studies have explored the relationships between psycho-physiological measures and flow. The present study was an attempt to determine the EEG correlates of flow under conditions of peak performance. Twenty participants were asked to perform a continuous visuomotor task 10 times. Time taken per task was used as an indicator of task performance. EEG recordings were done concurrently. Participants completed an Abbreviated Flow Questionnaire (AFQ) after each task and a Game Flow Inventory (GFI) after having finished all 10 tasks. On completion, performance times and associated flow scores were standardised where after the sample was segmented into a high flow - peak performance and a low flow - low performance level. Multi-variate analysis of variance (MANOVA) was conducted on the performance, flow and EEG data to establish that a significant difference existed between the two levels. In addition, a one-way analysis of variance between high and low flow data was conducted for all variables and main effects were established. Inter-correlations of all EEG data at both levels were then conducted across four brain sites (F3, C3, P3, O1). In high flow only, results indicated increased lobeta power in the sensorimotor cortex together with a unique EEG pattern showing beta band synchronisation between the prefrontal and sensori-motor areas and de-synchronisation between all other areas, while all other frequencies (delta, theta, alpha, lobeta, hibeta, and gamma) remained synchronised across all scalp locations. These findings supported a theoretical neuropsychological model of flow.PsychologyD. Com. (Consulting Psychology

Effect of Psycho-Pharmacological Modulation of the Autonomic Nervous System on Human Oesophageal Pain Hypersensitivity

Background: Altered autonomic nervous system (ANS) function has been proposed as a mechanism in the development of central sensitisation (CS) and visceral pain hypersensitivity (VPH). The contribution of the parasympathetic nervous system (PNS) and the factors that mediate differences in sensitisation to acid are unclear and their study will clarify risk factors for oesophageal pain hypersensitivity (OPH) in gastrooesophageal reflux disease. Aims: To investigate psychophysiological and pharmacological manipulation of PNS tone in the development of OPH, and to determine factors which predict the development of OPH to acid infusion in healthy volunteers in a validated model of acid induced OPH. Methods: Pain thresholds to electrical stimulation in the proximal oesophagus were determined before and after a 30-minute distal oesophageal infusion of 0.15 mol/L hydrochloric acid in subjects. Sympathetic (SNS) and PNS parameters were measured at baseline and continuously thereafter. Subjects underwent psychological profiling for anxiety, depression, attachment vulnerability and personality type. Using this model, five studies were undertaken: Study 1 a pilot study to trail modulation suitability for further study used. In Study 2, subjects who demonstrated secondary hyperalgesia in the proximal non-acid-exposed oesophagus performed deep or sham breathing. Study 3 subjects, who did not sensitise to acid, underwent a validated stress test to induce OPH. With Study 4, deep breathing with IV saline (placebo) or atropine (PNS antagonist) was used to evaluate deep breathing’s induced PNS tone in OPH reduction. Study 5, a genetic pilot study, exploring the role of the GCH-1 haplotype in VPH. Results: ANS control’s key role in CS was clarified. Deep breathing increased PNS tone and prevented acid-induced OPH in comparison to sham breathing and confirmed increased PNS tone’s reversal of OPH. Psychological factors of anxiety, alexithymia and attachment status influence ANS modulation of CS. Individuals’ predisposition to VPH due to psychogenetic profiles were clarified and their biopsychosocial role illustrated. Conclusions and Inferences: A mechanistic explanation for the analgesic effect of deep breathing is provided with potential therapeutic implications in the treatment of VPH syndromes. Further clinical study is warranted to develop cost-effective treatments for chronic VPH syndromes

Muscle activation patterns in shoulder impingement patients

Introduction: Shoulder impingement is one of the most common presentations of shoulder joint problems 1. It appears to be caused by a reduction in the sub-acromial space as the humerus abducts between 60o -120o – the 'painful arc'. Structures between the humeral head and the acromion are thus pinched causing pain and further pathology 2. Shoulder muscle activity can influence this joint space but it is unclear whether this is a cause or effect in impingement patients. This study aimed to observe muscle activation patterns in normal and impingement shoulder patients and determine if there were any significant differences. Method: 19 adult subjects were asked to perform shoulder abduction in their symptomatic arm and non-symptomatic. 10 of these subjects (age 47.9 ± 11.2) were screened for shoulder impingement, and 9 subjects (age 38.9 ± 14.3) had no history of shoulder pathology. Surface EMG was used to collect data for 6 shoulder muscles (Upper, middle and lower trapezius, serratus anterior, infraspinatus, middle deltoids) which was then filtered and fully rectified. Subjects performed 3 smooth unilateral abduction movements at a cadence of 16 beats of a metronome set at 60bpm, and the mean of their results was recorded. T-tests were used to indicate any statistical significance in the data sets. Significance was set at P<0.05. Results: There was a significant difference in muscle activation with serratus anterior in particular showing a very low level of activation throughout the range when compared to normal shoulder activation patterns (<30%). Middle deltoid recruitment was significantly reduced between 60-90o in the impingement group (30:58%).Trends were noted in other muscles with upper trapezius and infraspinatus activating more rapidly and erratically (63:25%; 60:27% respectively), and lower trapezius with less recruitment (13:30%) in the patient group, although these did not quite reach significance. Conclusion: There appears to be some interesting alterations in muscle recruitment patterns in impingement shoulder patients when compared against their own unaffected shoulders and the control group. In particular changes in scapula control (serratus anterior and trapezius) and lateral rotation (infraspinatus), which have direct influence on the sub-acromial space, should be noted. It is still not clear whether these alterations are causative or reactionary, but this finding gives a clear indication to the importance of addressing muscle reeducation as part of a rehabilitation programme in shoulder impingement patients

Analysis of the backpack loading efects on the human gait

Gait is a simple activity of daily life and one of the main abilities of the human being. Often during leisure, labour and sports activities, loads are carried over (e.g. backpack) during gait. These circumstantial loads can generate instability and increase biomechanicalstress over the human tissues and systems, especially on the locomotor, balance and postural regulation systems. According to Wearing (2006), subjects that carry a transitory or intermittent load will be able to find relatively efficient solutions to compensate its effects.info:eu-repo/semantics/publishedVersio