Électrophysiologie des commotions cérébrales chez les athlètes

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal

Quand l’action surpasse la perception : rôle de la vision et de la proprioception dans la perception et le contrôle en temps réel de l’orientation spatiale de la main

Cette recherche a pour but d’évaluer le rôle de la vision et de la proprioception pour la perception et le contrôle de l’orientation spatiale de la main chez l’humain. L’orientation spatiale de la main est une composante importante des mouvements d’atteinte et de saisie. Toutefois, peu d’attention a été portée à l’étude de l’orientation spatiale de la main dans la littérature. À notre connaissance, cette étude est la première à évaluer spécifiquement l’influence des informations sensorielles et de l’expérience visuelle pour la perception et le contrôle en temps réel de l'orientation spatiale de la main pendant le mouvement d’atteinte naturel vers une cible stationnaire. Le premier objectif était d’étudier la contribution de la vision et de la proprioception dans des tâches de perception et de mouvement d’orientation de la main. Dans la tâche de perception (orientation-matching task), les sujets devaient passivement ou activement aligner une poignée de forme rectangulaire avec une cible fixée dans différentes orientations. Les rotations de l’avant-bras et du poignet étaient soit imposées par l’expérimentateur, soit effectuées par les sujets. Dans la tâche de mouvement d’orientation et d’atteinte simultanées (letter posting task 1), les sujets ont réalisé des mouvements d’atteinte et de rotation simultanées de la main afin d’insérer la poignée rectangulaire dans une fente fixée dans les mêmes orientations. Les tâches ont été réalisées dans différentes conditions sensorielles où l’information visuelle de la cible et de la main était manipulée. Dans la tâche perceptive, une augmentation des erreurs d’orientation de la main a été observée avec le retrait des informations visuelles concernant la cible et/ou ou la main. Lorsque la vision de la main n’était pas permise, il a généralement été observé que les erreurs d’orientation de la main augmentaient avec le degré de rotation nécessaire pour aligner la main et la cible. Dans la tâche de mouvement d’orientation et d’atteinte simultanées, les erreurs ont également augmenté avec le retrait des informations visuelles. Toutefois, les patrons d’erreurs étaient différents de ceux observés dans la tâche de perception, et les erreurs d’orientation n’ont pas augmenté avec le degré de rotation nécessaire pour insérer la poignée dans la fente. En absence de vision de la main, il a été observé que les erreurs d’orientation étaient plus petites dans la tâche de mouvement que de perception, suggérant l’implication de la proprioception pour le contrôle de l’orientation spatiale de la main lors des mouvements d’orientation et d’atteinte simultanées. Le deuxième objectif de cette recherche était d’étudier l’influence de la vision et de la proprioception dans le contrôle en temps réel de l’orientation spatiale de la main. Dans une tâche d’orientation de la main suivie d’une atteinte manuelle (letter posting task 2), les sujets devaient d’abord aligner l’orientation de la même poignée avec la fente fixée dans les mêmes orientations, puis réaliser un mouvement d’atteinte sans modifier l’orientation initiale de la main. Une augmentation des erreurs initiales et finales a été observée avec le retrait des informations visuelles. Malgré la consigne de ne pas changer l’orientation initiale de la main, une diminution des erreurs d’orientation a généralement été observée suite au mouvement d’atteinte, dans toutes les conditions sensorielles testées. Cette tendance n’a pas été observée lorsqu’aucune cible explicite n’était présentée et que les sujets devaient conserver l’orientation de départ de la main pendant le mouvement d’atteinte (mouvement intransitif; letter-posting task 3). La diminution des erreurs pendant l’atteinte manuelle transitive vers une cible explicite (letter-posting task 2), malgré la consigne de ne pas changer l’orientation de la main pendant le mouvement, suggère un mécanisme de corrections automatiques pour le contrôle en temps réel de l’orientation spatiale de la main pendant le mouvement d’atteinte naturel vers une cible stationnaire. Le troisième objectif de cette recherche était d’évaluer la contribution de l’expérience visuelle pour la perception et le contrôle de l’orientation spatiale de la main. Des sujets aveugles ont été testés dans les mêmes tâches de perception et de mouvement. De manière générale, les sujets aveugles ont présenté les mêmes tendances que les sujets voyants testés dans la condition proprioceptive (sans vision), suggérant que l’expérience visuelle n’est pas nécessaire pour le développement d’un mécanisme de correction en temps réel de l’orientation spatiale de la main basé sur la proprioception.The goal of this research was to study the contribution of vision and proprioception to the perception and control of hand orientation in human subjects. Spatial orientation of the hand is an important component of reaching and grasping movements. However, not much attention has been given to spatial hand orientation in the literature. To our knowledge, this study is the first to specifically investigate the influence of sensory information for the perception and on-line control of hand orientation during natural reaching movement to stationary targets. The first objective of this research was to study the contribution of vision and proprioception in perceptual orientation-matching and motor letter posting tasks. In the perceptual orientation-matching task, subjects attempted to passively or actively align a match handle, to a target that was fixed in different orientations. In the passive perceptual task, passive rotations of the forearm and wrist were imposed by the experimenter; whereas in the active perceptual task, the rotations were actively executed by the subjects. In letter posting task 1, subjects simultaneously reached and rotated the right hand to insert a match handle into a target slot fixed in the same orientations. The tasks were performed in different sensory conditions where the visual information about the target and the hand was manipulated. In the perceptual orientation-matching task, augmentation of hand orientation errors was observed with the withdrawal of visual information related to either the target and/or the hand. When full vision was not allowed, hand orientation errors were larger overall when larger rotations of the wrist were required to match the target, whether the rotations were made actively by the subject or were imposed passively by the experimenter. In letter posting task 1, augmentation of hand orientation errors was also observed with the withdrawal of visual information related to either the target and/or the hand. However, errors patterns were different from those observed in the perceptual task, and hand orientation errors were not larger for larger target orientations. Without vision of the hand, final hand orientation errors were smaller overall in letter-posting task 1 than in the orientation-matching task. This suggests the implication of the proprioceptive information for the control of spatial hand orientation during reach-and-orient movements. The second objective of this research was to study the influence of vision and proprioception in on-line control of spatial hand orientation. In letter posting task 2, subjects first aligned their hand to the angle of the target and then reached to it with the instruction not to change their initial hand orientation. The augmentation of initial and final errors was observed with the withdrawal of vision. Although subjects were instructed to not change their hand orientation, in all sensory condition tested, hand orientation changed overall during reaching in a way that reduced the initial orientation errors. This trend did not occur when there was no explicitly defined target toward which the subjects reached (letter-posting task 3; intransitive movement). The reduction in hand orientation errors during transitive reach in letter-posting task 2, even when told not to change it, suggests the engagement of an automatic error correction mechanism for hand orientation during natural reaching movements toward stationary targets. The third objective of this research was to investigate the contribution of visual experience to the perception and control of spatial orientation of the hand. Blind subjects were tested in the same perceptual and motor tasks. Overall, no differences were observed between performance of blind subjects and normally-sighted subjects tested without vision (proprioceptive condition), suggesting that prior visual experience is not necessary for the development of an on-line error correction mechanism for hand orientation guided by proprioceptive inputs

Main features of the timber structure building industry business models

The use of timber as structural building material is growing and a greater number of firms are looking to enter this raising market. Erecting a complex timber building usually involves combining the work of architects, structural engineers, builders, suppliers and/or supplier–builders, all of them having their own business models. The purpose of this research was to uncover the specific nature of business models in the timber structure building industry. First, a thorough mapping of these business models was undertaken. Second, underlying patterns were uncovered within these models. A triangulation method of secondary data, semi-structured interviews and participant observation was used to allow for an in-depth study of 23 stakeholder business models. The analysis shows that knowledge sharing appears as crucial and may be achieved through sustained collaboration. As a result, collaborative contract procurement modes seem to be the most appropriate for timber construction. Tight relationships with suppliers and supplier–builders also appear as prerequisites. Furthermore, stakeholder partnerships with universities appear common in the field, while prefabrication is increasing in popularity. These findings can be useful to grasp the prevailing business models in this industry given the sustained growth of the timber structure building market

Driving Difficulties and Adaptive Strategies: The Perception of Individuals Having Sustained a Mild Traumatic Brain Injury

Introduction. After a mild traumatic brain injury (mTBI), individuals quickly resume driving. However, relatively little is known about the impact of mTBI on driving ability and, notably, on the perceived influence of postconcussive symptoms on driving. Hence, the objective of this study was to document the perception of driving abilities in individuals with mTBI. Method. Twenty-seven drivers with mTBI were interviewed to document their perception regarding their driving abilities. Both driving-related difficulties and compensatory strategies used to increase driving safety were documented. A mixed quantitative and qualitative analysis of the data was completed. Results. 93% of participants reported at least one difficulty perceived as having an impact on everyday activities. Most frequently named problems affecting driving were fatigue and reduced concentration. In addition, 74% of participants had adapted their driving or developed strategies to compensate for driving difficulties. Discussion/Conclusion. Postconcussive symptoms have repercussions on driving ability. However, people with mTBI tend to be aware of their difficulties and develop, over time, adaptive strategies. Preventive measures are thus warranted to increase health care professionals' awareness of the potential consequences of mTBI on driving ability and to promote guidelines for the safe resumption of driving after injury

A longitudinal investigation of sleep and daytime wakefulness in children and youth with concussion

A high proportion of adults who sustain a concussion identify changes in their sleep during the acute stage, typically reporting an increased need for sleep or nonrestful sleep. Our understanding of sleep following concussion is less well understood within a pediatric population. In this study, we investigated the trajectory of sleep and daytime sleepiness in a prospective cohort of 40 children and youth (6–18 years old) with concussion, 40 age-and sex-matched healthy children and youth, and 40 with upper-extremity orthopedic injury. Evaluations occurred during the acute stage (<2 weeks) and at 3-, 6-, and 12-month postinjury using the Sleep Disturbance Scale for Children and the Postconcussion Symptom Scale. There were no significant differences within- or between-group differences in sleep across all four time points with analysis of the groups as a whole. When groups were divided by age (6–11 and 12– < 18 years), there was a significant difference in the ability to initiate sleep for the younger concussed group during the acute stage, compared with healthy controls, as well as significantly greater daytime nap duration that decreased over time. Significant correlations were also found between the frequency and duration of daytime naps and Postconcussion Symptom Scale total score and subscores (cognitive, physical/migraine, mood, and sleep) in the concussed group during the acute stage. Our results suggest that in a group with noncomplicated concussion, children and youth have transient alterations in daytime sleepiness that are related to concussion symptoms. Younger children may be more vulnerable to disturbances in sleep and daytime wakefulness

The impact of poor sleep on cognition and activities of daily living after traumatic brain injury : a review

Background/aim : Patients frequently report sleep disrup-tions or insomnia during their hospital stay, particularlyafter a traumatic brain injury (TBI). The consequences ofthese sleep disturbances on everyday activities are not welldocumented and are therefore not considered in the evalu-ation of independence in activities of daily living (ADLs).The goal of this narrative review is to explore the conse-quences of poor sleep quality on cognition and ADLs inthe acute and subacute stages of a moderate and severeTBI, when patients are in acute care or inpatient rehabili-tation.Methods:We will present an overview of normal sleepand its role in cognitive functioning, and then present thefindings of studies that have investigated sleep characteris-tics in hospital settings and the consequences of sleep dis-turbances on ADLs.Results:During hospitalisation, TBI patients presentsevere sleep disturbances such as insomnia and sleepfragmentation, which are probably influenced by both themedical condition and the hospital or rehabilitation environ-ment. Sleep disruption is associated with several cognitivedeficits, including attention, memory and executive func-tion impairments. Poor quality and/or insufficient quantityof sleep in acute TBI probably affect general functioningand ADLs calling for these cognitive functions.Conclusions and Significance:The cognitive impair-ments present following TBI are probably exacerbated bypoor sleep quality and sleep deprivation during hospitali-sation, which in turn impact ADLs among this popula-tion. Health-care personnel should further consider sleepdisturbances among people with TBI and a sleep protocolshould be established

Evolution of severe sleep-wake cycle disturbances following traumatic brain injury: a case study in both acute and subacute phases post-injury

Abstract Background Sleep-wake disturbances are frequently reported following traumatic brain injury (TBI), but they remain poorly documented in the acute stage of injury. Little is known about their origin and evolution. Case presentation This study presents the case of a patient in the acute phase of a severe TBI. The patient was injured at work when falling 12 m into a mine and was hospitalized in the regular wards of a level I trauma centre. From days 31 to 45 post-injury, once he had reached a level of medical stability and continuous analgosedation had been ceased, his sleep-wake cycle was monitored using actigraphy. Results showed significant sleep-wake disturbances and severe sleep deprivation. Indeed, the patient had an average nighttime sleep efficiency of 32.7 ± 15.4 %, and only an average of 4.8 ± 1.3 h of sleep per 24-h period. After hospital discharge to the rehabilitation centre, where he remained for 5 days, the patient was readmitted to the same neurological unit for paranoid delusions. During his second hospital stay, actigraphy recordings resumed from days 69 to 75 post-injury. A major improvement in his sleep-wake cycle was observed during this second stay, with an average nighttime sleep efficiency of 96.3 ± 0.9 % and an average of 14.1 ± 0.9 h of sleep per 24-h period. Conclusion This study is the first to extensively document sleep-wake disturbances in both the acute and subacute phases of severe TBI. Results show that prolonged sleep deprivation can be observed after TBI, and suggest that the hospital environment only partially contributes to sleep-wake disturbances. Continuous actigraphic monitoring may prove to be a useful clinical tool in the monitoring of patients hospitalized after severe TBI in order to detect severe sleep deprivation requiring intervention. The direct impact of sleep-wake disturbances on physiological and cognitive recovery is not well understood within this population, but is worth investigating and improving

Waking EEG functional connectivity in middle-aged and older adults with obstructive sleep apnea

Objectives: The present study aimed at investigating changes in waking electroencephalography (EEG), most specifically regarding spectral power and functional connectivity, in middle-aged and older adults with OSA. We also explored whether changes in spectral power or functional connectivity are associated with polysomnographic characteristics and/or neuropsychological performance. Methods: 19 OSA subjects (apnea-hypopnea index ≥ 20, age: 63.6 ± 6.4) and 22 controls (apneahypopnea index ≤ 10, age: 63.6 ± 6.7) underwent a full night of in-laboratory polysomnography followed by a waking EEG and a neuropsychological assessment. Waking EEG spectral power and imaginary coherence were compared between groups for all EEG frequency bands and scalp regions. Correlation analyses were performed between selected waking EEG variables, polysomnographic parameters and neuropsychological performance. Results: No group difference was observed for EEG spectral power for any frequency band. Regarding the imaginary coherence, when compared to controls, OSA subjects showed decreased EEG connectivity between frontal and temporal regions in theta and alpha bands as well as increased connectivity between frontal and parietal regions in delta and beta 1 bands. In the OSA group, these changes in connectivity correlated with lower sleep efficiency, lower total sleep time and higher apnea-hypopnea index. No relationship was found with neuropsychological performance. Conclusions: Contrary to spectral power, imaginary coherence was sensitive enough to detect changes in brain function in middle-aged and older subjects with OSA when compared to controls. Whether these changes in cerebral connectivity predict cognitive decline needs to be investigated longitudinally

Regional cerebral blood flow during wakeful rest in older subjects with mild to severe obstructive sleep apnea

Objectives: To evaluate changes in regional cerebral blood flow (rCBF) during wakeful rest in older subjects with mild to severe obstructive sleep apnea (OSA) and healthy controls, and to identify markers of OSA severity that predict altered rCBF. Design: High-resolution 99mTc-HMPAO SPECT images during wakeful rest. Setting: Research sleep laboratory affiliated with a University hospital. Participants: Fifty untreated OSA patients aged between 55 and 85 years divided into mild, moderate and severe OSA and 20 age-matched healthy controls. Interventions: N/A Measurements: Using statistical parametrical mapping, rCBF was compared between groups and correlated with clinical, respiratory and sleep variables. Results: Whereas no rCBF change was observed in mild and moderate groups, participants with severe OSA had reduced rCBF compared to controls in the left parietal lobules, precentral gyrus, bilateral postcentral gyri, and right precuneus. Reduced rCBF in these regions and in areas of the bilateral frontal and left temporal cortex was associated with more hypopneas, snoring, hypoxemia, and sleepiness. Higher apnea, micro-arousal, and body mass indexes were correlated to increased rCBF in the basal ganglia, insula, and limbic system. Conclusions: While older individuals with severe OSA had hypoperfusions in the sensorimotor and parietal areas, respiratory variables and subjective sleepiness were correlated with extended regions of hypoperfusion in the lateral cortex. Interestingly, OSA severity, sleep fragmentation and obesity correlated with increased perfusion in subcortical and medial cortical regions. Anomalies with such a distribution could result in cognitive deficits and reflect impaired vascular regulation, altered neuronal integrity, and/or undergoing neurodegenerative processes

EEG functional connectivity prior to sleepwalking : evidence of interplay between sleep and wakefulness

Study Objectives: Although sleepwalking (somnambulism) affects up to 4% of adults, its pathophysiology remains poorly understood. Sleepwalking can be preceded by fluctuations in slow-wave sleep EEG signals, but the significance of these pre-episode changes remains unknown and methods based on EEG functional connectivity have yet to be used to better comprehend the disorder. Methods: We investigated the sleep EEG of 27 adult sleepwalkers (mean age: 29 ± 7.6 years) who experienced a somnambulistic episode during slow-wave sleep. The 20-second segment of sleep EEG immediately preceding each patient’s episode was compared with the 20-second segment occurring 2 minutes prior to episode onset. Results: Results from spectral analyses revealed increased delta and theta spectral power in the 20 seconds preceding the episodes’ onset as compared to the 20 seconds occurring 2 minutes before the episodes. The imaginary part of the coherence immediately prior to episode onset revealed (1) decreased delta EEG functional connectivity in parietal and occipital regions, (2) increased alpha connectivity over a fronto-parietal network, and (3) increased beta connectivity involving symmetric inter-hemispheric networks implicating frontotemporal, parietal and occipital areas. Conclusions: Taken together, these modifications in EEG functional connectivity suggest that somnambulistic episodes are preceded by brain processes characterized by the co-existence of arousal and deep slee