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Hand dominance is the preferential use of one hand over the other for motor tasks. 90% of people are right-hand dominant, and the majority of injuries (acute and cumulative trauma) occur to the dominant limb, creating a double-impact injury whereby a person is left in a functional state of single-handedness and must rely on the less-dexterous, non-dominant hand. When loss of dominant hand function is permanent, a forced shift of dominance is termed injury-induced hand dominance transfer (I-IHDT). Military service members injured in combat operation may face I-IHDT following mutilating injuries (crush, avulsion, burn and blast wounds) that result in dominant limb amputation or limb salvage. Military occupational therapy practitioners utilize an intervention called Handwriting For Heroes to facilitate hand dominance transfer. This intervention trains the injured military member how to write again using the previously non-dominant hand. Efficacy and clinical effectiveness studies were needed to validate the use of this intervention. This dissertation contains three studies related to I-IHDT. One study measured handwriting performance in adults who previously (greater than 2 years ago) lost function of their dominant hands. Results verified that handwriting performance, when measured on two separate occasions (six-weeks apart) was similar (stable). A second study examined the efficacy of Handwriting For Heroes in non-impaired participants. Results demonstrated a positive effect on the variables that measured the written product: legibility, writing speed (letters-per-minute); as well as a positive effect on the variables that measured the writing process: kinematic and kinetic parameters. The final study examined the clinical effectiveness of Handwriting For Heroes in an injured military population. Results did not show as positive results as the efficacy study, despite similar compliance with the intervention. Specifically, non-impaired participants started with faster writing speeds in their non-dominant hands (higher letters-per-minute) and made more gains (wider ranges). The non-impaired participants also started with faster dexterity (betters scores on the Grooved Pegboard) but they made fewer gains than the injured service members (smaller ranges). Nevertheless, injured participants clearly made gains in all dependent variables thereby demonstrating clinical effectiveness of the intervention

Elektroneurografi är en undersökningsmetod som används för att undersöka nervledingskapaciteten i perifera nerver. Det är en metod som ofta används på sjukhuskliniker vid diagnostisering av perifera nervsjukdomar. Syftet med studien är att undersöka om det finns en signifikant skillnad i motorisk och sensorisk nervledningshastighet, amplitud och F-respons mellan dominant och icke-dominant hand. I studien undersöktes det även om en korrelation finns mellan handgreppsstyrka och svarsamplitud från motorisk elektroneurografi.  I studien deltog 26 testpersoner från biomedicinska analytikerprogrammet i termin 6. Testpersonernas genomsnittsålder är 24 år (range 21-32 år), och testpersonernas kroppslängd är i genomsnitt 169 cm (range 155- 185). Elektroneurografi utfördes motoriskt och sensoriskt på nervus medianus bilateralt. Handgreppsstyrka undersöktes bilateralt med Jamar Hydraulic Hand dynamometer. För samtliga mätvariabler bestämdes signifikantnivån till α=0,05.  Resultatet visar att det finns en signifikant skillnad i sensorisk nervledningshastighet, motorisk amplitud och sensorisk amplitud mellan dominant och icke-dominant hand. Sensorisk nervledningshastighet är högre i icke-dominant hand, medan motorisk och sensorisk amplitud är högre i dominant hand. Däremot kan inte en signifikant skillnad påvisas i motorisk nervledningshastighet, FM-latens samt antalet F-svar mellan dominant och icke-dominant hand. Resultatet visar att det inte finns någon korrelation mellan handgreppsstyrka och amplitud i motorisk elektroneurografi. I dag används samma referensvärden för dominant och icke-dominant hand. Den här studien visar att det kan finnas ett värde i att utforma referensintervall som baseras på handdominans. / Electroneurography is an examination method used for examining the nerve conduction capacity of the peripheral nerve. The method is often used in hospitals in the diagnosis of peripheral nerve injuries. The aim of this study is to examine if there is a significant difference in motor and sensory nerve conduction velocity, amplitude, and F-response between dominant and non-dominant hands. The correlation between hand grip strength and the amplitude in motor electroneurography was also examined in this study.  The study involved 26 students from Biomedical Scientist Programme term 6. The average age of the participants is 24 years (range 21-32 years), and the participants body length is on average 169 cm (range 155-185 cm). Electroneurography was performed on the median nerve bilaterally. Hand grip strength was examined bilaterally with Jamar Hydraulic Hand dynamometer. For all measurement variables, the significant level was determined to α=0,05.  The result shows that there is a significant difference in sensory nerve conduction velocity, motor amplitude, and sensory amplitude between dominant and non-dominant hands. Sensory nerve conduction velocity is higher in non-dominant hand, while motor and sensory amplitude is higher in dominant hand. However, a significant difference cannot be detected in motor nerve conduction velocity, FM-latency, and the number of F-responses between dominant and non-dominant hands. The result shows no correlation between hand grip strength and the amplitude in motor electroneurography.  Today, the same reference values are used for dominant and non-dominant hands. This study shows that there may be a value in creating reference intervals based on hand dominance.

La nociception est un système d’alarme spécialisé dans la détection d’évènements potentiellement nocifs pour l’organisme. Les informations nociceptives sont traitées en priorité par le cerveau et captent l’attention involontairement (un mécanisme ascendant). Cependant, l’information sensorielle à laquelle nous portons attention volontairement est sélectionnée pour être priorisée (un mécanisme descendant). Ainsi, le traitement de l’information nociceptive est déterminé par une balance attentionnelle résultant de la compétition entre les signaux ascendants et descendants. Or, des situations où plusieurs stimuli nociceptifs ont lieu simultanément se produisent couramment. Mais quels mécanismes permettent au système nerveux central de s’adapter à de telles situations? Cela demeure méconnu à ce jour. L’objectif principal de cette thèse était de mieux comprendre les mécanismes d’intégration cérébrale de l’information nociceptive. Cette thèse inclut quatre études examinant l’intégration cérébrale de l’information nociceptive bilatérale dans différentes conditions expérimentales. Dans ces études, nous avons investigué comment l’intégration de l’information nociceptive est affectée par 1) la latéralisation hémisphérique présumée distincte entre les droitiers et les gauchers, 2) la modalité utilisée pour induire la douleur (stimuli laser sélectifs aux nocicepteurs et stimuli électriques non spécifiques), 3) l’attention spatiale et 4) la proximité des régions corporelles stimulées. Dans chaque étude, au moins vingt participants furent recrutés et reçurent soit des stimuli électriques (étude 1 et 3) ou lasers (étude 2 à 4) douloureux. L’activité du cerveau fut enregistrée avec l’électroencéphalographie. Les stimulations unilatérales et bilatérales furent appliquées sur les chevilles (étude 1) et sur les mains (études 2 à 4). Les variables d’intérêts étaient la perception de la douleur, les potentiels évoqués, et les oscillations cérébrales évoquées entre 2 et 100 Hz. Nos résultats indiquent que l’effet le plus reproductible lors d’une stimulation laser ou électrique bilatérale comparée à une stimulation unilatérale, est une augmentation de l’amplitude des réponses cérébrales (potentiels évoqués et oscillations cérébrales dans certaines bandes de fréquences). De plus, la comparaison entre les gauchers et les droitiers indique que ces effets sont comparables malgré la latéralisation hémisphérique présumée. Par ailleurs, l’augmentation des réponses cérébrales est modulée par la proximité des régions corporelles stimulées. Quant à la perception de la douleur, elle augmente pour les stimuli bilatéraux lorsque ces derniers sont appliqués sur les chevilles ou les mains. Pour les mains, cet effet dépend toutefois de la distance entre les mains et de l’attention spatiale, étant observé seulement lorsque les mains sont rapprochées l’une de l’autre ou lorsque l’attention spatiale est dirigée vers les deux mains plutôt qu’une seule. Ces résultats montrent que l’intégration cérébrale de l’information nociceptive bilatérale est modulable, et nous proposons que l’augmentation des réponses cérébrales lors d’une stimulation bilatérale reflète une augmentation de la saillance et de la capture attentionnelle. Cette intégration et sa modulation par différents facteurs permettraient au système nerveux central de produire des réponses adaptées selon les sources de nociception et la balance attentionnelle. / Nociception is an alarm system specialized in the detection of events that are potentially harmful to the body. Nociceptive processing is prioritized in the brain and is particularly adept at capturing attention automatically and involuntarily (i.e., a bottom-up mechanism). However, the sensory information to which we voluntarily pay attention (a top-down mechanism) is also prioritized. Thus, the processing of nociceptive information is subject to a bottom-up and top-down attentional balance. However, situations where several nociceptive stimuli take place simultaneously are common. The mechanisms that allow the nervous system to manage this attentional balance in such situations remain poorly understood. The main objective of this thesis was to better understand the integration of nociceptive information. This thesis presents four studies examining the cortical integration of bilateral nociceptive stimuli. These studies investigated the role of 1) the hemispherical lateralization of pain that is presumed to be different between left- and right-handed individuals, 2) the modality (a bottom-up mechanism) used to induce pain, 3) spatial attention (a top-down mechanism), and 4) between-limb proximity in the integration of bilateral painful stimuli. In each study, at least twenty participants were recruited and received either painful but tolerable electrical (Studies 1 and 3) or laser (Studies 2 to 4) stimulation. Brain activity was recorded via electroencephalography. Unilateral and bilateral stimulations were delivered to the ankles (Study 1) and to the hands (Studies 2 to 4). The variables of interest were pain perception, evoked potentials (ERP), and event-related spectral perturbations (ERSP) from 2 to 100 Hz. In the first study, the impact of the hemispherical lateralization of pain processing (located mainly in the right hemisphere) on the integration of pain stimuli was examined by comparing left-handed and right-handed participants. In the second study, lasers selectively activating nociceptors were used to study the integration of bilateral nociceptive stimuli specifically. The third study sought to explain the observed discrepancies between laser and electrical modalities in Studies 1 and 2 by comparing these modalities in the same participants and in two separate experiments. The fourth study explored the role of spatial attention and limb proximity in the integration of bilateral nociceptive stimuli. The results show that bilateral painful stimuli led to increases in ERP and some ERSP frequencies compared to unilateral stimuli. These results were similar between left-handed and right-handed people. More variability was noted for laser compared to electrical stimuli with the most reproducible response being an increase in ERP and ERSP. Finally, this increase was modulated by limb proximity. Pain perception was increased for bilateral stimuli to the ankles. It was also increased for bilateral stimuli to the hands, but only when the limbs were in close proximity or when spatial attention was global. These results suggest that bilateral painful stimuli are integrated, which possibly reflects an increase in salience and attentional capture. This would allow the central nervous system to produce adapted responses in the face of increased danger.