The neural correlates of bilateral upper limb movement are poorly understood. It has been proposed that interhemispheric pathways contribute to the modulation of motor cortical excitability during bimanual movements, possibly via direct connections between primary motor areas (M1), or via a central cortical structure, such as the supplementary motor area (SMA). The ability of one hemisphere to facilitate activation in the other presents a unique opportunity for motor rehabilitation programs using bilateral movements. The focus of this thesis was to investigate the mechanisms underlying bimanual movements in a group of healthy control participants using functional magnetic resonance imaging (fMRI), and subsequently to identify the types of movements that are most likely to maximize M1 activity. It was hypothesized first, that movements involving more proximal muscles, which are known to have a greater number of transcallosal connections, would produce a larger facilitation of M1 activity; and secondly, that the greatest facilitation would occur during those phases of movements where homologous muscles are active simultaneously (i.e. in-phase bilateral movements). The current results demonstrate that the M1 regions and the SMA work together to modulate motor cortical excitability, and that the greatest modulation of activity is seen during movements involving proximal muscles. The findings presented may have clinical relevance to motor rehabilitation programs involving bilateral movements.

The neural correlates of bilateral upper limb movement are poorly understood. It has been proposed that interhemispheric pathways contribute to the modulation of motor cortical excitability during bimanual movements, possibly via direct connections between primary motor areas (M1), or via a central cortical structure, such as the supplementary motor area (SMA). The ability of one hemisphere to facilitate activation in the other presents a unique opportunity for motor rehabilitation programs using bilateral movements. The focus of this thesis was to investigate the mechanisms underlying bimanual movements in a group of healthy control participants using functional magnetic resonance imaging (fMRI), and subsequently to identify the types of movements that are most likely to maximize M1 activity. It was hypothesized first, that movements involving more proximal muscles, which are known to have a greater number of transcallosal connections, would produce a larger facilitation of M1 activity; and secondly, that the greatest facilitation would occur during those phases of movements where homologous muscles are active simultaneously (i.e. in-phase bilateral movements). The current results demonstrate that the M1 regions and the SMA work together to modulate motor cortical excitability, and that the greatest modulation of activity is seen during movements involving proximal muscles. The findings presented may have clinical relevance to motor rehabilitation programs involving bilateral movements.

The purpose of this study was to investigate the influence of amplitude scaling on bimanual coordination in a circle drawing task. Eleven right-handed subjects traced the perimeter of 5 circles measuring 3, 6, 9, 12, and 15 cm in diameter under the following coordination conditions: (1) both hands move inward together (symmetric coordination pattern), and (2) both hands move counterclockwise together (asymmetric coordination pattern). In a set of self-paced trials, subjects traced each circle separately at a preferred frequency and separately for each coordination pattern. Although subjects matched the required amplitude of the target circles quite well, radial amplitude variability increased with increasing circle diameter. No transitions or movement reversals were observed in the self-paced trials, and the symmetric pattern was more stable than the asymmetric pattern. In a set of amplitude scaling trials, subjects continuously traced the 5 circles from small (3 cm) to big (15 cm) (SB) and from big to small (BS) at two fixed pacing frequencies (1.25 Hz and 1.5 Hz). Observed cycling frequency decreased with increasing circle diameter, and observed radial amplitude was most accurate when tracing the 9 cm diameter circle, with larger than required amplitude when tracing the 3 cm and 6 cm diameter circles, and smaller than required amplitude when tracing the 12 cm and 15 cm diameter circles. Radial amplitude variability also increased with increasing circle diameter in the amplitude scaling trials. The symmetric coordination pattern was more stable than the symmetric coordination pattern. Transitions from the asymmetric to symmetric coordination pattern as well as movement reversals were observed in both scaling directions. No transitions occurred while producing the symmetric pattern in any scaling direction or pacing frequency condition. The results show that amplitude scaling influenced the spatiotemporal aspects of bimanual circle drawing. Moreover, amplitude scaling induced more transitions than previous research that scaled movement frequency as a control parameter in bimanual circle drawing tasks.

Orientador: Ana Maria Pellegrini / Banca: Sérgio Tosi Rodrigues / Banca: Cynthia Yukiko Hiraga / Resumo: A coordenação bimanual é um comportamento manifestado diariamente pelas pessoas na execução de tarefas do dia-a-dia. Controlar as duas mãos para varrer a casa, soltar pipa, costurar ou tocar piano são situações rotineiras que podem ser melhoradas e desempenhadas com precisão como resultado da prática. As tarefas unimanuais e as tarefas bimanuais que devem ser lideradas por uma das mãos, geralmente, são executadas apenas com a mão preferida, a mão direita para o maior número de pessoas. As ferramentas utilizadas nas tarefas do dia-a-dia são fabricadas para a mão direita e como conseqüência a diferença no desempenho é menor entre as mãos de pessoas com preferência manual esquerda. Manter um ritmo qualquer ou acertar alvos são tarefas que requeiram integridade de estruturas orgânicas, como por exemplo, os membros superiores e os sistemas visual e auditivo. O direcionamento da atenção visual pode ser muito importante na captura da informação para tocar alvos no plano horizontal, principalmente se as características espaciais e temporais das tarefas das duas mãos são diferentes. Contudo, as duas mãos estão separadas fisicamente e no desempenho em uma tarefa que requeira deslocamentos diferentes para as duas mãos o executante deve identificar a informação de uma das mãos para a execução precisa. O objetivo deste estudo foi verificar o efeito do direcionamento da atenção visual a uma das mãos no desempenho de uma tarefa bimanual com diferentes níveis de complexidade, em função da preferência manual. Pessoas com preferência manual direita e esquerda executaram uma tarefa de coordenação bimanual com deslocamentos dos membros superiores para o toque em um ou mais alvos que estavam igualmente distantes no plano horizontal e em intervalos temporais iguais ou diferentes. O direcionamento da atenção visual foi manipulado... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Bimanual coordination is a behavior showed by people during the performance of many daily tasks. Actions that require the control of the hands as to sweep the room, to free pipe, to sew or to play piano are very common actions that can be improved and performed with accuracy as a result of practice. The unimanual tasks and the bimanual tasks that must be led by one of the hands, in general, are performed by the preferred hand, the right hand for a large number of individuals. Tools used in daily tasks are tailored for right hand and as a consequence the difference in performance between hands is smaller for those left-handed. To keep moving in a rhythm or to reach targets are tasks that require a full functioning of organic structures as the upper limbs or visual and auditory systems. The direction of visual attention can be very important in capturing relevant information for touching targets in the horizontal plane mainly if the characteristics of tasks of the two hands are different. However, the hands are physically apart and in the performance of a task that requires different displacements for the two hands the performer must pick up information from one of the hands for performance accuracy. The objective of the present study was to verify the effect of directing visual attention to one of the hands in the performance of bimanual tasks with different levels of complexity as a function of hand preference. Right- and left-handers performed a bimanual coordination task with displacement of the upper arms to reach one or more targets that were equally distant in the horizontal plane and in equal or different temporal intervals. The direction of visual attention was manipulated in three experimental conditions, in a condition directed to the right hand, in another to the left hand and in a third condition of free choice of the performer. The variables selected... (Complete abstract click electronic access below) / Mestre

Two siblings have a muscular degenerative condition that has rendered them mostly blind, deaf and paraplegic. Currently, the siblings receive communication by close range sign language several feet in front of their vision. Due to the degenerative nature of their condition, it is believed that the siblings will eventually become completely blind and unable to communicate in this fashion. There are no augmented communication devices on the market that allow communication reception for individuals who cannot see, hear or possess hand dexterity (such as braille reading). To help the siblings communicate, the proposed communication device will transmit Morse code information tactically with vibration motors to either the forearm or bicep in the form of an armband wearable. However, no research has been done to determine the best haptic interface for displaying Morse code in a tactile modality. This research investigates multiple haptic interfaces that aim to alleviate common mistakes made in Morse code reception. The results show that a bimanual setup, discriminating dots/dashes by left/right location, yields 56.6% the amount of Morse code errors made under a unimanual setup of Morse code that uses temporal discrimination to distinguish dots and dashes. The bimanual condition resulted in less judgment interference that is either due to the brain having an easier time processing two separate tasks when judgments are shared between the hemispheres or a judgment buffer effect being present for temporal discrimination.

The human hand is critically important for the performance of many activities of daily living (ADL). This dissertation used three human subject studies to investigate how different types of motor repetition interact with the process of sensorimotor adaptation and learning in complex dexterous manipulation tasks that depend on finger force control or bimanual coordination. Moreover, these investigations were conducted in both young adults (YA) and older adults (OA) to reveal the extent to which the process of aging may alter such interactions. In the first study, it was found that the repetition of simple ballistic force exertion allowed YA to better adapt to external mechanical perturbation with their dominant hand during fast object transport than the repetition of continuous movement. In contrast, OA were not differently affected by these two types of repetition training. In the second study, the effect of the same two repetition types on learning to perform an inverted pendulum balance task was examined. It was found that OA but not YA were able to balance the pendulum longer with the ballistic force repetition than the continuous movement repetition. In the last study, participants must move both hands to simultaneously follow moving targets. It was revealed that adaption to unilateral visual or mechanical constraints was driven by the dominant hand in YA, but OA were not able to adapt to these constraints. Together with additional findings about balance control and visual attention, these results on the effect of motor repetition provide new insights into the mechanisms underlying sensorimotor learning, which will support future studies to improve the efficacy of neurorehabilitation for dexterous manual functions.

As afecções umbilicais merecem destaque entre as enfermidades que acometem bezerros no primeiro mês de vida, pela alta incidência durante essa fase da vida dos neonatos e pelas relevantes perdas econômicas, decorrentes da mortalidade, custos de tratamento e atendimento veterinário, além de sequelas que poderão determinar menores ganho de peso e produção leiteira. O diagnóstico dessas enfermidades muitas vezes é prejudicado pela dificuldade em se detectar os acometimentos das estruturas intra-abdominais do umbigo, o que afetará negativamente a escolha do tratamento mais adequado e o estabelecimento do real prognóstico para cada animal. O presente estudo determinou as limitações e as vantagens de cada recurso semiológico, e demonstrou uma maior sensibilidade da ultrassonografia na detecção das afecções umbilicais intra-abdominais quando comparada com o método semiológico de rotina (palpação bimanual), com incompatibilidade de 20% dos animais no grupo onfalopatia. A maior exatidão no diagnóstico foi observada principalmente nos acometimentos das veias umbilicais, e também em afecção do úraco que foi erroneamente identificada como sendo alteração de artéria umbilical. Durante a análise com ultrassonografia dos animais com inflamação/infecção dos componentes umbilicais, foi observada que a espessura da parede dos vasos umbilicais é a medida mais adequada para determinar as alterações nesses componentes, quando comparada com aquela do diâmetro dos vasos umbilicais. Ainda, a partir desse estudo foi possível verificar algumas particularidades da involução fisiológica dos componentes intra-abdominais do cordão umbilical em bezerros da raça Holandesa, as quais foram utilizadas no grupo controle para caracterizar o comportamento das estruturas umbilicais com o evoluir da idade dos neonatos. Destaca-se que o confronto desses resultados com aqueles da rara literatura disponível mostrou-se com notáveis diferenças. Por fim validou-se critério para definir o grau de gravidade das inflamações dos componentes umbilicais a partir dos resultados obtidos pelo uso desses recursos diagnósticos, a fim de permitir uma alternativa na classificação dessa enfermidade com vistas à adequada escolha do tratamento e possibilitar uma avaliação da comparação da transferência de imunidade passiva frente às diversas apresentações clínicas das afecções inflamatórias umbilicais. / The umbilical disorders has importance among the illness that affects calves in the first month of life, by the high incidence during the current stage of life of newborns and relevant economic losses stemming due to mortality, treatment costs and veterinary care, and sequelae that may determine lower weight gain and milk production. The diagnosis of these diseases is often hampered by the difficult in detecting the extension of affected navel structures, which negatively affect the choice of the most appropriate treatment and establish a prognosis for calves. The present study verified the limitations and advantages of each semiological resource, and demonstrated a higher sensitivity of ultrasonography in the detection of intra-abdominal umbilical disorders compared with the semiological routine method (bimanual palpation), with 20% incompatibility of animals at navel illness group. The increased accuracy in diagnosis was mainly observed in the affections of the umbilical vein, and also in disease of the urachus which was erroneously identified as alteration of umbilical artery. During the ultrassonography of animals with inflammation/infection of umbilical components was observed that the wall thickness of the umbilical vessels is more appropriate extent for determining amendments in these components, as compared to that diameter of the umbilical vessels. Although, from this study we observed some peculiarities of the physiological involution of intra-abdominal umbilical cord components in Holstein calves, which were used in the control group to characterize the regression of the umbilical structures with increasing age of newborns. It is noteworthy that the comparison of these results with those of rare literature available showed up with notable differences. Finally validated the criterion for defining the severity of inflammation of the umbilical components from the results obtained from the use of these diagnostic methods in order to allow an alternative in the classification of this disease aiming to appropriate treatment choice and enable an assessment of comparison of passive transfer of immunity in front the various clinical presentations of umbilical inflammatory disorders.

As afecções umbilicais merecem destaque entre as enfermidades que acometem bezerros no primeiro mês de vida, pela alta incidência durante essa fase da vida dos neonatos e pelas relevantes perdas econômicas, decorrentes da mortalidade, custos de tratamento e atendimento veterinário, além de sequelas que poderão determinar menores ganho de peso e produção leiteira. O diagnóstico dessas enfermidades muitas vezes é prejudicado pela dificuldade em se detectar os acometimentos das estruturas intra-abdominais do umbigo, o que afetará negativamente a escolha do tratamento mais adequado e o estabelecimento do real prognóstico para cada animal. O presente estudo determinou as limitações e as vantagens de cada recurso semiológico, e demonstrou uma maior sensibilidade da ultrassonografia na detecção das afecções umbilicais intra-abdominais quando comparada com o método semiológico de rotina (palpação bimanual), com incompatibilidade de 20% dos animais no grupo onfalopatia. A maior exatidão no diagnóstico foi observada principalmente nos acometimentos das veias umbilicais, e também em afecção do úraco que foi erroneamente identificada como sendo alteração de artéria umbilical. Durante a análise com ultrassonografia dos animais com inflamação/infecção dos componentes umbilicais, foi observada que a espessura da parede dos vasos umbilicais é a medida mais adequada para determinar as alterações nesses componentes, quando comparada com aquela do diâmetro dos vasos umbilicais. Ainda, a partir desse estudo foi possível verificar algumas particularidades da involução fisiológica dos componentes intra-abdominais do cordão umbilical em bezerros da raça Holandesa, as quais foram utilizadas no grupo controle para caracterizar o comportamento das estruturas umbilicais com o evoluir da idade dos neonatos. Destaca-se que o confronto desses resultados com aqueles da rara literatura disponível mostrou-se com notáveis diferenças. Por fim validou-se critério para definir o grau de gravidade das inflamações dos componentes umbilicais a partir dos resultados obtidos pelo uso desses recursos diagnósticos, a fim de permitir uma alternativa na classificação dessa enfermidade com vistas à adequada escolha do tratamento e possibilitar uma avaliação da comparação da transferência de imunidade passiva frente às diversas apresentações clínicas das afecções inflamatórias umbilicais. / The umbilical disorders has importance among the illness that affects calves in the first month of life, by the high incidence during the current stage of life of newborns and relevant economic losses stemming due to mortality, treatment costs and veterinary care, and sequelae that may determine lower weight gain and milk production. The diagnosis of these diseases is often hampered by the difficult in detecting the extension of affected navel structures, which negatively affect the choice of the most appropriate treatment and establish a prognosis for calves. The present study verified the limitations and advantages of each semiological resource, and demonstrated a higher sensitivity of ultrasonography in the detection of intra-abdominal umbilical disorders compared with the semiological routine method (bimanual palpation), with 20% incompatibility of animals at navel illness group. The increased accuracy in diagnosis was mainly observed in the affections of the umbilical vein, and also in disease of the urachus which was erroneously identified as alteration of umbilical artery. During the ultrassonography of animals with inflammation/infection of umbilical components was observed that the wall thickness of the umbilical vessels is more appropriate extent for determining amendments in these components, as compared to that diameter of the umbilical vessels. Although, from this study we observed some peculiarities of the physiological involution of intra-abdominal umbilical cord components in Holstein calves, which were used in the control group to characterize the regression of the umbilical structures with increasing age of newborns. It is noteworthy that the comparison of these results with those of rare literature available showed up with notable differences. Finally validated the criterion for defining the severity of inflammation of the umbilical components from the results obtained from the use of these diagnostic methods in order to allow an alternative in the classification of this disease aiming to appropriate treatment choice and enable an assessment of comparison of passive transfer of immunity in front the various clinical presentations of umbilical inflammatory disorders.

Les asimetries funcionals manuals han estat àmpliament estudiades en els primats no humans i altres espècies animals durant les últimes dues dècades. Resulta especialment interessant observar si l'especialització hemisfèrica cerebral, tan característica de l'ésser humà, està o no present i en quin grau dins del regne animal. En ximpanzés, trobem pocs treballs en què s'hagin avaluat les preferències manuals en una única mostra des d'un punt de vista observacional i experimental conjuntament, i cap en ambients intermedis (naturalitzats). El nostre objectiu ha estat comparar els patrons de preferència manual en situacions espontànies i experimentals en una mateixa mostra de ximpanzés i veure quines situacions incideixen sobre la direcció, intensitat i grau d'asimetria individual versus poblacional en els individus. En la fase observacional es van estudiar 53 comportaments espontanis unimanuals i bimanuals que feien referència a contextos tròfics, manipulatius-exploratoris, autodirigits, posturals i socials, entre d'altres. En la fase experimental es van avaluar dues tasques: una unimanual (simple reaching: recollida d'ítems petits d'aliment amb prensions de precisió) i una altra bimanual (tube task: extracció bimanual d'aliment d'un tub). Durant la fase observacional es van dur a terme 2.226 sessions (2005 a 2008: 33 mesos). La fase experimental va tenir una durada total de 4 mesos (2007). La mostra estava formada per un grup de 14 ximpanzés (Pan troglodytes) allotjats al Centre de Recuperació de Primats de la Fundació Mona (Girona). En ambdues fases es va utilitzar un mostreig focal amb registre activat per transicions. Globalment, tant durant la fase observacional com experimental, la major part de la mostra va presentar preferències individuals laterals de manera significativa. Es van comparar els índexs de lateralitat per a les quatre condicions d'estudi: unimanual-espontani (UES), bimanual-espontani (BES), unimanual-experimental (UEX) i bimanual-experimental (BEX). No es van trobar diferències en la direcció de les preferències entre les quatre condicions tot i que sí en la intensitat de la lateralització. D'aquesta manera, la intensitat de la preferència manual era major en les accions bimanuals que en les unimanuals, i també en les tasques experimentals que en les espontànies. L'ús d'instruments i el tipus de prensió també van augmentar la intensitat de les preferències encara que no van tenir cap efecte sobre la direcció d'aquestes. Es va detectar una asimetria dretana poblacional en les accions bimanuals espontànies però no en les experimentals. També es va detectar una asimetria dreta a nivell poblacional en tenir en compte totes les tasques conjuntament. D'aquesta manera, ha estat la primera ocasió que s'evidencia que els ximpanzés allotjats en ambients intermedis són dretans a nivell poblacional. En conclusió, els ximpanzés presentarien un patró de lateralització homòleg al dels éssers humans, sobretot en aquelles accions que impliquen una complexitat en la seva execució (bimanualitat, instrumentalitat i precisió) i que són les més rellevants per entendre el procés d'hominització conductual d'aquest tret a Homo sapiens. / Las asimetrías funcionales manuales han sido ampliamente estudiadas en los primates no humanos y otras especies animales durante las últimas dos décadas. Resulta especialmente interesante observar si la especialización hemisférica cerebral, tan característica del ser humano, está o no presente y en qué grado dentro del reino animal. En chimpancés, encontramos pocos trabajos en los que se hayan evaluado las preferencias manuales en una única muestra desde un punto de vista observacional y experimental conjuntamente, y ninguno en ambientes intermedios (naturalizados). Nuestro objetivo ha sido comparar los patrones de preferencia manual en situaciones espontáneas y experimentales en una misma muestra de chimpancés y ver qué situaciones inciden sobre la dirección, intensidad y grado de asimetría individual versus poblacional en los individuos. En la fase observacional se estudiaron 53 comportamientos espontáneos unimanuales y bimanuales que hacían referencia a contextos tróficos, manipulativos-exploratorios, autodirigidos, posturales y sociales, entre otros. En la fase experimental evaluaron dos tareas: una unimanual (simple reaching: recogida de ítems pequeños de alimento con prensiones de precisión) y otra bimanual (tube task: extracción bimanual de alimento de un tubo). Durante la fase observacional se llevaron a cabo 2226 sesiones (2005 a 2008: 33 meses). La fase experimental tuvo una duración total de 4 meses (2007). La muestra estaba formada por un grupo de 14 chimpancés (Pan troglodytes) alojados en el Centro de Recuperación de Primates de Fundación Mona (Girona). En ambas fases se utilizó un muestreo focal con registro activado por transiciones. Globalmente, tanto durante la fase observacional como experimental, la mayor parte de la muestra presentó preferencias individuales laterales de manera significativa. Se compararon los índices de lateralidad para las cuatro condiciones de estudio: unimanual-espontáneo (UES), bimanual-espontáneo (BES), unimanual-experimental (UEX) y bimanual-experimental (BEX). No se encontraron diferencias en la dirección de las preferencias entre las cuatro condiciones aunque sí en la intensidad de la lateralización. De esta manera, la intensidad de la preferencia manual era mayor en las acciones bimanuales que en las unimanuales, y también en las tareas experimentales que en las espontáneas. El uso de instrumentos y el tipo de prensión también aumentaron la intensidad de las preferencias aunque no tuvieron ningún efecto sobre la dirección de éstas. Se detectó una asimetría diestra poblacional en las acciones bimanuales espontáneas aunque no en las experimentales. También se detectó una asimetría diestra a nivel poblacional al tener en cuenta todas las tareas conjuntamente. De esta manera, ha sido la primera ocasión que se evidencia que los chimpancés alojados en ambientes intermedios son diestros a nivel poblacional. En conclusión, los chimpancés exhibirían un patrón de lateralización homólogo al de los seres humanos, sobre todo en aquellas acciones que implican una complejidad en su ejecución (bimanualidad, instrumentalidad y precisión) y que son las más relevantes para entender el proceso de hominización conductual de este rasgo en Homo sapiens. / Manual functional asymmetries have been extensively studied in nonhuman primates and other animals for the last two decades. It is particularly interesting to see if brain hemispheric specialization, so characteristic human beings, is present or not and to what extent within the animal kingdom. In chimpanzees, there are few studies that have assessed hand preferences in a single sample from an experimental and observational standpoint, and none have been done within intermediate (naturalized) environments. Our objective was to compare the patterns of hand preference for spontaneous and experimental actions in the same sample of chimpanzees and observe what situations impact on the direction, strength and the degree of individual versus population asymmetry in individuals. In the observational phase, we studied 53 spontaneous unimanual and bimanual behaviors related to feeding contexts, manipulative-exploratory, self-directed, postural and social, among others. In the experimental phase, we evaluated two tasks: unimanual (simple reaching: collection of small items of food with precision grips) and bimanual (tube task: bimanual removal of food from a tube). During the observational phase, we conducted 2.226 sessions (from 2005 to 2008: 33 months). The experimental phase lasted a total of four months (2007). The sample was composed of a group of 14 chimpanzees (Pan troglodytes) housed at the Mona Foundation Primate Rehabilitation Center (Girona). In both phases, a focal sampling method was used. Overall, during both observational and experimental phases, the majority of the sample showed significant individual lateral preferences. We compared the handedness index for four study conditions: unimanual-spontaneous (UES), bimanual-spontaneous (BES), unimanual-experimental (UEX) and bimanual-experimental (BEX). There were no differences in the direction of preferences among the four conditions, but there were differences in the strength of lateralization. The strength of hand preference was higher in bimanual than in unimanual ones, and also in the experimental tasks than in the spontaneous ones. The use of tools and the type of grip also increased the strength of preferences, but had no effect on the direction of such preferences. We detected right-handedness at population-level for spontaneous bimanual actions, but not for the experimental ones. There was also a right asymmetry at the population level when considering all the tasks together. In this way, this was the first evidence that chimpanzees housed in an intermediate environment demonstrate right-handedness at population-level. In conclusion, chimpanzees exhibit a pattern of lateralization homologous to human beings, especially those actions that involve a complexity of execution (bimanual, tool use and precision grip) and that are most relevant for understanding the behavioral process of hominization of this trait in Homo sapiens.

Have you ever attempted to rub your abdomen with one hand while tapping your head with the other? Separately these movements are easy to perform but doing them together (bilateral task) requires motor adaptation. Motor adaptation is the process through which the Central Nervous System improves upon performance. Transfer of learning is the process through which learning a motor task in one condition improves performance in another condition. The purpose of this study was to determine whether transfer of learning occurs during bilateral goal-directed reaching tasks. It was hypothesized that transfer of learning would occur from the non-dominant to the dominant arm during bilateral tasks and that position and load feedback from the arms would affect the rate of adaptation and transfer of learning. During the experiments, subjects reached with one or both their index finger(s) to eight targets while a velocity dependent force perturbation (force environment) was applied to the arm(s). Three groups of bilateral tasks were examined: (1) unilateral reaching, where one arm learned to reach in a force environment, while the other arm remained stationary and therefore did not provide movement related position or load feedback; (2) bilateral reaching single load, where both arms performed reaching movements but only one arm learned a force environment and therefore the other arm provided movement related position feedback but not load feedback; (3) bilateral reaching two loads, where both arms performed reaching movements and both learned a force environment, while providing movement related position and load feedback. The rate of adaptation of the force environment was quantified as the speed at which the perturbed index finger trajectory became straight over the course of repeated task performance. The rate of adaptation was significantly slower for the dominant arm during the unilateral reaching tasks than during the bilateral reaching single load tasks (p<0.05). This indicates that the movement related position feedback from the non-dominant arm improved significantly the motor adaptation of the dominant arm; therefore transfer of learning occurred from the non-dominant to the dominant arm. The rate of adaptation for the non-dominant arm did not differ significantly (p>0.05) between the unilateral reaching and bilateral reaching single load tasks. Results also indicated that the rate of adaptation was significantly (p<0.05) faster for both the non-dominant and the dominant arms during the bilateral reaching two loads tasks than during the bilateral reaching single load tasks. The latter results indicate that transfer of learning occurred in both directions - from the dominant to the non-dominant arm and from the non-dominant to the dominant arm - when position and load feedback was available from both arms, but only when the force environment acted in the same joint direction. This study demonstrated that transfer of learning does occur during bilateral reaching tasks and that the direction and degree of transfer of learning may be modulated by the position and load feedback that is available to the central nervous system. This information may be used by physical therapists in order to improve rehabilitation strategies for the upper extremity.