While motor neuron activity has been studied for many decades, the relative contribution of synaptic and non-synaptic mechanisms underlying this activity during natural behaviors is not well understood. Thus, the goal of this dissertation was to further understand the role of non-synaptic properties of motor neurons during voluntary activity. In particular, I considered three non-synaptic properties: persistent inward currents (PICs) that boost synaptic inputs, spike-threshold accommodation that affects recruitment threshold as excitation rates of rise slow, and spike-frequency adaptation that leads to a decrease in firing rate despite constant excitation levels. Computer simulations were employed to understand the potential effect that these properties could have on firing rate behavior. In particular, the focus was on paired motor unit recordings where a lower threshold motor unit’s firing rate served as a proxy for synaptic drive, and differences in firing rate (ΔF) were compared at a higher threshold unit’s recruitment and derecruitment. While ΔF has been used by others to estimate PIC activation, the simulation results indicated that each of these non-synaptic mechanisms could lead to positive ΔF. Furthermore, by varying contraction speed and duration it seemed possible to determine which property contributes to ΔF in vivo. The results from human experiments indicated that adaptation is most likely the predominant contributor to ΔF during natural behaviors. Additionally, positive ΔF was even observed in the genioglossus muscle of the tongue, where the role of PICs has been debated. These results suggested that ΔF may not the best method to detect PICs during natural behaviors. As such, I also considered whether there might be another metric to infer PIC activation during natural behaviors. Motor unit firing rates tend to plateau, or saturate, despite continued force increase, and one hypothesis is that PICs contribute to this behavior. Indeed, motor unit firing rate saturation was diminished by the addition of inhibition, which should have limited PIC activation. Therefore, this final study provided possible evidence for PIC activation during natural behaviors. Overall, this dissertation highlights that non-synaptic properties of motor neurons are activated during natural behaviors and that they contribute significantly to firing rate output.

The problem investigated is that of determining if there are differences in the ability of mentally retarded persons over age 21 to learn motor skills as opposed to those under 21. Data were gathered at the Denton State School on 110 subjects. The first chapter is concerned with the theoretical background, purpose, and the hypothesis. The second chapter contains information on subjects, materials, method, and statistical treatment. The third chapter covers presentation and discussion of the data, and the fourth chapter includes the summary, conclusions and recommendations. Results of the study indicated that there were few differences between the two groups. Future studies should be run with samples from individual age groups extending from 6 through 21. This would be realistic in establishing a motor learning curve for this population.

Le membre fantôme correspond à la persistance de perceptions sensitives et motrices attribuées au membre amputé. Des douleurs chroniques parfois invalidantes ainsi que des capacités d’évocation de mouvements dans le membre absent sont fréquemment rapportées. Très peu connue, cette motricité résiduelle est souvent considérée comme de l’imagerie motrice. Le premier objectif de cette thèse est de réinterroger le statut psychologique des mouvements de membre fantôme. Le second objectif est d’étudier le lien entre le contrôle moteur dans le membre fantôme et les réorganisations corticales dans le cortex moteur du sujet amputé. Au moyen de tests comportementaux et d’examens en Imagerie par Résonnance Magnétique fonctionnelle (IRMf), ces travaux de thèse ont permis de dissocier expérimentalement une forme de perceptions kinesthésiques associée à de l’imagerie motrice et une autre forme associée à de l’exécution motrice dans le membre fantôme. Cette distinction repose à la fois sur des différences de performances et sur le recrutement de régions cérébrales partiellement distinctes. Au-delà de cette distinction physiologique, les résultats obtenus suggèrent que les mouvements de membre fantôme s’apparentent à une forme d’exécution motrice plutôt qu’à de l’imagerie motrice. A travers le modèle du membre fantôme, ce travail aborde donc la question de la nature des informations menant à la perception d’un mouvement comme étant « exécuté ». Les altérations du fonctionnement cortical mises en évidence chez l’amputé peuvent représenter un modèle d’étude intéressant des différents mécanismes physiopathologiques relevés dans des situations de déficiences liées à une forme de plasticité « maladaptative ». Les observations cliniques et les examens en neuroimagerie menés au cours de cette thèse dressent en effet, un modèle relativement cohérent de l’organisation fonctionnelle du cortex après amputation. En particulier, l’existence d’un lien entre les réorganisations fonctionnelles au sein du cortex moteur et la qualité du contrôle moteur résiduel dans le membre fantôme permet de mieux comprendre les mécanismes sur lesquels reposent certaines thérapies antalgiques, comme les thérapies visuomotrices / The phantom limb is a sensory experience that is perceived to originate from the missing part. Amputees report that the phantom limb had certain sensory properties like touch and pain, as well as kinesthetic properties like being able to be moved voluntarily. Phantom limb movements are little-known and generally considered to reflect motor imagery rather than motor execution. The first aim of this thesis is to investigate whether amputees distinguish between executing a movement of the phantom limb and imagining moving the missing limb. The second aim is to examine the link between the quality of the motor control in the phantom limb and cortical reorganizations in the motor cortex of amputees. Behavioral tests and functional Magnetic Resonance Imaging (fMRI) results reveal the ability of amputees to make the distinction between execution and motor imagery in the phantom limb. This distinction is based both on differences in performances associated with the two tasks and the recruitment of partially distinct brain regions. Beyond this physiological distinction, this result suggests that phantom limb movements are similar to executed movements and differ from imagined movements. This raises important questions about the very nature of the processes underlying the awareness of a movement as being executed or imagined. The functional alterations in the motor cortex of amputees are somewhat similar to the pathophysiological mechanisms of maladaptative plasticity. Amputation could be a great model for its study. Indeed, the clinical and neuroimaging examinations conducted during this thesis led to a relatively coherent model of the functional reorganizations in the motor cortex after a limb-amputation and their relationships with behavioral variables. In particular, the relationship between functional reorganizations in the motor cortex and the quality of residual motor control in the phantom limb helps to understand the mechanisms underlying some analgesic therapies, such as the “visuomotor therapy”

O objetivo desta pesquisa foi investigar o efeito do conhecimento sobre a presença da câmera filmadora no desempenho motor avaliado pelo teste de desenvolvimento motor global (TGMD-2; Ulrich, 2000). Participaram da pesquisa 31 escolares do gênero masculino, com idades entre 7 e 9 anos. O questionário de ansiedade traço-estado IDATE-C foi utilizado para avaliar os níveis de ansiedade, antes e durante a realização do teste. As 12 habilidades motoras do TGMD-2 foram executadas em duas situações, com câmera visível e com câmera oculta. Cada participante foi testado nas duas condições, com intervalo de três meses entre elas. Em ambos os momentos de coleta, empregou-se um procedimento de contrabalanceamento da amostra em cada condição. Os testes t para amostras dependentes indicaram que houve diferenças significativas entre as duas condições, com desempenhos melhores para a condição de câmera visível no subteste controle de objeto e no coeficiente motor geral. Não foram encontradas correlações significativas entre ansiedade e desempenho motor. Além disso, em ambas as condições, o teste qui-quadrado apontou frequências maiores no nível muito pobre de coordenação motora grossa em relação aos níveis pobre e abaixo da média. Os resultados foram discutidos com base em teorias de motivação para o desempenho (autodeterminação, fluxo e nível de ativação) / The purpose of the present study was to investigate the effects of knowledge about the camcorders presence on motor performance assessed by the Test of Gross Motor Development (TGMD-2; Ulrich, 2000). Participants were 31 male scholars, ranging from 7 to 9 years of age, who responded the STAI trait-state anxiety questionnaire, before and during the motor test. The 12 motor skills of the TGMD-2 were performed in two conditions: visible and hidden cam. Each participant was tested on both conditions, with a three-month time interval. A procedure of counterbalancing the sample in each condition were used for both moments. T tests for paired samples indicated significant differences between conditions, the performances having been better when the cam was visible in the subtest object control and in the general gross motor quotient. No significant correlations were detected among anxiety and motor performance. Moreover, on both conditions, the chi-square test showed that the level very poor on gross co-ordination were more frequent than the other levels (poor and below average). The findings were discussed through motivation theories about performance (self-determination, flow, and arousal)

Para algumas crianças ações motoras típicas do cotidiano infantil tornam-se desafios que elas não conseguem superar adequadamente. Para intervir nesse quadro, é necessário selecionar instrumentos para identificar essas crianças com dificuldades motoras na idade mais precoce possível e, concomitantemente, identificar seus déficits para futura intervenção. O presente estudo teve como objetivo a tradução e adaptação transcultural do Early Years Movement Skills Checklist (CHAMBERS; SUGDEN, 2006) e a verificação de sua validade concorrente e fidedignidade (teste-reteste e entre observadores) no contexto da pré-escola da cidade de São Paulo. Para tanto, foram desenvolvidos quatro Estudos. Estudo 1 tradução e adaptação transcultural: foram adotados procedimentos sugeridos na literatura e como resultado foi produzida a Lista de Checagem das Habilidades Motoras na Primeira Infância (LCHMPI), a qual foi considerada adequada. Estudo 2 validade concorrente: 245 crianças (entre três e cinco anos de idade) foram avaliadas por suas professoras por meio da LCHMPI e pela pesquisadora por meio do Movement Assessment Battery for Children 2- Test (HENDERSON; SUGDEN; BARNETT, 2007) MABC-teste 2. Observou-se que 76,7% das crianças tiveram a mesma classificação nas duas avaliações, entretanto o coeficiente Kappa foi de apenas 0,20 e o coeficiente de correlação de postos de Spearman (- 0,10) não foi significante (p = 0,087). Apenas para o grupo de cinco anos de idade (n = 150) o coeficiente de correlação de postos de Spearman (- 0,204) foi considerado significantemente diferente de zero (p = 0,012). Dessa maneira, foi observada baixa concordância da LCHMPI com o MABC-teste 2. Apenas para a idade de cinco anos foi verificada melhor concordância. Estudo 3 fidedignidade teste-reteste: 39 crianças do Estudo 2 foram reavaliadas por suas professoras por meio da LCHMPI. Observou-se que 87,2% das crianças obtiveram a mesma classificação nas duas avaliações, porém o coeficiente Kappa foi de apenas 0,23 e o ICC de 0,67. Por meio do teste de postos com sinais de Wilcoxon não foi encontrada diferença significativa entre as pontuações das duas avaliações (p = 0,353). Dessa maneira, a fidedignidade teste-reteste foi considerada razoável. Estudo 4 fidedignidade entre observadores: 18 crianças foram avaliadas por dois diferentes avaliadores. Foi observada, entre as duas avaliações, concordância de 77,8%, com coeficiente Kappa de 0,75 e ICC de 0,80. Dessa maneira, a fidedignidade entre observadores foi considerada boa. Como conclusão, entendeu-se que o procedimento de tradução e adaptação foi satisfatório e a LCHMPI adequada. Porém, a verificação de suas características psicométricas mostrou que essas não foram mantidas da sua versão original. Entendemos que a LCHMPI pode vir a auxiliar na identificação de dificuldades motoras, porém seus resultados ainda devem ser analisados com cautela. Alguns resultados apontam que a LCHMPI pode não ter sido aplicada de maneira adequada por alguns professores, dessa maneira, acreditamos que a eficiência do instrumento pode ser melhorada se for oferecido melhor treinamento aos professores para sua utilização / For some children, typical daily motor actions become a challenge they cannot overcome properly. To intervene in this context it is necessary to select instruments to identify children with motor difficulties at the earliest age and, concomitantly, identifying their deficits for future intervention. The objective of the present study was to translate and adapt (transcultural) the Early Years Movement Skills Checklist (CHAMBERS; SUGDEN, 2006) and verify its concurrent validity and reliability (test-retest and inter-rater) in the context of São Paulo citys pre-school. For this end, we developed four Studies. Study 1 - translation and transcultural adaptation: it was adopted a process suggested in the literature and, as a result, the Lista de Checagem das Habilidades Motoras na Primeira Infância (LCHMPI) was produced. The LCHMPI was considered adequate. Study 2 - concurrent validity - 245 children (between three and five years old) were assessed by their teachers using the LCHMPI, and by the researcher using the MABC-test 2 (HENDERSON; SUGDEN; BARNETT, 2007). It was observed that 76.7% of children obtained the same classification in both evaluations, however the Kappa coefficient was only 0.20 and Spearman´s rank coefficient correlation (- 0.10) was not statistically significant (p = 0.087). The Spearman´s rank coefficient correlation of - 0.204 was significant (p = 0.012) only for the five year-old group (n = 150). There was poor agreement with the MABC-test 2. Only the five year-old group showed a better agreement. Study 3 - test-retest reliability: 39 children from Study 2 were reassessed by their teachers using the LCHMPI. It was observed that 87.2% of the children obtained the same classification in both assessments, but the Kappa coefficient was only 0.23. The ICC was 0.67 and the Wilcoxon signed-rank test showed no significant difference between the scores of the two assessments (p = 0.353). The test-retest reliability was considered reasonable. Study 4 - inter-rater reliability: 18 children were assessed by two different evaluators using the LCHMPI. It was observed an agreement of 77.8%, a Kappa coefficient of 0.75 and an ICC of 0.80 among the different evaluations. The inter-rater reliability was good. In conclusion, the process of translation and transcultural adaptation was considered satisfactory and LCHMPI was considered adequate. However, the verification of its psychometric characteristics showed that they were not retained from the original version. Thus, we conclude that the LCHMPI may help in the identification of motor difficulties, but its results must be carefully analyzed. The results point to problems in the use of the instrument by some teachers. Then, we believe the efficiency of the instrument can be improved if the teachers were offered more training for its use

Para algumas crianças ações motoras típicas do cotidiano infantil tornam-se desafios que elas não conseguem superar adequadamente. Para intervir nesse quadro, é necessário selecionar instrumentos para identificar essas crianças com dificuldades motoras na idade mais precoce possível e, concomitantemente, identificar seus déficits para futura intervenção. O presente estudo teve como objetivo a tradução e adaptação transcultural do Early Years Movement Skills Checklist (CHAMBERS; SUGDEN, 2006) e a verificação de sua validade concorrente e fidedignidade (teste-reteste e entre observadores) no contexto da pré-escola da cidade de São Paulo. Para tanto, foram desenvolvidos quatro Estudos. Estudo 1 tradução e adaptação transcultural: foram adotados procedimentos sugeridos na literatura e como resultado foi produzida a Lista de Checagem das Habilidades Motoras na Primeira Infância (LCHMPI), a qual foi considerada adequada. Estudo 2 validade concorrente: 245 crianças (entre três e cinco anos de idade) foram avaliadas por suas professoras por meio da LCHMPI e pela pesquisadora por meio do Movement Assessment Battery for Children 2- Test (HENDERSON; SUGDEN; BARNETT, 2007) MABC-teste 2. Observou-se que 76,7% das crianças tiveram a mesma classificação nas duas avaliações, entretanto o coeficiente Kappa foi de apenas 0,20 e o coeficiente de correlação de postos de Spearman (- 0,10) não foi significante (p = 0,087). Apenas para o grupo de cinco anos de idade (n = 150) o coeficiente de correlação de postos de Spearman (- 0,204) foi considerado significantemente diferente de zero (p = 0,012). Dessa maneira, foi observada baixa concordância da LCHMPI com o MABC-teste 2. Apenas para a idade de cinco anos foi verificada melhor concordância. Estudo 3 fidedignidade teste-reteste: 39 crianças do Estudo 2 foram reavaliadas por suas professoras por meio da LCHMPI. Observou-se que 87,2% das crianças obtiveram a mesma classificação nas duas avaliações, porém o coeficiente Kappa foi de apenas 0,23 e o ICC de 0,67. Por meio do teste de postos com sinais de Wilcoxon não foi encontrada diferença significativa entre as pontuações das duas avaliações (p = 0,353). Dessa maneira, a fidedignidade teste-reteste foi considerada razoável. Estudo 4 fidedignidade entre observadores: 18 crianças foram avaliadas por dois diferentes avaliadores. Foi observada, entre as duas avaliações, concordância de 77,8%, com coeficiente Kappa de 0,75 e ICC de 0,80. Dessa maneira, a fidedignidade entre observadores foi considerada boa. Como conclusão, entendeu-se que o procedimento de tradução e adaptação foi satisfatório e a LCHMPI adequada. Porém, a verificação de suas características psicométricas mostrou que essas não foram mantidas da sua versão original. Entendemos que a LCHMPI pode vir a auxiliar na identificação de dificuldades motoras, porém seus resultados ainda devem ser analisados com cautela. Alguns resultados apontam que a LCHMPI pode não ter sido aplicada de maneira adequada por alguns professores, dessa maneira, acreditamos que a eficiência do instrumento pode ser melhorada se for oferecido melhor treinamento aos professores para sua utilização / For some children, typical daily motor actions become a challenge they cannot overcome properly. To intervene in this context it is necessary to select instruments to identify children with motor difficulties at the earliest age and, concomitantly, identifying their deficits for future intervention. The objective of the present study was to translate and adapt (transcultural) the Early Years Movement Skills Checklist (CHAMBERS; SUGDEN, 2006) and verify its concurrent validity and reliability (test-retest and inter-rater) in the context of São Paulo citys pre-school. For this end, we developed four Studies. Study 1 - translation and transcultural adaptation: it was adopted a process suggested in the literature and, as a result, the Lista de Checagem das Habilidades Motoras na Primeira Infância (LCHMPI) was produced. The LCHMPI was considered adequate. Study 2 - concurrent validity - 245 children (between three and five years old) were assessed by their teachers using the LCHMPI, and by the researcher using the MABC-test 2 (HENDERSON; SUGDEN; BARNETT, 2007). It was observed that 76.7% of children obtained the same classification in both evaluations, however the Kappa coefficient was only 0.20 and Spearman´s rank coefficient correlation (- 0.10) was not statistically significant (p = 0.087). The Spearman´s rank coefficient correlation of - 0.204 was significant (p = 0.012) only for the five year-old group (n = 150). There was poor agreement with the MABC-test 2. Only the five year-old group showed a better agreement. Study 3 - test-retest reliability: 39 children from Study 2 were reassessed by their teachers using the LCHMPI. It was observed that 87.2% of the children obtained the same classification in both assessments, but the Kappa coefficient was only 0.23. The ICC was 0.67 and the Wilcoxon signed-rank test showed no significant difference between the scores of the two assessments (p = 0.353). The test-retest reliability was considered reasonable. Study 4 - inter-rater reliability: 18 children were assessed by two different evaluators using the LCHMPI. It was observed an agreement of 77.8%, a Kappa coefficient of 0.75 and an ICC of 0.80 among the different evaluations. The inter-rater reliability was good. In conclusion, the process of translation and transcultural adaptation was considered satisfactory and LCHMPI was considered adequate. However, the verification of its psychometric characteristics showed that they were not retained from the original version. Thus, we conclude that the LCHMPI may help in the identification of motor difficulties, but its results must be carefully analyzed. The results point to problems in the use of the instrument by some teachers. Then, we believe the efficiency of the instrument can be improved if the teachers were offered more training for its use

O objetivo desta pesquisa foi investigar o efeito do conhecimento sobre a presença da câmera filmadora no desempenho motor avaliado pelo teste de desenvolvimento motor global (TGMD-2; Ulrich, 2000). Participaram da pesquisa 31 escolares do gênero masculino, com idades entre 7 e 9 anos. O questionário de ansiedade traço-estado IDATE-C foi utilizado para avaliar os níveis de ansiedade, antes e durante a realização do teste. As 12 habilidades motoras do TGMD-2 foram executadas em duas situações, com câmera visível e com câmera oculta. Cada participante foi testado nas duas condições, com intervalo de três meses entre elas. Em ambos os momentos de coleta, empregou-se um procedimento de contrabalanceamento da amostra em cada condição. Os testes t para amostras dependentes indicaram que houve diferenças significativas entre as duas condições, com desempenhos melhores para a condição de câmera visível no subteste controle de objeto e no coeficiente motor geral. Não foram encontradas correlações significativas entre ansiedade e desempenho motor. Além disso, em ambas as condições, o teste qui-quadrado apontou frequências maiores no nível muito pobre de coordenação motora grossa em relação aos níveis pobre e abaixo da média. Os resultados foram discutidos com base em teorias de motivação para o desempenho (autodeterminação, fluxo e nível de ativação) / The purpose of the present study was to investigate the effects of knowledge about the camcorders presence on motor performance assessed by the Test of Gross Motor Development (TGMD-2; Ulrich, 2000). Participants were 31 male scholars, ranging from 7 to 9 years of age, who responded the STAI trait-state anxiety questionnaire, before and during the motor test. The 12 motor skills of the TGMD-2 were performed in two conditions: visible and hidden cam. Each participant was tested on both conditions, with a three-month time interval. A procedure of counterbalancing the sample in each condition were used for both moments. T tests for paired samples indicated significant differences between conditions, the performances having been better when the cam was visible in the subtest object control and in the general gross motor quotient. No significant correlations were detected among anxiety and motor performance. Moreover, on both conditions, the chi-square test showed that the level very poor on gross co-ordination were more frequent than the other levels (poor and below average). The findings were discussed through motivation theories about performance (self-determination, flow, and arousal)

O objetivo desse estudo foi analisar a preferência podal e assimetrias interlaterais de desempenho no chute de potência em crianças. Vinte e quatro meninos praticantes de futsal foram divididos em três grupos etários: seis, oito e 10 anos. A análise da preferência podal foi realizada por meio da observação da preferência de uso por uma das pernas em diferentes tarefas motoras, classificadas nas categorias: estabilização, mobilização geral (sem relação com tarefas do futebol) e mobilização específica (tarefas relacionadas ao futebol). A análise da assimetria de desempenho foi feita em função de parâmetros cinemáticos, após as crianças terem sido filmadas no desempenho do chute com a perna preferida e com a perna não-preferida com marcadores nas articulações do ombro, quadril, joelho e tornozelo. A avaliação da preferência podal indicou diferenças significativas entre as tarefas de estabilização e as de mobilização. Nas tarefas de estabilização os três grupos apresentaram grande variabilidade, o que abrangeu desde preferência esquerda consistente a preferência direita consistente. Nas tarefas de mobilização a grande maioria das crianças apresentou preferência podal direita consistente em todas as idades. Os resultados indicaram que a preferência podal é dependente da tarefa. A avaliação de desempenho indicou vantagem da perna direita na maioria das variáveis e nenhuma alteração da relação de desempenho entre uma perna e outra foi detectada entre as idades. Esses achados sugerem um desenvolvimento bilateral do chute, propiciado por mecanismos de transferência interlateral de aprendizagem. Tais resultados indicam que a preferência podal e as assimetrias interlaterais de desempenho são similares entre crianças de diferentes faixas etárias com prática regular em ações motoras relacionadas ao futebol / This study aimed at assessing podal preference and interlateral asymmetries in the performance of kicking in children. Twenty-four soccer player males were assigned to three age groups: 6, 8, and 10-year olds. Lateral preference was assessed on the basis of frequency of use of the right and the left foot/leg to perform different podal tasks, characteristic of the following categories: stabilization (balance tasks), general mobilization (tasks unrelated to soccer), and specific mobilization (tasks related to soccer). Performance asymmetry was quantified with different kinematic parameters, on the basis of images of kicking of either body side, using markers on the shoulder, hip, knee, and ankle joints. The results from assessment of podal preference indicated that for the stabilization tasks the three age groups presented a great variability, ranging from consistent preference for the left leg to consistent preference for the right leg. In both categories of mobilization tasks consistent preference for the right leg was prevalent in all ages. These results showed that podal preference is task-dependent. Analysis of performance asymmetry revealed a right leg advantage in most variables, and that no modification of the relationship between the legs was detected across ages. These findings suggest a bilateral development of kicking, possibly due to mechanisms of interlateral transfer of learning. These results indicate that both podal preference and interlateral podal asymmetries of performance are similar between children of different ages having regular practice in motor actions related to soccer

Uno de los problemas más importantes en los sistemas de realidad virtual es la diversidad de los dispositivos visuales y de interacción que existen en la actualidad. Junto a esto, la heterogeneidad de los motores gráficos, los motores físicos y los motores de inteligencia artificial, propicia que no exista un modelo que aúne todos estos aspectos de una forma integral y coherente. Con el objetivo de unificar toda esta diversidad, presentamos un modelo formal que afronta de forma integral el problema de la diversidad en los sistemas de realidad virtual, así como la definición de los módulos principales que los constituyen. El modelo propuesto se basa en la definición de varias gramáticas que integra su actividad, su visualización y su interacción con el usuario. La descripción de un mundo se presenta como una cadena de un lenguaje L(M) que representa una secuencia ordenada de agentes que aceptan eventos y que definen la actividad del sistema. Por otro lado, la visualización del estado actual del sistema se traduce en otra cadena del lenguaje de visualización L(V) y que está compuesta de primitivas y transformaciones. Los conceptos de primitiva y transformación son mucho más amplios de lo que es habitual en estos sistemas. Las primitivas no son simples primitivas de dibujo sino acciones que se deben ejecutar en un determinado sistema de representación que es definida mediante otro lenguaje L(G) y que representa las acciones ordenadas en un determinado dispositivo visual o no. Las transformaciones, por otro lado, modifican las primitivas, dependiendo de su naturaleza. Los agentes desarrollan una o varias actividades en el mundo virtual, se visualizan mediante primitivas y transformaciones, y usan eventos que también se definen en sentido amplio. El modelo presentado tiene como virtud la separación de la actividad del sistema de los dispositivos visuales y de interacción concretos que lo componen. Esto supone varias ventajas: los dispositivos pueden ser sustituidos por otros dispositivos o por simulaciones de estos, los elementos del sistema pueden ser reutilizados, y la representación gráfica puede ser diferente dependiendo del dispositivo visual. En definitiva, se ha pretendido diseñar un sistema integral, adaptativo, reutilizable y genérico. Por último, se presentan varios casos prácticos que permiten concretar cómo se utiliza el modelo propuesto.

[Truncated astract] Talent Identification (TI) in sports begins by mass screening individuals' motor abilities. du Randt (2000) wrote that, as test items from one country might not necessarily suit another, appropriate basic motor skill test items are important for developing a TI mass screening instrument. Three hundred and thirty Malaysian adolescents aged from 12-15 years were tested on three motor skill test batteries: the McCarron Assessment of Neuromuscular Development (MAND, McCarron, 1982); the Australian Talent Identification Test (AIS, Australian Sports Commission, 1998); and a Balance and Movement Coordination Test which was specifically developed for this project. In the current research, the motor performance data recorded from the adolescents underwent several types of analyses. Principal Component analyses were conducted on the MAND, AIS and BMC motor skill instruments to understand what the three motor skill instruments were assessing globally in the Malaysian adolescents. Then, first-order and higher-order factor analyses were conducted on the 13 parameters making up the AIS+BMC motor skill instrument to examine the concept of general motor ability (GMA). After descriptive analyses of the adolescents' motor skill performances, age and gender differences were examined using two (gender) by four (age) ANOVAs. Finally, stepwise discriminant function analyses were conducted on a combined AIS+BMC motor skill instrument to determine the best sub-set of motor skills that reliably classified the Malaysian adolescents into three levels of motor performance.... Two stepwise discriminant analyses were undertaken to find the best set of motor skills for classifying Malaysian adolescents into three motor coordination groups based on scores on the MAND and three motor ability groups derived from scores on the motoric 'g'. The ability of a combined AIS+BMC motor skill instrument to classify Malaysian adolescents into the three groups was good for those classified as Normal, not so great for those adolescents classified as High, and poor for those adolescents classified as Low. The motor skills consistently reported across both sets of analyses were Balance-Eyes-Open, Balance-Eyes-Closed, Dynamic Balance, Hopping Speed, Quadrant Jump, Hopping-in-Square, Basketball Throw and Shuttle-Run-with-Object. Hence, motor skills assessing static balance, dynamic balance and postural control appeared to reliably discriminate the Malaysian adolescents into three motor performance groups. Finally, an examination of the misclassifications found in the discriminant analyses revealed two things. Those individuals being predicted into a lower group performed a large number of the motor skills to a lesser standard when compared with their correctly classified cohorts. Conversely, those predicted into a higher group performed a number of motor skills to a standard higher than their correctly classified cohorts. Thus, at a global level, certain individuals could be overlooked for further athletic development and is a concern when developing a rigorous TI program. Therefore, practitioners need to be cautious of any single ability score, and how that represents an individual's athletic potential. These results are discussed, limitations noted, and directions for future research provided.