Unilateral Brachial Plexus Lesion Impairs Bilateral Touch Threshold.

Unilateral brachial plexus injury (BPI) impairs sensory and motor functions of the upper limb. This study aimed to map in detail brachial plexus sensory impairment both in the injured and the uninjured upper limb. Touch sensation was measured through Semmes-Weinstein monofilaments at the autonomous regions of the brachial plexus nerves, hereafter called points of exclusive innervation (PEIs). Seventeen BPI patients (31.35 years±6.9 SD) and 14 age-matched healthy controls (27.57 years±5.8 SD) were tested bilaterally at six selected PEIs (axillary, musculocutaneous, median, radial, ulnar, and medial antebrachial cutaneous [MABC]). As expected, the comparison between the control group and the brachial plexus patients' injured limb showed a robust difference for all PEIs (p ≤ 0.001). Moreover, the comparison between the control group and the brachial plexus uninjured limb revealed a difference for the median (p = 0.0074), radial (p = 0.0185), ulnar (p = 0.0404), and MABC (p = 0.0328) PEIs. After splitting the sample into two groups with respect to the dominance of the injured limb, higher threshold values were found for the uninjured side when it occurred in the right dominant limb compared to the control group at the median (p = 0.0456), radial (p = 0.0096), and MABC (p = 0.0078) PEIs. This effect was absent for the left, non-dominant arm. To assess the effect of the severity of sensory deficits observed in the injured limb upon the alterations of the uninjured limb, a K-means clustering algorithm (k = 2) was applied resulting in two groups with less or more severe sensory impairment. The less severely affected patients presented higher thresholds at the median (p = 0.0189), radial (p = 0.0081), ulnar (p = 0.0253), and MABC (p = 0.0187) PEIs in the uninjured limb in comparison with the control group, whereas higher thresholds at the uninjured limb were found only for the median PEI (p = 0.0457) in the more severely affected group. In conclusion, an expressive reduction in touch threshold was found for the injured limb allowing a precise mapping of the impairment caused by the BPI. Crucially, BPI also led to reduced tactile threshold in specific PEIs in the uninjured upper limb. These new findings suggest a superordinate model of representational plasticity occurring bilaterally in the brain after a unilateral peripheral injury.

Modulações dos efeitos Simon e Stroop espacial por tarefas prévias de compatibilidade espacial / Modulations of Simon and spatial Stroop effects due to previous spatial compatibility tasks / Modulaciones de los efectos Simon e Stroop espacial por tareas anteriores de compatibilidad espacial

A localização espacial é uma característica intrínseca do estímulo que não pode ser ignorada e afeta a seleção da resposta correta em várias tarefas. Este efeito, denominado Compatibilidade Estímulo-Resposta, está presente nas tarefas de Compatibilidade espacial, Simon e Stroop espacial. O efeito Simon é modulado se, antes de executar a tarefa, os participantes executam uma tarefa incompatível de compatibilidade espacial. Essa modulação, chamada de transferência de aprendizagem é atribuída a dissociações entre memórias de longo e curto prazo. Não foi ainda estudado se esta prática incompatível modula o efeito Stroop espacial. Neste trabalho, testamos 32 participantes empregando um desenho experimental que permite estudar e separar os efeitos Simon e Stroop espacial na mesma tarefa e testar a hipótese de uma transferência generalizada do aprendizado por uma prática incompatível. Os resultados indicaram que a tarefa prévia incompatível modula apenas o efeito Simon, contrariando a hipótese da transferência generalizada do aprendizado.

Spatial location is an intrinsic characteristic of the stimulus that influences the execution of the correct response in various tasks. The effect is named Stimulus-Response Compatibility, with the Spatial Compatibility, Simon, and Spatial Stroop tasks being examples of this phenomenon. The Simon effect is modulated if participants perform a previous incompatible spatial compatibility task. This modulation, called transfer-of-learning effect, has been attributed to dissociations between long-term memory and short-term memory. It had not yet studied whether this incompatible practice modulates the spatial Stroop effect. In this work, we tested 32 volunteers in an experimental design that allows us to study and separate the Simon and spatial Stroop effects in the same task and test the hypothesis of a generalized transfer-of-learning effect by an incompatible practice. The results indicate that a previous incompatible task modulates only the Simon effect, contradicting the hypothesis of the generalized transfer of learning after an incompatible practice.

La localización espacial es una característica intrínseca del estímulo que afecta la selección de la respuesta en diversas tareas. Este efecto, denominado la compatibilidad estímulo-respuesta, es presente en la tarea compatibilidad espacial, Simon y Stroop espacial. El efecto Simon es modulado si los participantes realizan previamente una tarea incompatible de compatibilidad espacial. Esta modulación, llamada efecto de transferencia de aprendizaje, se ha atribuido a las disociaciones entre memoria a largo e corto plazo. Todavía no se ha estudiado si esta práctica incompatible modula el efecto Stroop Espacial. En este trabajo, probamos 32 estudiantes en un diseño experimental que nos permite estudiar y separar los efectos de Simon y Stroop espacial en la misma tarea y probar la hipótesis de un efecto generalizado de transferencia de aprendizaje por una práctica incompatible. Los resultados indican que la tarea incompatible anterior modula sólo el efecto Simón, contrariamente a la hipótesis de la transferencia generalizada de aprendizaje.

Devastação, o que há de novo?

Este trabalho indaga sobre o que há de novo na devastação (ravage) como fato clínico, que se relaciona à lei materna e à histeria. Com o desenvolvimento do Campo freudiano e da Orientação Lacaniana, é possível pensar a devastação de um novo ponto de vista. Assim, o texto objetiva enfatizar a relação entre a lei materna e a devastação nos primeiros anos da infância, que tem consequências no adulto, produzindo sintomas. O tratamento da devastação pode ser articulado à histeria, cujo atual paradigma contempla o gozo masculino, fálico, como gozo todo, e o gozo feminino como nãotodo fálico(AU)

Primary Motor Cortex Representation of Handgrip Muscles in Patients with Leprosy.

BACKGROUND: Leprosy is an endemic infectious disease caused by Mycobacterium leprae that predominantly attacks the skin and peripheral nerves, leading to progressive impairment of motor, sensory and autonomic function. Little is known about how this peripheral neuropathy affects corticospinal excitability of handgrip muscles. Our purpose was to explore the motor cortex organization after progressive peripheral nerve injury and upper-limb dysfunction induced by leprosy using noninvasive transcranial magnetic stimulation (TMS). METHODS: In a cross-sectional study design, we mapped bilaterally in the primary motor cortex (M1) the representations of the hand flexor digitorum superficialis (FDS), as well as of the intrinsic hand muscles abductor pollicis brevis (APB), first dorsal interosseous (FDI) and abductor digiti minimi (ADM). All participants underwent clinical assessment, handgrip dynamometry and motor and sensory nerve conduction exams 30 days before mapping. Wilcoxon signed rank and Mann-Whitney tests were performed with an alpha-value of p<0.05. FINDINGS: Dynamometry performance of the patients' most affected hand (MAH), was worse than that of the less affected hand (LAH) and of healthy controls participants (p = 0.031), confirming handgrip impairment. Motor threshold (MT) of the FDS muscle was higher in both hemispheres in patients as compared to controls, and lower in the hemisphere contralateral to the MAH when compared to that of the LAH. Moreover, motor evoked potential (MEP) amplitudes collected in the FDS of the MAH were higher in comparison to those of controls. Strikingly, MEPs in the intrinsic hand muscle FDI had lower amplitudes in the hemisphere contralateral to MAH as compared to those of the LAH and the control group. Taken together, these results are suggestive of a more robust representation of an extrinsic hand flexor and impaired intrinsic hand muscle function in the hemisphere contralateral to the MAH due to leprosy. CONCLUSION: Decreased sensory-motor function induced by leprosy affects handgrip muscle representation in M1.

Left-right judgment of haptic stimuli representing the human hand

The handedness recognition of visually perceived body parts engages motor representations that are constrained by the same biomechanical factors that limit the execution of real movements. In the present study, we used small plastic cutouts that represented the human hand to investigate the properties of mental images generated during their haptic exploration. Our working hypothesis was that any handedness recognition task that involves body parts depends on motor imagery. Forty-four blindfolded, right-handed volunteers participated in a handedness evaluation experiment using their index finger to explore either the back or palm view of a haptic stimulus that represented the human hand. The stimuli were presented in four different orientations, and we measured the subjects' response times. Our results showed that stimulus configurations that resemble awkward positions of the human hand are associated with longer response times (p < .006), indicating that the haptic exploration of stimuli that represent body parts also leads to motor imagery that is constrained by biomechanical factors.(AU)

Left-right judgment of haptic stimuli representing the human hand

The handedness recognition of visually perceived body parts engages motor representations that are constrained by the same biomechanical factors that limit the execution of real movements. In the present study, we used small plastic cutouts that represented the human hand to investigate the properties of mental images generated during their haptic exploration. Our working hypothesis was that any handedness recognition task that involves body parts depends on motor imagery. Forty-four blindfolded, right-handed volunteers participated in a handedness evaluation experiment using their index finger to explore either the back or palm view of a haptic stimulus that represented the human hand. The stimuli were presented in four different orientations, and we measured the subjects' response times. Our results showed that stimulus configurations that resemble awkward positions of the human hand are associated with longer response times (p < .006), indicating that the haptic exploration of stimuli that represent body parts also leads to motor imagery that is constrained by biomechanical factors

Deficiência visual e plasticidade no cérebro humano / Visual impairment and cerebral plasticity in the human brain / Deficiencia visual y plasticidad cerebral

O ser humano é capaz de analisar o mundo à sua volta por meio de informações provenientes das diversas modalidades sensoriais. A percepção do mundo a cada momento envolve a integração dessas informações em áreas multissensoriais existentes no cérebro humano. Dessa forma, podem-se imaginar as profundas transformações que ocorrem no cérebro após a perda de uma aferência sensorial. Estudos anatômicos, fisiológicos e comportamentais em animais têm sugerido que mudanças plásticas compensatórias devem também ocorrer nos seres humanos, alterando as conexões do córtex visual com os córtices somestésico e auditivo. Utilizando as novas idéias sobre as áreas multimodais e metamodais, pretendemos analisar como ocorre a reorganização dos sentidos remanescentes após a perda da visão.

Humans are able to analyze the world through information derived from various sensory modalities. After the loss of a given sense, anatomical, physiological and behavioral studies have shown that compensatory plastic changes take place in the cortex, first through the unmasking of synaptic contributions from other modalities, even in primary sensory areas. This fact underscores the metamodal theory of sensory cortical function and can be used to devise effective strategies to train the blind to compensate their loss through better use of the remaining sensory modalities.

El ser humano es capaz de analizar el mundo que lo rodea a través de información de las diversas modalidades sensoriales. La percepción del mundo en cada momento implica la integración de información multisensorial en las áreas existentes en el cerebro humano. Así, uno puede imaginar los profundos cambios que ocurren en el cerebro después de la pérdida de un aferente sensorial. Los cambios anatómicos, fisiológicos y de comportamiento en animales han sugerido que los cambios compensatorios plásticos también debem ocurrir en los seres humanos, cambiando las conexiones de la corteza visual con las cortezas auditivas y somestésicas. Con nuevas ideas sobre las áreas multimodal y metamod, analizamos la reorganización de los sentidos restantes después de la pérdida de la visión.

Deficiência visual e plasticidade no cérebro humano / Visual impairment and cerebral plasticity in the human brain / Deficiencia visual y plasticidad cerebral

O ser humano é capaz de analisar o mundo à sua volta por meio de informações provenientes das diversas modalidades sensoriais. A percepção do mundo a cada momento envolve a integração dessas informações em áreas multissensoriais existentes no cérebro humano. Dessa forma, podem-se imaginar as profundas transformações que ocorrem no cérebro após a perda de uma aferência sensorial. Estudos anatômicos, fisiológicos e comportamentais em animais têm sugerido que mudanças plásticas compensatórias devem também ocorrer nos seres humanos, alterando as conexões do córtex visual com os córtices somestésico e auditivo. Utilizando as novas idéias sobre as áreas multimodais e metamodais, pretendemos analisar como ocorre a reorganização dos sentidos remanescentes após a perda da visão.(AU)

Humans are able to analyze the world through information derived from various sensory modalities. After the loss of a given sense, anatomical, physiological and behavioral studies have shown that compensatory plastic changes take place in the cortex, first through the unmasking of synaptic contributions from other modalities, even in primary sensory areas. This fact underscores the metamodal theory of sensory cortical function and can be used to devise effective strategies to train the blind to compensate their loss through better use of the remaining sensory modalities.(AU)

El ser humano es capaz de analizar el mundo que lo rodea a través de información de las diversas modalidades sensoriales. La percepción del mundo en cada momento implica la integración de información multisensorial en las áreas existentes en el cerebro humano. Así, uno puede imaginar los profundos cambios que ocurren en el cerebro después de la pérdida de un aferente sensorial. Los cambios anatómicos, fisiológicos y de comportamiento en animales han sugerido que los cambios compensatorios plásticos también debem ocurrir en los seres humanos, cambiando las conexiones de la corteza visual con las cortezas auditivas y somestésicas. Con nuevas ideas sobre las áreas multimodal y metamod, analizamos la reorganización de los sentidos restantes después de la pérdida de la visión.(AU)

Feixes de luz e os efeitos compatibilidade espacial e cruzamento / Light beams for the study of compatibility and crossed-hand effects / Estudio de los efectos de compatibilidad y cruzamiento usando haces luminosos

Em tarefas de compatibilidade espacial, o cruzamento das mãos aumenta os tempos de reação manual (TRM). Isto ocorre porque a posição das mãos deve ser processada antes da execução da resposta. Este trabalho empregou apontadores luminosos para investigar se a posição do local iluminado corresponde ao local da projeção da ação da mão. Comparando a localização dos estímulos, a posição das mãos e a projeção da ação das mãos (local iluminado) identificamos os efeitos compatibilidade e cruzamento pela comparação dos TRMs nas condições compatível (estímulo e local iluminado no mesmo lado) e incompatível (estímulo e local iluminado em lados opostos) e nas condições cruzada (feixe dirigido para o lado oposto) e não-cruzada (feixe dirigido para o mesmo lado). Os resultados mostram que estes efeitos dependem do local iluminado e não do local de ação imediata da mão (a tecla).(AU)

The crossing of hands increases Manual Reaction Time (MRT) in spatial compatibility tasks. This occurs because the position of the hands has to be first taken into account by the brain before response is executed. This study tested the influence of two parameters on MRT: the position of the effector hand and the location of its projected action, both properly dissociated with the aid of laser pointers. While hands were kept on their respective sides the laser beam was either directed towards the stimulus (compatible condition) or to the opposite side (incompatible condition). Besides, the laser beam could be either directed towards the effector (hand) side or across the midline towards the opposite hemifield (uncrossed and crossed conditions). Our results show both compatibility and crossed effects on MRTs, indicating that spatial interactions occur between the projected action and both the stimulus (compatibilityeffect) and response key (crossed effect) positions.(AU)