Neuroscience
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Response inhibition - the suppression of prepotent behaviours when they are inappropriate - has been thought to rely on executive control. Against this received wisdom, it has been argued that external cues repeatedly associated with response inhibition can come to trigger response inhibition automatically without top-down command. The current project endeavoured to provide evidence for associatively-mediated motor inhibition. ⋯ Once trained, the subjects received transcranial magnetic stimulation applied over their primary motor cortex during passive observation of either the stop signal (i.e. without any need to stop a response) or an equally familiar control stimulus never associated with stopping. Analysis of motor-evoked potentials showed that corticospinal excitability was reduced during exposure to the stop signal, which likely involved stimulus-driven activation of intracortical GABAergic interneurons. This result provides evidence that, through associative learning, stop-associated stimuli can engage local inhibitory processes at the level of the motor cortex.
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L2 processing is shaped by L1 experience; however, it is not completely understood whether L1 reading experience also influences how the brain learns L2 under different learning conditions. In this study, we compare brain mechanisms of Spanish word learning in Chinese and English speakers using two learning conditions: speech-based learning and handwriting-based learning. The behavioral data suggest an advantage for learning that uses handwriting over speech-based learning across all participants. ⋯ Thus, the handwriting-based learning engaged visuo-orthographic regions to a greater degree in highly skilled Chinese speakers. In summary, the current findings suggest that handwriting facilitates lexical learning by enhancing orthographic involvement in Chinese speakers, while the handwriting condition enhanced phonological involvement in English speakers. This difference between Chinese and English speakers might be due to different L1 learning experience.
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We have recently shown that the efficiency of stopping a response is correlated with GABAergic activity in primary motor cortex (M1) measured using the short interval intracortical inhibition (SICI) protocol. However, this finding was observed when SICI was measured in left M1 and when stopping efficiency was measured with a bimanual response task. The aim of the present study was to examine the extent to which the relationship between SICI and stopping is lateralized to the hemisphere controlling the response (e.g. left M1 and stopping a right hand response) and/or reflects bilateral inhibitory mechanisms (as might be seen between left M1 and left hand stopping). ⋯ We found that SICI was significantly correlated between hemispheres (r = 0.51) and stopping efficiency was correlated between hands (r = 0.77). When controlling for other relevant variables, we found that stopping efficiency in each hand was uniquely predicted by SICI in the contralateral hemisphere, but not the ipsilateral hemisphere. These results suggest that there is a hemispheric-specific contribution of SICI to stopping efficiency.
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Sexually explicit material (SEM) is increasingly used in western societies. One reason for this high usage might be the rewarding property of SEM demonstrated in many brain imaging studies showing an activation of the reward system during the presentation of SEM. It is not yet well understood why women use SEM to a remarkably lesser extent than men. ⋯ There were some sex differences in hemodynamic responses to SEM during the presentation phase, but not during the expectation phase to SEM cues in any of the regions of interest. The influence of the investigated person characteristics was only small if existent. The results suggest that sex specific cue processing cannot explain sex differences in the use of SEM.
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p53 and parkin are involved in mitochondrial quality control. The present study aimed to characterize the functional significance of parkin/p53 in the development of mitochondrial dysfunction and the pathophysiology of neuropathic pain in type I diabetes. Type I diabetes was induced in mice (N = 170) using streptozotocin (STZ). ⋯ Methylglyoxal also decreased mitochondrial membrane potential in cultured DRG neurons. Alteration of p53/parkin expression produces mitochondrial dysfunction and ROS accumulation, leading to pain hypersensitivity in diabetic or methylglyoxal treated mice. Methylglyoxal produces neurological derangements similar to diabetes, via direct mechanisms on DRG neurons.