Neuroscience
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Randomized Controlled Trial
Training-induced cortical plasticity compared between three tongue-training paradigms.
The primary aim of this study was to investigate the effect of different training types and secondary to test gender differences on the training-related cortical plasticity induced by three different tongue-training paradigms: (1) therapeutic tongue exercises (TTE), (2) playing computer games with the tongue using the Tongue Drive System (TDS) and (3) tongue-protrusion task (TPT). Forty-eight participants were randomized into three groups with 1h of TTE, TDS, or TPT. Stimulus-response curves of motor evoked potentials (MEPs) and motor cortex mapping for tongue muscles and first dorsal interosseous (FDI) (control) were established using transcranial magnetic stimulation at three time-points: (1) before tongue-training, (2) immediately after training, (3) 1h after training. ⋯ Training with TDS was most motivating and fun (P<0.001) and TTE was rated the most painful (P<0.001). Fatigue level was not different between groups (P>0.071). These findings suggest a differential effect of tongue-training paradigms on training-induced cortical plasticity and subject-based scores of fun, motivation and pain in healthy participants.
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Randomized Controlled Trial
Reorganization of the auditory, visual and multimodal areas in early deaf individuals.
Plasticity resulting from early sensory deprivation has been investigated in both animals and humans. After sensory deprivation, brain areas that are normally associated with the lost sense are recruited to carry out functions in the remaining intact modalities. Previous studies have reported that it is almost exclusively the visual dorsal pathway which is affected by auditory deprivation. ⋯ No significant differences between deaf and hearing individuals were found in target visual and auditory areas when the motion and form components of the stimuli were isolated (contrasted with a static visual image). However, increases in activation were found in the deaf group in the superior temporal gyrus (BA 22 and 42) and in an area located at the junction of the parieto-occipital sulcus and the calcarine fissure (encompassing parts of the cuneus, precuneus and the lingual gyrus) for the GMS and FFM conditions as well as for the static image, relative to a baseline condition absent of any visual stimulation. These results suggest that the observed cross-modal recruitment of auditory areas in deaf individuals does not appear to be specialized for motion processing, but rather is present for both motion and static visual stimuli.
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Randomized Controlled Trial
Temporal accuracy and variability in the left and right posterior parietal cortex.
Several brain-imaging and lesion studies have suggested a role for the posterior parietal cortex (PPC) in computing interval-timing tasks. PPC also seems to have a key role in modulating visuospatial mechanisms, which are known to affect temporal performance. By applying transcranial direct current stimulation (tDCS) over the left and right PPC, we aimed to modulate timing ability performance in healthy humans performing a cognitively controlled timing task. ⋯ No effect was reported for anodal stimulation. These results expand current knowledge on the role of the parietal cortex on temporal processing. We provide evidence that the parietal cortex of both hemispheres is involved in temporal processing by acting on distinct components of timing performance such as accuracy and variability.
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Randomized Controlled Trial
Are postural responses to backward and forward perturbations processed by different neural circuits?
Startle pathways may contribute to rapid accomplishment of postural stability. Here we investigate the possible influence of a startling auditory stimulus (SAS) on postural responses. We formulated four specific questions: (1) can a concurrent SAS shorten the onset of automatic postural responses?; and if so (2) is this effect different for forward versus backward perturbations?; (3) does this effect depend on prior knowledge of the perturbation direction?; and (4) is this effect different for low- and high-magnitude perturbations? Balance was perturbed in 11 healthy participants by a movable platform that suddenly translated forward or backward. ⋯ Increasing the perturbation magnitude accelerated postural responses, but again with a larger acceleration for backward perturbations. We conclude that postural responses to backward and forward perturbations may be processed by different neural circuits, with influence of startle pathways on postural responses to backward perturbations. These findings give directions for future studies investigating whether deficits in startle pathways may explain the prominent backward instability seen in patients with Parkinson's disease and progressive supranuclear palsy.
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Randomized Controlled Trial
Effects of COMT genotype on sensory gating and its modulation by nicotine: Differences in low and high P50 suppressors.
Elevated smoking rates seen in schizophrenia populations may be an attempt to correct neuropathologies associated with deficient nicotinic acetylcholine receptors and/or dopaminergic systems using exogenous nicotine. However, nicotine's effects on cognitive processing and sensory gating have been shown to be baseline-dependent. Evidence of a restorative effect on sensory gating deficits by nicotine-like agonists has been demonstrated, however, its underlying mechanisms in the context of dopamine dysregulation are unclear. ⋯ Using a randomized, double-blind, placebo-controlled design with 57 non-smokers, this study examined the effects of COMT genotype on sensory gating and its modulation by nicotine in low vs. high suppressors. The results were consistent with the hypothesis that increased dopamine resulting from nicotine stimulation or Met allelic activity would benefit gating in low suppressors and impair gating in high suppressors, and that this gating improvement with nicotine would be more evident in Val carriers who were low suppressors, while the gating impairment would be more evident in Met carriers who were high suppressors. These findings reaffirm the importance of baseline-dependency and suggest a subtle relationship between COMT genotype and baseline-stratified levels of sensory gating, which may help to explain the variability of cognitive abilities in schizophrenia populations.