Neuroscience
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Numerous clinical investigations have reported that children with cerebral palsy (CP) have tactile discrimination deficits that likely limit their ability to plan and manipulate objects. Despite this clinical awareness, we still have a substantial knowledge gap in our understanding of the neurological basis for these tactile discrimination deficits. Previously, we have shown that children with CP have aberrant theta-alpha (4-14 Hz) oscillations in the somatosensory cortices following tactile stimulation of the foot. ⋯ This inference is plausible since the participating children with CP had Manual Ability Classification System (MACS) levels between I and II. In contrast to the theta-alpha results, children with CP did exhibit a sharp increase in beta activity during the same time period, which was not observed in TD children. This suggests that children with CP still have deficits in the computational aspect of somatosensory processing.
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Spatial orientation and navigation depends on information from the vestibular system. Previous work suggested impaired spatial navigation in patients with bilateral vestibular failure (BVF). The aim of this study was to investigate event-related brain activity by functional magnetic resonance imaging (fMRI) during spatial navigation and visual memory tasks in BVF patients. ⋯ Cerebellar activity during spatial navigation in BVF patients may reflect increased non-vestibular efforts to counteract the development of spatial navigation deficits in BVF. Conceivably, cerebellar activity indicates a change in navigational strategy of BVF patients, i.e. from a more allocentric, landmark or place-based strategy (hippocampus) to a more sequence-based strategy. This interpretation would be in accord with recent evidence for a cerebellar role in sequence-based navigation.
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The neural substrates of fatigue induced by muscular activity have been addressed in depth in relation to isometric tasks. For these activities, when fatigue develops, it has been noted that the duration of the silent periods (SPs) increases in response to both transcranial magnetic stimulation (TMS) of primary motor cortex or electric cervicomedullary stimulation (CMS). However, fatigue is known to be task-dependent and the mechanisms giving rise to a decrease in motor performance during brief, fast repetitive tasks have been less studied. ⋯ They increased TMS-SPs, but not CMS-SPs. On the other hand, isometric contraction had a clear impact on spinal circuits. The consideration of these differences might help to optimize the study of fatigue in physiological conditions and neurological disorders.
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Two event-related potential (ERP) experiments were conducted to investigate whether Cantonese lexical tones are processed with general auditory perception mechanisms and/or a special speech module. Two tonal features (f0 direction and f0 height deviation) were manipulated to reflect acoustic processing, and the contrast between syllables and hums was used to reveal the involvement of a speech module. Experiment 1 adopted a passive oddball paradigm to study a relatively early stage of tonal processing. ⋯ Moreover, detecting tonal deviants of syllables elicited N1 and P2 that were not found in hum detection. Together, these findings suggest that the processing of lexical tone relies on both acoustic and linguistic processes from the early stage. Another noteworthy finding is the absence of brain lateralization in both experiments, which challenges the use of a lateralization pattern as evidence for processing lexical tones through a special speech module.
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Recent functional magnetic resonance imaging (fMRI) studies consistently revealed contributions of fronto-parietal and related networks to the execution of a visuospatial judgment task, the so-called "Clock Task". However, due to the low temporal resolution of fMRI, the exact cortical dynamics and timing of processing during task performance could not be resolved until now. In order to clarify the detailed cortical activity and temporal dynamics, 14 healthy subjects performed an established version of the "Clock Task", which comprises a visuospatial task (angle discrimination) and a control task (color discrimination) with the same stimulus material, in an electroencephalography (EEG) experiment. ⋯ We divided this window in two parts: an early phase - from 192 ms to ∼440 ms, and a late phase - from ∼440 ms to 776 ms. For both tasks, the order of network activations and the types of networks were the same, but, in each phase, activations for the two conditions were dominated by differing network states with divergent temporal dynamics. Our results provide an important basis for the assessment of deviations in processing dynamics during visuospatial tasks in clinical populations.