Neuroscience
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The causal connections among small-scale regions based on resting-state fMRI data have been extensively studied and a lot of achievements have been demonstrated. However, the causal connection among large-scale regions was seldom discussed. In this paper, we applied global Granger causality analysis to construct the causal connections in the whole-brain network among 103 healthy subjects (33 M/66F, ages 20-23) based on a resting-state fMRI dataset. ⋯ There were 817 directed edges identified as significant among the 8010 possible causal connections; seven driving hubs and ten driven hubs were identified in the whole-brain network. In CEN, dorsolateral prefrontal cortex (DlPFC) and superior parietal cortex (SPC) were the driven and driving hubs, respectively; in DMN, they were posterior cingulate cortex (PCC) and medial prefrontal cortex (MPFC); in DAN, they were frontal eye fields (FEF) and intraparietal sulcus (IPS); and in SN, they were frontoinsular cortex (FIC) and medial frontal cortex (MFC). These findings may provide insights into our understanding of human brain function mechanisms and the diagnosis of brain diseases.
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Motor expertise has recently been associated with differences in domain-general cognition. Studies using averaged neurophysiological signals (e.g., event-related potentials) have shown varying degree of expertise-related differences in neural activity. As a result, the precise mechanisms underlying these differences remain to be described. ⋯ The interceptive sport players showed superior behavioral performance overall on the task relative to the static sport players. Although both groups exhibited greater sample entropy across most time scales in high-conflict relative to low-conflict trials over the parietal site, this effect was only evident at coarser time scales over the midfrontal site for the interceptive sport players. Together, our results suggest that individual differences in motor expertise may be associated with difference in information-processing capacity and information integration during cognitive processing, as demonstrated by differential cognitive modulation of brain signal variability.
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Visual self-face and proprioceptive postural recognition predominantly activate the right inferior frontoparietal cortices in human right-handers at the population level. In the present study, prompted by the finding that left-handedness may alter lateralized cortical organization for language, sensory-motor, and cognitive functions observed in right-handers, we investigated individual variations in right-dominant use of the cortices in 50 right-handers and 50 left-handers during self-body recognition (self-face and proprioceptive) tasks. We also investigated possible between-tasks differences in this right-dominant use, and possible atypical left-right reversed lateralization (right-dominance for language and left-dominance for self-body recognition) in left-handers. ⋯ Atypical left-right reversed lateralization was only observed in left-handed participants, but during both self-body recognition tasks. The present study provides novel and valuable knowledge about right-hemispheric dominance in self-body recognition affected by left-handedness. We discuss how functional lateralization of self-body recognition is shaped in human brain, in terms of handedness, language lateralization, and development.
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Endolymphatic hydrops is associated with low-frequency sensorineural hearing loss, with a large body of research dedicated to examining its putative causal role in low-frequency hearing loss. Investigations have been thwarted by the fact that hearing loss is measured in intact ears, but gold standard assessments of endolymphatic hydrops are made postmortem only; and that no objective low-frequency hearing measure has existed. Yet the association of endolymphatic hydrops with low-frequency hearing loss is so strong that it has been established as one of the important defining features for Ménière's disease, rendering it critical to detect endolymphatic hydrops early, regardless of whether it serves a causal role or is the result of other disease mechanisms. ⋯ The ANOW detected low-frequency hearing loss with perfect sensitivity and specificity in all ears after endolymphatic hydrops developed, where there was a strong linear relationship between degree of endolymphatic hydrops and severity of low-frequency hearing loss. Further, histological data demonstrated that endolymphatic hydrops is seen first in the high-frequency cochlear base, though the ANOW demonstrated that dysfunction begins in the low-frequency apical cochlear half. The results lay the groundwork for future investigations of the causal role of endolymphatic hydrops in low-frequency hearing loss.
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The effects of muscle fatigue are known to be altered in older adults, and age-related changes in the brain are likely to be a contributing factor. However, the neural mechanisms underlying these changes are not known. The aim of the current study was to use transcranial magnetic stimulation combined with electroencephalography (TMS-EEG) to investigate age-related changes in cortical excitability with muscle fatigue. ⋯ For TMS-EEG, the amplitude of the P30 and P180 potentials were unaffected by fatigue in older participants (P > 0.05). In contrast, the amplitude of the N45 potential in older adults was significantly reduced both during (positive cluster: mean voltage difference = 0.7 µV, P < 0.005; negative cluster: mean voltage difference = 0.9 µV, P < 0.0005) and after (mean voltage difference = 0.5 µV, P < 0.005) fatiguing exercise, whereas this response was absent in young participants. These results suggest that performance of maximal intermittent isometric exercise in old but not young adults is associated with modulation of cortical inhibition likely mediated by activation of gamma-aminobutyric acid type A receptors.