Neuroscience
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Comparative Study
Categorical perception of lexical tones in Chinese revealed by mismatch negativity.
The present study investigated the neurophysiological correlates of categorical perception of Chinese lexical tones in Mandarin Chinese. Relative to standard stimuli, both within- and across-category deviants elicited mismatch negativity (MMN) in bilateral frontal-central recording sites. The MMN elicited in the right sites was marginally larger than in the left sites, which reflects the role of the right hemisphere in acoustic processing. ⋯ These results provide strong neurophysiological evidence in support of categorical perception of lexical tones in Chinese. More important, they demonstrate that acoustic and phonological information is processed in parallel within the MMN time window for the perception of lexical tones. Finally, homologous nonspeech stimuli elicited similar MMN patterns, indicating that lexical tone knowledge influences the perception of nonspeech signals.
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Comparative Study
Sustained sleep fragmentation results in delayed changes in hippocampal-dependent cognitive function associated with reduced dentate gyrus neurogenesis.
Sleep fragmentation (SF) is prevalent in human sleep-related disorders. In rats, sustained SF has a potent suppressive effect on adult hippocampal dentate gyrus (DG) neurogenesis. Adult-generated DG neurons progressively mature over several weeks, and participate in certain hippocampal-dependent cognitive functions. ⋯ The use of random search strategies was negatively correlated with NREM sleep bout length during SF. Sustained sleep fragmentation reduced DG neurogenesis and induced use of a non-spatial search strategy, which could be seen 2 weeks after terminating the SF treatment. The reduction in neurogenesis induced by sleep fragmentation is likely to underlie the delayed changes in cognitive function.
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Comparative Study
Estrogen receptor α and G-protein coupled receptor 30 mediate the neuroprotective effects of 17β-estradiol in novel murine hippocampal cell models.
The hippocampus is a multifaceted, complex brain structure considered to be the learning center. The use of primary hippocampal cell cultures has uncovered important cellular mechanisms involved in overall physiological function. Yet, the use of primary culture is inherently difficult, and the lack of immortalized cell lines from the murine hippocampus for mechanistic studies at the molecular level is evident. ⋯ Pretreatment with the GPR30 agonist G-1 (10 and 100 nM) for 1 h, but not 24 h, significantly attenuated cell death in both mHippoE-14 and mHippoE-18 cells. The use of specific ER antagonist ICI 182780 and GPR30 antagonist G-15 linked these effects to both ER and GPR30 receptors. This is the first evidence that GPR30 may play a role in the protective effects of estrogen in hippocampal neurons.
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Comparative Study
Quinolinate induces selective loss of melanin-concentrating hormone neurons, rather than orexin neurons, in the hypothalamus of mice and young rats.
Orexins are neuropeptides produced in the lateral hypothalamus and implicated in regulation of sleep-wake cycle. Selective loss of orexin neurons is found in the brain of patients with narcolepsy, but the mechanisms of this pathological change are unclear. A previous study showed that excessive stimulation of N-methyl-d-aspartate (NMDA) receptors by quinolinic acid (QA) caused selective loss of orexin neurons in rat hypothalamic slice culture. ⋯ A significant decrease in the number of orexin neurons was induced when QA injection was performed in the dark phase of diurnal cycle, but the degree of the decrease was still lower than that in the number of MCH neurons. Finally, QA (60 nmol) induced selective loss of MCH neurons also in young rats at 3-4 weeks of age. These results do not support the hypothesis that acute excitotoxicity mediated by NMDA receptors is responsible for the pathogenesis of narcolepsy.
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Randomized Controlled Trial Comparative Study
What does autonomic arousal tell us about locomotor learning?
Walking onto a stationary sled previously experienced as moving induces locomotor aftereffects (LAE, or "broken escalator phenomenon"). This particular form of aftereffect can develop after a single adaptation trial and occurs despite subjects being fully aware that the sled will not move. Here, we investigate whether such strong LAE expression may relate to arousal or fear related to instability during the gait adaptation process. ⋯ Hence, gait velocity and trunk sway components of the LAE are differentially related to kinematic and autonomic parameters during the early and late adaptation phase. The finding that EDA is a predictor of LAE expression indicates that autonomic arousal or fear-based mechanisms can promote locomotor learning. This could in turn explain some unusual characteristics of this LAE, namely its resistance to explicit knowledge and its generation with just a single adaptation trial.