Neuroscience
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Central chemoreceptors are primarily sensitive to changes in CO2/H+, and such changes lead to intense breathing activity. Medullary raphe and retrotrapezoid nucleus (RTN) neurons are candidates for central chemoreceptors because they are unusually pH sensitive. The pathophysiology of Parkinson's disease (PD) is related to the reduction of neurons in the substantia nigra pars compacta (SNpc) that express dopamine, although other neurons can also be degenerated in this pathology. ⋯ In PD animals, we noticed a reduction in the number of RPa neurons that project to the RTN, without a change in the number of hypercapnia-activated (7% CO2) raphe neurons. The PD animals that received injection of the toxin saporin anti-SERT into the RPA/PPy region did not show a further reduction of respiratory frequency (fR) or ventilation (VE) at rest or during hypercapnia challenge. These experiments demonstrate that serotonergic neurons of RPa/PPy are not involved in the breathing responses induced by central chemoreceptor activation in a PD animal model.
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Malaria, parasitic disease considered a major health public problem, is caused by Plasmodium protozoan genus and transmitted by the bite of infected female Anopheles mosquito genus. Cerebral malaria (CM) is the most severe presentation of malaria, caused by P. falciparum and responsible for high mortality and enduring development of cognitive deficits which may persist even after cure and cessation of therapy. In the present study we evaluated selected behavioral, neurochemical and neuropathologic parameters after rescue from experimental cerebral malaria caused by P. berghei ANKA in C57BL/6 mice. ⋯ Interestingly, no changes in the neuropathological markers Fluoro-Jade C, Timm staining or IBA-1 were detected. Altogether, present data indicate that behavioral and neurochemical alterations persist even after parasitemia clearance and CM recovery, which agrees with available clinical findings. Some of the molecular mechanisms reported in the present study may underlie the behavioral changes and increased seizure susceptibility that persist after recovery from CM and may help in the future development of therapeutic strategies for CM sequelae.
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Previous studies proposed that selecting which hand to use for a reaching task appears to be modulated by a factor described as "task difficulty". However, what features of a task might contribute to greater or lesser "difficulty" in the context of hand selection decisions has yet to be determined. There has been evidence that biomechanical and kinematic factors such as movement smoothness and work can predict patterns of selection across the workspace, suggesting a role of predictive cost analysis in hand-selection. ⋯ Although the data are necessarily preliminary due to small sample size, our data suggested an influence of cognitive-perceptual load on hand selection, such that the dominant hand was selected more frequently as cognitive load increased. Interestingly, cognitive-perceptual loading also increased cross-midline reaches with both hands. Because crossing midline is more costly in terms of kinematic and kinetic factors, our findings suggest that cognitive processes are normally engaged to avoid costly actions, and that the choice not-to-cross midline requires cognitive resources.
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The CHAT gene encodes choline acetyltransferase, which is an enzyme responsible for the biosynthesis of the neurotransmitter acetylcholine in the brain. This study collected structural MRI, genetic, and behavioral data from 324 healthy Chinese adults, and examined the associations between CHAT genetic variants, parahippocampal and hippocampal structure, and short-term memory span. After controlling for intracranial volume, sex, and age, CHAT SNP rs12246528 had the strongest association with parahippocampal structure, with the A allele being linked to smaller volume, surface area, and thickness. ⋯ After controlling for sex and age, CHAT rs3729496 had the strongest association with memory span, with the T allele being associated with a greater memory span. Finally, the left parahippocampal gyrus surface area was positively associated with memory span. This study provides the first evidence for the involvement of the CHAT gene in parahippocampal and hippocampal structures and memory span in healthy Chinese adults.
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Many studies have described the dynamic modulation of corticospinal excitability of the prime movers during motor preparation. However although anticipatory postural adjustments (APA) are an inherent part of most voluntary movements, investigation of trunk muscle corticospinal excitability during motor preparation has been neglected in the literature. In the present study, the corticospinal excitability of the superficial multifidus (sMF) and rectus abdominis (RA) muscle has been assessed during the preparation of rapid arm flexions and extensions in fifteen participants. ⋯ During the Motor Execution period for arm extension, sMF displayed even more inhibition, along with a large and significant facilitation of RA. During the Motor execution period for arm flexion, sMF presented a trend toward larger motor-evoked potential amplitude compared to Delay period. These results suggest the existence of two concurrent mechanisms underlying motor preparation for APA: (i) before the Go signal, a nonspecific inhibitory mechanism for sMF, likely to preclude motor program release; (ii) after the Go signal, a task-specific modulation of corticospinal excitability consistent with the EMG pattern during the early phase of movement.