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Brain Motor Centers and Pathways
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
The negative feedback via the indirect and the hyperdirect pathways hinders movement and could be used to terminate movement or prevent particular movements. It is believed that the indirect pathway normally predominates, but an increase in dopamine levels in the dorsal striatum, which occurs just before the onset of movement, shifts the balance in favor of the direct pathway. In addition, there are many feedback connections between the nuclei of the basal ganglia themselves, only some of which are shown in Figure 12.6.
The effects of Alzheimer's disease related striatal pathologic changes on the fractional amplitude of low-frequency fluctuations
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2020
Dopamine has a dual action on MSNs; it inhibits the (D2-type) MSNs in the indirect pathway and excites (D1-type) MSNs in the direct pathway. Therefore, depending on D1 or D2 type dopamine receptors inclusion, MSNs population is split in two population of roughly equal size. These receptors have different effects on both intrinsic and synaptic ion channels, (Humphries et al. 2009). Dopaminergic modulation of intrinsic ion channels in D1 MSNs is given by where is for simulating the hyperpolarizing effect of D1 activation. ϕ1 is the parameter for specifying the level of dopamine receptor for D1. For D2 MSNs, dopaminergic modulation of intrinsic ion channels is given as
Vestibulo-ocular reflex characteristics during unidirectional translational whole-body vibration without head restriction
Published in Ergonomics, 2020
Tomoko Sugawara, Hiroyuki Sakai, Yutaka Hirata
However, detailed analysis indicates that our data regarding transmissibility characteristics are not necessarily consistent with previous reports. In particular, to our knowledge, no other study has shown bimodal transmissibility of vibration to the head. According to a review paper on body vibration transmissibility (Paddan and Griffin 1998c), when the trunk of the body is tightly fixed to a motion base by a four-point racing harness, the high frequency components of head vibration tend to increase, suggesting that body vibration transmissibility is sensitive to the experimental setup. In the current study, two vibration transduction pathways to the head were assumed: one was an indirect pathway from the motion base via the trunk; the other was a more direct pathway from the headrest, on which they had been instructed to put their heads. The existence of two transduction pathways for vibration might explain the bimodal body-vibration transmissibility that we observed.
Heterogeneous Catalytic Ozonation of Aqueous p-nitrophenol over MIL-100(Fe) Metal–Organic Framework
Published in Ozone: Science & Engineering, 2022
Tien Khoa Le, Quoc Vuong Ca, Luu Chuong Nguyen, Thanh Son Cu, Ha Tran Nguyen, Quoc-Thiet Nguyen, Thi Thanh Thuy Nguyen
In ozonation processes, ozone can react via two possible reaction pathways: the direct pathway, which involves the reaction between molecular ozone and dissolved solutes, or the indirect pathway, which involves the reaction between dissolved compounds and highly reactive hydroxyl radicals arising from ozone decomposition (Hoigné and Bader 1976). The direct pathway usually occurs under acidic conditions, whereas the indirect pathway is favorable under basic conditions (Singer and Gurol 1983).