Neuroscience
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The mammalian main olfactory epithelium (MOE) is exposed to a wide spectrum of external chemicals during respiration and relies on adaptive plasticity to maintain its structural and functional integrity. We previously reported that the chemo-responsive and cholinergic transient receptor potential channel M5 (TRPM5)-expressing-microvillous cells (MCs) in the MOE are required for maintaining odor-evoked electrophysiological responses and olfactory-guided behavior during two-week exposure to an inhaled chemical mixture. Here, we investigated the underlying factors by assessing the potential modulatory effects of TRPM5-MCs on MOE morphology and cell proliferation and apoptosis, which are important for MOE maintenance. ⋯ In addition, a greater number of isolated OSNs from chemical-exposed Skn-1a-/- mice displayed unhealthily high levels of resting intracellular Ca2+. Intriguingly, in the anterior MOE where we found a higher density of TRPM5-MCs, chemical-exposed TRPM5-GFP mice exhibited a time-dependent increase in apoptosis and a loss of mature OSNs without a significant increase in proliferation or neurogenesis to compensate for OSN loss. Together, our data suggest that TRPM5-MC-dependent region-specific upregulation of cell proliferation in the majority of the MOE during chemical exposure contributes to the adaptive maintenance of OSNs and olfactory function.
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Bisphenol-A (BPA) exposure can affect cognitive functions of rodents and humans. However, whether information inputs for these functions in the brain are perturbed by BPA remains unclear. Here, visual perception in rats was assessed by testing their ability to discriminate between vertical and horizontal grating. ⋯ However, BPA-exposed rat pups exhibited a significant decrease in IL-1β expression in the V1, accompanied by a decline in P38 phosphorylation. After local injection of IL-1β (10 ng/ml) in the V1, these two visual properties recovered to normal levels. Thus, our findings imply that physiological dysfunction of IL-1β may contribute to orientation perception deficits in BPA-exposed rats.
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Our choices are often informed by temporally integrating streams of sensory information. This has been well demonstrated in the visual and auditory domains, but the integration of tactile information over time has been less studied. We designed an active touch task in which participants explored a spheroid-shaped object to determine its inclination with respect to the horizontal plane (inclined to the left or the right). ⋯ The behavioral results were fit with a bounded accumulation model and an independent sampling model that assumes no sensory accumulation. The results of model fits favor an accumulation-to-bound mechanism and suggest that participants integrate the first 600 ms of 1800 ms-long stimuli. This means that the somatosensory system benefits from longer streams of information, although it does not make use of all available evidence.
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Timing of Modulation of Corticospinal Excitability by Heartbeat Differs with Interoceptive Accuracy.
Interoceptive inputs are ascending information from the internal body. Cortical activities have been shown to be elicited by interoceptive inputs from the heartbeat at approximately 200-600 ms after the R wave, and sensory processing is modulated by the heartbeat within the time window. However, the influence of interoceptive inputs and their timing on corticospinal excitability has not yet been fully elucidated. ⋯ Conversely, we found a significant negative correlation between the modulation of corticospinal excitability at 400 ms after the R wave and interoceptive accuracy. These results indicated that the corticospinal excitability was modulated at 200-400 ms after the R wave (systolic phase) and that the timing of excitatory or inhibitory states in the corticospinal pathway differed with interoceptive accuracy. Although the neural mechanism remains unclear, these findings may aid in determining new factors influencing corticospinal excitability.
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Wallerian degeneration (WD) and axon regeneration generally take place following peripheral nerve injury (PNI). Schwann cells (SCs) and macrophages play major role in WD. SCs, acting as repair cells and primary signal mediators, dedifferentiate and proliferate to remove the debris, form Büngner's bands and secrete trophic factors during these processes. ⋯ Mechanism studies revealed that PKCα functioned through activating the ERK signaling pathway. Furthermore, PKCα also exhibited a neuroprotective role by upregulating the expression of neurotrophic factors in SCs. To sum up, this study offers novel insights for clarifying our understanding of the involvement of PKCα in the mechanism of peripheral nerve degeneration as well as regeneration.