Neuroscience
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Thrombospondins (TSPs) are cell adhesion molecules that play an important role in the maintenance of hearing and afferent synaptic connections. Based on their reported function in restoring synaptic connections after stroke, we tested a potential role for TSP1 and TSP2 genes in repairing cochlear synapses following noise injury. We observed a tonotopic gradient in the expression of TSP1 and TSP2 mRNA in control mouse cochleae and an upregulation of these genes following noise exposure. ⋯ Noise trauma affecting mid to high frequencies triggered severe seizures in the TSP2-/- mice. We found that decreased susceptibility to audiogenic seizures in TSP1-/- mice was correlated with increased TSP2 protein levels in their inner ears, suggesting that TSP2 might functionally compensate for the loss of TSP1 in these mice. Our data indicate that TSP1 and TSP2 are both involved in susceptibility to NIHL, with TSP2 playing a more prominent role.
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It is commonly recognized that physical exercise positively affects several CNS regions and improves cognitive abilities. For example, exercise is associated with an increase in neurogenesis and facilitation of long-term potentiation in the hippocampus. Conversely, animal models for depression are associated with a decrease in neurogenesis and a reduction of long-term potentiation in the hippocampus. ⋯ Unexpectedly, in dexamethasone-exposed animals, dentate gyrus long-term potentiation was facilitated, whereas long-term potentiation in CA1 was unaffected by prenatal dexamethasone or by 10 or 21 days of voluntary running. Irrespective of age, prenatal dexamethasone and running had limited effects on synaptic transmission and presynaptic release in CA1 and dentate gyrus. In summary, running facilitates dentate gyrus long-term potentiation in adult animals that resembles the effects of prenatal dexamethasone.
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Following spinal cord trauma, axonal regeneration in the mammalian spinal cord does not occur and functional recovery may be further impeded by retrograde neuronal death. By contrast, lampreys recover after spinal cord injury (SCI) and axons re-connected to their targets in spinal cord. However, the identified reticulospinal (RS) neurons located in the lamprey brain differ in their regenerative capacities - some are good regenerators, and others are bad regenerators - despite the fact that they have analogous projection pathways. ⋯ Here we report that, after SCI, expression of RGMa mRNA was upregulated around the transection site, while its receptor Neogenin continued to be synthesized almost inclusively in the "bad-regenerating" RS neurons. Inhibition of Neogenin by MO prohibited activation of caspases and improved the survival of RS neurons at 10 weeks after SCI. These data provide new evidence in vivo that Neogenin is involved in retrograde neuronal death and failure of axonal regeneration after SCI.
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Spatial orientation necessitates the integration of visual and vestibular sensory cues, in-turn facilitating self-motion perception. However, the neural mechanisms underpinning sensory integration remain unknown. Recently we have illustrated that spatial orientation and vestibular thresholds are influenced by interhemispheric asymmetries associated with the posterior parietal cortices (PPC) that predominantly house the vestibulo-cortical network. ⋯ We observed that right-handed individuals experienced illusionary self-motion (vection) quicker than left-handers and that the degree of vestibular cortical dominance was correlated with the time taken to experience vection, only during conditions that induced interhemispheric conflict. To conclude, we demonstrate that interhemispheric asymmetries associated with vestibulo-cortical processing in the PPC functionally and mechanistically link sensory integration and self-motion perception, facilitating spatial orientation. Our findings highlight the importance of dynamic interhemispheric competition upon control of vestibular behavior in humans.
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Trait anxiety, the disposition to experience anxiety, is known to facilitate perception of threats. Trait anxious individuals seem to identify threatening stimuli such as fearful facial expressions more accurately, especially when presented under temporal constraints. In past studies on anxiety and emotion face recognition, only self-report or explicit measures of anxiety have been administered. ⋯ Activation of the caudate nucleus seems be of particular importance for recognizing fear and happiness from facial expressions. Processes of somatosensory resonance appear to be involved in identifying fear from facial expressions. The present data indicate that, regardless of assessment method, trait anxiety does not affect the recognition of fear or other emotions as has been proposed previously.