Neuroscience
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Meta Analysis
The human vestibular cortex revealed by coordinate-based activation likelihood estimation meta-analysis.
The vestibular system contributes to the control of posture and eye movements and is also involved in various cognitive functions including spatial navigation and memory. These functions are subtended by projections to a vestibular cortex, whose exact location in the human brain is still a matter of debate (Lopez and Blanke, 2011). The vestibular cortex can be defined as the network of all cortical areas receiving inputs from the vestibular system, including areas where vestibular signals influence the processing of other sensory (e.g. somatosensory and visual) and motor signals. ⋯ The only area of convergence between all three methods of stimulation was located in Ri. The data indicate that Ri, parietal operculum and posterior insula are vestibular regions where afferents converge from otoliths and semicircular canals, and may thus be involved in the processing of signals informing about body rotations, translations and tilts. Results from the meta-analysis are in agreement with electrophysiological recordings in monkeys showing main vestibular projections in the transitional zone between Ri, the insular granular field (Ig), and SII.
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Postsynaptic densities (PSDs) are responsible for organizing receptors and signaling proteins that regulate excitatory transmission in the mammalian brain. To better understand the assembly and 3D organization of this synaptic structure, we employed electron cryotomography to visualize general and fine structural details of PSDs isolated from P2, P14, P21 and adult forebrain in the absence of fixatives and stains. PSDs at P2 are a loose mesh of filamentous and globular proteins and during development additional protein complexes are recruited onto the mesh. ⋯ One striking morphological feature is the appearance of lipid raft-like structures, first evident in PSDs from 14 day old animals. These detergent-resistant membranes stain for GM1 ganglioside and their terminations can be clearly seen embedded in protein "bowls" within the PSD complex. In total, these results lead to the conclusion that the PSD is assembled by the gradual recruitment and stabilization of proteins within an initial mesh that systematically adds complexity to the structure.
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Brain-derived neurotrophic factor (BDNF) plays important roles in the development, maintenance, and plasticity of the mammalian forebrain. These functions include regulation of neuronal maturation and survival, axonal and dendritic arborization, synaptic efficacy, and modulation of complex behaviors including depression and spatial learning. Although analysis of mutant mice has helped establish essential developmental functions for BDNF, its requirement in the adult is less well documented. ⋯ To identify an anatomical correlate of the abnormal behavior, we quantified dendritic spines in cortical neurons. The spine density of CaMK-BDNF(KO) mice was normal at P35, but by P84, there was a 30% reduction in spine density. The strong similarities we find between early- and late-onset BDNF knockouts suggest that BDNF signaling is required continuously in the CNS for the maintenance of some forebrain circuitry also affected by developmental BDNF depletion.
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Neonatal treatment of rat pups with clomipramine (CLI) has been shown to cause long-lasting and persistent depression-related behaviors and changes in sleep architecture and in brain-derived neurotrophic factor (BDNF) signaling in adult animals, producing an animal model of depression. However, the molecular mechanisms which mediate these effects of early-life CLI treatment on adult animals remain largely unknown. In order to characterize these further, we investigated in neonatally CLI-treated rats the sleep architecture as well as the extracellular and cellular levels of sleep regulators (nitric oxide, adenosine) and BDNF, respectively, in the basal forebrain (BF), i.e. the brain area which is implicated in sleep and depression. ⋯ At the molecular level, the normal homeostatic response was dissociated: the rise in the adenosine level was not accompanied by a rise in the nitric oxide concentration. Moreover, while BF BDNF levels decreased during SD in control rats, such a decline was not observed in CLI rats. Taken together, neonatal CLI treatment produces long-lasting functional changes in the sleep architecture and sleep regulation in adult rats, accompanied by dysregulated BDNF signaling in the BF.
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Vision (V) and touch (T) help stabilize our standing body, but little is known on the time-interval necessary for the brain to process the sensory inflow (or its removal) and exploit the new information (or counteract its removal). We have estimated the latency of onset and the time-course of the changes in postural control mode following addition or withdrawal of sensory information and the effect of anticipation thereof. Ten subjects stood in tandem position. ⋯ Changes in postural behavior require a finite amount of time from visual or haptic shift, much longer than reflexes or rapid voluntary responses, suggesting a time-consuming central integration process. This process is longer on addition than removal of haptic information, indicating a heavier computational load. These findings should be taken into account when considering problems of sensorimotor integration in elderly subjects or patients and when designing simulation models of human balance.