The Neuroscientist : a review journal bringing neurobiology, neurology and psychiatry
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The adult cerebral cortex possesses the remarkable ability to change its neuronal connectivity through experience, a phenomenon termed "synaptic plasticity." Synaptic plasticity constitutes a cellular mechanism that is thought to underlie information storage and memory formation in the brain, and represents a use-dependent long-lasting increase or decrease in synaptic strength. Recent findings, that the adult visual cortex undergoes dynamic synaptic plasticity that is driven by active visual experience, suggest that it may be involved in information processing that could contribute to memory formation. ⋯ An understanding of how visual cortical neurons respond with synaptic plasticity to visual experience, and whether these responses influence the induction of hippocampal plasticity, is fundamental to our understanding of the neuronal mechanisms and functional consequences of visuospatial information processing. In this review, we summarize recent findings with regard to the expression of dynamic synaptic plasticity in the visual cortex and how this plasticity may influence information processing in the hippocampus.
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This article presents evidence that fibromyalgia patients have alterations in CNS anatomy, physiology, and chemistry that potentially contribute to the symptoms experienced by these patients. There is substantial psychophysical evidence that fibromyalgia patients perceive pain and other noxious stimuli differently than healthy individuals and that normal pain modulatory systems, such as diffuse noxious inhibitory control mechanisms, are compromised in fibromyalgia. Furthermore, functional brain imaging studies revealing enhanced pain-related activations corroborate the patients' reports of increased pain. ⋯ The cerebral alterations offer a compelling explanation for the multiple symptoms of fibromyalgia, including widespread pain and affective disturbances. The frequent comorbidity of fibromyalgia with stress-related disorders, such as chronic fatigue, posttraumatic stress disorder, irritable bowel syndrome, and depression, as well as the similarity of many CNS abnormalities, suggests at least a partial common substrate for these disorders. Despite the numerous cerebral alterations, fibromyalgia might not be a primary disorder of the brain but may be a consequence of early life stress or prolonged or severe stress, affecting brain modulatory circuitry of pain and emotions in genetically susceptible individuals.
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Magnetoencephalography (MEG) is a noninvasive neuroimaging method for detecting, analyzing, and interpreting the magnetic field generated by the electrical activity in the brain. Modern hardware can capture the MEG signal at hundreds of points around the head in a snapshot lasting only a fraction of a millisecond. The sensitivity of modern hardware is high enough to permit the extraction of a clean signal generated by the brain well above the noise level of the MEG hardware. ⋯ A number of recent studies have scrutinized brain function in the new spatiotemporal window that real-time tomographic analysis of MEG signals has opened. The results have allowed the variability in a single area to be seen in the context of activity in other areas and background rhythmic activity. In this view, normal brain function is seen as a cascade of extremely fast events and the unfolding of specialized processes, segregated in space and time and organized into well-defined stages of processing.
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During the development of the nervous system, neurons must first migrate to their appropriate locations and then send out axons to make connections. Various environmental cues guide these migrating neurons and growing axons. After axons reach their target regions, neuronal contacts are created through the formation of synapses. ⋯ Here, we discuss semaphorins and plexins, the largest family of axon guidance ligand-receptor pairs. Because the roles of semaphorins in neuronal migration and axonal repulsion have been extensively reviewed, we will focus on plexin receptors. We will discuss how semaphorin signals are specifically passed through these receptors into cells and how plexins mediate their newly identified roles in axon pruning and synaptic development.
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What does the visual cortex of the blind do during Braille reading? This process involves converting simple tactile information into meaningful patterns that have lexical and semantic properties. The perceptual processing of Braille might be mediated by the somatosensory system, whereas visual letter identity is accomplished within the visual system in sighted people. Recent advances in functional neuroimaging techniques, such as functional magnetic resonance imaging, have enabled exploration of the neural substrates of Braille reading. The primary visual cortex of early-onset blind subjects is functionally relevant to Braille reading, suggesting that the brain shows remarkable plasticity that potentially permits the additional processing of tactile information in the visual cortical areas.