Neuroscience
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Few minutes of focal vibration (FV) on limb muscles can improve motor control in neurological (stroke, Parkinson) patients for unknown underlying neurophysiological mechanisms. Here we hypothesized that in healthy volunteers this FV would increase excitability in the primary sensorimotor cortex (S1-M1) during an isometric contraction of the stimulated muscle. The design included an initial control condition with no FV stimulation (Baseline) as well as three short experimental sessions of FV and a Sham (fake) session in a pseudo-random order. ⋯ Results showed that, compared to the Baseline (no FV) or Sham stimulation, the first two FV sessions showed a cumulative increase in alpha (but not beta) MRPD at C3 electrode, suggesting a specific effect of vibration on the excitability of contralateral S1-M1 generating EEG "mu" rhythms. FV over limb muscles modulates neurophysiological oscillations enhancing excitability of contralateral S1-M1 in healthy volunteers. The proposed mechanism may explain the clinical effects of vibratory rehabilitation in neurological patients with motor deficits.
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Phonological facilitation (PF) refers to a reduction of naming latencies when a phonologically related word is presented concurrently with the target picture, as compared to the presentation of phonologically unrelated words. According to spread of activation models of word production, this effect arises after lexical selection, during phonetic encoding, and is due to the co-activation of the phonemes shared by the target word and the distracter. Conversely, semantic interference (SI) is characterized by longer naming latencies when semantically related distracters are concurrently presented with the target picture. ⋯ In two experiments, we applied anodal transcranial direct current stimulation (tDCS) over the left superior temporal gyrus (LSTG) and left inferior frontal gyrus (LIFG) before a picture-word interference task in which auditory distracters, which could be phonologically related or unrelated, were presented at a SOA of 150ms or 300ms. While stimulating the LSTG significantly reduced the PF by decreasing RTs in phonologically unrelated trials, anodal tDCS over the LIFG did not affect PF. In line with previous results, our findings support the "activation by competition" model, pointing to inhibition between target and distracters nodes as the mechanism involved in the occurrence of PF and SI.
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Fyn is a non-receptor protein tyrosine kinase that belongs to Src family kinases. Fyn plays a critical role in neuronal migration, but the mechanism remains unclear. ⋯ Moreover, Fyn inhibition increased the length of leading process and decreased the branching number of the migrating cortical neurons. Together, these results indicate that Fyn controls neuronal migration by regulating the cytoskeletal dynamics and multipolar-bipolar transition of newly generated neurons during cortical development.
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Neonatal brain injury is a problem of global importance. To date, no causal therapies are available. A substance with considerable therapeutic potential is the endogenous neuropeptide secretoneurin (SN), which has proven to be beneficial in adult stroke. ⋯ SN has neuroprotective potential in neonatal brain injury. Its main action seems to be inhibition of apoptosis in the aftermath of the insult, predominantly in the hypoxic-only hemisphere. This might be explained by the less pronounced injury in this hemisphere, where blood flow and thus nutrient supply are maintained.
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The present experiments investigated the involvement of N-methyl-d-aspartate (NMDA) receptors of the dorsolateral striatum (DLS) in consolidation of extinction in a habit memory task. Adult male Long-Evans rats were initially trained in a food-reinforced response learning version of a plus-maze task and were subsequently given extinction training in which the food was removed from the maze. In experiment 1, immediately after the first day of extinction training, rats received bilateral intra-DLS injections of the NMDA receptor antagonist 2-amino-5-phosphonopentanoic acid (AP5; 2µg/side) or physiological saline. ⋯ In contrast, post-training intra-DLS infusions of DCS (20µg) enhanced extinction. Intra-DLS administration of AP5 or DCS given two hours after extinction training did not influence extinction of response learning, indicating that immediate post-training administration of AP5 and DCS specifically influenced consolidation of the extinction memory. The present results indicate a critical role for DLS NMDA receptors in modulating extinction of habit memory and may be relevant to developing therapeutic approaches to combat the maladaptive habits observed in human psychopathologies in which DLS-dependent memory has been implicated (e.g. drug addiction and relapse and obsessive compulsive disorder).