Neuroscience
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Survival depends on adaptation to shifting environmental risks and opportunities. Regarding risks, the mechanisms which permit acquisition, recall, and flexible use of aversive associations is poorly understood. Drawing on the evidence that the orbital frontal cortex is critical to integrating outcome expectancies with flexible appetitive behavioral responses, we hypothesized that OFC would contribute to behavioral flexibility within an aversive learning domain. ⋯ In a recall test, rats exhibit greater freezing to the CS+ than the CS-. Temporary inactivation of the ventrolateral OFC with muscimol prior to conditioning did not affect later discrimination, but inactivation after learning and prior to recall impaired discrimination between safety and danger cues. This result complements prior research in the appetitive domain and suggests that the OFC plays a general role in behavioral flexibility regardless of the valence of the CS.
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Slow-wave activity (SWA) in the electroencephalogram during slow-wave sleep (SWS) varies as a function of sleep-wake history. A putative sleep-active population of neuronal nitric oxide synthase (nNOS)-containing interneurons in the cerebral cortex, defined as such by the expression of Fos in animals euthanized after protracted deep sleep, may be a local regulator of SWA. We investigated whether electrophysiological responses to activation of these cells are consistent with their role of a local regulator of SWA. ⋯ Optogenetic stimulation of the cerebral cortex of animals expressing Channelrhodopsin2 in nNOS interneurons triggered an acute positive deflection of the local field potential that was followed by protracted oscillatory events only during quiet wake and slow wave sleep. The response during wake was maximal when the electroencephalogram (EEG) was in a negative polarization state and abolished when the EEG was in a positive polarization state. Since the polarization state of the EEG is a manifestation of slow-wave oscillations in the activity of underlying pyramidal neurons between the depolarized (LFP negative) and hyperpolarized (LFP positive) states, these data indicate that sleep-active cortical neurons expressing nNOS function in sleep slow-wave physiology.
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It has been shown that brain-injured patients (BIP) have exacerbated mirror movements (MM). MM are involuntary contractions occurring in homologous muscles contralateral to voluntary movements, particularly in distal upper limb muscles. Attentional and inhibitory processes have been proposed as key factors to explain the level of MM. ⋯ Moreover, (3) in all participants - independent of the type of task used to evaluate MM - the amount and intensity of MM was predicted by the level of executive control, assessed by the Trail Making Test. High level of MM was associated with weak executive control abilities. This study is the first to highlight the link between MM and executive functioning, which may have implications for rehabilitation in BIP.
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Emerging evidence indicates that transcriptome alterations due to epigenetic deregulation concur to ALS pathogenesis. Accordingly, pan-histone deacetylase (HDAC) inhibitors delay ALS development in mice, but these compounds failed when tested in ALS patients. Possibly, lack of selectivity toward specific classes of HDACs weakens the therapeutic effects of pan-HDAC inhibitors. ⋯ Conversely, increase in specific Class II HDACs (-4, -5 and -6) occurs in skeletal muscle of mice with severe neuromuscular impairment. Importantly, treatment with MC1568 causes early improvement of motor performances that vanishes at later stages of disease. Notably, motor improvement is not paralleled by reduced motor neuron degeneration but by increased skeletal muscle electrical potentials, reduced activation of mir206/FGFBP1-dependent muscle reinnervation signaling, and increased muscle expression of myogenic genes.
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Parkinson's disease (PD) is a neurodegenerative disorder caused by loss of dopaminergic neurons in the substantia nigra, leading to motor dysfunction. Growing evidence has demonstrated that endurance exercise (EE) confers neuroprotection against PD. However, the exact molecular mechanisms responsible for exercise-induced protection of dopaminergic neurons in PD remain unclear. ⋯ Our biochemical data showed that EE-induced neuroprotection occurs in combination with multiple synergic neuroprotective pathways: (1) increased neurogenesis shown by an increase in BrdU-positive neurons; (2) diminished loss of dopaminergic neurons evidenced by upregulated tyrosine hydroxylase (TH) and dopamine transporter (DAT) levels; (3) increased antioxidant capacity (e.g., CuZnSOD, CATALASE, GPX1/2, HO-1, DJ1 and PRXIII); and (4) enhanced autophagy (LC3 II, p62, BECLIN1, BNIP3, LAMP2, CATHEPSIN L and TFEB). Our study suggests that EE-induced multiple synergic protective pathways including enhanced neurogenesis, antioxidative capacity, and concordant autophagy promotion contribute to restoration of impaired dopaminergic neuronal function caused by PD. Thus, PD patients should be encouraged to actively participate in regular EE as a potent nonpharmacological therapeutic strategy against PD.