Neuroscience
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Nodal-related protein, Ndr2, and transcription factors such as Lmx1b, Otp, Nurr1 and Pitx3 are very important in the differentiation, function and maintenance of mesodiencephalic dopaminergic neurons, and are necessary for the activation of tyrosine hydroxylase (TH) and dopamine (DA) transporter expression. Hence, the aim of the present work was to evaluate the effects of cocaine on the expression of genes related to the embryogenesis development of the dopaminergic system. Zebrafish embryos were exposed to cocaine hydrochloride at 5h post-fertilization (hpf), and collected at two important stages - 24 and 48hpf - to study the effects of cocaine on the expression of ndr2, the lmx1b.1, lmx1b.2, otpa, otpb, nurr1 transcription factors, and their target genes: TH and DA transporter expression. ⋯ We also show the importance of Lmx1b and Otp in th expression through the knockdown of Lmx1b.1 and Lmx1b.2, and of Otpa and Otpb. Additionally, cocaine produced an increase and a decrease in TH levels at 24 and at 48hpf, respectively, possibly due to the change in the expression of the transcription factors and ndr2 expression. We conclude that cocaine alters the correct development of dopaminergic system affecting the expression of transcription factors, during the embryogenesis.
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Pretreatment with estrogen has been shown to increase subventricular zone (SVZ) neurogenesis and improve neurological outcome after cerebral ischemia reperfusion injury in mice. However, the potential of post-stroke estrogen administration to enhance neurogenesis is largely unknown. In this study, we explored whether post-stroke estradiol administration had any effect on SVZ neurogenesis in a rat model of permanent focal cerebral ischemia and elucidated the potential mechanism of its effects. ⋯ Post-stroke estradiol administration increased BrdU-labeled cells, nestin-positive cells, doublecortin (DCX)-positive cells and BrdU+/DCX+ cells in the ischemic ipsilateral SVZ at all time points (P<0.05). Treatment with estradiol also increased HIF-1α and VEGF protein levels in the ischemic ipsilateral SVZ at all time points examined (P<0.05). These findings indicate that post-stroke estradiol administration promotes SVZ neurogenesis in rats, probably by increasing HIF-1α and VEGF protein expression.
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This review aims to characterize fatigue-related changes in corticospinal excitability and inhibition in healthy subjects. Transcranial magnetic stimulation (TMS) has been extensively used in recent years to investigate modifications within the brain during and after fatiguing exercise. Single-pulse TMS reveals reduction in motor-evoked potentials (MEP) when measured in relaxed muscle following sustained fatiguing contractions. ⋯ This review examines the mechanical and EMG responses elicited by TMS (single- and paired-pulse) and cervicomedullary stimulation both during and after a fatiguing exercise. Particular attention is given to the muscle state and the type of fatiguing exercise when assessing and interpreting fatigue-induced changes in these parameters. Methodological concerns and future research interests are also considered.
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Randomized Controlled Trial
The neural substrate of the ideomotor principle revisited: evidence for asymmetries in action-effect learning.
Ideomotor theory holds that the perception or anticipatory imagination of action effects activates motor tendencies toward the action that is known to produce these effects, herein referred to as ideomotor response activation (IRA). IRA presupposes that the agent has previously learned which action produces which effects, and that this learning process has created bidirectional associations between the sensory effect codes and the motor codes producing the sensory effects. Here, we refer to this process as ideomotor learning. ⋯ We replicated earlier findings of a hand asymmetry in ideomotor processing with significantly stronger IRA by left-hand than right-hand action effects. Crucially, we traced this effect back to more pronounced associative learning for action-contingent effects of the left hand compared with effects of the right hand. In this context, our findings point to the caudate nucleus and the angular gyrus as central structures of the neural network underlying ideomotor learning.
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Diffusion tensor imaging (DTI) provides information regarding white matter microstructure; however, macroscopic fiber architectures can affect DTI measures. A larger brain (fiber tract) has a 'relatively' smaller voxel size, and the voxels are less likely to contain more than one fiber orientation and more likely to have higher fractional anisotropy (FA). Previous DTI studies report left-to-right differences in the white matter; however, these may reflect true microscopic differences or be caused purely by volume differences. ⋯ Voxel-wise analysis with adjustment for volume asymmetry revealed many white matter FA asymmetries, including leftward asymmetry of the arcuate fasciculus and cingulum. The voxel-wise analysis showed a reduced number of regions with significant FA asymmetry compared with analysis performed without adjustment for volume asymmetry; however, the overall trend of the results was unchanged. The results of the present study suggest that these FA asymmetries are not caused by volume differences and reflect microscopic differences in the white matter.