Neuroscience
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Comparative Study
The effect of sex and handedness on white matter anisotropy: a diffusion tensor magnetic resonance imaging study.
Diffusion tensor magnetic resonance imaging provides a way of assessing the asymmetry of white matter (WM) connectivity, the degree of anisotropic diffusion within a given voxel being a marker of coherently bundled myelinated fibers. Voxel-based statistical analysis was performed on fractional anisotropy (FA) images of 42 right- and 40 left-handers, to assess differences in underlying WM anisotropy and FA asymmetry across the whole brain. Right-handers show greater anisotropy than left-handers in the uncinate fasciculus (UF) within the limbic lobe, and WM underlying prefrontal cortex, medial and inferior frontal gyri. ⋯ Leftward (left-greater-than-right) anisotropy is found in regions of the arcuate fasciculus (AF), UF, and WM underlying pars triangularis in both handedness groups, with right-handers alone showing additional leftward FA asymmetry along the length of the superior temporal gyrus. Overall results indicate that although both handedness groups show anisotropy in similar WM regions, greater anisotropy is observed in right-handers compared with left-handers. The largest differences in FA asymmetry are found between males and females, suggesting a greater effect of sex than handedness on FA asymmetry.
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Early-life stress has been shown to increase susceptibility to anxiety and substance abuse. Disrupted activity within the anterior insular cortex (AIC) has been shown to play a role in both of these disorders. Altered serotonergic processing is implicated in controlling the activity levels of the associated cognitive networks. ⋯ Our data indicate that chronic alcohol consumption leads to greater AIC activity and may indicate a compensatory upregulation of presynaptic 5-HT(1A) receptors. Our results also indicate that AIC activity may be less effectively regulated by 5-HT in ethanol-naive NR animals than in NR monkeys in response to chronic ethanol self-administration. These data suggest possible mechanisms for increased alcohol seeking and possible addiction potential among young adults who had previously experienced early-life stress that include disruptions in both AIC activity and serotonin system dynamics.
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Cardiorespiratory control neurons in the brainstem nucleus tractus solitarius (NTS) undergo dramatic expansion of dendritic arbors during the early postnatal period, when functional remodeling takes place within the NTS circuitry. However, the underlying molecular mechanisms of morphological maturation of NTS neurons are largely unknown. Our previous studies point to the neurotrophin brain-derived neurotrophic factor (BDNF), which is abundantly expressed by NTS-projecting primary sensory neurons, as a candidate mediator of NTS dendritogenesis. ⋯ Moreover, previously documented dramatic increases in NTS glial proliferation in victims of sudden infant death syndrome (SIDS) underscore the importance of our findings and the need to better understand the role of glia and their interactions with BDNF during NTS circuit maturation. Furthermore, while it has previously been demonstrated that the specific effects of BDNF on dendritic growth are context-dependent, the role of glia in this process is unknown. Thus, our data carry important implications for mechanisms of dendritogenesis likely beyond the NTS.
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Comparative Study
Differential maturation of the molecular clockwork in the olfactory bulb and suprachiasmatic nucleus of the rabbit.
Recent studies suggest that the main olfactory bulb (OB) represents a functional circadian pacemaker. In many altricial mammals, during pre-visual stages of development the olfactory system plays a vital role in their survival. One remarkable example is the European rabbit; the newborns are normally raised in a dark nursery burrow, and the lactating female briefly visits her young approximately once every 24 h. ⋯ We report for the first time that Per1, Cry1, and Bmal1 are expressed in the OB of newborn and juvenile rabbits. In addition, the diurnal pattern of clock gene expression develops earlier in the OB than in the SCN of newborn rabbits. Given the early maturation of the molecular clockwork and the biological relevance of this structure during development, it is possible that the OB plays an important role in temporal regulation during pre-visual life in rabbits.
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Human movements are quickly adjusted to variations of inertial load. However, this adjustment does not always imply a full compensation, so that kinematic movement characteristics vary. The present experiment served to explore the consequences of a complex dynamic transformation, implemented by a sliding first-order lever, on the endpoint distributions of goal-directed movements. ⋯ However, when the lever was used, the effect of the inertial anisotropy of the arm on movement amplitudes was reduced, accompanied by a longer movement time overall, in particular for movements with higher inertial load of the arm. These observations suggest an interaction of the use of internal models and impedance control in the presence of variable inertial loads. Most likely the influence of the dynamic transformation of the sliding lever is absorbed by increased joint impedance, which also reduces the influence of the inertial anisotropy of the arm which otherwise is (incompletely) compensated based on an internal model of the dynamic transformation of the arm.