Brain structure & function
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To date, hampered physiological function after exposure to microgravity has been primarily attributed to deprived peripheral neuro-sensory systems. For the first time, this study elucidates alterations in human brain function after long-duration spaceflight. ⋯ In addition, the cosmonaut showed changes in the supplementary motor areas during a motor imagery task. These results highlight the underlying neural basis for the observed physiological deconditioning due to spaceflight and are relevant for future interplanetary missions and vestibular patients.
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Navigated transcranial magnetic stimulation (nTMS) gains increasing importance in presurgical language mapping. Although bipolar direct cortical stimulation (DCS) is regarded as the gold standard for intraoperative mapping of language-related areas, it cannot be used to map the healthy human brain due to its invasive character. Therefore, the present study employed a non-invasive virtual-lesion modality to provide a causality-confirmed cortical language map of the healthy human brain by repetitive nTMS (rTMS) with functional specifications beyond language-positive/language-negative distinction. ⋯ Within females, 10,238 stimulation trains elicited 2032 language errors (19.8 %). PCA revealed that the inferior parietal lobe (IPL) and middle frontal gyrus (MFG) were causally involved in object naming as a semantic center and an executive control center. For the first time, this study provides causality-based data and a model that approximates the distribution of language-related cortical areas grouped for different functional aspects of single-word production processes by PCA.
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In utero exposure of rats to nicotine (NIC) provides a useful animal model for studying the impact of smoking during pregnancy on human offspring. Certain sequelae of prenatal NIC exposure suggest an impact on the development of the midbrain dopamine (DA) system, which receives a robust cholinergic innervation from the mesopontine tegmentum. We therefore investigated whether prenatal NIC induced structural changes in cells and synapses within the midbrain that persisted into adulthood. ⋯ Within the ventral tegmental area, electron microscopic physical disector analysis showed no significant differences in the number of axon terminals or the number of asymmetric (putative excitatory) or symmetric (putative inhibitory) synapses. Although too infrequent to estimate by unbiased stereology, no obvious difference in the proportion of cholinergic axons was noted in NIC- versus VEH-treated animals. These data suggest that activation of nicotinic receptors during prenatal development induces no significant modifications in the structure of cells in the ventral midbrain when assessed in adulthood.
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Using immunohistochemical techniques, we characterized changes in the expression of several neurochemical markers in lumbar 4-sacral 2 (L4-S2) dorsal root ganglion (DRG) neuron profiles (NPs) and the spinal cord of BALB/c mice after axotomy of the L6 and S1 spinal nerves, major tributaries of the pelvic (targeting pelvic visceral organs) and pudendal (targeting perineum and genitalia) nerves. Sham animals were included. Expression of cyclic AMP-dependent transcription factor 3 (ATF3), calcitonin gene-related peptide (CGRP), transient receptor potential cation channel subfamily V, member 1 (TRPV1), tyrosine hydroxylase (TH) and vesicular glutamate transporters (VGLUT) types 1 and -2 was analysed seven days after injury. ⋯ Finally, a moderate decrease in CGRP- and TRPV1-like-immunoreactivities was observed in the ipsilateral superficial dorsal horn neuropil. In conclusion, injury of a mixed visceral/non-visceral nerve leads to considerable neurochemical alterations in DRGs matched, to some extent, in the spinal cord. Changes in these and potentially other nociception-related molecules could contribute to pain due to injury of nerves in the abdominopelvic cavity.
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The present study investigated the projections of the gigantocellular reticular nucleus (Gi) and its neighbors--the dorsal paragigantocellular reticular nucleus (DPGi), the alpha/ventral part of the gigantocellular reticular nucleus (GiA/V), and the lateral paragigantocellular reticular nucleus (LPGi)--to the mouse spinal cord by injecting the anterograde tracer biotinylated dextran amine (BDA) into the Gi, DPGi, GiA/GiV, and LPGi. The Gi projected to the entire spinal cord bilaterally with an ipsilateral predominance. Its fibers traveled in both the ventral and lateral funiculi with a greater presence in the ventral funiculus. ⋯ Their terminals were present in the ventral horn with a large portion of them terminating in the motor neuron columns. The present study is the first demonstration of the termination pattern of fibers arising from the Gi, DPGi, GiA/GiV, and LPGi in the mouse spinal cord. It provides an anatomical foundation for those who are conducting spinal cord injury and locomotion related research.