The corticospinal tract (CST) is the most important motor pathway in the human brain. Detailed knowledge of CST somatotopy is important in terms of rehabilitative management and invasive procedures for patients with brain injuries. In this study, I conducted a review of nine previous studies of the somatotopical location and arrangement at the brainstem in the human brain. The results of this review indicated that the hand and leg somatotopies of the CST are arranged medio-laterally in the mid to lateral portion of the cerebral peduncle, ventromedial-dorsolaterally in the pontine basis, and medio-laterally in the medullary pyramid. However, few diffusion tensor imaging (DTI) studies have been conducted on this topic, and only nine have been reported: midbrain (2 studies), pons (4 studies), and medulla (1 study). Therefore, further DTI studies should be conducted in order to expand the literature on this topic. In particular, research on midbrain and medulla should be encouraged.
Brain Stem/*anatomy & histology ; Diffusion Tensor Imaging ; Hand/innervation ; Humans ; Leg/innervation ; Medulla Oblongata/anatomy & histology ; Pons/anatomy & histology ; Pyramidal Tracts/*anatomy & histology/physiology ; Tegmentum Mesencephali/anatomy & histology

OBJECTIVETo observe the alterations of the auditory function and morphology of the ear in the mouse sialidosis models which has been generated by targeted deletion of lysosomal neuraminidase gene (Neul) and closely resembled the phenotypes in corresponding human conditions, and to explore pathophysiological mechanisms of hearing impairment.

METHODSNeul homozygous (Neul -/-) mice at 3 weeks, 2 and 4 months of age, and their wildtype littermates (Neu1 +/+) were examined for auditory thresholds through auditory brainstem responses (ABR) to click, 8, 16, and 32 kHz stimuli. Morphological analyses in ears were performed by series temporal bone section and light microscopy.

RESULTSNeul -/- mice at 3 weeks of age showed an elevated ABR threshold, 50-55 dB above those of Neul +/+ mice. Up to 2 and 4 months of age, their thresholds were further elevated for 60-68 dB. There were distinct pathological changes of middle and inner ear of 3 weeks of age in Neul -/- mice, especially at 2-4 months of age there were significant cerumen occlusion in the external auditory canal and severe otitis media. Vacuolation associated with lysosomal storage was observed within ossicles and cochlear bone cells, stria vascularis cells, spiral ganglion neurons and macrophages, spiral limbus, spiral prominence, Reissner's membrane cells, and the mesothelial cells of the perilymphatic scala and basilar membrane, but not within the organ of Corti. Vestibular ganglion neurons, hair cells and supporting cells in cristae and maculae also showed vacuolation.

CONCLUSIONSThe deficiency of lysosomal neuraminidase may result in a serious hearing loss and morphological alterations of ear. The external auditory canal obstruction, otitis media and ossicle changes may cause conductive hearing loss, and the defects in lysosomal storage of neurons, stria vascularis, spiral limbus, Reissner's membrane and basilar membrane cells may contribute to sensorineural deafness.

Animals ; Ear, Middle ; anatomy & histology ; pathology ; Evoked Potentials, Auditory, Brain Stem ; Hearing Loss ; pathology ; physiopathology ; Mice ; Mice, Knockout ; Mucolipidoses ; pathology ; physiopathology ; Neuraminidase ; genetics ; Otitis Media ; pathology

The GABAergic neurons in the parafacial zone (PZ) play an important role in sleep-wake regulation and have been identified as part of a sleep-promoting center in the brainstem, but the long-range connections mediating this function remain poorly characterized. Here, we performed whole-brain mapping of both the inputs and outputs of the GABAergic neurons in the PZ of the mouse brain. We used the modified rabies virus EnvA-ΔG-DsRed combined with a Cre/loxP gene-expression strategy to map the direct monosynaptic inputs to the GABAergic neurons in the PZ, and found that they receive inputs mainly from the hypothalamic area, zona incerta, and parasubthalamic nucleus in the hypothalamus; the substantia nigra, pars reticulata and deep mesencephalic nucleus in the midbrain; and the intermediate reticular nucleus and medial vestibular nucleus (parvocellular part) in the pons and medulla. We also mapped the axonal projections of the PZ GABAergic neurons with adeno-associated virus, and defined the reciprocal connections of the PZ GABAergic neurons with their input and output nuclei. The newly-found inputs and outputs of the PZ were also listed compared with the literature. This cell-type-specific neuronal whole-brain mapping of the PZ GABAergic neurons may reveal the circuits underlying various functions such as sleep-wake regulation.
Animals ; Axons ; physiology ; Brain ; anatomy & histology ; Brain Mapping ; Brain Stem ; cytology ; GABAergic Neurons ; physiology ; Green Fluorescent Proteins ; genetics ; metabolism ; Mice ; Mice, Inbred C57BL ; Mice, Transgenic ; Neural Pathways ; physiology ; Peptide Elongation Factor 1 ; genetics ; metabolism ; Rabies virus ; genetics ; metabolism ; Transduction, Genetic ; Vesicular Inhibitory Amino Acid Transport Proteins ; genetics ; metabolism