Showing papers on "Cuneate nucleus published in 2009"

Restoration of hand function in a rat model of repair of brachial plexus injury

Abstract: The incurability of spinal cord injury and subcortical strokes is due to the inability of nerve fibres to regenerate. One of the clearest clinical situations where failure of regeneration leads to a permanent functional deficit is avulsion of the brachial plexus. In current practice, surgical re-implantation of avulsed spinal roots provides a degree of motor recovery, but the patients neither recover sensation nor the use of the hand. In the present rat study, we show that transplantation of cultured adult olfactory ensheathing cells restores the sensory input needed for a complex, goal-directed fore-paw function and re-establishes synaptic transmission to the spinal grey matter and cuneate nucleus by providing a bridge for regeneration of severed dorsal root fibres into the spinal cord. Success in a first application of human olfactory ensheathing cells in clinical brachial plexus injury would open the way to the wider field of brain and spinal cord injuries.

Early Withdrawal of Axons from Higher Centers in Response to Peripheral Somatosensory Denervation

Abstract: The mechanisms responsible for long-term, massive reorganization of representational maps in primate somatosensory cortex after deafferentation are poorly understood. Sprouting of cortical axons cannot account for the extent of reorganization, and withdrawal of axons of deafferented brainstem and thalamic neurons, permitting expression of previously silent synapses, has not been directly demonstrated. This study is focused on the second of these. In monkeys, deafferented for two years by section of the cuneate fasciculus at the C1 level, there was extensive withdrawal of axon terminals from thalamus and cortex, detectable a decade before visible atrophy of their parent neuronal somata in the cuneate nucleus or thalamus. Slow, inexorable progression of lemniscal and thalamocortical axonal withdrawal is a neurodegenerative phenomenon likely to be a powerful inducement to compensatory long-term plasticity, a mechanism that can explain the long-term evolution of cortical reorganization and, with it, phantom sensations in spinal patients and amputees.

Neuropeptide Y modulates c-Fos protein expression in the cuneate nucleus and contributes to mechanical hypersensitivity following rat median nerve injury.

Abstract: This study sought to investigate the effects of injury-induced neuropeptide Y (NPY) on c-Fos expression in the cuneate neurons and neuropathic pain after median nerve injury. Four weeks after median nerve transection (MNT), the injured nerves stimulated at low intensity (0.1 mA) expressed significantly less NPY-like immunoreactive (NPY-LI) fibers in the cuneate nucleus (CN) than those stimulated at high intensities (1.0 mA and 10 mA). Conversely, a significantly higher number of c-Fos-LI cells were observed in the CN in rats stimulated with 0.1 mA compared to those stimulated with 1.0 mA or 10 mA. These results suggest that more NPY was released following low-intensity stimulation, and consequently fewer NPY-LI fibers and more c-Fos-LI cells were identified in the CN. Furthermore, the number of c-Fos-LI cells as well as the percentage of c-Fos-LI cuneothalamic projection neurons (CTNs) in the CN was markedly decreased after injection of NPY receptor antagonist along with retrograde tract-tracing ...

Morphometric analysis of infant and adult medullary nuclei through optical disector method.

Abstract: In the literature, comprehensive and comparative morphometric studies of infant and adult medullary nuclei performed with unbiased methods are still lacking. In this study, the unbiased quantitative method of the optical disector was applied to analyze neuronal densities, nuclear volumes, and total neuron numbers of the hypoglossal nucleus (XII), dorsal motor nucleus of the vagus (DMNV), nucleus tractus solitarii (NTS), medial vestibular nucleus (MedVe), cuneate nucleus (Cu), nucleus of the spinal trigeminal tract, principal inferior olivary nucleus (PION), medial inferior olivary nucleus (MION), and dorsal inferior olivary nucleus (DION) in adults (16 male, six female; mean age: 37 years) and infants (five male, five female; mean age: 5 months). In both infants and adults, higher neuronal densities were found in the more ventrally located nuclei of the spinal trigeminal tract (mean values (coefficient of variation): 20,947 (0.29) and 8,990 (0.18) neurons/mm(3), respectively) and inferior olivary complex (PION: 20,010 (0.15) and 9,076 (0.10); MION: 18,667 (0.20) and 9,989 (0.13); DION: 22,424 (0.17) and 10,986 (0.20), respectively) than in the nuclei of the medullary tegmentum, that is, XII (2,747 (0.39) and 1,026 (0.31)), DMNV (2,876 (0.19) and 1,553 (0.26)), NTS (7,993 (0.17) and 2,877 (0.13)), MedVe (7,010 (0.17) and 2,918 (0.12)), and Cu (2,563 (0.23) and 1,038 (0.16)). All the medullary nuclei showed higher volumes and lower neuronal densities in adults than in infants, without statistically significant differences in total neuron numbers, probably because of postnatal development of the neuropil and microvascularization.

Mathematical modeling of brain circuitry during cerebellar movement control

Abstract: Reconstruction of movement control properties of the brain could result in many potential advantages for application in robotics. However, a hampering factor so far has been the lack of knowledge of the structure and function of brain circuitry in vivo during movement control. Much more detailed information has recently become available for the area of the cerebellum that controls arm-hand movements. In addition to previously obtained extensive background knowledge of the overall connectivity of the controlling neuronal network, recent studies have provided detailed characterizations of local microcircuitry connectivity and physiology in vivo. In the present study, we study one component of this neuronal network, the cuneate nucleus, and characterize its mathematical properties using system identification theory. The cuneate nucleus is involved in the processing of the sensory feedback evoked by movements. As a substrate for our work, we use a characterization of incoming and outgoing signals of individual neurons during sensory activation as well as a recently obtained microcircuitry characterization for this structure. We find that system identification is a useful way to find suitable mathematical models that capture the properties and transformation capabilities of the neuronal microcircuitry that constitute the cuneate nucleus. Future work will show whether specific aspects of the mathematical properties can be ascribed to a specific microcircuitry and/or neuronal property.