Cuneate nucleus

About: Cuneate nucleus is a research topic. Over the lifetime, 614 publications have been published within this topic receiving 24859 citations. The topic is also known as: cuneate nucleus of spinal cord.

Functional metabolic mapping during forelimb movement in rat. II. Stimulation of forelimb muscles

Abstract: Repetitive electrical stimulation of wrist extensor muscles in rat was combined with quantitative 14C-deoxyglucose autoradiography to study sensory systems functionally activated during forelimb movement. Metabolism increased ipsilaterally in the wrist extensors, the dorsal horn of the cervical spinal cord, the cuneate nucleus and cerebellar hemisphere. The metabolic activation in cerebellum occurred in cortex surrounding the primary fissure anteriorly (lobules simplex and V), and the prepyramidal fissure posteriorly (lobules paramedian and copula pyramis). Metabolism was increased in both granule cell and molecular layers and was uniform throughout the zone of activation. Hindlimb stimulation primarily activated the medial aspect of copula pyramis, demonstrating the somatotopic specificity of changes. Forelimb stimulation also activated contralateral sites in the dorsal accessory nucleus of the inferior olive, ventrobasal thalamus, and SI and SII in cortex. Studies of the relationship between the magnitude of the response and the frequency of the stimulation revealed a positive correlation in muscle, dorsal horn and cuneate nucleus. Other activated sites only showed a significant change at the highest rates of stimulation. Comparison of the pattern of metabolic activation during forelimb movements induced centrally (Collins et al., 1986) with the pattern induced peripherally revealed overlap primarily in the paramedian zone of anterior and posterior cerebellum, and the granular cortex of SI and SII. These studies suggest that forelimb movement initiated centrally would have considerable influence on feedback sensation from the moving limb in these sites.

Processing afferent proprioceptive information at the main cuneate nucleus of anesthetized cats

Abstract: Medial lemniscal activity decreases before and during movement, suggesting prethalamic modulation, but the underlying mechanisms are largely unknown. Here we studied the mechanisms underlying proprioceptive transmission at the midventral cuneate nucleus (mvCN) of anesthetized cats using standard extracellular recordings combined with electrical stimulation and microiontophoresis. Dual simultaneous recordings from mvCN and rostroventral cuneate (rvCN) proprioceptive neurons demonstrated that microstimulation through the rvCN recording electrode induced dual effects on mvCN projection cells: potentiation when both neurons had excitatory receptive fields in muscles acting at the same joint, and inhibition when rvCN and mvCN cells had receptive fields located in different joints. GABA and/or glycine consistently abolished mvCN spontaneous and sensory-evoked activity, an effect reversed by bicuculline and strychnine, respectively; and immunohistochemistry data revealed that cells possessing strychnine-sensitive glycine receptors were uniformly distributed throughout the cuneate nucleus. It was also found that proprioceptive mvCN projection cells sent ipsilateral collaterals to the nucleus reticularis gigantocellularis and the mesencephalic locomotor region, and had slower antidromic conduction speeds than cutaneous fibers from the more dorsally located cluster region. The data suggest that (1) the rvCN-mvCM network is functionally related to joints rather than to single muscles producing an overall potentiation of proprioceptive feedback from a moving forelimb joint while inhibiting, through GABAergic and glycinergic interneurons, deep muscular feedback from other forelimb joints; and (2) mvCN projection cells collateralizing to or through the ipsilateral reticular formation allow for bilateral spreading of ascending proprioceptive feedback information.

Effect of transcutaneous electrical nerve stimulation (TENS) on central nervous system amplification of somatosensory input

Abstract: The effect of transcutaneous electrical nerve stimulation (TENS) on the central nervous system amplification process was investigated focusing on the dorsal column-medial lemniscal pathway, because the dorsal column nucleus was recently shown to receive multiple sources of sensory information, including pain. Short latency somatosensory evoked potentials (SSEPs) were recorded in ten healthy normal volunteers. Amplitude changes in each SSEP component (the N9 brachial plexus potential, the P14 potential that originates from the cervicomedullary junction, spinal N13/P13 generated by the cervical dorsal horn and the cortical N20/P25 potential) were studied at stimulus strenghts ranging from the threshold (40% maximum stimulus) to 2.5 times the threshold (maximum). The findings suggest that sensory amplification begins at the P14 generator source near the cuneate nucleus. There was no statistically significant difference in sensory amplification between P14 and cortical N20/P25, indicating that the cuneate nucleus is the main site of the central amplifying process. When TENS was applied to the palm distal to the median nerve stimulation used for SSEP, cortical N20/P25 amplification disappeared, evidence that TENS suppresses the central amplification phenomenon, most probably at the level of the cuneate nucleus.

Cortical responses to paired stimuli applied peripherally and at sites along the somato‐sensory pathway

Abstract: 1. Experiments have been performed on animals anaesthetized with various anaesthetics to determine the responsiveness of the cortex to the second of a pair of identical stimuli applied at three sites along the sensory pathway, i.e. to the periphery, the medial lemniscus and to thalamocortical fibres. 2. It has been found that in deeply anaesthetized animals the mass response recorded from the cerebral cortex to the second of a pair of peripheral or lemniscal stimuli became reduced in size if the interval between the stimuli was 30-500 msec. If the interval was less than 30 msec for peripheral stimuli or between 10 and 30 msec for lemniscal stimuli responses were not obtained to the second stimulus. This was found to be a basic pattern which could be modified in animals less deeply anaesthetized. In these animals, periods of relatively increased responsiveness were seen after peripheral stimulation. 3. The post-synaptic responses recorded from the ventrobasal thalamus showed the same behaviour to the second of a pair of peripheral stimuli as did the cortex both as regards size and latency of the responses. 4. The post-synaptic responses recorded from the cuneate nucleus rarely showed any reduction in size unless the separation between the stimuli was 10 msec or less; even at intervals as low as 3 msec there was no increase in the latency of the response. 5. When a pair of stimuli were applied to thalamocortical fibres, a different pattern of cortical responsiveness was found. At the time the cortical response to stimulation at pre-thalamic sites was reduced or abolished, the response to stimulation at post-thalamic sites was unaltered or increased in size. 6. Finally an attempt was made to correlate the mass response recorded from the cortical surface and the activity of single cortical cells. Two types of cell could be distinguished in the rat. Those lying from 0·35 to 1·2 mm deep in the cortex showed a response pattern, to paired stimuli, closely resembling that of the cortical mass response. Others situated deeper in the cortex were found which had a very long absolute unresponsive time, from 50 to 80 msec and a very long relative unresponsive time of 1 sec.