ISSN:
1432-1106
Keywords:
Neck afferents
;
Neck-labyrinth interaction
;
Vestibulospinal neurons
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary The effects of neck afferent stimulation on vestibulospinal neurons in Deiters' nucleus and in the descending nucleus, and the interaction of cervical and vestibular input, were examined extracellularly in decerebrate, decerebellate cats. Many of the vestibulospinal neurons were identified as having axons in the lateral or medial vestibulospinal tract (LVST or MVST) and as being driven antidromically from C3 or C6. Half of the spontaneously active neurons were excited with a latency of 2.5–5.5 ms (early excitation) by stimulation of the contralateral C2 ganglion. In some neurons early excitation was followed by late excitation (latency 〉 6 ms), which was in other neurons the only effect seen. Early excitation was due to stimulation of proximal afferents because stimulation of the C2 dorsal or ventral rami usually produced late excitation only. Early excitation was seen in LVST and MVST neurons terminating between C3 and C6 and in those projecting beyond C6. Neurons with early excitation were scattered throughout Deiters' nucleus and the rostral part of the descending nucleus. In some neurons, mainly in the descending nucleus, the initial effect of contralateral C2 ganglion stimulation was inhibition. Inhibition could be evoked by stimulation of the ganglion or dorsal rami bilaterally. The axons of all tested inhibited neurons were in the MVST. Thirty-five percent of the population studied received convergence of early excitation and short-latency input from the labyrinth, sometimes from the semicircular canals. There was also convergence between late excitation or inhibition and vestibular input. The influence of neck afferent input on vestibulospinal neurons provides one pathway for this input to the neck and limb segments of the spinal cord. This pathway may be part of the substrate of the tonic neck reflex. In addition, vestibulospinal neurons are one site of interaction between neck and vestibular reflexes.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00236647
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