Bulbospinal inhibition of PAD elicited by stimulation of afferent and motor axons in the isolated frog spinal cord and brainstem

González, Hernán F J; Jiménez, Ismael; Rudomín, P.

doi:10.1007/bf02259132

Cited by 9 publications

(1 citation statement)

References 39 publications

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“…Studies on the action of descending fibers on PAD elicited by stimulation of afferent fibers and/or stimulation of the motor axons were continued in the 1990s with Hortensia González and Ismael Jiménez (González et al, 1992(González et al, , 1993. These studies showed that, as in the cat, stimulation of the bulbar reticular formation produced PAD in cutaneous afferents and inhibited the PAD elicited in muscle spindle afferents.…”

Section: Frogsmentioning

confidence: 99%

Pablo Rudomin

2014

The History of Neuroscience in Autobiography, Volume 8

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Section: Frogsmentioning

confidence: 99%

Pablo Rudomin

2014

The History of Neuroscience in Autobiography, Volume 8

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A neural network model rapidly learning gains and gating of reflexes necessary to adapt to an arm's dynamics

Kalveram

1992

Biol. Cybern.

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Effects of dynamic coupling, gravity, inertia and the mechanical impedances of the segments of a multi-jointed arm are shown to be neutralizable through a reflex-like operating three layer static feedforward network. The network requires the proprioceptively mediated actual state variables (here angular velocity and position) of each arm segment. Added neural integrators (and/or differentiators) can make the network exhibit dynamic properties. Then, actual feedback is not necessary and the network can operate in a pure feedforward fashion. Feedforward of an additional load can easily be implemented into the network using "descendent gating", and a negative feedback control loop added to the feedforward control reduces errors due to external noise. A training, which combines a least squared error based simultaneous learning rule (LSQ-rule) with a "self-imitation algorithm" based on direct inverse modeling, enables the network to acquire the whole inverse dynamics, limb parameters included, during one short training movement. The considerations presented also hold for multi-jointed manipulators.

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Reticulospinal actions on primary afferent depolarization of cutaneous and muscle afferents in the isolated frog neuraxis

1993

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The effects of the brainstem reticular formation on the intraspinal excitability of low threshold cutaneous and muscle afferents were studied in the frog neuraxis isolated together with the right hindlimb nerves. Stimulation of low threshold fibers (less than two times threshold) in cutaneous nerves produced short latency, negative field potentials in the ipsilateral dorsal neuropil (200-400 microns depth) that reversed to positivity at deeper regions (500-700 microns). Stimulation of low threshold fibers (less than two times threshold) in muscle nerves produced, instead, negative response that acquired their maximum amplitude in the ventral neuropil (700-900 microns depth). These electrophysiological findings suggest, in agreement with observations in the cat, that low threshold cutaneous and muscle afferents end at different sites in the spinal cord. Intraspinal microstimulation applied within the dorsal neuropil produced antidromic responses in low threshold cutaneous afferents that were increased in size following stimulation of the dorsal or ventral roots, as well as of the brainstem reticular formation. This increase in excitability is interpreted as being due to primary afferent depolarization (PAD) of the intraspinal terminals of cutaneous fibers. Antidromic responses recorded in muscle nerves following intraspinal stimulation within the ventral neuropil were also increased following conditioning stimulation of adjacent dorsal or ventral roots. However, stimulation of the bulbar reticular formation produced practically no changes in the antidromic responses, but was able to inhibit the PAD of low threshold muscle afferents elicited by stimulation of the dorsal or ventral roots. It is suggested that the PAD of low threshold cutaneous and muscle afferents is mediated by independent sets of interneurons. Reticulospinal fibers would have excitatory connections with the interneurons mediating the PAD of cutaneous fibers and inhibitory connections with the interneurons mediating the PAD of muscle afferents. Although our results provide no direct information on whether the reticulospinal depression of the PAD elicited in low threshold muscle afferents is due to inhibition along the pathways producing PAD of muscle spindle or of tendon organ afferents, it seems likely-by analogy with what has been seen in the cat spinal cord-that these inhibitory actions are mostly restricted to the pathways producing PAD in the terminal arborizations of muscle spindle afferents. These results emphasize the specificity of the descending control of the synaptic efficacy of low threshold cutaneous and muscle afferents which could be of importance for motor performance.

show abstract

Bulbospinal inhibition of PAD elicited by stimulation of afferent and motor axons in the isolated frog spinal cord and brainstem

Cited by 9 publications

References 39 publications

Pablo Rudomin

Pablo Rudomin

A neural network model rapidly learning gains and gating of reflexes necessary to adapt to an arm's dynamics

Reticulospinal actions on primary afferent depolarization of cutaneous and muscle afferents in the isolated frog neuraxis

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