Medullary reticulospinal tract mediating the generalized motor inhibition in cats: Parallel inhibitory mechanisms acting on motoneurons and on interneuronal transmission in reflex pathways

Takakusaki, Kaoru; Kohyama, Jun; Matsuyama, Kiyoji; Mori, Shigemi

doi:10.1016/s0306-4522(00)00586-8

Cited by 99 publications

(82 citation statements)

References 60 publications

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“…Cholinergic projections from the PPN may excite the "muscle tone inhibitory system" arising from the cholinoceptive pontine reticular formation neurons (PRF), which consecutively activate medullary reticulospinal neurons and spinal inhibitory interneurons. The inhibitory system exerts postsynaptic inhibitory effects on α-and γ-motoneurons of extensor and flexor muscles and interneurons intercalated in spinal reflex pathways [16,62,64]. Consequently, it is worthwhile to note that the muscle tone inhibitory system controls not only the level of muscle tone by regulating the excitability of motoneurons, but also locomotor rhythm and pattern by modulating the excitability of spinal interneurons.…”

Section: ■ Muscle Tone Control Systemsmentioning

confidence: 99%

Substrates for normal gait and pathophysiology of gait disturbances with respect to the basal ganglia dysfunction

2008

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In this review, we have tried to elucidate substrates for the execution of normal gait and to understand pathophysiological mechanisms of gait failure in basal ganglia dysfunctions. In Parkinson's disease, volitional and emotional expressions of movement processes are seriously affected in addition to the disturbance of automatic movement processes, such as adjustment of postural muscle tone before gait initiation and rhythmic limb movements during walking. These patients also suffer from muscle tone rigidity and postural instability, which may also cause reduced walking capabilities in adapting to various environments. Neurophysiological and clinical studies have suggested the importance of basal ganglia connections with the cerebral cortex and limbic system in the expression of volitional and emotional behaviors. Here we hypothesize a crucial role played by the basal ganglia-brainstem system in the integrative control of muscle tone and locomotion. The hypothetical model may provide a rational explanation for the role of the basal ganglia in the control of volitional and automatic aspects of movements. Moreover, it might also be beneficial for understanding pathophysiological mechanisms of basal ganglia movement disorders. A part of this hypothesis has been supported by studies utilizing a constructive simulation engineering technique that clearly shows that an appropriate level of postural muscle tone and proper acquisition and utilization of sensory information are essential to maintain adaptable bodily functions for the full execution of bipedal gait. In conclusion, we suggest that the major substrates for supporting bipedal posture and executing bipedal gait are 1) fine neural networks such as the cortico-basal ganglia loop and basal ganglia-brainstem system, 2) fine musculoskeletal structures with adequately developed (postural) muscle tone, and 3) proper sensory processing. It follows that any dysfunction of the above sensorimotor integration processes would result in gait disturbance.

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Section: ■ Muscle Tone Control Systemsmentioning

confidence: 99%

Substrates for normal gait and pathophysiology of gait disturbances with respect to the basal ganglia dysfunction

2008

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“…In contrast, their results showed increased motoneuronal activity and reflex excitability. Besides the above-mentioned possible mechanisms of subthreshold activation, motoneurons could be actively inhibited from discharging through "parallel inhibitory mechanisms" (Takakusaki et al, 2001) despite increased corticospinal input during motor imagery.…”

Section: Potential Mechanisms For Enhanced Spinal Excitabilitymentioning

confidence: 99%

The Effect of Motor Imagery on Spinal Segmental Excitability

Li¹,

Kamper²,

Stevens³

et al. 2004

J. Neurosci.

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The purpose of this study was to investigate the effect of motor imagery on spinal segmental excitability by recording the reflex responses to externally applied stretch of the extrinsic finger flexors and extensors during the performance of an imaginary task. Nine young healthy subjects performed a series of imagined flexion-extension movements of the fingers. Muscle stretch was imposed concurrently by applying rotations of the metacarpophalangeal joints at 100, 300, or 500°/sec. Three of the nine tested subjects also generated 0.2 Newton meter voluntary flexion torque in preloading tasks before stretch.At 300°/sec stretch, electromyogram (EMG) and torque reflex responses, which were observed in the finger flexors in four of nine subjects during motor imagery, were activated at a short latency (38.6 Ϯ 10.6 msec). This latency was similar to that recorded during a stretch of preactivated flexor muscles (34.4 Ϯ 3.6 msec), in which motoneurons are already suprathreshold and in which monosynaptic effects of muscle afferents are likely to be discernable. In a similar manner, for stretches imposed at 500°/sec, responses to stretch of the flexors were observed in all five tested subjects in imaginary flexion tasks at very short latencies (26.4 Ϯ 3.7 msec), again similar to those induced by tendon taps (22.8 Ϯ 1.2 msec). No EMG response was observed at rest during stretches.These observations support the view that effects must have been mediated by imagery-related subthreshold activation of spinal motoneurons and/or interneurons, rather than by long-latency transcortical reflex responses. We conclude that motor imagery has a potent effect on the excitability of spinal reflex pathways.

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“…However, it was reported that in cats, the electrical stimulus of the medullary enhanced the 13 activity of the inhibitory interneurons; thus, the interneurons inhibit motoneuron activity [26].…”

Section: Methodsmentioning

confidence: 99%

Anticipation of elbow joint perturbation shortens the onset time of the reflex EMG response in biceps brachii and triceps brachii

Koike

Yamada

2007

Neuroscience Letters

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This study aimed to investigate the influence of the anticipation of a perturbation torque applied to extend the elbow joint on the onset time of reflex electromyogram (EMG) responses. A perturbation torque generated by an electromagnetic torque motor system was applied to the forearm of five subjects during trials. The trials were divided into an anticipated (AN) condition-perturbation torque applied after the auditory signal-and an unanticipated (UAN) condition-suddenly applied perturbation. To detect the reflex EMG response in the biceps brachii (Bb) and triceps brachii (Tb) muscles, a new method involving the discrete wavelet transform and outlier tests was used. We found that the onset time of the reflex response in both the muscles in the AN condition was significantly shorter than that in the UAN condition. The angle of transition from flexion to extension, which was induced by the reflex response of Bb, was also significantly smaller in the AN condition than in the UAN condition. The results indicate that the anticipation of an applied perturbation torque decreases the onset time of the reflex response in the Bb and Tb.

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Medullary reticulospinal tract mediating the generalized motor inhibition in cats: Parallel inhibitory mechanisms acting on motoneurons and on interneuronal transmission in reflex pathways

Cited by 99 publications

References 60 publications

Substrates for normal gait and pathophysiology of gait disturbances with respect to the basal ganglia dysfunction

Substrates for normal gait and pathophysiology of gait disturbances with respect to the basal ganglia dysfunction

The Effect of Motor Imagery on Spinal Segmental Excitability

Anticipation of elbow joint perturbation shortens the onset time of the reflex EMG response in biceps brachii and triceps brachii

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