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PubMed1996

Premotor interneurons in generation of adaptive leg reflexes and voluntary movements in stick insects.

We investigated the role of local nonspiking interneurons involved in motor control of legs in the stick insects, Carausius morosus. In a preparation that allowed the animals to perform active leg movements such as adaptive tactile reflexes, proprioceptive reflexes, and walking, we gathered the following results. Almost all tested nonspiking interneurons that provide synaptic drive onto moto-neurons of the proximal leg muscles contribute to all of the motor programs underlying tactile reflexes and voluntary leg movements such as walking, searching, and rocking. Most of them are also involved in the generation of proprioceptive reflexes. All motor programs for coactivation, avoidance reflexes, resistance reflexes, and voluntary leg movements result from parallel pathways including nonspiking interneurons that support and others that oppose the motoneuronal activity. The contribution of a single interneuron to the different motor program is specific: it can be supporting for one motor program but opposing for the other. Even for the same motor program, for example, coactivation, the contribution of an individual interneuron can depend on the stimulus site from where the response is elicited. Our results support the idea that the different motor patterns for adaptive tactile reflexes, resistance reflexes, and voluntary leg movements emerge from a multifunctional neuronal circuit that is reorganized corresponding to the motor behavior performed. The actual motor pattern is then shaped by distributed information processing in parallel supporting and opposing pathways.

Acclimatization↗
PubMed1976

[Electromyographic and neurological aspects of leprosy. Study of 100 cases].

By the neurological, electromyographic, anatomopathological and bacterioscopic examinations of 100 pacients with leprosy the following conclusions have been drawn: There was a high incidence of reflex abnormalities. The proprioceptive reflexes were abnormal in 64.5% and the superficial reflexes in 70.8% of the cases. According to the topography of the segments examined, the deep reflexes showed the following abnormal values: 25.3% in the cephalic segment; 69.1% in the upper limbs and 74.5% in the lower limbs. Of the 2,289 reflexes investigated, abnormalities were found in 773 superficial reflexes (70.8%), while in relation to the proprioceptive reflexes the figures rose to 901 (64.5%). In the early stages of the infirmity, the reflexes were normal in 41.2% of the cases examined, and in all the stages of the evolution of the disease those numbers were always high. Also in the first stage, whose average duration was of 4.9 years, several alternations were noted, although there was a predominance of brisk reflexes (25.1%) over diminshed reflexes (17%), followed by hyperactive (8.6%) and absent reflexes (8%). In the final stage of the infirmity there was a decrease of normal reflexes, in contrast to absent and decreased reflexes, whose rates increased to 32.7% and 30.6% respectively. The disappearance of hyperactive reflexes and the clear decrease of brisk reflexes should also be noted. There was a high percentage of patients (31%) who suffered agression of the eighth nerve, 17 of which (54.8%) were found to suffer from neural deafness. The values related to hearing deficit were rarely in accordance with the histopathological and bacterioscopic positive results. The indexes of abnormalities found out in the examination of the fifth and of the seven nerve (7% and 5% respectively) were much lower in relation to the eighth nerve. These results are in contradiction with the ones stated in the literature. In some of the patients, hyperesthesia of the skin of the plantar region prognosticated the appearance of the infirmity. Among the objective changes, anesthesia of superficial sensibilities combined with deep hyperesthesia and anesthesia of superficial sensibilities with abolition of profound sensibilities were rarely observed. No case was found with exclusive alterations of deep sensibilities. Peripheral motor neuron lesions demonstrable by electromyography were observed in 82 patients (82%)...

Adult↗
PubMed1981

Transcortical reflexes and servo control of movement.

Sherrington proposed that the major role of proprioceptors is in processing afferent inputs generated by the active movements of the animal itself, and noted that the reflex effects of proprioceptive inputs are "mild." Current experimental results are consistent with the view that the major role of both segmental and transcortical proprioceptive reflexes is in small active movements and active postural stability, with muscle afferent inputs reducing "...errors of muscle length produced by fluctuating levels of motor discharge..." as stated by Goodwin and coworkers in 1978. Exteroceptive reflexes generate intense muscular responses and are of critical importance in prompt reprogramming essential for effective responses to environmental stimuli. Within the motor cortex (MI) there is a caudal region (MI/c) which receives exteroceptive cutaneous inputs and a rostral region (MI/r) which receives proprioceptive inputs. Transcortical reflexes mediated via pyramidal tract neurons (PTNs) of MI/r have properties which are analogous to segmental proprioceptive reflexes: changes of muscle length elicit PTN discharges which oppose the length change and so act to maintain stability. Furthermore, MI/r PTNs which are recruited earliest for small active movements are most sensitive to proprioceptive inputs. Data are not yet available concerning transcortical reflexes via MI/c during voluntary movement, but it is speculated that the cutaneous reflexes via MI/c might be functionally analogous to segmental cutaneous reflexes. Short-latency reflex responses also occur in postcentral (PoC) PTNs, and in this report we present results concerning the properties of PoC PTNs during active and passive movement. Caudal (area 2-5) PoC PTNs were similar to MI PTNs in that they often discharged prior to electromyogram (EMG) activity with active movement, and had different discharge frequencies with different steady state loads, but were unlike most MI PTNs in having the same changes of discharge with active and passive movement. Our finding of PoC discharge prior to movement onset, confirming that of Soso and Fetz in 1980, is discussed in connection with the concept of corollary discharge.

Afferent Pathways↗
PubMed1981

[Transcortical reflexes of proprioceptive origin and motor epilepsy (author's transl)].

The long-loop reflex involved in the triggering of paroxysmal activities by proprioceptive afferents is examined in monkeys with a chronic alumina focus and in cats with an acute penicillin focus. Electrical stimulation of a tibial nerve in monkeys as well as muscle stretch in cats elicit a cortical 'evoked spike', i.e., an evoked potential followed by an epileptic spike, accompanied by one or two motor bursts in the muscles concerned. With a very small acute focus, this transcortical reflex is shown to be quite topical: muscles in the vicinity are not affected. Relationships between evoked spike and myoclonic jerk are examined and it is shown that motor efferents usually follow the pyramidal tract. The concept of a transcortical reflex of proprioceptive origin is discussed on the basis of data collected from these models.

Afferent Pathways↗
PubMed2004

Re-examination of the possible role of Golgi tendon organ and muscle spindle reflexes in proprioceptive neuromuscular facilitation muscle stretching.

Literature concerning the theoretical role of spinal reflex circuits and their sensorimotor signals in proprioceptive neuromuscular facilitation (PNF) muscle stretching techniques was examined. Reviewed data do not support the assertion commonly made in PNF literature that contraction of a stretched muscle prior to further stretch, or contraction of opposing muscles during muscle stretch, produces relaxation of the stretched muscle. Further, following contraction of a stretched muscle, inhibition of the stretch reflex response lasts only 1 s. Studies examined suggested that decreases in the response amplitude of the Hoffmann and muscle stretch reflexes following a contraction of a stretched muscle are not due to the activation of Golgi tendon organs, as commonly purported, but instead may be due to presynaptic inhibition of the muscle spindle sensory signal. The current view on the complex manner by which the spinal cord processes proprioceptive signals was discussed. The ability of acute PNF stretching procedures to often produce a joint range of motion greater than that observed with static stretching must be explained by mechanisms other than the spinal processing of proprioceptive information. Studies reviewed indicate that changes in the ability to tolerate stretch and/or the viscoelastic properties of the stretched muscle, induced by PNF procedures, are possible mechanisms.

Elasticity↗
PubMed1981

Modulation of proprioceptive transcortical reflexes in the cat with a penicillin epileptic motor focus.

Mechanisms responsible for the triggering of paroxysmal events by proprioceptive afferents, previously described in the monkey with a chronic epileptic focus, were studied in more detail in the cat with a penicillin focus. To analyse the topical organization of this reflex triggering, the focus was restricted to very small areas of the motor cortex; in this study only pericruciate areas were considered in which stimulation elicited a motor response in one of the several forelimb muscles tested, and which received afferents from that muscle. When the focus was located in the post-sigmoid gyrus, stimulation (usually by stretch) of the given (target) muscle first elicited a cortical spike following the evoked response, and secondly a late phasic EMG response (about 40 msec latency) quite distinct from purely spinal reflexes. Cortical spikes and late EMG responses were closely correlated, especially considering their probability of occurrence or their parallel latency fluctuations. In most cases, this effect was limited to the muscle whose motor area had been treated with penicillin: stretching muscles in the vicinity was ineffective, nor were these muscles activated when the target muscle was stimulated. Evidence is given for the participation of a transcortical reflex in the generation of the late phasic response and for the involvement of the pyramidal tract in this reflex.

Animals↗
PubMed1981

Experimentally induced thiamine deficiency in beagle dogs: clinical observations.

Twenty-three 2- to 5-month-old Beagle dogs were fed a purified thiamine-deficient ration (2 to 3 micrograms of thiamine/100 g of ration) at a rate of 40 to 70 g/kg of body weight/day depending on age. Eleven dogs were used as principles, 6 as pair-fed controls, and 6 as ad libitum-fed controls. Controls were treated once a week with an IM dose of 300 micrograms of thiamine hydrochloride/kg of body weight. Three stages of clinical disease occurred in the principals: (i) an initial short (18.0 +/- 7.9 days) stage of induction, during which the dogs usually grew suboptimally, but were otherwise healthy, (ii) an intermediate stage of preliminary clinical signs of deficiency, characterized by a variable period (58.5 +/- 37.0 days) of progressive inappetance, failure to grow, loss of body weight, and coprophagia, and (iii) a terminal stage, which, in most dogs, was abrupt in onset and short (7.6 +/- 6.0 days) and consisted of either a neurologic syndrome or sudden unexpected death syndrome. Eight of the principals developed the neurologic syndrome characterized by anorexia, emesis, CNS depression, paraparesis, sensory ataxia, torticollis, circling, exophthalmos, tonic-clonic convulsions, profound muscular weakness, recumbency, and then died. Common reflex abnormalities included exaggerated patella reflex, proprioceptive and supporting reflex deficits, induced torticollis and ventroflexion of head, and absent eye menace (blink) reflex. Three other principals developed the sudden unexpected death syndrome. Common signs of deficiency were inappetance and paresis. Two were found dead and 1, with severe ECG abnormalities (including elevation of ST segment and tall or deeply inverted T waves), was killed.

Animals↗
PubMedDate not supplied

[Physiological mechanisms limiting external respiratory resistance].

A study was performed on 8 healthy male subjects to investigate the effect of nonelastic resistance 6-40 GPa (the air flow velocity being 90 l/min) on the duration of proprioceptive reflexes of respiratory muscles, volume and velocity parameters of forced exhalation. Resistances of 15 and 25 GPa combined with a workload of 100-150 W increased the duration of proprioceptive reflexes from 0.18 +/- 0.015 to 0.29 +/- 0.012 sec and to 0.38 +/- 0.06 sec, respectively, which indicates fatigue of respiratory muscles. Resistance of 25 GPa reduced significantly (by 55%) the maximum volume velocity of forced exhalation and increased its duration by 31%, the exhalation volume decreasing insignificantly (by 6%). The major factor limiting man's tolerance to external respiration resistance is functional deficiency of proprioceptive regulation of respiration and strength and velocity of respiratory muscles.

Adolescent↗
PubMed1998

[Masticatory muscles. Part VIII. Reflexes in the masticatory system].

A reflex is an involuntary response on a specific nerve stimulus. Several types of receptors are present in the masticatory system which can be involved in reflex activity. A short mechanical tap on an incisor, for example, evokes a specific pattern of several so-called exteroceptive reflexes in the electromyographic (EMG) activity of jaw-closing muscles, which includes periods with decreased activity (inhibitory reflex) as well as increased activity (excitatory reflex). In this case, periodontal mechanoreceptors are detecting the stimulus. The second type of reflex that is dealt with is the jaw-jerk reflex as an example of a proprioceptive reflex. A transient increase in length of a jaw-closing muscle, detected by length sensors (muscle spindles), evokes an excitatory reflex in the EMG. Dependent on the motor task, the amplitude of both reflexes is modified. The various reflex mechanisms play an important role in normal physiological functions such as posture control and chewing.

Electromyography↗
PubMed1990

[Stabilization of the gaze in chameleons: visual and vestibular reflexes].

Some visual, vestibular and proprioceptive reflexes which contribute to gaze (head + eye) stabilization were quantified in the chameleon. All the reflexes were analysed in the horizontal plane, and the visual reflexes were also studied in the vertical plane. In restrained-head animals, both the optokinetic nystagmus (OKN) and the vestibulo-ocular reflex (VOR) had low gains. In free-head animals, the head (opto-collic or vestibulo-collic reflex) and eye (OKN or VOR) responses added their effects, thus improving gaze stabilization, especially during vestibular stimulation. Cervical stimulation provoked both a cervico-ocular reflex (COR) in the compensatory direction and a large number of saccades. The saccadic response was especially marked in the presence of patterned visual surroundings.

Animals↗