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PubMed1995

The primary afferent pathway of extraocular muscle proprioception in the pigeon.

Recent physiological experiments in our laboratory suggest that extraocular muscle proprioceptive signals are involved in oculomotor control in the pigeon [e.g., Knox and Donaldson (1993) Proc. R. Soc. Lond. B 253, 77-82]; the present results provide information about the primary afferent pathway involved in these actions. In other physiological experiments [Hayman et al. (1993) Proc. R. Soc. Lond. B 254, 115-122] we have shown that extraocular muscle afferent signals modify vestibularly driven neck reflexes in the pigeon; the present results suggest an anatomical substrate for these effects. The localization of the cell bodies and of the central terminations of afferent fibres from the extraocular muscles of the pigeon was examined using transport of horseradish peroxidase. The results showed that primary afferent cell somata subserving extraocular muscle proprioception are located within the ipsilateral trigeminal ganglion. The presence of heavily labelled brainstem neurons reported in a previous study [Eden et al. (1982) Brain Res. 237, 15-21] was confirmed; however, these cells were shown to be accessory abducens motoneurons innervating the quadratus muscle, and presumably the pyramidalis muscle also, and not proprioceptive afferent somata as had been suggested. The central projections of extraocular muscle afferent neurons were found consistently in a restricted area of the external cuneate nucleus. This is in contrast to findings in a number of mammals in which the terminal label has been seen to cluster in portions of the spinal trigeminal nucleus. The presence of a lateral trigeminal tract in the pigeon, through which the afferent axons course, which terminates exclusively in the ventral portion of the external cuneate nucleus may explain this finding.

Afferent Pathways↗
PubMed1987

Human jaw muscle motor behaviour. I. Motor drive.

Jaw muscle motor behaviour, however complicated, has important implications for the every day dental practice. In recent years the understanding of jaw and other skeletal muscle function has increased considerably. Direct recording of primary afferent discharge in conscious human beings and animals during normal function has caused radical changes of the concepts of muscle receptor function. Central pattern generators at segmental levels and suprasegmental programming centres are important mechanisms behind voluntary and automatic movements of different kinds. The most important proprioceptive function is probably to provide reassurance of correct movement pattern, to adjust the central programming to environmental changes and to directly influence slow movements requiring precision. Muscle spindle receptors contribute to mandibular kinesthesia. Muscle spindles are rarely present in jaw opening muscles. Despite this fact an excitatory reflex similar to the stretch reflex but with longer latency has been demonstrated. Further on a reciprocal organisation with antagonist inhibition has been shown to exist between jaw openers and closers. Motor behaviour of jaw and limb muscles thus seem to have many characteristics in common.

Humans↗
PubMed1973

Reflex responses of respiratory muscles to tilting and positive pressure breathing.

We have recorded the action potentials of muscle fibres of External Oblique in anaesthetized rabbits in supine and horizontal position. During head-up tilting the inspiratory activity is inhibited and the abdominal activity is excited. Both these two responses are reflexly mediated through vagal afferent fibres. The positive pressure was chosen as to determine a shift in end-expiratory volume similar to that induced by the head-up tilting. Also at positive pressure breathing (PPB) the abdominal activity increases but less than during head-up tilting. This result seems to indicate the importante of the proprioceptive afferents of the external oblique during the vertical posture. The blockade of vagal nervous conduction markedly reduces the abdominal activity both during tilting and P.P.B. and similar results are obtained either by "total" or "partial" vagal blockade. Therefore it seems possible to conclude that both these two reflexes (introduced by head-up tilting and PPB) be due to the activation of the same receptors (pulmonary stretch receptors).

Action Potentials↗
PubMed1989

Compensation of translational and rotational perturbations in human posture: stabilization of the centre of gravity.

EMG responses in the leg muscles, head acceleration and joint movements induced by dorsiflexing rotation of the ankle have been analysed. Perturbations were induced while subjects were standing on a platform with the ankle joints co-linear with the axis of rotation or while standing above the axis (between 5 and 25 cm), which introduced an additional translational component to the displacement. The former condition was followed by a monosynaptic gastrocnemius reflex potential and a late tibialis anterior activation (latency about 100 ms); in the latter condition the monosynaptic reflex response became smaller and a longer latency gastrocnemius response (latency about 70 ms) appeared, the strength and duration of which increased in parallel with the translational component, while the amplitude of the tibialis anterior activity decreased. Neither vestibulospinal nor muscle proprioceptive mechanisms can solely account for this effect as the biomechanical parameters were little changed in the different conditions. It is suggested that the controlled variable in the investigated task is to hold the bodies' centre of gravity over the feet which makes the change in the pattern meaningful: pure dorsiflexion of the feet is followed by a backwards sway of the body, thus a tibialis anterior activation is functionally essential to hold the centre of gravity over the feet. A backwards translation of the feet withdraws the supporting surface, thus a gastrocnemius activation is needed to restore the centre of gravity over the feet. The inhibition of the monosynaptic reflex with increasing translation is suggested to arise from a reciprocal modulation of mono- and polysynaptic gastrocnemius reflex responses.

Acceleration↗
PubMed2002

Active high-frequency vestibulo-ocular reflex and seasickness susceptibility.

OBJECTIVES/HYPOTHESIS: The vestibular autorotation test (VAT) examines responses to active head oscillations at frequencies between 2 and 6 Hz in the horizontal and vertical planes while the subject is fixating a visible target. At these frequencies, the vestibulo-ocular reflex (VOR) is the main source of eye movement for ocular stabilization, although other visual and somatosensory information interacts with the response. Because the neural mismatch theory places emphasis on multimodal sensory interactions as the cause of motion sickness, using the VAT, which measures eye movements resulting from vestibular, visual, and, to a certain extent, proprioceptive information and depends on the conscious participation and cooperation of the subject, could be of advantage in evaluating individuals with differing susceptibility to motion sickness. The purpose of the present study was to evaluate high-frequency VOR parameters in seamen at the two extremes of the seasickness susceptibility scale. STUDY DESIGN: Cross-sectional, parallel-group design. METHODS: Participants in the study were 35 healthy male volunteers aged 18 to 23 years, of whom 20 were highly susceptible to seasickness and 15 were nonsusceptible. The vestibulo-ocular reflex was evaluated by the VAT at frequencies ranging from 2.0 to 5.9 Hz. RESULTS: The lag of the vertical phase was significantly higher in the susceptible group. A significant interaction was also found between group and frequency, the vertical phase being significantly higher in the 3.9- to 5.9-Hz range. Although no group effect was detected for the lag of the horizontal phase, there was a significant interaction between group and frequency, the horizontal phase being higher in the susceptible group at 5.5 and 5.9 Hz. No significant group differences were found for horizontal or vertical gain. CONCLUSIONS: The present findings support the contention that the VAT, which measures eye movements resulting from multimodal vestibular, visual, and, to a certain extent, proprioceptive information and depends on the conscious participation and cooperation of the subject, may produce different results in subjects at the two extremes of the seasickness susceptibility scale. Despite the statistical differences that were found, VAT measurements could not be used for practical purposes to categorize individual motion sickness susceptibility.

Adolescent↗
PubMed1986

'Switching-off' of an auditory interneuron during stridulation in the acridid grasshopper Chorthippus biguttulus L.

In freely moving grasshoppers of the species Chorthippus biguttulus compound potentials were recorded from the neck connectives with chronically implanted hook electrodes. The spikes of one large auditory interneuron, known as the G-neuron (Kalmring 1975a, b) were clearly distinguishable in the recordings and the neuron was identified by its physiology and morphology. In quiescent grasshoppers the G-neuron responds to auditory and vibratory stimuli, but responses to both stimuli are suppressed during stridulation in males. When a male's wings were removed so that the stridulatory movements of its hindlegs produced no sound, the suppression of the G-neuron response still occurred. When proprioceptive feedback from the hindlegs was reduced, by forced autotomy of the legs, the switching-off remained incomplete (production of stridulatory patterns was inferred on the basis of electromyograms from the relevant thoracic musculature). Imposed movement of the hindlegs, on the other hand, suppressed the G-neuron response in a graded fashion, depending on the frequency of the movement. These experiments suggest that the switching-off is brought about by a combination of proprioceptive feedback and central efferences. The switching-off phenomenon could either protect the grasshopper's auditory pathway from undesired effects of overloading by its own intense song (e.g. self-induced habituation as described by Krasne and Wine 1977) and should therefore apply for most auditory neurons. Alternatively it could prevent escape reflexes from being triggered by stridulatory self-stimulation and consequently might apply only for neurons involved in such networks (as the G-neuron might be).

Animals↗
PubMed2001

A central pattern-generating network contributes to "reflex-reversal"-like leg motoneuron activity in the locust.

We introduce a new rhythmic preparation of the locust mesothoracic segment that exhibits long-lasting rhythmicity without pharmacological treatment. In most experiments, isolation of the locust mesothoracic ganglion from the anterior and posterior ganglia causes episodes of patterned activity to be generated in leg motoneurons that supply the femur-tibia (FT) joint. Flexor and extensor tibiae motoneuron pools exhibit alternating bursts of activity mostly composed of doublets and triplets of bursts. Motor activity during these episodes appears to be centrally generated because it persisted after complete deafferentation in 37% of the preparations; however, proprioceptive signals from the middle leg strongly influenced the patterning of motoneuron activity. Mimicking FT joint flexion by elongating the femoral chordotonal organ during an extensor burst terminates extensor activity and initiates flexor activity. The reverse is true for a mimicked extension during a flexor burst. This motor activity represents a reflex reversal that is typically observed in the locomotor state of the stick insect walking system. Our results provide evidence that this "reversed" reflex is caused by the action of central pattern-generating networks.

Animals↗
PubMed1986

Incidence of peripheral neuropathy and cerebellar ataxia in chronic alcoholics.

A total of 78 chronic alcoholics were examined neurologically as well as by electroneurography, myography and posturography. Clinical signs of peripheral neuropathy were detected in 45% of these patients, with electromyographic and neurographic abnormality in 67% and 55% respectively. Clinical signs of cerebellar ataxia were found in 33% of our patients, whereas posturographic measurements of increased sway were recorded in 69%. The posturographic characteristics of cerebellar anterior lobe atrophy were observed in two-thirds of the latter patients. The severity of cerebellar-ataxia did not correlate with the degree of neuropathy. This lack of correlation is interpreted as an indication of different pathogenetic mechanisms acting on peripheral nerves and cerebellum.

Adult↗
PubMed1987

Discharge of abdominal muscle alpha and gamma motoneurons during expiratory loading in cats.

Expiratory responses were elicited in abdominal alpha and gamma motoneurons of anesthetized cats by continuous positive airway pressure, tracheal occlusion, lung inflation, or step-changes in expiratory airflow resistance. Abdominal alpha motoneurons were silent during quiet breathing but became rhythmically active whenever expiration was opposed. In addition, the responses of abdominal alpha motoneurons to an increase in expiratory airflow resistance included an increase in discharge frequency, an earlier firing time of individual neurons, recruitment of successively larger motor fibers, and an increased duration of discharge. Abdominal gamma motoneurons discharged continuously during quiet breathing and an increased frequency of discharge during the expiratory phase of the respiratory cycle was evident in approximately one-third of the fibers. This respiratory modulation was enhanced, or initiated if absent, by imposing a load during expiration. Bilateral cervical vagotomy abolished both the respiratory modulation of abdominal gamma motoneurons and expiratory activity in abdominal alpha motoneurons indicating the importance of supraspinal structures. Coactivation of abdominal alpha and gamma motoneurons during active expiration also suggests that a segmental reflex involving abdominal muscle spindles may be capable of providing automatic compensation for changes in expiratory load. In conclusion, both vagal and dorsal root information appear to contribute to the proprioceptive control of abdominal muscle expiratory activity.

Abdominal Muscles↗
PubMed2003

Cases from the Osler Medical Service at Johns Hopkins University.

A 50-year-old African American woman presented with bilateral lower extremity pain, a history of falls during the past several months, and personality and behavior changes. She had been in good health until approximately 5 months before admission, when she began to fall with increasing frequency, often while going down a flight of stairs. She described these falls as her "legs giving out" and feeling very heavy and unsteady. There was no head trauma or loss of consciousness. Her daughter noticed that her gait had become somewhat unsteady during the last several months. Her family also noted a change in her personality at this time. Previously, she had been a very tidy person who took great care with her appearance, who was working as a customer service representative. However, she had become less social and very withdrawn. She had been observed putting on dirty clothes after showering, as well as eating constantly. The patient denied any fevers, chills, night sweats, headaches, vision changes, or tinnitus. She also denied any rashes, muscle pain, or intolerance to heat or cold. There was no history of seizure disorder or depression. Her past medical history was notable only for hypertension and being a passenger in a motor vehicle crash 1 year before admission. She denied any alcohol, tobacco, or illicit drug use, and had no travel history other than coming to the United States, as she was originally from Trinidad. On physical examination, she was a moderately obese African American woman with a flat affect, psychomotor slowing, and alopecia of the scalp. She was alert and oriented to person, place, and time, but had a score of 26 out of 30 on the Mini-Mental State Examination. She lost points only for recall; she had no difficulty with serial 7s. Her cranial nerves were intact and her speech was fluent, although sparse, and she did not make any paraphasic errors. Her muscle strength was 5/5 in both the upper and lower extremities. Reflexes were 2+ in the upper extremities and 1+ in the lower extremities, and toes were downgoing bilaterally. She had intact sensation to light touch and pinprick, but markedly diminished proprioception of her lower extremities bilaterally. She had a wide-based gait with a positive Romberg sign and was markedly ataxic. Rectal examination yielded a positive guaiac test with brown stool, normal tone, and no masses. The remainder of the physical examination was normal. Laboratory studies revealed pancytopenia with a hematocrit of 22.7% and a mean corpuscular volume of 118.2 fL. A peripheral smear that was performed on admission, prior to transfusion, revealed macrocytic red cells and hypersegmented neutrophils.

Accidental Falls↗
PubMed1991

Effect of proprioceptor stimulation on postural stability in patients with peripheral or central vestibular lesion.

Body sway in upright stance at rest and after inducing proprioceptor stimulation, elicited by vibration applied to the calf or neck muscles, was studied in 11 patients with peripheral lesion and in 17 patients with central vestibular lesion. The responses were compared with those of 20 normal subjects. Vibratory stimulus was applied at five different frequencies, ranging from 32 to 150 Hz, and at a constant amplitude of 2.1 mm. Postural stability was measured with a force platform in terms of average deviation of body position (ADBP) analyzed in relation to the individual maximum support distance in the anterio-posterior direction. In patients with peripheral vestibular lesion ADBP was moderately increased, compared to normal subjects, when the calf muscles were exposed to vibration under eyes closed conditions (i.e. no visual information available); stimulation of neck muscles both under eyes open and eyes closed conditions and stimulation of calf muscles with open eyes produced an ADBP of the same magnitude as in controls. In patients with central vestibular lesion, proprioceptor stimulation of calf and neck muscles caused increased ADBP whether with eyes open or closed. The ADBP induced by stimulation of neck muscles was significantly greater in patients with a central lesion than in those with a peripheral vestibular lesion. The results indicate that patients with peripheral lesion differ from those with central vestibular lesion in their reaction to proprioceptor stimulus; and that in patients with central vestibular lesion proprioceptor stimulation of the neck muscles produces disproportionately powerful cervico-collic reflexes.

Brain Stem↗
PubMed1982

Adaptation to altered support and visual conditions during stance: patients with vestibular deficits.

Patients whose deficits were limited to clinically well qualified vestibular disorders have been exposed to a number of altered support surface and visual environments while standing unsupported. A six-degrees-of-freedom platform employing movable support surfaces for each foot and a movable visual surround deprived patients of normal inputs derived from a fixed level support surface and from an immobile surround. Various tests employing EMG, force, and body movement recording identified quantitative changes in the patients' strategy for the relative weighting of proprioceptive, vestibular, and visual inputs. The most dramatic performance deficit of patients was their inability to suppress the influence of visual and proprioceptive inputs appropriately whenever motions of external surface disturbed the orientation information provided by these inputs. Thus, the more mildly afflicted patients experienced instability not so much because of the loss of vestibular inputs directly to posture but because of their inappropriate responses to proprioceptive inputs and vision. Discussion is centered on the role of vestibular input as an internal reference system for orientation about which adaptive changes in proprioceptive and visual inputs are made.

Humans↗
PubMed2004

The reference values of the T-wave of the patellar tendon reflex in normal dogs.

The T-wave of the patellar tendon reflex (PTR) was recorded in 24 neurologically normal dogs. The surface electromyogram (EMG) was recorded as the T-wave from the vastus lateralis muscle (VL) in response to percussion of the patellar tendon. The distance of the reflex arc (DRA) was measured along the straight line between the spinous process of L5 and the greater trochanter (GT), and between GT and the patellar ligament (PL). There was a significant correlation (P<0.001) of the latency with the DRA on each side, but no difference in the slopes of the relationships between right and left VL was shown. The regression line between the DRA and the latency of all data was Y = 0.0216X + 1.693, where Y = latency in ms, X = DRA in mm. The mixed sensory-motor conduction velocity was estimated as 84.6 +/- 5.5 m/s. In contrast, there was no significant correlation between the DRA and the amplitude of the T-waves. The mean (mean-CV) and standard deviation (SD-CV) of all CV (coefficient of variation) in each dog were 9.14 +/- 3.65% in latency and 3.54 +/- 1.14% in amplitude, indicating that the use of a simple hand-held reflex hammer is sufficient to record the reproducible T-wave of the PTR even in unanesthetized dogs. This method was applied to a case with minimal paraparesis, and the latency of the T-wave of the PTR in the right hind limb with slight proprioceptive deficit was outside of the upper limit of the 95% confidence interval between latency and the DRA. In conclusion, this method may be used in neurological diagnosis to quantify more precisely the PTR in dogs.

Animals↗
PubMed1993

Gravitoinertial force level influences arm movement control.

1. The ability to move the forearm between remembered elbow joint angles immediately after rapid increases or decreases of the background gravitoinertial force (G) level was measured. The movements had been well-practiced in a normal 1G environment before the measurements in high-(1.8G) and low-force (0G) environments. The forearm and upper arm were always unsupported to maximize the influence of altered G-loading and to minimize extraneous cues about arm position. 2. Horizontal and vertical movement planes were studied to measure the effects of varying the G load in the movement plane within a given G background. Rapid and slow movements were studied to assess the role of proprioceptive feedback. 3. G level did not affect the amplitude of rapid movements, indicating that subjects were able to plan and to generate appropriate motor commands for the new G loading of the arm. The amplitude of slow movements was affected by G level, indicating that proprioceptive feedback is influenced by G level. 4. The effects of G level were similar for horizontal and vertical movements, indicating that proprioceptive information from supporting structures, such as the shoulder joint and muscles, had a role in allowing generation of the appropriate motor commands. 5. The incidence and size of dynamic overshoots were greater in 0G and for rapid movements. This G-related change in damping suggests a decrease in muscle spindle activity in 0G. A decrease in muscle spindle activity in 0G and an increase in 1.8G are consistent with the results of our prior studies on the tonic vibration reflex, locomotion, and perception of head movement trajectory in varying force backgrounds.

Adult↗
PubMed1982

A somatotopic and functional organization of the masticatory proprioceptors in the mesencephalic trigeminal nucleus of the frog.

A stratified organization of the first-order neurons of the masticatory proprioception has been observed in the frog mesencephalic trigeminal nucleus (MeNV). Extracellular records of unit activity have shown that in this nucleus neurons responding either to jaw raising muscles or to jaw lowering muscles reveal a somatotopy. A consistent topography pattern is evident by exploring in dorsoventral direction the layers 4 and 6 in the optic tectum. The jaw closing muscles are represented in the dorsal part of the MeNV, whereas the jaw opening ones are distributed more ventrally. Since MeNV neurons represents the afferent limb of the masticatory reflex, the motor effects elicited by electrical stimulation of these cells have been tested.

Afferent Pathways↗
PubMed2000

Distribution of presynaptic inhibition on type-identified motoneurones in the extensor carpi radialis pool in man.

The question was addressed as to whether the magnitude of Ia presynaptic inhibition might depend on the type of motor unit activated during voluntary contraction in the wrist extensor muscles. For this purpose, we investigated the effects of applying electrical stimulation to the median nerve on the responses of 25 identified motor units to radial nerve stimulation delivered 20 ms after a conditioning stimulation. The reflex responses of the motor units yielded peaks in the post-stimulus time histograms with latencies compatible with monosynaptic activation. Although median nerve stimulation did not affect the motoneurone net excitatory drive assessed from the mean duration of the inter-spike interval, it led to a decrease in the contents of the first two 0.25 ms bins of the peak. This decrease may be consistent with the Ia presynaptic inhibition known to occur under these stimulation conditions. In the trials in which the median nerve was being stimulated, the finding that the response probability of the motor units, even in their monosynaptic components, tended to increase as their force threshold and their macro-potential area increased and as their twitch contraction time decreased suggests that the median nerve stimulation may have altered the efficiency with which the Ia inputs recruited the motoneurones in the pool. These effects were consistently observed in seven pairs of motor units each consisting of one slow and one fast contracting motor unit which were simultaneously tested, which suggests that the magnitude of the Ia presynaptic inhibition may depend on the type of motor unit tested rather than on the motoneurone pool excitatory drive. The present data suggest for the first time that in humans, the Ia presynaptic inhibition may show an upward gradient working from fast to slow contracting motor units which is able to compensate for the downward gradient in monosynaptic reflex excitation from 'slow' to 'fast' motor units. From a functional point of view, a weaker Ia presynaptic inhibition acting on the fast contracting motor units may contribute to improving the proprioceptive assistance to the wrist myotatic unit when the contraction force has to be increased.

Adult↗
PubMed1986

Role of visual and static vestibular influences on dynamic posture control.

Postural stabilization in altered visual and vestibular conditions was investigated in humans subjected to fast transient disturbances and during sinusoidal movement of the standing support. Visual inputs were varied by applying stroboscopic illumination, stabilizing the visual surround in respect to head movements, inducing apparent body movement in pitch by continuously moving stripe patterns up or down and by eye closure. Static vestibular input was modified by bending the head forwards or backwards, or to the right or left shoulder (eyes closed). Neither biomechanical parameters of standing nor EMG responses of the anterior tibial and triceps surae muscles were modified by the different visual and vestibular conditions during fast transient (80 degrees/s) platform movements 4 degrees toe-up. Continuous regulation of upright stance during sinusoidal movements (1 Hz, 0.3 Hz), however, clearly depended on the different modifications of visual and vestibular inputs. Fast transient disturbances are easily compensated in a reflex-like manner independent of visual and vestibular feedback. Continuous regulation of upright posture during slow disturbances, however, clearly depends on the evaluation of afferent information from the visual, vestibular, and proprioceptive systems.

Adolescent↗