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PubMed1994

Development of righting when falling from a bipedal standing posture: evidence for the dissociation of dynamic and static righting reflexes in rats.

Righting to prone when placed supine on the ground by rats is present at birth, albeit in incomplete form. In contrast, righting in the air when falling from the supine position does not begin to emerge until the end of the first week and is not complete until the end of the third week postnatally. On the ground, the animals have sensory information from proprioceptive-tactile sources, as well as vestibular; in the air, they have only vestibular. Thus, it is possible that the difference between contact righting and air righting is a reflection of the relative difference in the maturation of tactile vs. vestibular mechanisms. In this study, pups were tested by pushing them backwards from a bipedal standing position. Such a context provided proprioceptive-tactile information during the fall. The results showed that the developmental onset and maturation of righting from the bipedal position resembled that of air righting rather than contact righting. This suggests that the difference between air righting and contact righting is not due to differences in sensory inputs, but to differential maturation of neural mechanisms for acceleratory (i.e., falling) vs. stationary (i.e., lying on the ground) forms of righting. That is, the appropriate neural systems are organized for the type of righting, not for the sensory systems used. Even so, some evidence is provided suggesting a developmental dissociation between righting from falling with vestibular information only, and with proprioceptive-tactile information in addition. Therefore, righting systems appear to need two dimensions of classification--one based on sensory systems involved, and the other in terms of the context of righting (i.e., falling vs. stationary).

Aging↗

PubMed1996

Influence of the extraocular muscle proprioceptors on the orientation of the vestibulo-ocular reflex.

In the intact brain lamb, unilateral electrolytic lesion of the medial dorso-lateral portion of the semilunar ganglion containing the first order neurons of the eye muscle proprioception induced modifications of the horizontal and vertical vestibulo-ocular reflex (HVOR and VVOR) which consisted in marked alterations of the trajectories of the quick phases, while the slow phases were scarcely affected. Similar results were observed after section of the branches described by Winckler in the retrobulbar region along the extraocular muscle proprioceptive information travels. These findings extend those of previous investigations carried out in decorticate animals.

Animals↗

PubMed2004

Development of sensory motor reflexes in 2 G exposed rats.

During gestation and early postnatal development, the animal's size and weight rapidly increase. Within that period, gravity affects sensory and motor development. We studied age-dependent modifications of several types of motor reflexes in 5 groups of rats conceived, born and reared in hypergravity (HG; 2 g). These rats were transferred to normal gravity (NG; 1 g) at various postnatal days, and their behavioral reflexes were compared with a control group which was constantly kept under NG. HG induced a retarded development of vestibular dependent reflexes. Other types of motor behavior were not delayed.

Animals↗

PubMed1986

New perspectives in the investigation of disorders of balance.

It is a common misconception that all disorders of balance can be attributed to derangements of the vestibular system. In fact spatial orientation is dependent upon the proper coordination of a number of sensory inputs and each of these is susceptible to damage by disease or injury. A variety of new tests is described which have as their aim the indentification of balance disorders resulting specifically from derangements of visual processing, proprioception and the neck reflexes. In addition, attention is given to the differential impairment of linear and circular vection and to the possible clinical application of vestibular evoked potentials.

Diagnosis, Differential↗

PubMed1999

[The vestibulo-cervico-ocular reflex in healthy persons].

The vestibular-cervical-ocular reflex (VCOR) results from interaction of the labyrinthine and cervical proprioceptive afferent flows. VCOR study was performed in 20 healthy test subjects. Analyzed were the coefficient of reactivity, VCOR phase shift, coefficient of COR involvement, and the coefficient of VOR-VCOR asymmetry. Functional dependence of cervical proprioceptive and vestibular afferentation in the healthy test subjects was demonstrated.

Adolescent↗

PubMed1988

Classical conditioning of the eye withdrawal reflex in the green crab.

Eye withdrawal in the green crab, Carcinus maenas was conditioned by pairing a mild vibration to the carapace as a conditioned stimulus (CS) with a puff of air to one of the eyes as an unconditioned stimulus (US). Animals subjected to repeated pairings showed an increased probability of eye retraction during CS presentation. Significantly less responding was found in several control groups subjected to backward conditioning, unpaired stimuli, stimuli alone, or simply time in the apparatus. Although conditioned animals showed few responses to CS alone after 24 hr, retention could be demonstrated by acquisition that was much more rapid on day 2 than on day 1. Conditioning could also be effected in the eye when it was restrained, a result consistent with reports in the literature that this reflex does not require proprioceptive feedback. Because the neuromuscular circuitry of eye withdrawal is already well defined in Carcinus, this is a promising candidate for studying the neuronal basis of classical conditioning.

Animals↗

PubMed1995

Effects of tonic neck reflex on optokinetic nystagmus in rabbits.

In this study, rabbits with black-pigmented eyes were suspended in air with none of their limbs touching the ground, and surrounded by a full-field optokinetic drum. The drum was rotated counterclockwise at 60 degrees/s. Horizontal eye movement was recorded by electronystagmograph with the animals in three postures: 1) initial posture, head and trunk aligned along the same body axis, 2) trunk rotated clockwise by 60 degrees with head stationary, and 3) trunk rotated counterclockwise by 60 degrees with head stationary. The recordings were repeated after cervical nerve roots were sectioned unilaterally. The speed of the slow phase of nystagmus was significantly faster in the second than in the initial posture, but significantly slower in the third than in the initial posture. These effects of trunk rotation on the speed of the slow phase were not seen when the side of cervical nerve section was extended. The results indicate that smooth following eye movement is influenced by the neck reflex. It is accelerated when the head turns in the same direction as the visual field, whereas it is inhibited when the head turns in the opposite direction. Proprioceptors of the extended neck appear to account for the effects observed.

Animals↗

PubMed1996

Changes in motor activity and biomechanics during balance recovery following cutaneous and muscular deafferentation.

The effects of lower limb deafferentation were examined during execution of a balance recovery step following a forward fall induced by release of an initial inclined posture. The subjects were healthy control subjects and patients with a unilateral loss of the Achilles tendon reflex following S1 radiculitis. Deafferentation of healthy subjects was obtained by unilateral leg ischemia (four subjects) and by foot anesthesia (five subjects). The balance recovery step was characterized by the surface electromyographic (EMG) activity of right and left soleus and tibialis anterior muscles and the kinetics of the center of gravity and center of foot pressure. Experimentally induced and pathological deafferentation decreased the EMG activity of the ipsilateral soleus and lowered the vertical ground reaction force. The lower limb motor activity was more affected by loss of muscle proprioceptive afferents than by loss of plantar cutaneous afferents. Patients showed early and bilateral changes in soleus and tibialis activities, whichever side was affected. The step length of patients was also shorter than that of controls, but it remained similar before and after deafferentation in the healthy subjects. The results are discussed in terms of ipsilateral and crossed pathway connections and functional adaptive strategies.

Achilles Tendon↗

PubMed1979

H-reflex latency in uremic neuropathy: correlation with NCV and clinical findings.

Sixty-two uremic patients on dialysis of varying durations were tested bilaterally for posterior tibial nerve H-reflex latency, at 3-month intervals. Bilateral nerve conduction velocities (NCVs) of the peroneal, tibial, and sural nerves were concomitantly determined in all subjects. Proprioception sense, vibration perception threshold at the great toes, and deep tendon reflexes at the knee and ankle were determined in all subjects on the day of electrodiagnostic testing. The sensitivity of the H-reflex latency in detection of the onset and severity of uremic neuropathy was assessed. H-reflex latency changes were compared to NCV and clinical test results. The following was found: (1) of the parameters studied, the H-reflex latency appeared to be the most sensitive indicator of early uremic polyneuropathies, (2) electrodiagnostic tests were more sensitive to the onset of neuropathies than the clinical testing parameters studied, and (3) the sural sensory nerve appeared to be involved earlier than peroneal and tibial motor nerves in neuropathies studied.

Adolescent↗

PubMed1988

The induction and compensation of asymmetric eye movements following unilateral blockage of a horizontal semicircular canal in the rabbit.

The influence of unilateral plugs of the left horizontal semicircular canal (LHC plugs) of rabbits on the development and compensation of asymmetric eye movements evoked by horizontal vestibular stimulation was studied. LHC plugs caused an immediate reduction of 50-65% in the gain of the horizontal vestibuloocular reflex (HVOR). This reduction in gain was achieved without altering the symmetry of the HVOR, and was accompanied by a change in the axial alignment of eye movements evoked by vestibular stimulation about the vertical (HVOR) and longitudinal (VVOR) axes. Postoperative asymmetry of eye movements developed 12-48 hr after the plugging operation. The development of asymmetry was reduced if the rabbit was restrained for 24 hr, thereby minimizing vestibular stimulation following the plugging operation. Over a 3-4 week period, the normal symmetry of eye movements was restored and the axial alignments of the HVOR and VVOR returned to the preoperative values. The gain of the HVOR did not recover. The horizontal cervicoocular reflex (HCOR) was examined before the plugging operation and after compensation of asymmetry was complete. The gain and phase of the HCOR were not altered. A relatively simple set of explanations at a cellular level is proposed to account for the induction and compensation of asymmetric eye movements following a unilateral plug of the horizontal semicircular canal.

Adaptation, Physiological↗

PubMed1988

Constipation in the elderly. A physiologic study.

Colorectal motility was studied in 25 elderly patients with chronic constipation and compared with an asymptomatic control group (N = 17). Proctometrograms were performed to measure rectal volumes at sensory threshold and maximal tolerance, and rectal compliance. Anal sphincter pressures and reflexes were measured by conventional techniques. Indices of colonic motility were also assessed. Significant impairment of rectal sensory threshold was apparent in constipation. Six patients presenting with impaction demonstrated functional megarectums. The remaining 19 showed a significant reduction in maximal rectal volume and rectal compliance and 14 extruded the balloon. There were no differences in sphincter length or presence of the rectosphincteric reflex. Four patients had an absent pudendoanal reflex and the remainder significant prolongation. Total gastrointestinal transit times were prolonged in the constipation group, mainly distally due to rectal stasis. In two patients bisacodyl failed to elicit a sigmoid motor response. Constipation in the elderly is not merely due to delayed transit. Neurogenic deficits of sacral spinal cord function may be responsible for abnormalities in rectal motor and sensory function.

Adult↗

PubMed1985

Vertigo due to whiplash injury: a neurotological approach.

A series of examinations were carried out to elucidate the characteristics of vertigo due to whiplash injury. In patients with whiplash injury, there are over-excitation of the cervical and/or the lumbar proprioceptors on one hand, and dysfunction of the central nervous system, such as the hypothalamus, the brain stem and the cerebellum, on the other hand. These two etiological factors induce disequilibrium by a trigger-and-target relationship in which the above proprioceptors act as a trigger and the central nervous system acts as a target. This postulate is applicable to the explanation of aural vertigo following whiplash injury. Autonomic reflexes in patients with whiplash injury can be explained not only as due to over-excitation of the cervical sympathetic nerves, but also to that of the cervical and lumbar proprioceptors. In other words, these reflexes are considered as being the proprio-autonomic reflexes. These reflexes are more evident in patients with cervical pain. Cerebellar symptoms can be manifested by over-excitation of the cervical and lumbar proprioceptors. These symptoms are more evident in patients with lumbar pain. The above differences in the autonomic reflexes and cerebellar symptoms of patients with cervical and/or lumbar pains can be explained on the basis of known fiber connections in the central nervous system. Hypertonicity of the cervical and lumbar erector muscles in patients with whiplash injury can be explained not only as due to over-excitation of gamma fibers, but also to that of sympathetic nerves in these muscles. This hypertonicity affects the central nervous system, causing disequilibrium following whiplash injury.

Adult↗

PubMed1993

Methods to assess the development and recovery of locomotor function after spinal cord injury in rats.

The ability to assess recovery of function after spinal cord injury is a very important part of spinal cord injury research. Recent progress has been made in a number of avenues of treatment designed to ameliorate the consequences of spinal cord injury and enhance recovery of function. This potential for intervention to modify the sequellae of spinal cord injury requires stringent criteria for methods used to evaluate the effects of injury and subsequent recovery of function. Methods which rely on composite ratings of an animal's overall performance, while appropriate for screening groups of animals with spinal cord injury, are not sufficient to demonstrate whether a particular treatment has had a specific effect on motor function or the degree to which function is affected. We have designed a series of sensitive quantitative methods to assess the recovery of locomotor function in rats. The methods examine specific reflex responses and specific components of motor behavior and are sensitive to subtle differences in the pattern of locomotion and individual limb movements. Several of the tests can be used to assess the development of locomotor function as well as the mature response. Postural reflex testing and locomotor function under conditions of graded difficulty are examined and the motor capacity of individual limbs is assessed. Animals are trained to cross runways, to walk on a treadmill, and to climb onto a platform. The animals' performance is videotaped for subsequent quantitative analysis. The pattern of overground and treadmill locomotion is also examined by footprint analysis. Spinal cord injury alters an animal's reflex responses and deficits are evident in locomotor function. Examples are given of the quantitative measurements obtained from analysis of the animals' performance on each of the tests. No single test is sufficient to assess recovery of function after spinal cord injury. Rather, a combination of tests, each examining particular components of normal and recovered motor function, is required. The methods used to assess recovery of locomotor function are specific, are sensitive, and allow individual limb movements to be isolated. Such specific methods allow one to begin to address the mechanisms underlying recovery of function following spinal cord injury.

Animals↗

PubMed1986

Morphine subtracts subcomponents of haloperidol-isolated postural support reflexes to reveal gradients of their integration.

Although cataleptic rats do not spontaneously orient, scan, or walk, they will cling, stand, right themselves in the air, and resist being displaced from a stable position (Schallert, Whishaw, De Ryck, & Teitelbaum, 1978). Morphine produces a state of immobility in which all reflexes used for stable static support (e.g., standing, righting, clinging, and bracing) appear to be inhibited (De Ryck, Schallert, & Teitelbaum, 1980). Addition of morphine to haloperidol abolished or reduced those reflexes used to defend against slow postural displacements (e.g., bracing) but left intact those used to protect against fast postural displacements (e.g., righting in the air). However, although intact, these responses to fast postural displacements were completely abolished by labyrinthectomy, showing that they were controlled only by vestibular inputs. During recovery from morphine's effects, the responses to slow postural displacements reemerged, revealing fractional subcomponents. Furthermore, the reorganization of the subcomponents proceeded along specific body gradients; for example, bracing and standing reemerged caudorostrally, while at the same time, righting and clinging reemerged rostrocaudally.

Animals↗

PubMed1987

Vestibular contribution to the orientation of cervico-ocular reflex in rabbit.

In the rabbit the cervico-ocular reflex (COR) helps to maintain the gaze stability during passive head displacements, by increasing the gain and decreasing the phase lead of low frequency vestibular responses and by diminishing in amplitude the anticompensatory vestibular fast phases. These cervical influences appear only for horizontal stimulations, while they are scarce or absent in the vertical and sagittal planes. Ocular responses to horizontal body displacements are oriented in the horizontal plane and remain in the same plane when the head is statically pitched at various degrees, in spite of the directional changes in the extraocular muscle (EOM) lines of force with respect to space. Tension recordings from the EOMs show that the oculomotor system is differently activated depending upon the degree of head inclination. This change in the EOM activation is not observed when the body, instead of the head, is pitched. Furthermore, after bilateral labyrinthectomy (BL) the cervico-ocular responses lose their appropriate directionality. It is concluded that the information for determining the plane of the eye movements during cervical stimulations does not originate from the neck proprioception but is provided by the otolithic receptors.

Animals↗

PubMed2003

Behavioural changes induced by early and long-term gravito-inertial force modification in the rat.

The study concerns rats conceived, born and raised in a hypergravity environment (HG: 2 g) for 3 months using a centrifuge. They were then exposed to terrestrial gravity (1 g) and submitted to behavioural tests investigating their spontaneous locomotor activity (open-field), their posture (support surface), and their vestibular function (air-righting reflex). Performances were compared to age-matched control rats housed at 1 g for the same time period. Results showed static and dynamic behavioural deficits as early as the rats were exposed to normal gravity. They exhibited strongly increased motor activity in open-field, with longer travelled distances and more scattered trajectories; in addition, the HG rats displayed more numerous rearings than controls did. They showed postural changes characterized by an enlarged support surface and they did not succeed in the air-righting reflex, due to increased time-delay for head righting. None of these changes were permanent. Indeed, for all tests, the HG rats tested after 3 weeks spent in normal terrestrial gravity exhibited behaviours similar to those of the controls. HG-induced changes in the functional properties of the vestibular system may explain the deficits showed by the HG rats once exposed to normal gravity. The adaptation process to 1 g leading to the appearance of normal behaviour takes about 3 weeks. It likely implicates a central re-evaluation of the sensory inputs and an updating of the motor commands.

Adaptation, Physiological↗

PubMed1989

Modulation of a viscerosomatic reflex by electrical and chemical stimulation of hypothalamic structures in the rat.

Ventromedial forebrain structures were stimulated electrically with short (10-ms) trains of pulses to test for effects on a viscerosomatic reflex. Stimulation at many hypothalamic sites led to an attenuation or even a complete inhibition of reflex activity. The most sensitive sites, however (i.e. those requiring currents of 50 microA or less to inhibit the reflex), were located in the anterior hypothalamus/preoptic area (AH/POA) and rostrally in the diagonal band of Broca (DBB). At certain sites the effects of electrical stimulation were compared with those of microinjection of an excitatory amino acid (DL-homocysteic acid) which is known to excite neuronal cell bodies and not axons. The results of this part of the study indicated that activation of cell bodies located in the ventromedial AH/POA (from the level of the optic chiasma caudally to the level of DBB rostrally) mediate, at least in part, the inhibitory effects on visceral afferent processing. These data are discussed in relation to a possible role of AH/POA in the spinal processing of nociceptive information of visceral origin.

Animals↗

PubMed1981

The horizontal and vertical cervico-ocular reflexes of the rabbit.

Horizontal and vertical cervico-ocular reflexes of the rabbit (HCOR, VCOR) were evoked by sinusoidal oscillation of the body about the vertical and longitudinal axes while the head was fixed. These reflexes were studied over a frequency range of 0.005-0.800 Hz and at stimulus amplitudes of +/- 10 degrees. When the body of the rabbit was rotated horizontally clockwise around the fixed head, clockwise conjugate eye movements were evoked. When the body was rotated about the longitudinal axis onto the right side, the right eye rotated down and the left eye rotated up. The mean gain of the HCOR (eye velocity/body velocity) rose from 0.21 and 0.005 Hz to 0.27 at 0.020 Hz and then declined to 0.06 at 0.3Hz. The gain of the VCOR was less than the gain of the HCOR by a factor of 2-3. The HCOR was measured separately and in combination with the horizontal vestibulo-ocular reflex (HVOR). These reflexes combine linearly. The relative movements of the first 3 cervical vertebrae during stimulation of the HCOR and VCOR were measured. For the HCOR, the largest angular displacement (74%) occurs between C1 and C2. For the VCOR, the largest relative angular displacement (45%) occurs between C2 and C3. Step horizontal clockwise rotation of the head and body (HVOR) evoked low velocity counterclockwise eye movements followed by fast clockwise (resetting) eye movements. Step horizontal clockwise rotation of the body about the fixed head (HCOR) evoked low velocity clockwise eye movements which were followed by fast clockwise eye movements. Step horizontal clockwise rotation of the head about the fixed body (HCOR + HVOR) evoked low velocity counterclockwise eye movements which were not interrupted by fast clockwise eye movements. These data provide further evidence for a linear combination of independent HCOR and HVOR signals.

Acoustic Stimulation↗