Contralateral Reflex Research Articles

Characteristics of Glottic Closure Reflex in a Canine Model

PurposeThe most important function of the larynx is airway protection which is provided through a polysynaptic reflex closure triggered by the receptors in the glottic and supraglottic mucosa, evoking the reflex contraction of the laryngeal muscles especially by strong adduction of vocal cords. Based on the hypotheses that central facilitation is essential for this bilateral adductor reflex and that its disturbance can result in weakened laryngeal closure, we designed this study to elucidate the effect of central facilitation on this protective reflex.Materials and MethodsSeven adult, 20 kg mongrel dogs underwent evoked response laryngeal electromyography under 0.5 to 1.0 MAC (minimum alveolar concentration) isoflurane anesthesia. The internal branch of the superior laryngeal nerve was stimulated through bipolar platinum-iridium electrodes, and recording electrodes were positioned in the ipsilateral and contralateral thyroarytenoid muscles.ResultsIpsilateral reflex closure was consistantly recorded regardless of anesthetic levels. However, contralateral reflex responses disappeared as anesthetic levels were deepened. Additionally, late responses (R2) were detected in one animal at lower level of anesthesia.ConclusionsDeepened level of anesthesia affects central facilitation and results in the loss of the crossed adductor reflex, predisposing to a weakened glottic closure response. Precise understanding of this effect may possibly provide a way to prevent aspiration in unconscious patients.

Genetic Ablation of V2a Ipsilateral Interneurons Disrupts Left-Right Locomotor Coordination in Mammalian Spinal Cord

The initiation and coordination of activity in limb muscles are the main functions of neural circuits that control locomotion. Commissural neurons connect locomotor circuits on the two sides of the spinal cord, and represent the known neural substrate for left-right coordination. Here we demonstrate that a group of ipsilateral interneurons, V2a interneurons, plays an essential role in the control of left-right alternation. In the absence of V2a interneurons, the spinal cord fails to exhibit consistent left-right alternation. Locomotor burst activity shows increased variability, but flexor-extensor coordination is unaffected. Anatomical tracing studies reveal a direct excitatory input of V2a interneurons onto commissural interneurons, including a set of molecularly defined V0 neurons that drive left-right alternation. Our findings imply that the neural substrate for left-right coordination consists of at least two components; commissural neurons and a class of ipsilateral interneurons that activate commissural pathways.

Effects of Altered Consciousness on the Protective Glottic Closure Reflex

The sphincteric function of the larynx, essential to lower airway protection, is most efficiently achieved through strong reflex adduction by both vocal folds. We hypothesize that central facilitation is an essential component of a bilateral brain stem-mediated adductor reflex and that its disturbance by altered consciousness or physiologic sleep could result in weakened sphincteric closure. In 10 adult pigs the glottic closure response was evaluated under light and deep isoflurane anesthesia. The internal branch of the left superior laryngeal nerve was stimulated through bipolar platinum-iridium electrodes, and recording electrodes were positioned in the ipsilateral and contralateral thyroarytenoid muscles. The force of evoked glottic closure was measured with a pressure transducer positioned between the vocal folds. Consistent threshold responses (>90%) were obtained ipsilaterally from 0.5 to 2.0 minimal alveolar concentration (MAC) anesthesia. However, the contralateral reflex responses declined to 6.4% in successive trials as anesthetic levels approached 1.5 to 2.0 MAC. Furthermore, glottic closing force closely reflected these electromyographic changes, declining from 383 mm Hg at 0.5 to 1.0 MAC to 114 mm Hg at 1.5 to 2.0 MAC. Alteration of central facilitation by progressively deeper loss of consciousness abolishes a lower brain stem-mediated crossed adductor reflex, predisposing the subject to a weakened glottic closure response.

Identificação de sentenças sintéticas (SSI) e reflexo acústico contralateral

The study of the relationship of the contralateral acoustic reflex with the auditory skill of closure. To analyze the identification of a speech signal in the presence of competitive sounds in subjects with absence of contralateral acoustic reflex. Application of the synthetic sentence identification (SSI) test under the conditions of competitive contralateral message (SSI-CCM), with the signal-to-noise ratio of 0 and -40dB, and ipsilateral competitive message (SSI-ICM), with the signal-to-noise ratio of 0, -10, -15 and -20dB, in 43 young adults (group A = 21 subjects with contralateral acoustic reflex present in all of the investigated frequencies, and group B = 22 subjects with contralateral reflex absent at the frequency of 500Hz, or in all of the investigated frequencies, or still in some of the investigated frequencies necessarily including 500Hz), of both gender, with no hearing, otologic or learning disabilities. The acoustic reflex threshold was above 100dB NA in 59% of the individuals in group B and in 14% of the individuals in group A. All subjects performed according to the normal pattern suggested in the specialized literature for the SSI test. The performance of group B in the SSI-ICM test was inferior to that of group A for all the signal-to-noise ratios used, although the difference was not statistically significant. Group B, which presented an acoustic reflex threshold higher than 100dB NA or the absence of the acoustic reflex, was also the group that presented the worse performance in the SSI test. The absence of the contralateral acoustic reflex seems to interfere in the identification of the speech signal in the presence of competitive noises.

Influence of anaesthetic agents on transient evoked otoacoustic emissions and stapedius reflex thresholds

This aim of this study was to determine the effect of anaesthetic agents on stapedius reflex (SR) thresholds and transient evoked otoacoustic emissions (TEOAE). Fifty patients who were scheduled for operation and who had normal hearing were included in the study. All were given midazolam for premedication and propofol for induction. Anaesthesia was maintained in five different ways in each group of 10 patients. Groups I-IV received inhalational anaesthesia: group I received 70 per cent N2O plus 30 per cent O2, group II sevoflurane, group III desflurane and group IV halothane. Group V received total intravenous anaesthesia with propofol plus sufentanil. The SR and TEOAE of the patients were measured four times: on the day before surgery (first measurement), after premedication (second measurement), after induction of anaesthesia (third measurement) and during maintenance of anaesthesia (fourth measurement). Midazolam significantly increased ipsilateral and contralateral SR thresholds and decreased TEOAE wave reproducibility. Propofol significantly increased only the SR thresholds. The other anaesthetic agents significantly increased only the contralateral reflex thresholds. Of these, the highest increase was seen after sevoflurane and the lowest after halothane. The changes in TEOAE wave reproducibility due to anaesthetic agents used for maintenance were not significant. We concluded that midazolam premedication may affect audiological evaluation with SR and TEOAE tests, and sevoflurane should not be used when it is necessary to measure SR under general anaesthesia.

Unilateral application of an inflammatory irritant to the rat temporomandibular joint region produces bilateral modulation of the jaw-opening reflex

The aim of this study was to determine the effect of unilateral acute inflammation of craniofacial deep tissues on the ipsilateral and contralateral jaw-opening reflex (JOR). The effects of mustard oil (MO), injected into the temporomandibular joint region, were tested on the JOR recorded in the digastric muscle and evoked by low-intensity electrical stimulation of the ipsilateral and contralateral inferior alveolar nerve in anesthetized rats. The MO injection induced a long-lasting suppression of the amplitude of both ipsilaterally and contralaterally evoked JOR, although the latency and duration of the JOR were unaffected. The suppressive effect was more prominent for the contralaterally evoked JOR, and observed even when background activity in the digastric muscle was increased by the MO injection. The results indicate that changes in the JOR amplitude following MO injection do not simply reflect alterations in motoneuronal excitability, and suggest that inflammation of deep craniofacial tissues modulates low-threshold sensory transmission to the motoneurons.

Wideband Reflectance Measures of the Ipsilateral Acoustic Stapedius Reflex Threshold

The purpose of this study was to develop a method for acoustically measuring the ipsilateral acoustic stapedius reflex threshold by using wideband shifts in energy reflectance and admittance. A group of 27 young adult subjects with normal hearing participated in the study. Contralateral reflex thresholds were first measured for a 4000 Hz activator tone (maximum level, 92 dB SPL), using a clinical method with a 226 Hz probe tone. Ipsilateral and contralateral reflex thresholds were then measured by using an experimental wideband reflectance and admittance system that used a band-filtered click (200 to 2000 Hz) as the probe stimulus, presented simultaneously with the 4000 Hz activator tone. Reflex thresholds for the wideband system were determined by using statistical tests of the magnitude of the reflex responses as well as their correlation with other reflex responses. Clinical and experimental reflex thresholds were obtained for 9 of the 27 subjects for all conditions. Clinical reflex thresholds were absent for 8 subjects for whom experimental reflex thresholds were present and were present for 5 subjects who had absent experimental reflex thresholds for one or more conditions. An additional 5 subjects had absent reflex thresholds in all conditions, consistent with the low maximum level of the activator. Wideband measures of contralateral reflex thresholds were approximately 3 dB lower than those obtained with the clinical system. The magnitudes of the group means of the reflex responses were similar for ipsilateral and contralateral stimulations. Wideband measures of reflectance and admittance may be used to estimate the ipsilateral acoustic stapedius reflex threshold by separating in frequency the spectral energies of the wideband probe stimulus from the activator stimulus. This technique holds promise for measuring reflex thresholds for individuals with absent reflex thresholds through the use of standard clinical methods.

Central facilitation of the glottic closure reflex in humans.

The sphincteric function of the larynx, essential to lower airway protection, is most efficiently achieved through strong reflex adduction by both vocal cords. We hypothesize that central facilitation is an essential component of a bilateral adductor reflex and that its disturbance could result in weakened sphincteric closure. Five patients during supraglottic laryngectomy underwent evoked response laryngeal electromyography under 0.5 and 1.0 minimal alveolar concentration (MAC) isoflurane anesthesia. The internal branch of the superior laryngeal nerve was stimulated through bipolar platinum-iridium electrodes, and recording electrodes were positioned in the ipsilateral and contralateral thyroarytenoid muscles. Consistent threshold responses were obtained ipsilaterally from 0.5 to 1.0 MAC anesthesia. However, the contralateral reflex responses approached 0% in successive trials as anesthetic levels approached 1.0 MAC. In human subjects, alteration of central facilitation by deepening anesthesia abolishes the crossed adductor reflex, predisposing to a weakened glottic closure response. A precise understanding of this effect may improve the prevention of aspiration in patients emerging from prolonged sedation or under heavy psychotropic control.

Contralateral acoustic reflex thresholds for tonal activators using wideband energy reflectance and admittance.

The purpose of this study was to evaluate a new method for estimating the acoustic reflex threshold incorporating wideband (250-8000 Hz) measures of energy reflectance and admittance (M. P. Feeney & D. H. Keefe, 2001). The wideband technique incorporates both a correlation method to assess the pattern of the reflex-induced shifts in reflectance and admittance across frequency and a magnitude method to determine if the amplitude of the shifts exceeds baseline variability. Contralateral reflex thresholds for 1000- and 2000-Hz activators were obtained for 34 young adults with both the wideband method and a clinical method using a 226 Hz probe tone. Average reflex thresholds obtained with the new method were 12 to 13.7 dB lower than than obtained with the clinical method. When the bandwidth of analysis of admittance and reflectance responses was limited to 250 to 2000 Hz, the reduction in reflex thresholds was accompanied by the rejection of 96% of nonactivator-baseline responses as reflexes. The method holds promise for extending reflex threshold testing to patients with reflexes elevated beyond current equipment limits, for reducing the sound levels used in reflex testing, and for obtaining sensitive measures of reflex threshold in infants.

Estimating the acoustic reflex threshold from wideband measures of reflectance, admittance, and power.

A method was developed to estimate the contralateral acoustic reflex threshold using shifts in wideband energy reflectance, admittance magnitude and power. In the first experiment contralateral reflex thresholds for a noise activator were estimated on three adult participants using reflectance, admittance and power measurements at frequencies from 250 to 8000 Hz. The reflex threshold was defined using a magnitude and a correlation technique, both having the property of examining the pattern of the reflex-induced shift across a fairly broad frequency range (250 to 2000 Hz). In the second experiment, the magnitude method was modified to include an F test for the comparison of the magnitude of reflex-induced shifts in reflectance, admittance and power relative to response differences in a no-activator baseline condition. Data from four additional participants then were analyzed across a broader frequency range using a method that combined magnitude and correlation methods of estimating reflex thresholds. Acoustic reflex thresholds were obtained using reflectance, admittance and power-level measures in all subjects in both experiments. Individual reflex threshold estimates were as much as 24 dB lower than with the clinical system, with an average of approximately 14 dB lower for the three participants in the first experiment, and approximately 18 dB lower for the four participants in the second experiment. Wideband measures of reflectance, admittance and power were successfully used to estimate acoustic reflex thresholds in seven participants. A reflex threshold test was devised based on the magnitude of the response shift in the presence of a contralateral activator, and the similarity of the response shift spectra across frequency between successive activator levels. Across all participants in the study, the new test yielded a more sensitive measure of the acoustic reflex threshold than the clinical method. This finding has both clinical and theoretical implications for the study of the acoustic reflex.

Critical role of central facilitation in the glottic closure reflex.

The sphincteric function of the larynx, essential to lower airway protection, is most efficiently achieved through strong reflex adduction by both vocal cords. We hypothesize that central facilitation is an essential component of a bilateral adductor reflex and that its disturbance could result in weakened sphincteric closure. Six adult 50-kg pigs underwent evoked response laryngeal electromyography under 0.5 to 1.0 minimal alveolar concentration (MAC) isoflurane anesthesia. The internal branch of the superior laryngeal nerve was stimulated through bipolar platinum-iridium electrodes, and recording electrodes were positioned in the ipsilateral and contralateral thyroarytenoid muscles. Consistent threshold responses were obtained ipsilaterally from 0.5 to 1.0 MAC anesthesia. However, the contralateral reflex responses approached 0% in successive trials as anesthetic levels approached 1.0 MAC. Alteration of central facilitation by deepening anesthesia abolishes the crossed adductor reflex, predisposing to a weakened glottic closure response. A precise understanding of this effect may improve the prevention of aspiration in patients emerging from prolonged sedation or under heavy psychotropic control.

Wideband reflectance measurement of the contralateral acoustic reflex threshold for broadband noise and 1000-Hz tones

Recent work has suggested that wideband reflectance measures may provide a sensitive estimate of the acoustic reflex threshold [M. P. Feeney and D. H. Keefe, J. Speech, Lang. Hear. Res. 42, 1029–1041 (1999)]. This study examined contralateral reflex thresholds for broadband noise and 1000-Hz tones in 21 young adults. The acoustic reflex was detected with the reflectance system by assessing the correlation between pairs of wideband reflectance shifts for a given activator level. Reflex threshold estimates obtained with this method were compared with those obtained with a clinical admittance system. Reflex thresholds for the noise activator were around 10 dB lower for reflectance (M=77.4-dB SPL, Zwislocki coupler) than for the clinical measure [M=87.8-dB SPL, t (20)=6.2, p<0.001]. For the 1000-Hz activator, reflectance reflex thresholds averaged 5 dB lower (M=95.3-dB SPL) than for the clinical system [M=100.2-dB SPL, t (20)=8.2, p<0.001]. Moreover, the tone-noise reflex threshold difference was significantly larger for reflectance (M=17.9-dB SPL) than for the clinical measure [M=12.4-dB SPL, t (20)=6.2, p<0.001]. These results support the use of wideband reflectance as a sensitive measure of the acoustic reflex threshold. [Supported by NIH-R03DC04129.]

Clinical value of ipsi‐ and contralateral sacral reflex latency measurement: A normative data study in man

Clinical value of ipsi‐ and contralateral sacral reflex latency measurement: A normative data study in man

Electrically induced blink reflex and facial motor nerve stimulation in beagles.

Electrophysiologic assessment of the blink reflex test and the muscle-evoked potentials evoked by stimulation of the facial nerve were performed in 15 healthy adult Beagles before and after supraorbital (trigeminal) and facial anesthetic nerve blocks performed by lidocaine injections. Unilateral electrical stimulation of the supraorbital nerve elicited 2 ipsilateral (R1 and R2) and a contralateral (Rc) reflex muscle potential in orbicularis oculi muscles. Electrical stimulation of the facial nerve elicited 2 muscle potentials (a direct response [D] and a reflex faciofacial response [RF]) in the ipsilateral orbicularis oculi muscle. Anesthetic block of the left supraorbital nerve resulted in bilateral lack of responses upon left supraorbital nerve stimulation, but normal responses in right and left orbicularis oculi muscles upon right supraorbital stimulation. Right facial anesthetic block produced lack of responses in the right orbicularis oculi muscle regardless the side of supraorbital nerve stimulation. Results of this study demonstrate that the blink reflex can be electrically elicited and assessed in dogs. Reference values for the blink reflex responses and for the muscle potentials evoked by direct facial nerve stimulation in dogs are provided. The potential usefulness of the electrically elicited blink reflex test in the diagnosis of peripheral facial and trigeminal dysfunction in dogs was demonstrated.

Ipsilateral acoustic reflex detection using wideband acoustic reflectance, admittance, and power measurements

Progress has been achieved in measuring contralateral acoustic reflex shifts to tonal and noise activators in wideband reflectance, admittance, and power [Feeney and Keefe, J. Speech, Language, and Hearing Research (in press)], but no measurements have been made of the corresponding ipsilateral reflex shifts. Because the thresholds of these wideband contralateral reflex shifts were at least 8 dB lower than those obtained using standard clinical techniques, and because clinical research requires the use of both contralateral and ipsilateral testing, it is of interest to formulate a wideband technique to measure the ipsilateral reflex. Such an ipsilateral technique has been developed based on the observation that the major component of the contralateral reflex is below 1.6 kHz. Probe signals were designed with bandwidths from 0.25 kHz up to 1.6 or 2 kHz, and calibrated to measure reflectance (and related responses). The reflex activator signals consisted of tonal stimuli in the range from 2–4 kHz, with levels varied to measure reflex input–output functions. Ipsilateral reflex shifts have been detected using this technique. Work is in progress to compare ipsilateral and contralateral reflexes measured using the same probe and activator signals. [Work supported by NIDCD.]

Electrically elicited blink reflex in horses with trigeminal and facial nerve blocks

Abstract Objective To reassess reference values for the components of the electrically induced blink reflex, document reference values for facial motor nerve conduction velocity, and demonstrate usefulness of the blink reflex as a diagnostic tool in peripheral facial and trigeminal nerve dysfunction in horses. Animals 10 healthy adult horses (8 males, 2 females) without neurologic abnormalities. Procedure Blink reflex tests were performed by electrical stimulation of the supraorbital nerve and facial (auriculopalpebral) nerve. Reflex and direct muscle-evoked potentials of the orbicularis oculi muscles were recorded from concentric needle electrodes inserted bilaterally in these muscles. Supraorbital and auriculopalpebral nerve blocks were performed by lidocaine hydrochloride injections. Results Supraorbital nerve stimulation elicited 2 or 3 ipsilateral and 1 contralateral reflex muscle potential in the orbicularis oculi muscles. Auriculopalpebral nerve stimulation elicited a direct and a reflex potential in the ipsilateral orbicularis oculi muscle. After left supraorbital nerve block, no responses could be elicited ipsilaterally or contralaterally upon stimulation of the blocked nerve, but bilateral responses were obtained upon stimulation of the right supraorbital nerve. After right auriculopalpebral nerve block, no responses were recorded from the right orbicularis oculi muscle upon stimulation of left or right supraorbital nerves. Conclusions and Clinical Relevance Reference values for the components of the blink reflex and facial motor nerve conduction velocity will allow application of these tests to assist in the diagnosis of equine neurologic disorders involving the trigeminal and facial nerves, the brainstem, and the cranial end of the cervical segment of the spinal cord. This study reveals the usefulness of the blink reflex test in the diagnosis of peripheral trigeminal and facial nerve dysfunction in horses. (Am J Vet Res 1999;60:1287–1291)

A comparison of power-based and admittance measures of the acoustic reflex threshold

Contralateral acoustic reflex thresholds obtained using a standard clinical admittance system with a 220-Hz probe tone were compared to those obtained using a frequency-domain-based system for calculating wideband middle ear acoustic impedance and energy reflectance (ZR) [D. H. Keefe et al., J. Acoust. Soc. Am. 91, 470–485 (1992)]. A white noise activator presented through an ER-3A insert phone was used to elicit the contralateral reflex in ten normal-hearing young subjects. The probe signal, a 40-ms wideband chirp, was presented through an ER-10C microphone system for the ZR measures. The microphone signal was then digitized and stored for data analysis. Measurements of reflex-induced changes in the power absorbed by the middle ear and in wideband admittance were then derived to estimate reflex thresholds. An analysis of variance revealed that the average reflex threshold was about 16 dB lower for the power-based and wideband admittance measures than for the clinical measure (p<0.001). However, the two ZR measures were not significantly different from each other. These results have implications for reducing the level of sound exposure during clinical acoustic reflex testing, and for obtaining reflex thresholds that may be beyond system limits for standard clinical systems. [Work supported by OURC.]

Movement-induced modulation of soleus H reflexes with altered length of biarticular muscles

Passive pedaling movements of the leg results in the phasic modulation of the soleus H reflex of that leg. In contrast, the H reflex of the contralateral leg is attenuated tonically. The phasic modulation of the reflex ipsilaterally can be attributed to the afferent discharge associated with the cyclic lengthening of the extensor muscles. We hypothesized that the tonic attenuation of the contralateral reflex could be explained if the afferent feedback arising from the lengthening of the biarticular muscles had an increased importance in regulating the amplitude of the contralateral reflex. To test this, the passive pedaling movements were reduced to those about either the knee or hip alone. Despite the alteration in the pattern of stretching of the biarticular muscles, the contralateral soleus H reflex was tonically attenuated during both forms of single joint movements. We suggest that the same phasic afferent discharge responsible for the modulation of the ipsilateral soleus H reflex initiates the tonic attenuation contralaterally, but that the signal undergoes a complex transformation in crossing the cord. These results do not rule out the possibility that the stretching of the biarticular muscles contributes to the attenuation of the ipsilateral soleus H reflex, which is subsequently masked by a powerful influence from the stretching of the uniarticular extensor muscles. To test this possibility, a second experiment manipulated the lengths of the muscles of the leg by altering the positions of the static joints during isolated rotation of either the knee or hip and measuring the amplitude of the ipsilateral soleus H reflex. From the results, it was clear that stretching the uniarticular extensor muscles produced the most dramatic effects. However, the stretch of the biarticular muscles yielded mild inhibitory influences if these muscles were near their maximal lengths.

Changes in skin blood flow over the foot with warming of the contralateral heel.

Vasospasm in one leg is a common complication of umbilical artery catheterization in preterm infants. It is a common practice to wrap the contralateral leg in a warm washcloth. The rationale for this intervention is to induce reflex vasodilatation of the affected extremity, thereby avoiding the necessity to remove or replace the catheter. This study tested the hypothesis that heating the contralateral extremity in preterm infants would increase peripheral blood flow to the contralateral foot. Ten stable preterm infants who had had no umbilical catheter inserted for at least 2 weeks were studied. Skin perfusion was measured using the laser Doppler method in the distal leg after heating of the opposite foot to 40.5 degrees C. Blood flow to the skin of the contralateral foot was measured before and after warming the ipsilateral one. The skin blood flow measured with and without heat application to the contralateral foot was not significantly different. Direct heat does not induce contralateral reflex vasodilatation in the foot of preterm infants.

Changes in skin blood flow over the foot with warming of the contralateral heel

Vasospasm in one leg is a common complication of umbilical artery catheterization in preterm infants. It is a common practice to wrap the contralateral leg in a warm washcloth. The rationale for this intervention is to induce reflex vasodilatation of the affected extremity, thereby avoiding the necessity to remove or replace the catheter. This study tested the hypothesis that heating the contralateral extremity in preterm infants would increase peripheral blood flow to the contralateral foot. Ten stable preterm infants who had had no umbilical catheter inserted for at least 2 weeks were studied. Skin perfusion was measured using the laser Doppler method in the distal leg after heating of the opposite foot to 40.5°C. Blood flow to the skin of the contralateral foot was measured before and after warming the ipsilateral one. The skin blood flow measured with and without heat application to the contralateral foot was not significantly different. Direct heat does not induce contralateral reflex vasodilatation in the foot of preterm infants.