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PubMed1988

Participation of ventrolateral medullary neurons in the renal-sympathetic reflex in rabbits.

In an effort to locate medullary structures that mediate the renal-sympathetic reflex, the effect, on the excitatory (E) and inhibitory (I) components of that reflex, of certain drugs applied to the ventral surface of the medulla was investigated in urethane-anesthetized and vagotomized rabbits. Application of bicuculline, a GABA receptor antagonist, selectively abolished the I component of the renal-sympathetic reflex as well as the sympathoinhibition elicited by stimulation of the aortic nerve. The E component, on the other hand, was specifically eliminated by kynurenic acid, a glutamate receptor antagonist. Strychnine or atropine sulfate did not affect either reflex appreciably. Subsequently, within the region of the ventrolateral medulla (VLM) subjacent to the site of drug applications, we searched for neurons which responded to stimulation of the renal nerve and/or the aortic nerve. Of 68 responsive VLM neurons found, 50 (73.5%) responded to stimulation of both nerves. Of the 50 neurons, 40 were tested for their antidromic activation to stimulation of the spinal cord. Twenty-four neurons (60%) were antidromically activated. Responses of these reticulospinal neurons to stimulation of the renal nerve preceded that of renal nerve activity (RNA) by about 100 ms. All the antidromically activated, VLM neurons which responded to stimulation of the renal nerve also responded to stimulation of the aortic nerve. In conclusion, the renal-sympathetic reflex appears to be mediated by the same pool of bulbospinal neurons in the ventrolateral medulla that mediates the arterial baroreceptor reflex, and the E and I components of that reflex can be selectively abolished by pharmacological intervention of the subjacent ventral surface of the medulla.

Animals↗
PubMed1994

Role of prenatal position in grasp-reflex asymmetry in human neonates.

Grasp-reflex strengths were quantitatively measured from the right and left hands of 70 full-term human neonates. The right-left grasp-reflex linearly correlated with grasp-reflex only of the right hand in neonates with a right-ear-facing-out prenatal position. In neonates with left-ear-facing-out prenatal position, this grasp-reflex linearly increased with the grasp-reflex of the right hand and linearly decreased with the grasp reflex of the left hand. It was suggested that grasp-reflex asymmetry in neonates may, at least partly, depend upon prenatal position, which may also influence the later developing hand preference in humans.

Female↗
PubMed1999

Relationship between ankle invertor H-reflexes and acute swelling induced by inversion ankle sprain.

STUDY DESIGN: Single group, post-test design using the uninvolved lower extremity as the experimental control. OBJECTIVES: To determine relationships between ankle swelling and flexor digitorum longus and peroneus longus H-reflex amplitude and latency. BACKGROUND: Primary capsuloligamentous injury, neural injury, and joint effusion and swelling may contribute to H-reflex changes following inversion ankle sprain. The relationship between ankle swelling and invertor or evertor H-reflexes has not been reported. METHODS AND MEASURES: Fifteen subjects with acute grade I or II inversion ankle sprains (mean +/- SD) 6.5 +/- 3 days after onset participated in this study. Swelling was estimated using a tape measure and the figure-of-eight girth assessment method. H-reflexes were determined using standard techniques. Paired t-tests were used to compare mean differences in ankle girth (swelling) and ankle invertor or evertor H-reflex amplitude and latency between the involved and uninvolved limbs. Pearson product moment correlations were used to assess relationships between swelling and H-reflex variables. RESULTS: Involved limb ankle girth was increased with respect to the uninvolved limb (1.5 +/- 0.9 cm) and the involved ankle flexor digitorum longus latency was delayed (0.72 +/- 0.7 ms). There was a moderate positive association (r = 0.73) between the latency delay in the involved ankle flexor digitorum longus and swelling. There were no significant differences in H-reflex amplitude and peroneus longus latency between ankles. CONCLUSIONS: Grade I or II inversion sprains and the related swelling appear to delay involved ankle flexor digitorum longus latency to a greater extent than peroneus longus latency. Clinicians need to direct greater attention to the ankle invertors when designing and implementing ankle rehabilitation programs, particularly during the swelling management phase of treatment.

Acute Disease↗
PubMed1982

Time course of acoustic intra-aural muscle reflex in non-anesthetized rabbits, normative data.

The dynamic properties of the intra-aural reflex in response to tones of 2 000 Hz in non-anesthetized rabbits is described. Rise time (time from start of stimulus to response has reached half of its steady-state amplitude) decreased from about 300 msec at threshold to 54 msec at high level for the ipsilateral and 60 msec for the contralateral reflex. Offset time (time from end of stimulus to relaxation to 50% of steady-state amplitude) increased from 100-150 msec at threshold to 250-300 msec at high level, being longer for the crossed than for the ipsilateral reflex. Impulse response (response to 16 msec burst of pure tone) reach its peak after about 60 msec, a value independent of sound level. The ipsilateral reflex had a 5-8 msec shorter time lag than the contralateral reflex, after correction for difference in response amplitude. This difference is compatible with additional synapses and a longer neural pathway for the crossed reflex. It has been pointed out that the intensity dependence of rise time has to be carefully considered when evaluating 'normal ranges' of temporal parameters for reflex responses. The rise time is suggested as a suitable parameter for quantification of suprathreshold stapedius responses.

Acoustic Stimulation↗
PubMedDate not supplied

Post-operative stapedius reflex tests with simultaneous loudness scaling in patients supplied with cochlear implants.

The estimation of the maximum comfort loudness levels (MCL) by measurements of the electrically elicited stapedius reflex was examined in six experienced cochlear implant users supplied with the COMBI 40 implant system. The stapedius reflex was tested and loudness scaling was performed simultaneously using an up/down stimulation protocol close to the reflex threshold with automated recording of both test procedures. The electrical stapedius reflex threshold (ESRT) and loudness scaling were evaluated separately. Scaling at the reflex threshold ranged between normal and loud. The range of stimulus intensities corresponding to ESRT is much smaller than that at a particular loudness category. The overall correlation between ESRT and MCL was high (r=0.92), with a similar dependence of ESRT and MCL on the channel stimulated. Thus, when the stapedius reflex can be detected post-operatively, the ESRT can be applied successfully for the fitting procedure of the speech processor. Simultaneous loudness scaling during the entire reflex test showed that overstimulation via the implant can be avoided effectively.

Adult↗
PubMed1981

Low-level acoustic reflex thresholds.

The acoustic reflex threshold can be detected at lower than normal sound pressure levels by means of facilitation. This procedure entails simultaneous presentation of a high-frequency facilitating tone at a level just below reflex threshold and a second reflex-eliciting tone. The second tone is reduced in intensity until no further reflex activity is observed. When hearing was normal, less signal intensity was needed to elicit the acoustic reflex when facilitation was used. There was a greater amount of reflex threshold improvement when the facilitating and eliciting tones were presented monotically. Sensorineural hearing loss allowed small or no reflex threshold change with facilitation.

Acoustic Stimulation↗
PubMedDate not supplied

Acoustic reflexes in the measurement of auditory filters at high levels in normal listeners.

The possible influence of the acoustic reflex in auditory filter shape measurements was investigated in 4 normal listeners by measuring contralateral acoustic reflexes to stimuli used in the notched-noise method. For probe/masker combinations centred at 125 and 250 Hz, the reflex was, at most, barely detectable even at masker levels of 80 dB SPL/Hz. On the other hand, all listeners had a measurable reflex at a masker level of 70 dB SPL/Hz for a probe/masker combination centred at 1 kHz. Some listeners also evidenced reflexes at a masker level of 60 kB SPL/Hz at this frequency and at 70 dB SPL/Hz at 500 Hz. As it is known that the acoustic reflex significantly attenuates frequency components of sounds below about 2 kHz as they pass through the middle ear, it appears that estimates of auditory filter bandwidths at high levels at 0.5 and 1 kHz can be influenced to some degree by the reflex.

Adult↗
PubMed1992

Right-, left-dominance and ambidexterity in grasp reflex in human newborn: importance of left brain in cerebral lateralization.

The grasp reflex was studied in human newborn without familial sinistrality. Of 60 females, 26 (43.3%) were right-handed and 34 (56.7%) ambidextrous. Of 62 males, 20 (32.3%) were right-handed, 39 (62.9%) ambidextrous, and 3 (4.8%) left-handed. There was a nonsignificant preponderance of right-dominance in females and a significant preponderance of nonright-handedness in males. In right-handers, the mean right minus left (R-L) grasp-reflex showed a positive linear correlation with the grasp-reflex from the right and left hands, with a higher correlation for the right hand. In ambidexters, the R-L grasp reflex did not show any significant correlation with the grasp reflex from the right and left hands. The mean grasp-reflex from right and left were found to be significantly smaller in ambidextrous males and females then right-handed males and females, with a much higher significance for the right hand. It was concluded that females tended to have a more pronounced reflex lateralization than males. The results also indicated that the left brain may be more important than the right brain for the development of a spinocerebral motor lateralization in humans.

Brain↗
PubMed1994

Correlations between grasp-reflex strengths and serum thyroid-hormone levels depending upon sex and familial sinistrality in human neonates: importance of genetically predetermined cerebral organization.

Relations of grasp-reflex strengths to serum free-thyroid hormone levels were studied in human neonates. In right-dominant (RH) males and females without familial sinistrality (-FS), grasp-reflex strengths from right (R) and left (L) inversely correlated with serum triiodothyronine (T3). In RH, +FS males, grasp-reflex strengths from R and L hands directly correlated with T3 (no correlations in RH, +FS females). There was no significant correlation between grasp reflex and T3 in non-right-handed (NRH), -FS neonates. In NRH +FS neonates, there was a significant negative linear correlation between grasp reflex from left and T3 only in NRH, +FS males. The following correlations were found between grasp reflex and thyroxine (T4): direct relation in RH, +FS males and females; inverse relation in NRH, -FS females only for the right hand; inverse correlations in NRH, +FS females. The R-L grasp reflex directly correlated with T3 in RH, -FS males, and inversely correlated with T3 in RH, -FS females (no significant correlations in others). These results indicated that thyroid hormones may influence cerebral maturation and lateralization differentially according to genetically predetermined cerebral organization. The generalizations of the hormonal effects on, at least, cerebral functioning would be wrong, if the genetically predetermined main features of the brain are neglected.

Brain↗
PubMed1990

Dynamic range of the contralateral stapedius reflex in cochlear implant patients.

The dynamic range of the contralateral Stapedius reflex elicited by analog electrostimulation via cochlear implant was investigated in 8 subjects supplied with a Vienna prosthesis. The study comprised patients fitted with intracochlear devices as well as patients with extracochlear devices. Sinusoidal bursts of 125, 500, 1,000 and 2,000 Hz were used as stimulation signals. Only in one patient was saturation of reflex amplitude observed. The dynamic range of the Stapedius reflex was defined either by the difference in stimulus level for reflex saturation or individual uncomfortable loudness level and reflex threshold. Two different methods were used, yielding values between 0.1 and 12 dB, with a median of 4 dB. The individual results were compared with individual psychoacoustic quantities, i.e. subjective dynamic range (difference between sensation threshold and uncomfortable loudness level) and residual dynamic range (difference between most comfortable loudness level and uncomfortable loudness level). The reflex dynamic range is located within the residual dynamic range of electrostimulation. Thus the Stapedius reflex dynamic range can be applied as a rough estimate of minimum residual dynamic range.

Acoustic Stimulation↗
PubMed1977

Acoustic reflex measures of cochlear damage--a normative study.

It has been argued that certain reflex measures may indicate the presence of end-organ hearing loss. It has been noticed that the difference between wide band noise and pure tone thresholds is diminished, that the reflex threshold duration function is flattened and that the reflex relaxation index, as specified by Norris et al. (1974b), is reduced in cases of end-organ hearing loss. These aspects of the acoustic stapedial reflex, together with its growth with stimulus intensity, have been investigated in 25 normally hearing subjects. The overriding feature of the measures taken of the acoustic stapedial reflex, was the high inter-subject variability. The differences between the acoustic reflex thresholds for pure tone and WBN was found to be normally distributed about a mean value of 12 dB. The threshold-duration functions again were highly variable and encompassed the entire range of results from normal and end-organ impaired groups as reported by Woodford et al. (1975). The variability encountered in the RRI measures was found to increase with frequency. The growth of the acoustic stapedial reflex with intensity was found to be frequency dependent: the gradient of the function increasing with frequency for the long duration (500 ms) pulses and decreasing with the short duration (50 ms) pulses. It is concluded that considerable caution must be exercised in extrapolation from any one of these measures in isolation.

Acoustic Impedance Tests↗
PubMed2006

Reflex movements in patients with brain death: a prospective study in a tertiary medical center.

Reflex movements have been reported to occur in up to 75% of brain-dead patients, but this issue has not been addressed in Korea. The patients admitted to our hospital who met the criteria for brain death were enrolled between March 2003 and February 2005. The frequency and type of reflex movements in these patients were evaluated prospectively using a standardized protocol. Brain death was determined according to the guideline of Korean Medical Association. Of 26 patients who were included, five (19.2%) exhibited reflex movements such as the pronation-extension reflex, abdominal reflex, flexion reflex, the Lazarus sign, and periodic leg movements. This finding suggests that the frequency of spinal reflex movements is not rare and the awareness of these movements may prevent delays in brain-dead diagnosis and misinterpretations.

Adult↗
PubMed2005

Detection of the acoustic stapedius reflex in infants using wideband energy reflectance and admittance.

This study examined the measurement of the contralateral acoustic stapedius reflex in six-week-old infants and adults using wideband shifts in admittance and energy reflectance (YR). The reflex activator was bandpass noise from 2,500 to 11,000 Hz presented at a maximum spectrum level of 51 dB SPL measured in the ear canal. Reflexes were detected by calculating a cross-correlation between one-twelfth-octave measurements of YR for the highest activator level and responses to lower levels. The reflex-induced shifts in YR for the infant ears were similar in pattern to adult responses but were noisy at frequencies below 1000 Hz. Infant reflexes were more successfully detected when the cross-correlation was calculated from 1000 to 8000 Hz, whereas adult reflexes were more successfully detected for a cross-correlation from 250 to 2000 Hz. This method may be useful in capturing the most robust frequency region for acoustic reflex detection across postnatal middle ear development.

Acoustic Impedance Tests↗
PubMed1989

[Cremasteric reflex. Its application to urological diagnosis].

Responses to electrically evoked cremasteric reflex with bulbocavernous reflex and cystometrogram were observed on 55 male adults who have complaints of micturition or sexual disorders. As the reflex centers for these reflexes were localized in the lower spinal segments, the observed results were used for the estimation of the injured loci in combination with clinical symptoms. The cremasteric reflex which was dealt with in this paper was the cremasteric EMG responses evoked by single electric shock applied to the ventromedial surface of the thigh or to the dorsum of the penis. The stimuli used have usually tenfold intensity of the sensory threshold, having 0.2 msec duration. The EMG recording was made with a coaxial needle electrode inserted into the ipsilateral cremasteric muscle at the level of the pubic bone. All 20 controls without neurological disorders showed positive cremasteric responses, and the normal range of the latency and the burst length were 68-77 msec and 52-59 msec, respectively, in case of thigh stimulation. More than half of the patients suffered from the disorders of neural origins showed no reflex even for stronger stimulation. Combining with these data, the diagnostic usefulness for the localization of injuries in patients having disorders in either spinal cord or in cerebral vessels was positive. Cerebral influence to the cremasteric reflex was deduced to be a potentiating factor to elongate the burst duration for stronger stimuli. Further detailed observations would yield useful clues for neuro-urological diagnosis of the lower spinal cord injuries.

Adult↗
PubMed2000

Multiple sites of action in the inhibitory effect of nociceptin on the micturition reflex.

PURPOSE: Nociceptin, the endogenous peptide ligand for the opioid receptor-like1 (ORL1) receptors, exerts a naloxone-resistant suppressant effect on micturition reflex after intravenous administration. This work aims to elucidate the mechanism and the site of action of the inhibitory effect of nociceptin on the micturition reflex. MATERIALS AND METHODS: The bladder of urethane-anesthetized rats was cannulated through the dome (cystometries) or the urethra in isovolumetric conditions (distension-induced reflex contractions, DIRCs). In this latter model, the effect of the application of nociceptin onto the serosal surface of the urinary bladder was determined. The effect of intravenous, intrathecal and intracerebroventricular administration of nociceptin on ongoing cystometries at two different infusion rates (50 and 250 microL/min.) was assessed. The effect of the intravenous administration of nociceptin on cystometries was also studied in capsaicin-pretreated animals. RESULTS: When cystometric recordings were obtained at a low infusion-rate (50 microL/min.), the intravenous administration of nociceptin (10 to 100 nmol./kg.) induced a dose-dependent reduction in the micturition frequency associated to an increase of the pressure threshold for activating the micturition reflex, whereas the amplitude of micturition contractions was unaffected. These effects faded within 60 minutes. The intracerebroventricular administration of nociceptin (0.3 nmol./rat) produced urodynamic changes similar to those observed after the intravenous route and, in addition, also reduced the amplitude of micturition contractions. The intrathecal administration of nociceptin up to 1 nmol./rat was ineffective. Capsaicin pretreatment (164 micromol./kg., s.c. 5 to 6 days before) significantly reduced the micturition frequency as compared with controls. In capsaicin pretreated animals intravenous nociceptin was ineffective. When cystometries were recorded at a high infusion-rate (250 microL/min.) either intravenous (100 nmol./kg.), i.t. (1 nmol./rat) nociceptin or capsaicin pretreatment had no effect. In contrast, intracerebroventricular nociceptin (0.3 and 1 nmol./rat) inhibited the micturition reflex by reducing both the frequency and the amplitude of micturition contractions: these effect were not modified by naloxone (0.5 micromol./kg., i.v.). The topical application of nociceptin (5 and 50 nmol./rat) caused a dose-dependent inhibition of DIRCs. CONCLUSION: Nociceptin inhibits the micturition reflex at a peripheral and at a supraspinal site. The effects observed after the intravenous administration of nociceptin indicate that the functional integrity of capsaicin-sensitive bladder afferents is required for exerting its inhibitory activity at the peripheral level. In contrast, the supraspinal effect of nociceptin involves both the afferent and the efferent pathways of the micturition reflex, possibly through a direct effect on ORL1 receptors located in the pontine micturition center.

Animals↗
PubMed1998

[Hoffmann reflex elicited by magnetic stimulation of S1 nerve roots in the diagnosis of diabetic radiculopathy].

OBJECTIVE: To determine the incidence of radiculopathy in diabetic patients neurophysiologically. METHODS: The H-reflexes were elicited by magnetic stimulation to S1 nerve root at the first sacral foramen (S1 H-reflex) in 40 normal subjects and 41 diabetic patients. The action potentials of the H-reflex were recorded from the soleus muscle. For comparison, a popliteal H-reflex (stimulated at popliteal fossa), and a regular distal sensory and motor conduction of the tibial nerves were simultaneously evaluated. RESULTS: A significant correlation of the peak interval of H wave and M wave (HMI) of the S1 H-reflex with body height and age was confirmed by multiple regression analysis in the normal subjects. The simultaneous regression of the HMI adjusted on age and body height produced the formula as 0.02 x (age) + 0.03 x (height) + 0.92. At 95% normal limits of the significant test, 40.2% HMI and 53.7% amplitude of H waves of the S1 H-reflex, 54.9% latency and 46.3% amplitude of H waves of the popliteal H-reflex, 40.2% SCV and 40.2% amplitude of sensory action potentials were diagnosed as abnormal. CONCLUSIONS: A high incidence rate of diabetic radiculopathy was confirmed to be comparable to that of proximal neuropathy and distal symmetrical sensory polyneuropathy. This suggests that diabetic neuropathy may be related to metabolic and/or vascular disorders.

Adult↗
PubMedDate not supplied

[Registration of the silent period in masseter muscles during study of the mandibular reflex].

Under the application of clinical electromyography, nowadays is more widely used reflex investigation, i.e., the investigation of the reflexes to the extension. In stomatognathic system is the most frequently applied the investigation of mandibular reflex. Silent period was registered during the investigation of mandibular reflex. Silent period is the reflex pause or the period of suppressive activity that is subsequent to some sort of stimuli during or following muscle contraction. In current dentistry, silent period, registered by electromyography, represents an important parameter in functional diagnosis. The aim of the study was to establish the duration of silent period in masseter muscles during the investigation of mandibular reflex in edentulous patients with the pair of newly made full dentures and in the subjects with natural healthy intact dentition, respectively. The investigation included 20 subjects of average age 44 years. The results of registered silent period during the investigation of mandibular reflex in edentulous patients had the lower values (18.21 ms) than in the subjects with healthy intact dentition and with a pair of newly made full dentures (20.51 ms), respectively, which have confirmed the physiologic time of the duration of silent period.

Denture, Complete↗
PubMedDate not supplied

[Electromyographic studies of plantar-mental reflex].

The authors investigated the electromyographic response to mechanical stimulation of the palmar skin (palmo-mental reflex) and plantar skin (planto-mental reflex) in the mentalis muscle. The palmo-mental reflex was present in EMG in all 22 healthy subjects an in 51 cases of 51 cases of limited cerebral lesions. The planto-mental reflex was absent in healthy subjects, but it was found in 14 out of 31 cases of focal brain injury and in 2 out of 20 cases with diffuse lesions. The planto-mental reflex is a pathological reflex appearing mainly in severe focal cerebral lesions. No description of this reflex was found in the available literature.

Adult↗

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