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PubMed1986

Binaural acoustic reflex activity following monaural noise exposure in decerebrate chinchillas.

Acoustic reflex thresholds, latencies and magnitudes were recorded binaurally in decerebrate chinchillas suffering monaural, temporary noise trauma. Simultaneous recordings of cochlear microphonics from both cochleae during monaural reflex stimulation served as an index for acoustic reflex dynamics. Baseline values of threshold, latency and magnitude were recorded from ipsilateral and contralateral ears prior to a monaural 2-hour exposure to a 0.5-kHz octave-band noise at 100 dB SPL. Reflex dynamics were measured immediately after exposure and again following 1 h of recovery. Cochlear microphonic input-output functions for the exposed ear were completed prior to and after cessation of the noise and after 1 h of recovery. Acoustic reflex threshold and magnitude increased and latency decreased following exposure to noise for both the ipsilateral and contralateral recording conditions. Reflex activity in the nonexposed ear was unaffected. Reflex properties returned to pre-exposure values following recovery. These responses followed the same time course as changes in cochlear sensitivity. Alterations in reflex response following noise exposure is caused by changes at purely peripheral sites.

Animals↗
PubMed1987

[Efferent activity in the phrenic nerve during the startle reflex in chloralose-anesthetized cats].

Reflex activity in the phrenic nerve was studied in chloralose anesthetized cats during development of somatic startle reflexes in limb and lower intercostal nerves. It was shown that the main component of this activity during low-threshold reflexes evoked by acoustic, tactile and low-threshold somatic afferent stimulation was depression of phrenic inspiratory activity. The following reflex discharges were prevalent components of phrenic responses to high-threshold afferent stimulation: early, propriospinal (intercostal-to-phrenic reflex) and late, suprasegmental ones. The latter were of two types: inspiratory (observed mainly during inspiration in about 75% of experiments) and expiratory (observed during expiration in 25% of experiments) which could be classified as "phrenic startle reflexes". Modulation of all responses during the respiratory cycle was described. Structural characteristics of reflex responses evoked in the phrenic nerve by stimulation of various respiratory and nonrespiratory bulbar sites as well as their respiratory modulation have been analyzed. Organization of possible neurophysiological mechanisms of phrenic responses during startle reflexes is discussed.

Animals↗
PubMed1979

Role of the asymmetrical tonic neck reflex in hand visualization in normal infants.

Fourteen infants were each videotaped 7 times within the first 12 weeks of life to determine whether or not the asymmetrical tonic neck reflex had a role in placing their hands within their fields of vision. Infants' arms were more frequently out of the reflex position. Hands were within the peripheral visual field more often than in the focal visual field or not within the visual field. The proportion of observations that hands were in a particular visual field varied in accordance with the presence or absence of the reflex. A higher proportion of reflex observations occurred in the focal visual field, whereas a higher proportion of observations made when the infants were not in the reflex position occurred in the peripheral visual field. Further, the proportion of focal field observations in the reflex position was greater than the proportion of observations out of the reflex position for the first six of the seven ages. This study confirms that when infants are in the asymmetrical tonic neck reflex position, their hands are more likely to be in a position in which they can be visualized.

Age Factors↗
PubMed1984

Effect of hypoxia on the excitability of two cranial reflexes in unanaesthetized fetal sheep.

In fetal sheep acute hypoxia causes a decreased incidence of breathing movements and motor activity, and the excitability of polysynaptic reflexes in the hindlimbs is depressed. To determine whether this inhibitory effect extends to other areas in the fetal CNS, we have studied the effect of hypoxia on two reflexes with cranial pathways. The digastric (jaw opening) reflex was elicited by stimulation of the dental nerve through a pair of stainless steel electrodes implanted into the mandible (4 fetuses). The thyroarytenoid muscle of the larynx was reflexly activated by stimulation of the superior laryngeal nerve by a cuff electrode (4 fetuses). Low level stimulation at 1.5-2 X threshold was repeated at approximately 2 min intervals for 3-4 h; the stimulation did not alter the pattern of electrocortical activity, breathing movements, or cause arousal. The amplitude of the digastric reflex was greatest during low voltage electrocortical activity; conversely, the amplitude of the thyroarytenoid reflex was greatest during high voltage electrocortical activity. Isocapnic hypoxia lasting 30-60 min (16 trials), in which the PaO2 was reduced to 12-14 mmHg, did not reduce the amplitude of either reflex. The reduction of thyroarytenoid reflex amplitude which normally occurred during low voltage electrocortical activity was not present during hypoxia. These experiments show that the inhibitory effects of hypoxia on spinal reflexes, breathing movements and motor activity do not include these cranial pathways.

Animals↗
PubMed1978

[Studies on righting reflexes in newborn cats falling in the air (author's transl)].

The classical righting reflexes have been well illustrated in the familiar example of a falling adult cat, which always lands deftly on all four feet. It, however, has never been clear when newborn animals come to turn themselves in the air after birth. In the present studies the newborn cats were dropped in the air with legs pointed upward from a height of about 30 approximately 40 cm, and the observations were continued for the period of 36 days. The results were as follows: 1. The newborn cats fell plump on their back when they were dropped with legs pointed upward in the air. 2. No righting reflexes were observed in the cats of 27 days and downward. 3. The eyelids (rima palpebrarum) of the cats came to be open on the 8th approximately 14th after birth. 4. The cats which were suggested to obtain full eyesight judged from the observations of their behaviours had no visual righting reflexes when dropped with legs pointed upward. 5. The walking pattern of the cats changed in association with their growth. For the period of 20 days after birth the type of locomotion was creeping, for the period of 21st approximately 26th plantigradation, and after the 26th approximately 27th digitigradation. 6. It has been concluded that the righting reflexes as compound reflexes are never observed in the experimental cats for about one month after birth even though the cats have obtained each postural reflex, i.e. tonic neck or labyrinthine reflex which constitutes righting reflexes.

Animals↗
PubMed1982

[A quantitative analysis of the phrenic nerve activities during the cough reflex].

The phrenic nerve activity is an appropriate indicator for the output of the respiratory center as a whole, although a quantitative analysis of each of the frequency band components that constitute the neural activities during the respiratory reflex has not yet been made by other investigators. In the present study, we have made a quantitative analysis of each of the frequency band components of phrenic nerve activity during the cough reflex in anesthetized dogs. The efferent activities of the phrenic nerve were recorded from the central cut end of the phrenic nerve. Each fraction of phrenic nerve activity was separated into bands spanning a range of 100 Hz each by a variable filter and analyzed using a program for the power spectrum. The cough reflex was induced by mechanical stimulation of the tracheal mucosa. In the power spectrum analysis of each frequency band, increase in the power of each of the frequency band components was observed during the cough reflex. Particularly, the power of the 2 approximately 100 Hz band components increased significant as compared with the other frequency band components. Such as increase in the power of the 2 approximately 100 Hz band components toward the other frequency band components during the cough reflex was not observed after an i.v. administration of DMPP and lobeline, but the power increased extended over every frequency band. These findings suggest that the process for integrating the cough reflex was different from that of the other respiratory reflexes and that the present method is useful for investigating the central mechanisms of the cough reflex.

Action Potentials↗
PubMedDate not supplied

[Electrophysiological analysis of various brain stem reflexes in multiple sclerosis].

An electrophysiological study of "blink reflex" and "jaw reflex" was carried out on 20 sicilian patients with "definited" Multiple Sclerosis. The R1 component of the "blink reflex" was abnormal in 13 patients on 20 (65%), the R2 component in 8 patients on 20 (40%). Considering together the R1 and R2 responses, the abnormal percentage was 75%. The "jaw reflex" showed abnormal responses in 5 patients on 20 (25%). Considering both the "blink reflex" and "jaw reflex", the pathological percentage was 75%, in order that no patients had isolated changes of the "jaw reflex". The simultaneous study of the two reflexes does not increase the probability to prove pathological responses. The frequency of the clinically silent brain-stem lesions in our patients was not substantially different from that showed by other authors on different populations.

Adolescent↗
PubMed1995

Effects of intrathecal and intracerebroventricular buprenorphine on a C-fiber reflex in the rat.

A C-fiber reflex elicited by electrical stimulation within the territory of the ipsilateral sural nerve, was recorded from the biceps femoris muscle in anesthetized rats. The temporal evolution of the reflex was studied using a constant level of stimulus intensity (3 x threshold) and recruitment curves were built by varying stimulus intensity from 0 to 7 x threshold. Intrathecal doses of buprenorphine in the 0.2 to 10 micrograms range, elicited a facilitation of the C-fiber reflex in a dose-dependent manner. A large dose (100 micrograms) depressed but did not block the reflex. Intracerebroventricular doses of buprenorphine in the 0.1 to 10 micrograms range, facilitated the C-fiber reflex. A higher dose (100 micrograms) elicited a biphasic effect: depressive when the stimulus intensity was weak and facilitatory when the stimulus intensity was strong. It is concluded that the antinociceptive properties of buprenorphine cannot be related to a direct or indirect depressive spinal effect. In terms of spinal and supraspinal effects of buprenorphine, it is likely that buprenorphine facilitates the C-fiber reflex via a supraspinal mechanism that acts on sensory and/or motor components of the reflex arc although the depression of the reflex involves a spinal mechanism. The lipophilic properties of buprenorphine could explain a substantial diffusion from its spinal injection site to the brain. From a clinical standpoint, this study confirms that intrathecal administration of buprenorphine is an inadequate way of accessing spinal opioid receptors.

Analgesics, Opioid↗
PubMed1994

Image analysis of the tapetal-like reflex in carriers of X-linked retinitis pigmentosa.

PURPOSE: To increase understanding of the tapetal-like reflex (TLR), a unique retinal feature in carriers of X-linked retinitis pigmentosa (XLRP). METHODS: Color fundus photographs of XLRP carriers were digitized at high resolution. A mathematical model of the imaging system was used to restore the digital retinal images. TLR was separated from the retinal background with an automated segmentation method. Mathematical morphology was used to estimate directional properties. Images from serial photos were registered and compared to study temporal progression. RESULTS: Quantitative analysis of well-focused funduscopic images show point-like unit reflexes forming the TLR. The average unit reflex is circularly symmetric with a diameter of approximately 8.5 microns and has a maximum reflectance 40% higher than that of the neighboring nonreflex retina. Two or more unit reflexes form small elongate patches that can cluster together into larger patches. Both smaller and larger patches have a strong preferential direction toward the fovea. Comparison of images taken 23 years apart in one patient and 3 years apart in another patient show no detectable changes in the size and location of the reflexes. CONCLUSIONS: The pattern of reflexes at high and low resolution suggests that the TLR represents an X-inactivation mosaic. Based on the size of the unit reflexes, the authors speculate that the cone photoreceptors participate in the TLR. The stability of the reflex over more than two decades questions the longstanding assumption that the TLR is a stage of the retinal degeneration.

Adolescent↗
PubMed1995

[Non-reflex activity of the CNS].

Recent studies of biological rhythms have modified Sherrington's concept of nervous system as exclusively reflexive to include the fact that some neural activity is also endogenously rhythmic. Reflexes are undoubtedly the most important components of animal's and human behavior. But are reflexes the basic units of all complex movements and acts? Rhythmical movements such as respiration, walking and running and other forms of locomotion, as well as rhythmical alimentary processes such as respiration, walking and running and other forms of locomotion, as well as rhythmical alimentary processes such as licking, mastication, and the peristaltic propulsion of nutrients and waste are examples of acts controlled by intrinsic oscillators, so called central pattern generators. Information from the periphery is, however, essential for controlling the extent and rate of movements. Between reflex and non-reflex activity it is possible to place complex species-specific responses called by ethologists fixed-action patterns. Recent investigators have shown that many complex sequences of behavior like speech or piano playing are determined by an internal plan, rather than being generated by a "chain" of reflexes. Non-reflexive activity appears earlier in ontogeny, and is probably phylogenetically older than reflexes.

Animals↗
PubMed1998

Synergism between sevoflurane and intravenous fentanyl on A delta and C somatosympathetic reflexes in dogs.

UNLABELLED: In this study, we defined the nature of the interactions between sevoflurane and fentanyl on spontaneous and reflex-evoked sympathetic activity, resting heart rate (HR), and mean arterial pressure (MAP). Spontaneous renal sympathetic nerve activity (RSNA) and A delta- and C-fiber-mediated somatosympathetic reflexes, evoked by electrical stimulation of radial nerves, and HR and MAP were recorded in anesthetized dogs. In one group, the effects of incremental doses of 2-64 micrograms/kg fentanyl i.v. were observed. It had a greater inhibitory effect on C than on A delta reflexes, which were abolished by mean cumulative doses of 64 micrograms/kg and approximately 128 micrograms/kg, respectively. Although 1.5% sevoflurane reduced C reflexes by 28% and A delta reflexes by only 12%, it reduced the total doses of fentanyl required for their abolition to 32 micrograms/kg and 64 micrograms/kg, respectively. Mean RSNA, HR, and MAP values were reduced by 46%, 54%, and 30%, respectively, by fentanyl alone and by 23%, 11%, and 17%, respectively, in response to 1.5% sevoflurane. The combination of fentanyl and sevoflurane caused reductions of 44%, 54%, and 41%, respectively, which indicates a less than additive effect. These results indicate that sevoflurane interacts synergistically with fentanyl to depress A delta and C somatosympathetic reflexes, whereas for RSNA, HR, and MAP, their effects were less than the additive. IMPLICATIONS: Although fentanyl caused a greater depression of C than of A delta reflexes to the point of abolition, the maximal depression of spontaneous sympathetic activity, heart rate, and arterial pressure occurred at smaller doses. The combined depressant effects of sevoflurane and fentanyl were synergistic on somatosympathetic reflexes but were less than additive on spontaneous sympathetic activity, heart rate, and arterial pressure.

Analgesics, Opioid↗
PubMed1998

[Suppressive effect of isoflurane on somato-sympathetic reflexes in cats].

Effects of isoflurane on the reflex activity of the sympathetic nervous system were investigated in 35 cats by observing alteration of the amplitudes of somato-sympathetic medullary reflex potentials. A and C-reflex potentials, which are induced from lumbar sympathetic trunk by electric stimulation of ipsilateral femoral nerve are known to arise from A-fiber group and C-fiber group, respectively. One or two percent isoflurane in oxygen was administered for 30 minutes, because it is known that I MAC of isoflurane in cats is 1.61%. The amplitude and latency of the potentials were measured during and after inhalation of the test drug, and the results were presented as percentage change from that at prior levels of inhalation as control. The results were as follows. (1) The amplitudes of A- and C-reflex potentials were suppressed dose-dependently in rats with intact brain. (2) The amplitudes of both potentials increased by decerebration at midbrain level. (3) In decerebrate cats, the amplitudes of both potentials at each inhaled concentration were suppressed to the similar levels at inhalation of 2% isoflurane in intact cats, although a slight difference between intact and decerebrated cats was observed with A-potentials during inhalation of 1% isoflurane. (4) The latencies were prolonged slightly in A-reflex potentials, only in intact cats at both concentrations. (5) Blood pressure decreased during inhalation of the test drug in every condition, but their dose-dependencies were evident only in intact cats. (6) Selective suppression of C-reflex potential by inhalation of isoflurane could not be demonstrated. These results suggest that isoflurane has a strong suppressive effect on sympathetic reflex center in medulla oblongata with was demonstrated by greater degree of suppression of the reflex responses in decerebrate cats than that in intact animals. It was concluded that the effect of isoflurane on sympathetic nervous system is similar to that of halothane.

Anesthetics, Inhalation↗
PubMed1976

The relation between monosynaptic spinal reflex amplitudes and some EEG alpha activity parameters.

Some investigators have found that in normal human subjects the amplitudes of repetitively evoked tendon reflexes decrease as the number of evoked reflexes progresses. The question whether this decrement is a spinal phenomenon or that it can be ascribed to supraspinal influences that are related to the degree of cortical activation was investigated in two experiments designed to test whether a relation exists between the Hoffmann (H) and Achilles tendon (T) reflex amplitudes and EEG alpha activity parameters during a rest condition. The principal results can be summarized as follows: 1. A constant alpha index was accompanied by stable reflex amplitudes. 2. A decreasing alpha index was accompanied by decreasing reflex amplitudes. 3. A positive relation was found between H and T reflex amplitudes. 4. A positive relation was found between alpha index and alpha amplitude. 5. No circumscribed relation was found between the alpha wave period on the one side and the alpha index and amplitude on the other side. Apparently these relations are dependent on the state of activation of the subject. 6. The relations between the reflex amplitudes and the alpha parameters showed great interindividual differences.

Adult↗
PubMed2006

Reflexes in prior polio and their relation to weakness and anterior horn cell loss.

The aim of this study was to evaluate the reflex pattern in patients with prior polio and to relate these findings to the degree of anterior horn cell (AHC) involvement and loss of muscle force. Twenty-five prior polio subjects were investigated with electromyography (EMG), force testing and reflex studies, which included the patellar and Achilles reflex, H-reflex, T-response and interlimb reflex (ILR). The clinical reflexes, H/M-ratio and T-response amplitude at rest were positively correlated with force and negatively correlated with the degree of AHC loss. The H/M-ratio was decreased compared with age matched controls. ILR was present in 68% of the prior polio patients but did not exist in controls. The presence of the ILR was not correlated with the degree of AHC loss or force. The reflex studies gave two main findings. The first is reduced excitability of monosynaptic connections in the motor neuron pool, which is related to weakness. The other is the presence of ILR as an indicator of interneuronal hyper-excitability, which is not related to weakness.

Achilles Tendon↗
PubMed1984

Monosynaptic and oligosynaptic contributions to human ankle jerk and H-reflex.

Studies were undertaken in normal subjects to determine whether it is possible for oligosynaptic reflex pathways to affect motoneuron discharge in the ankle jerk and H-reflex of the soleus. It is argued that if the rising phase of the increase in excitability of the soleus motoneuron pool produced by tendon percussion or by electrical stimulation of the peripheral nerve lasts more than a few milliseconds and if the increase in excitability takes several milliseconds to reach the threshold for motoneuron discharge, these reflexes are unlikely to be exclusively monosynaptic. In relaxed subjects, changes in excitability of the soleus motoneuron pool produced by tendon percussion and by electrical stimulation of the tibial nerve were examined using conditioning stimuli just below threshold and a test H-reflex just above threshold for a reflex response. The increase in excitability due to tendon percussion had an average rise time of 10.8 ms and a total duration of approximately 25 ms. With electrical stimulation the rising phase appeared shorter, but it could not be measured accurately due to afferent refractoriness. In single motor units, the rise times of the composite excitatory postsynaptic potentials (EPSPs) set up by subthreshold tendon percussion and by subthreshold electrical stimulation of the tibial nerve were estimated from changes in the probability of discharge of voluntarily activated single motor units. Rise times were significantly longer with tendon percussion (mean +/- SD, 7.1 +/- 2.3 ms; n = 34) than with electrical stimulation (2.4 +/- 1.4 ms; n = 32). In four experiments in which a number of motor units were studied using identical mechanical and identical electrical stimuli, the poststimulus time histograms (PSTHs) for each stimulus were pooled to provide an estimate of the rise time of the excitability change in the motoneuron pool. The mean rise times of these four samples were 10.5 ms with mechanical stimulation and 4.5 ms with electrical stimulation. The spontaneous variability in latency of reflexly activated single motor units was 0.8-3.1 ms (average SD, 0.34 ms) in the tendon jerk, and 0.6-1.4 ms (average SD, 0.19 ms) in the H-reflex. Comparison of these figures with the measurements of rise time given above suggests that the composite EPSPs are larger than the background synaptic noise. With six motor units, the timing of reflex discharge in the tendon jerk when the subject was relaxed was compared with the timing of the change in probability of discharge due to apparently identical percussion when the units were activated voluntarily.(ABSTRACT TRUNCATED AT 400 WORDS)

Achilles Tendon↗
PubMed1987

Effect of cooling on H- and T-reflexes in normal subjects.

The local application of cold has been used to decrease spasticity and facilitate neuromuscular function, but previous attempts to identify its effect on the stretch reflex have not been entirely successful. We examined the effects of cold on the Hoffmann (H) reflex and on the tendon tap (T) reflex in 16 subjects. A series of H/M recruitment curves and T-reflexes were recorded via surface EMG electrodes before and during cooling of the triceps surae. Skin and intramuscular temperatures were recorded with average decreases of 18.4C and 12.1C, respectively. Peak-to-peak amplitude of the M, H, and T compound action potentials (CAPs) was measured. In all cases, the amplitude of the maximal M-wave decreased (p less than 0.001) in response to cooling. These changes in the recording of CAPs should be considered when cooling experiments result in alterations in H or T waveforms. When using the M-wave as a covariant in our analysis, there were no significant changes in the H-reflex amplitude; the height of CAPs elicited by T decreased (p = 0.025). Our findings do not support earlier claims that simple cooling facilitates the excitatory alpha motoneuron pool as measured by the H-reflex; we do confirm that muscle spindle activity, as measured by the T-reflex, is decreased by muscle cooling.

Adult↗
PubMed2005

Reflex human papilloma virus infection testing detects the same proportion of cervical intraepithelial neoplasia grade 2-3 in young versus elderly women.

BACKGROUND: The American Society for Colposcopy and Cervical Pathology recently recommended triage of women with atypical squamous cells of undetermined significance (ASCUS) through reflex human papilloma virus (HPV) infection testing. Because age is an important determinant of the incidence of both ASCUS and HPV infection, the current study was conducted to determine the impact of age on reflex HPV infection test performance. METHODS: The authors reviewed all liquid-based Papanicolaou tests submitted for reflex HPV infection testing to the University of Alabama Medical Center during the period from January 2002 to January 2004. To assess the impact of age on reflex HPV infection testing, women were divided into 6 age groups (<25, 25-34, 35-44, 45-54, 55-64, >64 years). Trend of different diagnostic categories with age was assessed using the chi-square test for linear trend. As a measure of test performance, the proportions of cervical intraepithelial neoplasia (CIN) lesions confirmed by biopsy through reflex testing (of the total CIN lesions detected in the study population) were then compared among different age groups. RESULTS: During the study period, 25,164 ThinPrep tests were performed during the study period, with 2672 (11%) cases of ASCUS and 1371 (5%) cases of squamous intraepithelial lesions (SILs). A total of 2309 (86%) ASCUS cases were tested for HPV infection, of which 789 (34%) were positive. Biopsy specimens were obtained from 831 patients with SILs and from 316 patients with HPV+ASCUS. Of 246 patients with CIN Grade 2-3 (CIN2-3) detected on biopsy, 36 (15%) were triaged through reflex HPV infection testing and the rest were triaged through cytologic diagnosis of SILs. Despite the trend in the prevalence of HPV+ASCUS and SILs with increasing age (P < 0.05), there was no significant difference in the proportion (range, 9-23%) of CIN2-3 detected through reflex HPV infection testing in different age groups. CONCLUSIONS: Reflex HPV infection testing performed similarly for women in different age groups, including perimenopausal and postmenopausal women.

Adult↗
PubMedDate not supplied

Effects of general anesthesia on the human blink reflex.

The blink reflex was studied in 10 patients undergoing elective procedures under general anesthesia. Anesthetic agents were isoflurane, halothane, nitrous oxide, methohexital, and thiopental in various combinations. At induction, blink reflexes were diminished by low-dose thiopental (1-1.5 mg/kg) and abolished by high-dose thiopental (4-8 mg/kg) and methohexital (1.5 mg/kg). Blink reflexes were absent during halogenated volitile inhalational anesthesia and did not return until patients were in the recovery room, well after end-tidal anesthetic levels were zero by mass spectroscopy. Recovery of consciousness and the ability to blink on command often preceded return of any blink reflex activity, indicating that the blink reflex is not useful as a postoperative test of facial nerve function in the operating room after anesthesia. In six patients, blink reflexes were still diminished 2-3 hours after cessation of anesthesia, at a time when patients were fully oriented and corneal and eyelid reflexes were clinically normal. This finding suggests that the blink reflex might be a sensitive test of subtle CNS dysfunction after inhalational anesthesia and potentially could serve as a useful objective indicator of recovery from anesthesia for outpatient surgery.

Adult↗