Differential effect of current rise time on short and medium latency vestibulospinal reflexes.

OBJECTIVES: To investigate the effect of varying current rise time on galvanic-evoked short (SL) and medium (ML) latency vestibulospinal reflexes. METHODS: We recorded the soleus EMG of standing subjects in response to 3 mA direct current transmastoid stimulation with a series of current ramps with rise times of 0-300 ms. RESULTS: Longer current rise times significantly delayed the onset of both SL (P<0.001) and ML (P<0.001) vestibulospinal responses, by approximately 20 and 39 ms, respectively. The SL response amplitude was reduced with increasing rise time (P<0.001), whereas the ML response amplitude was relatively unaffected by stimulus rise time. With very slow rise times a prolonged ML response alone was evoked. CONCLUSIONS: Both SL and ML reflexes can be evoked by changes in vestibular activity produced by transmastoid galvanic stimulation with a ramp onset. We found a differential effect of current rise time on SL and ML vestibulospinal reflexes, suggesting different potential functional roles for the two reflexes. SL reflexes can participate in the response to abrupt disturbances only. ML reflexes are evoked by both fast and slow changes in vestibular discharge and may be particularly effective for slowly-changing disturbances.     

Galvanic and acoustic vestibular stimulation activate different populations of vestibular afferents.

OBJECTIVE: To deduce whether similar or distinct populations of vestibular afferents are activated by acoustic and galvanic vestibular stimulation by comparing the effectiveness of 'matched' stimuli in eliciting vestibulospinal reflexes. METHODS: Twelve subjects (5 men, 7 women) underwent individual 'matching' of 2 ms tone burst and galvanic stimuli, using vestibulocollic reflexes so that corrected reflex amplitudes to tone burst and galvanic stimuli were within 10% of each other. These same intensities were then administered using 20 ms durations to determine whether they were equally effective in evoking vestibulospinal responses. RESULTS: Corrected reflex amplitudes for vestibulocollic responses to tone burst and galvanic stimulation were not significantly different for the right (P=0.45) or left (P=0.68) sides. All subjects had vestibulospinal responses to galvanic stimulation (average intensity 4.0 mA for both sides). The short latency (SL) and medium latency (ML) components of the vestibulospinal reflexes were larger after galvanic compared to tone burst stimulation in 11 of 12 subjects (P<0.01). CONCLUSIONS: Despite evoking equal-sized vestibulocollic reflexes, there was a clear dissociation between the magnitude of tone burst and galvanic-induced vestibulospinal reflexes. Galvanic stimulation evoked SL and ML reflexes in all subjects. Tone burst stimuli evoked only small SL reflexes and, in most cases, no ML reflexes. Acoustically-evoked vestibulocollic reflexes are likely to be due to saccular excitation. The limited effectiveness of longer tone burst stimuli to evoke ML vestibulospinal reflexes suggests that saccular afferents have, at most, only a minor role in the production of these reflexes. We conclude that galvanic stimulation is more effective in eliciting vestibulospinal reflexes than tone burst stimulation, and that the two methods activate different populations of vestibular afferents.     

EMG responses evoked by the termination of galvanic (DC) vestibular stimulation: 'off-responses'.

OBJECTIVE: Vestibular responses in soleus electromyography (EMG) evoked by the sudden onset of galvanic (DC) stimulation ('on-responses') have been described in detail previously. The aim of the present study was to describe responses in soleus triggered by the termination of galvanic stimulation ('off-responses'). METHODS: In 10 healthy human subjects, we studied responses to transmastoid (bilateral) stimuli of 200 ms and 2 s average duration and 3 or 4 mA intensity. We obtained both on- and off-responses using the same raw data. EMG activity was recorded onto tape while current pulses of systematically varying duration were delivered. Averaged on-responses were obtained by triggering from the beginning of the current pulses. Averaged off-responses were obtained by triggering from the termination of the current pulses. RESULTS: Short-latency (SL) and medium latency (ML) off-responses were both obtained in all but one study. The SL and the ML components of the off-responses were present and had similar latencies and amplitudes, but opposite excitability, to the on-responses obtained with the same stimuli. CONCLUSIONS: Off-responses to galvanic vestibular stimulation can be recorded from soleus EMG. Our findings imply that vestibular SL and ML reflex responses in the legs are dependent on the change in the rate of vestibular nerve discharge, not its absolute level. Both on- and off-responses have properties appropriate to a role in maintaining body stability.     

EMG responses in the soleus muscles evoked by unipolar galvanic vestibular stimulation

This study compared the effects of transmastoid galvanic stimulation with unilateral galvanic stimulation of vestibular afferents. We recorded the effects on soleus EMG occurring at short (SL) and medium (ML) latency, both in normal subjects and in patients with previous unilateral vestibular neurectomy. Unipolar cathodal and anodal stimulation on the same side produced opposite effects for both SL and ML responses. Responses to unilateral cathodal or anodal stimulation were smaller, but otherwise resembled those of transmastoid stimulation with the cathode or the anode placed on the same side, respectively. Unilateral cathodal stimulation resulted in a larger SL response, which occurred at shorter latency than unilateral anodal stimulation. With unipolar stimulation on the side of previous vestibular nerve section, typical SL and ML responses were absent. With stimulation of the intact side, the patients showed smaller SL responses than normal subjects with unilateral stimulation. The larger responses to unilateral cathodal compared to unilateral anodal stimulation are consistent with previous reports that cathodal stimulation produces an increase and anodal a decrease in vestibular nerve firing. The smaller SL responses in the patients may be a consequence of central nervous system reorganization following unilateral vestibular nerve section.     

EMG responses in leg muscles to postural perturbations in Huntington''s disease.

This paper compares leg muscle electromyogram (EMG) responses to sudden toe-up tilts of a moveable platform in patients with Huntington's disease (HD), clinically normal offspring at risk of developing HD (HD risks) and healthy controls. The EMG pattern in standing subjects and patients consisted of short- and middle-latency responses (SL and ML) in the stretched triceps surae muscles and long-latency responses (LL) in the shortened tibialis anterior muscles. The SL response could be further divided into two distinct subcomponents termed SL1 and SL2. An ML response was identified in only 50% of normal subjects and patients. HD patients differed from normal subjects by showing delayed onset latencies and prolonged durations for the LL response, and smaller amplitudes for the ML response. The subjects at risk also showed diminished ML amplitudes and prolonged LL durations, but normal LL onset latencies. In the sitting condition, the EMG responses of the HD patients and of the HD risks did not differ from those of controls: in all groups SL1 was reduced and delayed, SL2 slightly enhanced, while ML and LL were absent. Because both afferent and efferent conduction times are normal in HD, the delayed LL onset reflects abnormal supraspinal organisation of postural control in HD, and indicates that basal ganglia may have a modulatory effect on the LL responses. The normal EMG responses in the sitting patients suggest appropriate regulation of these responses according to postural set in HD.     

Vestibulocollic reflexes: normal values and the effect of age.

OBJECTIVES: To define normal values and examine the influence of ageing on vestibulocollic reflexes (VCR). METHODS: Vestibulocollic responses to 100 dB (normal hearing level; NHL) clicks, forehead taps and galvanic stimulation were measured in 70 healthy adults aged 25-85 years. RESULTS: Click- and galvanic-evoked responses were present bilaterally in all subjects below 60. Average click-evoked response amplitudes decreased with age, with a pronounced decline of 25-30% per decade from the 6th decade. The average click thresholds increased from 85 dB in the third decade to 96.5 dB in the 8th and 9th decades. Average galvanic-evoked VCR amplitudes decreased sharply from the seventh decade. Tap-evoked reflex amplitudes showed a milder decrease. When side to side differences in amplitude were expressed as asymmetry ratios (AR) in subjects below the age of 60, values of up to 35 and 46% were obtained for click amplitudes corrected and uncorrected for background electromyogram (EMG), up to 61% for both corrected and uncorrected tap response amplitudes, and up to 41 and 55% for corrected and uncorrected galvanic-evoked responses. CONCLUSIONS: A normative range of values can be specified for click- and galvanic-evoked VCRs for subjects up to the age of 60. Click- and galvanic-evoked VCR amplitudes decrease rapidly thereafter while tap-evoked responses are less affected. These changes are probably due to morphological changes in the vestibular system occurring with ageing and are more marked than in several previous reports of age-related changes in caloric responses and vestibulo-ocular reflexes.     

Galvanic evoked vestibulospinal and vestibulocollic reflexes in stroke.

OBJECTIVE: Following stroke, the startle reflex, mediated via the reticulospinal tract, is often facilitated. Vestibulospinal reflexes are another bulbospinal reflex, abnormalities of which may contribute to impaired body posture and stance following stroke. We recorded galvanic evoked vestibulospinal and vestibulocollic reflexes to assess whether these showed similar changes to those for startle following stroke affecting the pons and above. METHODS: Twenty-four stroke subjects (aged 40-82) were studied in the vestibulospinal part of the study, 21 stroke subjects (aged 40-81 years) were studied in the vestibulocollic part, including 18 studied in both. Transmastoid galvanic (DC) current was used to stimulate the vestibular nerve. Vestibulocollic responses were recorded from the sternocleidomastoid muscles and vestibulospinal responses from over soleus in standing subjects. RESULTS: Vestibulocollic reflex amplitudes and latencies showed no significant differences between the two sides. Similarly short latency (SL) and medium latency (ML) vestibulospinal reflexes did not differ significantly in frequency, latency or amplitude between the affected and unaffected legs. CONCLUSIONS: Vestibular reflexes are not facilitated by stroke at or above the pontine level. The exaggeration of startle by stroke may be specific to this reflex.     

Postural reflexes in patients on long-term neuroleptic medication.

It is not conclusively known whether the amplitude of medium latency postural reflexes is controlled by dopamine. To further assess the influence of supraspinal dopaminergic pathways on postural reflexes, we studied short (SL), medium (ML) and long latency (LL) reflexes in the lower extremity of 10 patients on long term (greater than 6 months) neuroleptic medication, 5 with and 5 without mild drug induced parkinsonism. A control group consisted of 10 age and sex matched healthy volunteers. In both patient groups, latencies and amplitudes of all 3 responses were identical to normal controls. These findings suggest that a moderate postsynaptic inhibition of central dopaminergic pathways is insufficient to cause enhanced amplitudes of ML responses.     

Anal sphincter responses after perianal electrical stimulation.

By perianal electrical stimulation and EMG recording from the external anal sphincter three responses were found with latencies of 2-8, 13-18 and 30-60 ms, respectively. The two first responses were recorded in most cases. They were characterised by constant latency and uniform pattern, were not fatigued by repeated stimulation, were most dependent on placement of stimulating and recording electrodes, and always had a higher threshold than the third response. The third response was constantly present in normal subjects. It had the longest EMG response and the latency decreased with increasing stimulation to a minimum of 30-60 ms. This response represented the clinical observable spinal reflex, "the classical anal reflex". The latencies of the two first responses were so short that they probably do not represent spinal reflexes. This was further supported by the effect of epidural anaesthesia which left the first responses unaffected but abolished the classical anal reflex. The origin of the two first responses is discussed and models involving antidromal impulse propagation in the efferent fibre as the afferent limbs of the responses are proposed.     

Modulation of the soleus H‐reflex following galvanic vestibular stimulation and cutaneous stimulation in prone human subjects

There is evidence to suggest that vestibular and somatosensory inputs may interact when they are processed by the central nervous system, although the nature of the individual sensory contributions to this interaction is unknown. We examined the effects of a combined vestibular and cutaneous conditioning stimulus on the motoneuron pool that supplies the soleus muscle via the Hoffman reflex (H‐reflex). We applied galvanic vestibular stimulation (GVS; bipolar, binaural, 500 ms, 2.5‐mA square‐wave pulse) and cutaneous stimulation (medial plantar nerve; 11 ms, three‐pulse train, 200 HZ ) to prone human subjects and examined changes in the amplitude of the H‐reflex. GVS alone caused facilitation (approximately 20%) of the H‐reflex, whereas ipsilateral cutaneous stimulation alone caused a 26% inhibition. Paired GVS and cutaneous stimulation resulted in a linear summation of the individual conditioning effects. H‐reflex amplitudes observed after paired conditioning with GVS and cutaneous stimulation could be predicted from the amplitudes observed with individual conditioning. These results suggest that in the prone position, when the muscles are not posturally engaged, vestibular and somatosensory information appear to sum in a linear fashion to influence the reflex response of lower limb motoneurons. Muscle Nerve 40: 213–220, 2009     

Effects of fatigue on the stretch reflex in a human muscle.

The effects of fatigue on the electromyographic (EMG) reflex activities were compared during sustained voluntary contractions and contractions evoked by electrical stimulation (30 Hz) in the human first dorsal interosseus (FDI). Short latency (SL), medium latency (ML) and long latency (LL) reflex responses to a ramp-and-hold stretch of the muscle were recorded and analysed in 27 healthy subjects of both sexes. The amplitude of the reflex components was normalized as function of the amplitude of the surface action potential (SAP) recorded in response to the supramaximal stimulation of the motor nerve. The results indicate that for a similar reduction of force, SL and ML are significantly reduced after fatigue induced by voluntary contractions but they are not when the fatigue test is performed by electrical stimulation at the motor point. In voluntary fatigue experiments, the LL component showed no significant decrease below control values, but an enhancement was observed during electrically evoked contraction. This enhancement remained above control values for at least 15 min during the recovery period, whereas SL and ML decreases returned to control within 5 min after the fatigue tests. The electrical stimulation applied to the skin overlying the FDI at an intensity lower than the motor threshold did not affect SL and ML, but enhanced LL for about 15 min. On the contrary, the anaesthesia of the skin overlying the FDI induced a decrease in LL without significant change of SL and ML. It is concluded that muscle reflex fatigue is present during sustained voluntary contractions and decreases SL and ML responses to quick stretches.(ABSTRACT TRUNCATED AT 250 WORDS)     

Measurement of tendon reflexes by surface electromyography in normal subjects

Summary A simple method for measuring the tendon reflexes was developed. A manually operated, electronic reflex hammer was applied that enabled measurement of the strength of tendon taps. Reflex responses were recorded by surface electromyography. Stimulus-response relations and latencies of tendon reflexes in the biceps, triceps, quadriceps and triceps surae were examined in 40 healthy subjects. A characteristic relation between stimulus strength and response amplitude was found which could be described by an empirical function. Latencies of both arm and leg reflexes were linearly related to the height of the subjects. Variations of reflex amplitudes within and between subjects were comparable with previous results obtained with more complicated techniques. Although repeatability of measurement of the amplitude is limited by the variability of reflexes, significant agreement was found between repeated measurements. Most reflex amplitudes were diminished during repeated examination after a short interval. Both measurement and clinical examination showed the frequent occurrence of left-right asymmetry of reflex amplitudes. These left-right differences were reproducible to a significant degree on repeated measurements after more than 2 years.     

Contribution of Galvanic Vestibular Stimulation for the Diagnosis of HTLV-1-Associated Myelopathy/Tropical Spastic Paraparesis

Background and Purpose

Galvanic vestibular stimulation (GVS) is a low-cost and safe examination for testing the vestibulospinal pathway. Human T-lymphotropic virus 1 (HTLV-1)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a slowly progressive disease that affects the vestibulospinal tract early in its course. This study compared the electromyographic (EMG) responses triggered by GVS of asymptomatic HTLV-1-infected subjects and subjects with HAM/TSP.

Methods

Bipolar galvanic stimuli (400 ms and 2 mA) were applied to the mastoid processes of 39 subjects (n=120 stimulations per subject, with 60 from each lower limb). Both the short latency (SL) and medium latency (ML) components of the EMG response were recorded from the soleus muscles of 13 healthy, HTLV-1-negative adults (56±5 years, mean±SD), and 26 individuals infected with HTLV-1, of whom 13 were asymptomatic (56±8 years) and 13 had HAM/TSP (60±6 years).

Results

The SL and ML EMG components were 55±4 and 112±10 ms, respectively, in the group of healthy subjects, 61±6 and 112±10 ms and in the HTLV-1-asymptomatic group, and 67±8 and 130±3 ms in the HAM/TSP group (p=0.001). The SL component was delayed in 4/13 (31%) of the examinations in the HTLV-1-asymptomatic group, while the ML component was normal in all of them. In the HAM/TSP group, the most common alteration was the absence of waves.

Conclusions

A pattern of abnormal vestibular-evoked EMG responses was found in HTLV-1-neurological disease, ranging from delayed latency among asymptomatic carriers to the absence of a response in HAM/TSP. GVS may contribute to the early diagnosis and monitoring of nontraumatic myelopathies.     

Phase-dependent modulation of cutaneous reflexes in tibialis anterior muscle during passive stepping

The purpose of this study was to determine whether the cutaneous reflex elicited in the tibialis anterior (TA) muscle would be modulated in a phase-dependent manner while human subjects were passively stepping on a treadmill (treadmill stepping) or in the air (air stepping). The passive stepping was produced by a robotic gait trainer, Lokomat. The cutaneous reflexes following electric stimulation to the distal tibial nerve were recorded at ten different phases of a step cycle under the condition of tonic dorsiflexion [10% of maximum electromyography activity (EMGmax)]. Cutaneous reflex EMG responses with peak latencies of 70-120 ms [middle latency responses (MLR)] were then analysed. The results showed that there were no visible differences in the background EMG activities at the ten phases or two passive stepping conditions. During treadmill stepping, however, the magnitude of the facilitatory reflex responses between the late stance and the early swing phase was strongly enhanced, whereas no clear modulation of the MLR during air stepping was observed. These results suggest that the load-related afferent information plays a key role in the modulation of the cutaneous reflex during human walking.     

Coexistent Hoffmann reflexes in human leg muscles are commonly due to volume conduction

The existence of "concomitant" (coexistent) electromyographic reflex responses in soleus and tibialis anterior muscles, produced by posterior tibial nerve stimulation, has been cited as evidence for "reciprocal excitation" between these antagonistic muscles normally reflexly linked by reciprocal inhibition. Using the Hoffmann reflex procedure and posterior tibial nerve stimulation, the existence of true reciprocal excitation was tested in six subjects with no neuromuscular impairment. Coexistent EMG responses were observed in all subjects. In no instance, however, could the tibialis anterior EMG volley to posterior tibial nerve stimulation of the soleus muscle be antidromically blocked by common peroneal nerve stimulation applied at 10 to 20 ms offset latencies. A second stimulation pulse applied to the common peroneal nerve at similar offset latencies did antidromically block a tibialis anterior reflex response to common peroneal nerve stimulation. Therefore, volume conduction of reflex activity from the posterior tibial compartment to the anterior tibial compartment was a common observance. We suggest that coexistent EMG reflex responses, presumed to reflect reciprocal excitation, should be tested by the procedure described to reject the possibility of EMG cross-talk as a confounding variable or as the actual variable under investigation.     

Vestibulo masseteric reflex and acoustic masseteric Reflex. Normative data and effects of age and gender

ObjectiveTo provide normative data for the Vestibulo-Masseteric Reflex (VMR) and Acoustic-Masseteric Reflex (AMR) in healthy subjects, stratified for age and gender.MethodsA total of 82 healthy subjects (M:F 43:39, mean age 39.3 ± 18.4 years, range 13–79 years) underwent recording of click-evoked VMR and AMR (0.1 ms duration, 5 Hz frequency) from active masseter muscles. Masseter responses to uni- and bilateral stimulation were recorded in a zygomatic and a mandibular configuration, according to the position of the reference electrode. Stimulation intensity curves were recorded for each reflex in ten subjects (mean age 20.7 ± 8.1 years). Gender effect was investigated in 62 subjects and age effect was analyzed in six 10-subject groups aged from <25 to >65 years. Onset and peak latencies, interpeak intervals, raw and corrected amplitudes, latency and amplitude asymmetries were analyzed.ResultsVMR had a higher elicitation rate than AMR. For both reflexes, rates of elicitation, and corrected amplitudes were higher in the zygomatic configuration, and bilateral stimulation elicited larger responses. Best acoustic ranges of elicitation were 98–113 dB for AMR and 128–138 dB for VMR. Reflex latencies were shorter in females than males. Frequency and amplitude of VMR and AMR decreased substantially over 55 year olds.ConclusionsVMR and AMR can be easily performed in any clinical neurophysiology laboratory.SignificanceThese reflexes can find application in the investigation of brainstem function in central neurological disorders.     

Comparison of spinal myotatic reflexes in human adults investigated with cross-correlation and signal averaging methods

A cross-correlation method for recording spinal myotatic reflexes has been developed to meet the need for brief test periods in babies and children and subjects with central neurological pathology. In normal adult subjects the method has been validated by comparing excitatory and inhibitory reflexes obtained with cross-correlation with those obtained with conventional signal averaging. In the cross-correlation method a pseudo-random binary sequence of 64 brief tendon taps was delivered in <1.5 s, and in the averaging method 20-150 taps at one per second. The reflexes were expressed as unit impulse responses to enable direct, quantitative comparisons to be made. With cross-correlation the responses were slightly expanded in time, had lower peak amplitudes, and onset latencies advanced by 10 ms, the clock period of the pseudo-random binary sequence. The amplitude of biceps phasic stretch reflex increased with muscle contraction in a similar manner with both methods. In tests for stationarity the amplitude of biceps phasic stretch reflex varied <10% in the first six repeats of the pseudo-random binary sequence. The tap force required at threshold for cross-correlation was approximately half that for averaging, but with both methods the magnitude of biceps phasic stretch reflex varied linearly with tap force over the range of one to two times threshold. The validity of responses obtained with cross-correlation was assessed by a statistical procedure. In conclusion, the cross-correlation method is robust and gives similar results to those obtained with averaging.     

Reflex responses of the human jaw-closing system depend on the locus of intraoral mechanical stimulation

Innocuous mechanical stimuli were applied to eight sites on the tongue dorsum and palate while subjects used feedback to maintain a constant isometric biting force. Reflex responses of the jaw-closing system were measured as changes in force and in EMGs recorded from right and left masseter muscles. Stimulation at each of the eight sites produced reflex force and EMG responses in most subjects tested. The nature of the reflex responses strongly depended on the site of stimulation. Stimulation of the palate tended to produce suppression of ongoing EMG activity and decreases in background biting force. In contrast, stimulation of sites on the tongue posterior to the tip, most often resulted in excitatory EMG responses and increases in jaw-closing force. Unilateral, early excitatory responses were observed in the right masseter with stimulation of the right side of the tongue. The existence of spatially organized responses of the human jaw-closing system to innocuous intraoral stimulation is not consistent with the view that these cutaneous reflexes are primarily of protective significance.     

Withdrawal reflexes in adductor muscles elicited by electrical and magnetic stimulation of the obturator nerve

The withdrawal reflex in the short head of the biceps femoris muscle after electrical stimulation of the sural nerve at the ankle has been investigated in numerous studies. These studies have described two distinct responses: early (R-II) and late (R-III). However, withdrawal reflex activity of the adductor muscles in the legs has not been studied systematically. Adductor muscle reflex activity is important because it can produce serious clinical problems, such as adductor spasticity and spasms, during bladder surgery. The present study examined withdrawal reflex features of adductor muscles obtained by electrical and magnetic stimulation of the obturator nerve (ON) in 34 normal healthy subjects. Early adductor muscle withdrawal reflex responses were elicited by ipsilateral ON electrical stimulation with a mean latency of 45.7+/-2.0 ms (responses in 94% of subjects). Reflex responses were also obtained using magnetic stimulation at a similar incidence rate. Contralateral ON electrical stimulation resulted in a similar reflex, but with a lower incidence. ON and femoral nerve electrical and magnetic coil stimulation produced similar low-incidence responses in the vastus medialis. These findings indicate that short latency adductor withdrawal reflexes are easily obtained on both sides following electrical or magnetic stimulation of the ON, and they can be elicited by both nociceptive and nonnociceptive stimuli. These reflexes prepare the body for a proper response to incoming signals and likely serve to protect the pelvic floor and pelvic organs.     

Different responses to auditory and somaesthetic stimulation in patients with an excessive startle: a report of pediatric experience.

OBJECTIVES: Children with cerebral injury often exhibit brief muscle contraction to a variety of stimuli. However, it remains to be determined whether or not the pattern of the reaction is stereotypical irrespective of the site stimulated. To answer this question, we studied electromyographic (EMG) responses to three types of stimuli in children. METHODS: The EMG responses of cranial and limb muscles were recorded after acoustic or somaesthetic stimulation in 6 patients and 23 control subjects. RESULTS: Acoustic stimuli evoked patterned motor activity with a rostrocaudal progression. Nose-tapping stimuli elicited reflex EMG activity in the VIIth cranial muscles that was similar to the R1 component of the electrical blink reflex. Sternum-tap stimuli evoked motor activity in the sternocleidomastoid and arm muscles, and this reflex was probably mediated through the cervical cord (H-reflex). Moreover, late reflexes were evoked following these early reflexes in the patients. In particular, atypical forms of myoclonic jerks were evoked on sternum-tap stimuli. CONCLUSIONS: Many types of primitive reflexes were evoked following three types of stimuli. These reflexes included startle reflex, trigeminomotor reflex, H-reflex and atypical forms of myoclonus, and they were enhanced in the patient group. There are many startle-mimicking reflexes.