Auditory Startle Reaction Research Articles

Orienting reaction may help recognition of patients with psychogenic nonepileptic seizures

Psychogenic nonepileptic seizures (PNES) are abrupt, paroxysmal changes in behavior or consciousness that may phenomenologically resemble epileptic seizures. Given the known association between anxiety and PNES, we hypothesized that in these subjects there may be evidence that the nervous system is hypersensitive to external stimuli. We aimed to test our hypothesis by means of the auditory startle reaction (ASR). By investigating ASR, we also had the opportunity to test presence of orienting reaction, which is generally defined as the second phase of response after the auditory stimulus, with longer latency. We included 22 patients diagnosed as PNES and 25 age- and gender-matched healthy subjects. Clinical assessments and ASR recordings were performed. Electrophysiological findings were compared between patients with PNES and healthy subjects, including the presence of an orienting reaction. Orienting reaction was defined as a late response with latency between 100-1000ms. The mean ages of patients with PNES and healthy subjects were 34.9±12.3 years and 33.3±10.9 years, respectively (P=0.709). All patients were diagnosed as having conversion disorder. Additionally, 19 patients had depressive disorder and four had anxiety. The recruitment pattern of muscles and probability were similar between patients with PNES and healthy subjects. Orienting reaction was solely observed in patients with PNES (n=13, 59.1% of the patients vs. no healthy subject). The sequence and contribution of muscles in the orienting reaction changed almost in all patients. The duration of these responses was long, sometimes more than 200ms. PNES is associated with orienting reaction. This provides a possible electrophysiological marker of altered nervous system function in patients with PNES and may also reflect the distorted emotional processing in these patients.

Sleep bruxism is related to decreased inhibitory control of trigeminal motoneurons, but not with reticulobulbar system.

Sleep bruxism (SB) is a stereotyped movement disorder characterized by grinding or clenching of the teeth during sleep. We aimed to understand the abnormal networks related to the excitability of masticatory pathways in patients with SB. Eleven patients with SB and age- and gender-matched 20 healthy subjects were prospectively enrolled in our study. The masseter inhibitory reflex (MIR) after electrical stimulation and auditory startle reaction (ASR) were examined. For MIR responses, durations of early and late silent period (SP) were shorter and the degree of suppression of SPs was significantly lower in SB group in comparison to those obtained in healthy subjects. The ASR responses even of the masseter muscle, however, were similar between patients with SB and healthy individuals. Abnormal MIR provides support for the decreased inhibitory control of the central masticatory circuits in SB whereas normal ASR suggests the integrity and normal functioning of brainstem pathways mediating startle reaction. Although the sample size is small, our results are in line with previous findings and suggest an abnormally decreased inhibition in trigeminal motoneurons to masseter muscle rather than reticulobulbar pathways in patients with SB.

Startle and blink reflex in high functioning autism

An important clinical feature of autism is the presence of atypical responses to sensory stimuli. In this study, we investigated if high functioning autistic patients had abnormalities in the blink reflex and the startle reaction to auditory or somatosensory stimuli. Fourteen patients aged between 7 and 16years were included in the study. We found a longer latency of the blink reflex, an increased duration and amplitude of the auditory startle reaction and a lower presence rate of the somatosensorial startle reaction in autistic patients. To better define the sensorial characteristics of the disease could improve the therapeutic management of children with autism spectrum disorder.

Startle responses after different stimulus modalities differ in stroke

The auditory startle reaction (ASR) and startle reflex to somatosensory inputs (SSS) are stereotypical responses to sudden and unexpected stimuli, which are generated in the caudal brainstem reticular formation. Changes of ASR are relatively well known in stroke. Here, we aimed to investigate central pathways of SSS and plasticity changes of SSS circuits in different stages and localizations of stroke, by comparing with ASR. We prospectively included 39patients with stroke between June2009 and June2013, and 23age and gender-matched healthy subjects. ASR and SSS were recorded over orbicularis oculi, sternocleidomastoid, biceps brachii (BB), and abductor policis brevis muscles (APB) using surface electrodes. There were supratentorial and infratentorial lesions in both acute and chronic stages. Overall, ASR probability was similar between groups (P=0.981). However, ASR probability was increased for BB and APB recordings on symptomatic sides of stroke patients with high amplitudes and long durations, most prominently on symptomatic sides of pontine strokes. Latencies and presence rates of SSS did not differ between any subgroups of stroke and healthy subjects. ASR is facilitated in arm and hand muscles on symptomatic sides of stroke patients, whereas SSS did not show any significant changes according to stroke.

Brainstem reflexes in patients with sleep bruxism: Masseter inhibitory reflex responses and auditory startle reaction

Background Sleep bruxism (SB) is a stereotyped movement disorder characterized by grinding or clenching of the teeth during sleep. Neurophysiologic methods offer approaches to study the excitability in SB by recording the motor potentials evoked by masseter muscles and masseter inhibitory reflex (MIR). Auditory startle reaction (ASR) has been found to be increased in restless leg syndrome but it has not been studied in SB. We aimed to show the hyperexcitability in the central jaw motor pathways in patients with SB by studying MIR and ASR responses. Methods 10 patients (mean age 48,4 ± 10,2 years; 8 male and 2 female) and 20 healthy subjects (mean age 34,4 ± 11,2 years; 6 male and 14 female) were enrolled in the study. The EMG activity was recorded from two masseter muscles by surface electrodes. The duration and latency of early and late silent periods and suppression ratios obtained from patient and control groups were compared. ASR was recorded from o. oculi, masseter, sternocleidomastoid, biceps brachii and tibialis anterior muscles and probability and latencies were evaluated. SPSS for Windows 11.5 package was employed. Results The differences in silent period onset latencies between patients and normal subjects were not significant but durations of early and late silent periods were shorter in SB group. Conclusions These results may indicate a reduced capacity for inhibition by the circuits responsible for the late period in SB and this increased excitability in central motor pathways could derive from an impaired modulation of subcortical structures especially brainstem inhibitory circuits and not from altered cortical mechanisms. Since ASR did not differ between the control and patient groups, it can be possible to say that there’s no abnormality in brainstem and reticulospinal circuits in SB patients.

Somatosensory and auditory startle reaction in patients with movement disorders

Background Startle reflex (SR) is a generalized defense reaction which is elicited by unexpected stimuli. To elicit SR, auditory and electrical stimulations are used in electrophysiological investigations. Somatosensory startle reflex (SS-SR) is recently described in healthy volunteers after median and tibial stimulation. Studies in patients with brainstem lesions showed importance of upper brainstem in development of SS-SR. Here, we aim to investigate SS-SR systematically in various movement disorders to address its characteristics in comparison to ASR. Methods We have examined ASR and SS-SR in patients with dystonia ( n = 12), multiple system atrophy ( n = 8), corticobasal degeneration ( n = 5), restless legs syndrome ( n = 14), progressive supranuclear palsy ( n = 11), essential tremor ( n = 18) and idiopathic PD (n = 16) and healthy volunteers ( n = 35) under the same conditions. ASR and SS-SR were recorded over orbicularis oculi (o.oc), sternocleidomastoid (SCM), and biceps brachii (BB) after bilateral auditory and median nerve electrical stimulations, respectively. Results The pattern and probability rates over each three muscle of ASR were similar in MSA, RLS, ET, PD and healthy individuals. Probability rates of responses over each muscle and total ASR probability were the highest in dystonia group whereas they were the lowest in CBD and PSP ( p o.oc = 0.016, p scm = 0.036, p bb = 0.000, p total = 0.009). Onset latencies of O.oc responses were also longer in CBD and PSP groups ( p = 0.001). Presence of SSR was also the highest in dystonia and lowest in PSP group similar to ASR. Latency of O.oc response was longest in CBD group. Pattern of SS-SR was similar to healthy individuals in all disease groups except dystonia and MSA in which BB responses were more common than SCM responses. Conclusions The findings of ASR parallel the previous findings. Dystonia patients are known to have exaggerated ASRs. The decreased response in PSP was previously suggested as a support to show extent of pathology. Findings regarding SS-SR also parallel ASR. SS-SR is also exaggerated in dystonia. Different pattern of response appears to be a reflection of overflow phenomenon. However, development of withdrawal reaction is a possibility. Shorter onset latencies in dystonia group probably also reflect increased excitability. Absence of SS-SR or longer latencies in PSP reflects impairment of its pathway which supports the opinion that it may share pathway with ASR and its generator is possibly in the upper brainstem.

Specific brainstem and cortico-spinal reflex abnormalities in coexisting essential tremor and Parkinson's disease (ET-PD)

We aimed to analyze functional changes at brainstem and spinal levels in essential tremor (ET), Parkinson's disease (PD) and coexisting essential tremor and Parkinson's disease (ET-PD). Age- and gender-matched patients with tremor (15 ET, 7 ET with resting tremor, 25 ET-PD and 10 PD) and 12 healthy subjects were enrolled in the study. Diagnosis was established according to standardized clinical criteria. Electrophysiological studies included blink reflex (BR), auditory startle reaction (ASR) and long latency reflex (LLR). Blink reflex was normal and similar in all groups. Probability of ASR was significantly lower in ET-PD group whereas it was similar to healthy subjects in ET and PD (P<0.001). LLR was recorded during voluntary activity in all three groups. LLR II was more common in ET, PD and ET-PD groups. LLR III was far more common in the PD group (n=3, 13.6% in ET; n=4, 16.0% in ET-PD and n=7, 46.7% in PD; p=0.037). Despite the integrity of BR pathways, ASR and LLR show distinctive abnormalities in ET-PD. In our opinion, our electrophysiological findings support the hypothesis that ET-PD is a distinct entity.

Laterality of auditory startle responses in humans

Objective To examine whether the auditory startle reaction in humans is a symmetrical or asymmetrical bilateral brainstem reflex in response to an unexpected loud stimulus. Methods We investigated physiological side-to-side differences of auditory startle responses (ASRs) in 28 healthy adult subjects. ASRs were elicited by randomly presented auditory stimuli. Reflex electromyographic activity was simultaneously recorded from masseter, orbicularis oculi, sternocleidomastoid and biceps brachii muscles bilaterally. Results ASR area-under-the-curve was significantly larger on the side contralateral to hand dominance in sternocleidomastoid, and tended to be larger on the dominant side in biceps brachii. In contrast, in orbicularis oculi, ASR area was significantly larger on the right vs. left side, irrespective of handedness. There was no significant side-to-side difference of ASR probability and ASR latency in any muscle. Conclusions The present data expand our knowledge on physiological variables influencing ASRs and provide evidence of laterality of ASRs in sternocleidomastoid and biceps brachii, being associated with hand dominance, and in orbicularis oculi, irrespective of handedness. Significance Normal limits of side-to-side differences offer an additional parameter to be taken into account in studies of patients presenting with asymmetric symptoms.

P20. Botulinum toxin treatment has no influence on auditory startle reaction in primary blepharospasm

P20. Botulinum toxin treatment has no influence on auditory startle reaction in primary blepharospasm

Auditory Startle Reaction is disinhibited in idiopathic Restless Legs Syndrome

Because the auditory startle reaction is abnormal in disorders with substantia nigra pathology, we hypothesized that auditory startle responses (ASRs) might also be altered in restless legs syndrome (RLS). Neurophysiologic study of the auditory startle reaction. Neurology departments of a university hospital and an affiliated local hospital. Fifteen patients with idiopathic RLS (6 de novo, 9 untreated after a 7-day wash-out period of levodopa, mean duration of RLS [corrected] symptoms 21.2 +/- 17.9 years, mean IRLS [corrected] severity score 23.5 +/- 6.7) and 15 sex- and age-matched healthy controls were investigated. Not applicable. ASRs were elicited by 8 high-intensity auditory stimuli differing randomly in tonal frequency and intensity. Reflex electromyographic activity was simultaneously recorded with surface electrodes from 8 facial, neck, arm, and leg muscles. In RLS patients, ASRs were significantly more frequent (541 of 960 possible responses; controls, 430 of 960), and ASR area under the curve was significantly larger (3812 +/- 450 microVms; controls, 1756 +/- 226 microVms). Analysis per body region revealed that ASRs were significantly more frequent in RLS patients than in controls in leg muscles (138/360 vs 55/360); ASR latencies to leg muscles were significantly shorter in RLS patients (129 +/- 6 ms vs 160 +/- 11 ms); ASR area under the curve was significantly larger in RLS patients in facial (7547 +/- 1326 mmicroVms vs 2982 +/- 448 microVms) and leg muscles (1373 +/- 308 microVms vs 541 +/- 193 microVms). Our data demonstrate disinhibition of reticulospinal pathways in RLS patients as compared to normal controls, likely originating from dysfunction rostral to the lower brainstem.

Auditory startle reaction in primary blepharospasm

Primary dystonia is associated with abnormal brainstem function, as shown by abnormalities of the blink reflex in blepharospasm (BSP) and of the auditory startle reaction in cervical dystonia. We examined the auditory startle reaction--a brainstem reflex elicited by an unexpected loud stimulus--in patients with primary BSP to expand knowledge on brainstem pathophysiology in primary focal dystonia. Thirteen patients with primary BSP were included and 13 age- and sex-matched healthy volunteers served as controls. Auditory startle responses (ASRs) were elicited by binaural high-intensity auditory stimuli, and reflex electromyographic activity was recorded simultaneously with surface electrodes bilaterally from masseter, orbicularis oculi, sternocleidomastoid, and biceps brachii muscles. Patients with BSP showed higher ASR probabilities (masseter, sternocleidomastoid, biceps brachii), shorter ASR onset latencies (masseter, orbicularis oculi, sternocleidomastoid), and larger ASR area-under-the-curve (masseter, sternocleidomastoid) as compared with normal controls. Habituation of ASRs did not differ significantly between patients and controls. These results corroborate previous findings of increased brainstem excitability in primary BSP but point to a different pattern of brainstem dysfunction compared to cervical dystonia, indicating that different pathophysiological mechanisms are involved in the two types of focal dystonia.

Influence of gender on auditory startle responses

The auditory startle reaction is considered a brainstem reflex in response to an unexpected loud stimulus. It may be abnormal in various neurological conditions. However, the influence of gender on physiological characteristics of auditory startle responses (ASRs) in humans has to date been studied only in orbicularis oculi muscle. We investigated 54 healthy adult subjects (27 males, 27 females). ASRs were elicited by binaural high-intensity auditory stimuli which differed randomly in tonal frequency and intensity (250 Hz–90 db; 500 Hz–105 dB; 750 Hz–110 db, 1000 Hz–110 dB nHL), presented through tubal insert phones. Reflex electromyographic activity was simultaneously recorded with surface electrodes from masseter, orbicularis oculi, sternocleidomastoid, biceps brachii, abductor pollicis brevis, rectus femoris, tibialis anterior, and soleus muscles. ASR probability was significantly lower, and ASR area under the curve was significantly smaller, in men versus women. Median onset latencies did not differ significantly, but tended to be shorter in the lower extremities of men despite greater body height. Habituation, measured as a reduction in response probability with repeated stimulation, was significant in all muscles except orbicularis oculi in both men and women. Our data provide evidence for a significant influence of gender on ASR characteristics. The observed differences are likely due to gender-specific variations of central processing in the brainstem centers involved in ASR generation, and should be taken into account when testing ASRs in health and disease.

Influence of age on auditory startle responses in humans

The auditory startle reaction is considered a brainstem reflex in response to an unexpected loud stimulus. We investigated the influence of age on auditory startle responses (ASRs) in 54 adult healthy subjects separated in three age groups (below 30; 30 to 50; above 50 years). ASRs were elicited by auditory stimuli randomly presented through tubal insert phones. Reflex electromyographic activity was simultaneously recorded from eight facial, neck, and extremity muscles. ASR probability was lower in extremity muscles of younger versus older subjects, but did not differ among age groups in facial and neck muscles. Median ASR latencies were significantly shorter in all muscles of younger versus older subjects. Our data provide evidence of a significant influence of age on ASRs. The observed differences are likely due to age-specific variations of central processing in the brainstem centers involved in ASR generation.

Prepulse modulation of the startle reaction and the blink reflex in normal human subjects.

Blink reflexes are usually considered the most representative and consistent response of the auditory startle reaction (ASR), and they are often the only response evaluated in human psychophysiological studies. However, auditory stimuli also induce an auditory blink reflex (ABR), the physiological characteristics and brainstem circuitry of which may be different from those of the ASR. This study aimed to investigate whether there were differences between the orbicularis oculi (OOc) responses elicited with the ABR (OOcABR) and those elicited with the ASR (OOcASR) regarding their behavior to prepulse modulation. For comparison, we also examined the OOc responses to supraorbital nerve stimulation (OOcEBR). Electromyographic responses were simultaneously recorded from the OOc, masseter (MAS) and sternocleidomastoid (SCM) muscles. ABRs were considered when auditory stimuli induced responses limited to the OOc, and ASRs were considered when responses were induced in all muscles recorded from. Prepulse stimuli were either a weak electrical stimulation at the third finger (somatosensory prepulse) or a weak acoustic tone (auditory prepulse) that preceded the response-eliciting stimuli by intervals ranging from 0 to 200 ms. Prepulse effects differed according to prepulse modality, but the OOcABR and the OOcASR were always modulated in the same way. In both responses, somatosensory prepulses induced facilitation from 20 to 50 ms, followed by inhibition beyond 75 ms, and auditory prepulses induced no facilitation but a significant inhibition beyond 30 ms. In the OOcEBR, both somatosensory and acoustic prepulses induced facilitation of R1 and inhibition of R2 beyond 30 ms. Our results suggest that the OOcABR and the OOcASR exhibit the same physiological behavior regarding prepulse modulation. It is hypothesized that prepulse facilitation is due to direct impingement of subthreshold excitatory inputs onto the facial motoneurons while prepulse inhibition results from the engagement of a presynaptic inhibitory circuit in the brainstem.

Habituation of the auditory startle reaction is reduced during preparation for execution of a motor task in normal human subjects

The generalized acoustic startle reaction is a useful but labile phenomenon that undergoes a relatively rapid habituation with repeated stimuli and can be modified by changes in the environmental context. In the present work, we examined the influence of the experimental set on size, latency and habituation rate of auditory startle reactions in 15 normal volunteers. Series of 5 acoustic startling stimuli were applied on each of the following 4 conditions: (1) at rest in a quiet and dull ambience; (2) at rest but engaged in a busy environment; (3) being prepared to execute a reaction time task; and (4) focussing the attention to an impending visual stimulus. We found that the amplitude of the response to the first stimulus was significantly larger in condition 1, and habituation rate was significantly reduced in condition 3, with respect to all other conditions. The enhancement of the startle reaction in a quiet ambience may result from reduction of the sensory inputs from the environment, which would otherwise act as prepulses and cause a certain degree of inhibition. The reduced habituation rate of the startle reaction with preparation for a reaction time task may be due to a transient block of the cortical inhibitory control on inputs from non-expected sensory afferents. A careful description of the experimental conditions with which the startle reactions are tested is required for meaningful comparison of the results from different laboratories. The possibility to reduce habituation of the startle reaction with preparedness for execution of a motor task has important implications with regard to the applicability of the startle reaction on research and clinical practice. © 1997 Elsevier Science B.V. All rights reserved.

Auditory startle (audio-spinal) reaction in normal man: EMG responses and H reflex changes in antagonistic lower limb muscles

The audiospinal reaction (ASR) to a 30 msec tone of 90 dB has been studied in 66 seated healthy volunteers. Electromyographic bursts induced in trapezius (Tra), soleus (Sol) and tibialis anterior (TA) have been looked for. Facilitation of Sol H reflex has been measured in 21 subjects in terms of delays from delivery of the sound. Among the subjects, 11 had a stable TA H reflex whose facilitation was compared to that of Sol H. Effects of selective isometric voluntary contraction of either Sol or TA were assessed both on EMG responses and H reflex facilitation.At rest, only 36% of subjects exhibited a response in Sol at a mean latency of 123 msec and 39% in TA at a latency of 119 msec. Responses were seen in antagonist muscles in 74% of subjects. Incidence in Tra was 96%. During voluntary contraction, the results were not significantly changed either in the contracted muscle or its antagonist. H reflex facilitation of both TA and Sol started 50 msec after the sound to peak after 75–125 msec and returned to baseline values after 250 msec. Extent of Sol H reflex facilitation remained similar during voluntary contraction of Sol and TA. It was observed that EMG responses were more frequent in subjects with brisk reflexes but not necessarily in those who exhibited the largest H reflex facilitation. The results are in agreement with assumptions that ASR is mediated through reticulo-spinal pathways but do not support the view that it corresponds to a flexor reaction. In addition to providing quantitative data for comparisons in pathological cases, they suggest differences in the mode of activation of motoneurones by the motor cortex and subcortical nuclei.

Phenobarbitone: adverse effects on reproductive performance and offspring development in the Mongolian gerbil, (Meriones unguiculatus)

Phenobarbitone at a concentration of 500 mg/l in drinking fluid of gerbils during pregnancy (60 mg/kg) and lactation (136 mg/kg) markedly reduced the proportion of animals bearing litters, decreased pup weights at birth and during later life and delayed development of the self-righting reflex, auditory startle reaction, eye opening and full fur coverage. It also prolonged the period of suckling. Scars of implantation were evident in uterine horns of 60% of treated and in none of control females that had failed to give birth. Treated offspring after weaning were given phenobarbitone (500 mg/l; 42-124 mg/kg) as their drinking fluid throughout life and a further group of gerbils received this concentration of the drug from the time of weaning. Seizure susceptibility was unaltered by the drug treatment, and the only evidence of behavioural change was seen in offspring gerbils at 6 weeks when the bout length of social investigation during encounters was increased. Drug-treated offspring showed no abnormality in brain weight relative to body weight. Weight gain and brain weight remained normal among the gerbils given phenobarbitone after weaning. The drug treatment reduced scent gland size in breeding males, though not in the offspring, and had no effect on weights of the testes or ovaries and uterus. no effect on weights of the testes or ovaries and uterus. Plasma concentrations of phenobarbitone in females of the postweaning group amounted on average to 4.4 mg/kg. Most of the adverse effects of this dose of phenobarbitone in the gerbil can thus be seen to be associated either with reproductive impairment or with exposure during sensitive periods of early development.

Effect of avoidance-avoidance conflict on magnitude of startle: reduced fear during conflict.

The present study used 13 male, hooded rats in a within-subjects design to test the hypothesis that a modified avoidance-avoidance conflict situation in a discrimination learning task would evoke a more intense auditory startle reaction than would the absence of such conflict. The presumed mechanism was an increase in drive or arousal, as a consequence of the conflict, resulting in greater startle. The findings were inconsistent with the hypothesis; the startle reactions of animals in a conflict situation were not different from those of animals in a non-conflict situation.