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PubMed2002

Rearing experience differentially affects somatic and cardiac startle responses in rhesus monkeys (Macaca mulatta).

The present study reports, for the first time, somatic and cardiac responses to acoustic startle in 2 groups of rhesus monkeys (Macaca mulatta) with different rearing experiences. Both groups showed a significant direct relationship between startle amplitude and the intensity of the acoustic startle stimulus (80-120 dB) and rapid heart rate acceleration after a 120-dB stimulus. Monkeys reared with a same-age peer (PR) showed higher startle amplitudes than those reared with their mothers (MR), consistent with rearing effects in rodents. The MR monkeys, however, showed faster heart rate acceleration of greater overall magnitude than that of the PR group. The results are discussed with regard to a monkey model for neuropsychiatric disease.

Acoustic Stimulation↗
PubMedDate not supplied

Exaggerated electrodermal startle responses after intracardiac shock discharges in patients with implanted cardioverter defibrillators.

OBJECTIVE: We studied whether repetitive intracardiac shock discharges of implantable cardioverter defibrillators (ICDs) provoke an enduring enhancement of startle responses. METHODS: The study population comprised 134 patients with an ICD. Among those, 67 patients had experienced shock delivery. Thirty-five patients had received five or more shocks. We used the startle reflex paradigm, which consisted of 15 acoustic stimuli (95 dB, 1000 Hz, 500 ms duration). Skin conductance response was measured using a constant 0.5 V through 8-mm electrodes placed on each subject's nondominant palm. Response magnitude was calculated by subtracting the baseline response level of the 2 seconds immediately preceding tone onset from the maximum response level within 1 to 4 seconds after tone onset. The left orbicularis oculi electromyogram (EMG) response was calculated by subtracting the mean EMG level during the 2 seconds immediately preceding tone onset from the highest EMG level measured within 40 to 200 ms after tone onset. Habituation was defined by the response slope of the regression equation and by the number of trials required to reach the nonresponse criterion. RESULTS: Although EMG response measures of magnitude and habituation failed to yield differences between study groups, patients who had experienced five or more ICD shocks exhibited a significantly larger skin conductance response magnitude in comparison to the patients who had experienced fewer than five shocks (median, interquartile range: 0.364, 0.209-0.618 vs. 0.512, 0.375-0.791; Mann-Whitney U test, p =.007). Poorer habituation in the group with five or more shocks in comparison with the low shock group was confirmed both by the number of trials needed to reach the nonresponse criterion (median, interquartile range: 10, 5-14 vs. 5, 2-13; p =.003) and by the response slope (median, interquartile range: 0.209, 0.116-0.274 vs. 0.262, 0.181-0.332; p =.008). After controlling for potential confounding factors (age, anxiety, aversiveness of stimuli, time since last shock experience, and use of beta-adrenoceptor antagonists), intracardiac shock discharges had the strongest impact on augmented skin conductance response magnitude (adjusted odds ratio = 3.0, 95% confidence interval = 1.3-7.2, p =.01) and impaired habituation (adjusted odds ratio = 2.8, 95% confidence interval = 1.2-6.3; p =.015). CONCLUSIONS: Intracardiac shock discharges are associated with augmented skin conductance responses and slower habituation, indicating sustained sympathetic arousability, which is presumably centrally mediated.

Defibrillators, Implantable↗
PubMed1999

Hypertonia, hyperreflexia, and excessive startle response in a neonate.

Following an uneventful gestation, a newborn girl presented with hypertonia, hyperreflexia, tremor, and excessive startle response. Nose tap elicited a dramatic head recoil. Her mother had similar symptoms beginning as a child that improved but persisted into adulthood. In addition, several members of mother's family died unexpectedly in infancy. Hypertonia in the newborn period indicates central nervous system dysfunction of several possible causes, most of which are associated with severe cognitive deficits and limited neurological development.

Anticonvulsants↗
PubMed2002

Effects of antipsychotics on prepulse inhibition of the startle response in drug-naïve schizophrenic patients.

BACKGROUND: Disturbances in sensorimotor gating measured by prepulse inhibition of the startle response (PPI) have frequently been reported in medicated and unmedicated schizophrenia spectrum patients and in their relatives, suggesting that the deficit represents a stable vulnerability marker for schizophrenia. Clinical data on the effects of antipsychotics on PPI disturbances are scarce, but from preclinical studies, antipsychotics have been shown to influence PPI. To differentiate pathogenetic mechanisms from drug related effects, longitudinal clinical studies on the effect of antipsychotic treatment on PPI in drug-naive first-episode schizophrenic patients are needed. METHODS: First-episode schizophrenic patients never previously medicated with antipsychotics were examined at inclusion and after 3 months of treatment with the atypical antipsychotic compound, risperidone, or the typical drug, zuclopenthixol. Healthy controls were used as a comparison group. RESULTS: The results confirm deficits in PPI in drug-naive first-episode patients. No effect of antipsychotic treatment on PPI dysfunction was observed in any of the treatment groups. CONCLUSIONS: The data are the first to show the possible effect of treatment with antipsychotic drugs on PPI disturbances in a longitudinal study of drug-naive schizophrenic patients. The data do not support any influence of treatment with antipsychotic drugs on sensorimotor gating deficits. Instead, the results point to the impairment in PPI as a stable vulnerability indicator.

Adult↗
PubMed2005

Effects of sex and estrous cycle on modulation of the acoustic startle response in mice.

Potential sex differences in amplitude, habituation, prepulse inhibition (PPI) and prepulse facilitation (PPF) of the acoustic startle response (ASR) were investigated using male and female mice from the two different inbred mouse strains C57BL/6J (C57) and C3H. Furthermore, the effects of the estrous cycle were tested. The estrous cycle appeared to have no effect on ASR amplitude, habituation, PPF and PPI, the latter being in contrast to results in rats and humans. While sex had no effect on PPI or PPF, males exhibited higher startle amplitudes than females, irrespective of strain, which we discuss to be due to increased male anxiety. In addition, long-term habituation was stronger in C57 males and short-term habituation was weaker in C3H males with respect to females. These results provide evidence for influence of the reproductive hormones on startle reactivity and startle habituation; we therefore conclude that future studies involving genetic influences on behavior using inbred strains are only complete if both sexes are included.

Acoustic Stimulation↗
PubMed1997

Hyperekplexia: abnormal startle response due to glycine receptor mutations.

BACKGROUND: Hyperekplexia is a rare but well-delineated clinical syndrome of pathological startle response and neonatal hypertonia. Many cases result from mutations in the alpha 1 subunit of the glycine receptor (GLRA 1). METHOD: The clinical features, management and recent genetic studies of hyperekplexia are reviewed. RESULTS: Diagnosis of the disorder should not be difficult, if one is aware of the syndrome. The treatment of first choice is with the benzodiazepine drug clonazepam, which often causes a dramatic although incomplete diminution of startle. Both recessive and dominant mutations in GLRA 1 have been found in affected individuals. The study of mouse mutants with startle phenotypes suggests that the remainder of cases may well be due to mutations in the beta subunit of the glycine receptor. CONCLUSIONS: Hyperekplexia is the first human disease shown to result from mutations within a neurotransmitter gene. The demonstration of both dominant and recessive inheritance resulting from different mutations in the same gene is of considerable interest, as other neuropsychiatric disorders may result from mutations in ligand-gated ion channels. Mutation analysis of GLRA 1 is also likely to be useful as an aid to genetic counselling and in diagnostic evaluation of neonatal hypertonia.

Diagnosis, Differential↗
PubMed1990

Effects of inferior colliculus lesions on the acoustic startle response.

"Nonspecific" electrolytic lesions (with respect to subdivision) of the mouse inferior colliculus (IC) resulted in the attenuation of acoustic startle response (ASR) amplitudes on the 1st post-operative day, but ASR amplitudes increased to above baseline levels 1 week later. Lesions of the IC central nucleus (CN) also attenuated ASR amplitudes on the 1st postsurgery day, but startle amplitudes recovered to baseline levels 1 week after surgery. Lesions of the IC lateral nucleus (LN) or dorsal cortex (DC) resulted in elevation of startle amplitudes above baseline 7 days after surgery and produced enhanced ASR amplitudes to repeated stimuli. Fourteen days after the surgery, lesion effects on startle amplitudes remained the same as those on Day 7 for each lesion condition. The present findings implicate the ICLN and the ICDC as inhibitory modulators of the ASR, but indicate only a minor role for the ICCN.

Animals↗
PubMed1996

Sensing platform for acoustic startle responses from rat forelimbs and hindlimbs.

A sensing platform with two piezoelectric transducers was designed and fabricated to measure acoustic startle responses from forelimbs and hindlimbs in the rat. Testing with a vibrator showed that separate forces were measured from 5 to 25 Hz with mean sensitivities of 2.395 and 2.022 V/N and mean linearity errors of 3.23 and 2.98% FS for the forelimb and hindlimb sensors, respectively. Forelimb and hindlimb response waveforms of male Sprague-Dawley rats had shapes similar to the commonly recorded wholebody response but were smaller in amplitude.

Acoustic Stimulation↗
PubMed1980

Ontogeny of the acoustic startle response in C57BL/6J mouse pups.

A cross-sectional design was used to study the development of acoustic startle behavior in C57BL/6J mice from the approximate onset of hearing (12 days) to 17 days of age. Startle incidence and latency were recorded in response to 5-, 7-, 10-, 15-, and 20-kHz tones each presented at 80, 90, and 100 dB (SPL). From 12 to 17 days of age, higher frequency and lower intensity tones became increasingly effective in eliciting the acoustic startle response. In addition, startle latency decreased substantially, and response incidence became more sensitive to changes in tone intensity and tone frequency. This rapid ontogeny of the acoustic startle response closely parallels previously demonstrated neurophysiological development of the mouse pup auditory system.

Aging↗
PubMed2001

Startle response of human neck muscles sculpted by readiness to perform ballistic head movements.

1. An acoustic startle stimulus delivered in place of a 'go' signal in a voluntary reaction time (RT) task has been shown previously to advance the onset latency of a prepared distal limb movement without affecting the amplitude of the muscle response or movement kinematics. The primary goal of this study was to use muscles with a larger startle response to investigate whether the startling stimulus only triggered the RT movement or whether some form of interaction occurred between a startle response and a temporally advanced RT movement. 2. Twenty healthy male or female subjects were instructed to react as quickly as possible to an acoustic 'go' stimulus by performing a ballistic head flexion or right axial rotation. The 'go' stimulus was periodically replaced by an acoustic stimulus capable of eliciting a startle reflex. Separate startle-inducing stimuli under relaxed conditions before and after the movement trials served as control trials (CT trials). Bilateral surface electromyography of the orbicularis oculi, masseter, sternocleidomastoid and cervical paraspinal muscles, and head-mounted transducers were used to measure the muscle response and movement kinematics. 3. Muscle activation times in startled movement trials (ST trials) were about half those observed in RT trials, and were not significantly different from those observed in the startle CT trials. The duration of head acceleration was longer in ST trials than in RT trials and the amplitude of both the neck muscle electromyogram (EMG) and head kinematics was larger during ST trials than during RT trials. The EMG amplitude of ST trials was biased upward rather than scaled upward compared with the EMG amplitude of RT trials. 4. Over the 14 ST trials used in this experiment, no habituation of the reflex response was observed in the muscles studied. This absence of habituation was attributed to a combination of motor readiness and sensory facilitation. 5. The results of this experiment indicated that the neck muscle response evoked by a startling acoustic stimulus in the presence of motor readiness could be described as a facilitated startle reflex superimposed on a temporally advanced, pre-programmed, voluntary RT movement. Parallel reticular pathways to the neck muscle motoneurones are proposed as a possible explanation for the apparent summation of the startle and voluntary movement responses.

Adult↗
PubMed2000

Fear-potentiated startle response in mice: genetic analysis of the C57BL/6J and DBA/2J intercross.

The role of genetic factors in the fear-potentiated startle (FPS) response was examined in the inbred C57BL/6J (B6) and DBA/2J (D2) mouse strains. Mice in the D2 strain displayed a significant potentiation in the acoustic startle response (ASR) when presented with a visual condition stimulus (CS) previously paired with an aversive unconditioned stimulus (US). The maximal FPS response was observed following 20 conditioning trials but a near maximal response was noted following as few as five trials. Forty conditioning trials produced a significant reduction in the FPS response that may be related to overtraining. The FPS response in the B6 strain was significantly lower than the D2 strain, regardless of the number of conditioning trials. The contrasting FPS responses were not related to differences in auditory sensitivity known to exist between these strains. Analysis of a full Mendelian cross formed from the B6 and D2 strains found that the FPS response was a highly heritable trait, best described by a simple additive model of inheritance and with a broad-sense heritability of 0.46. The distribution of the FPS response in F2 hybrids formed from the intercross of the D2 and B6 strains was continuous which suggests a multigenic substrate. The light + noise and noise-alone trial types were highly correlated, but no association was detected between the baseline ASR amplitude and the FPS response. Mice from the phenotypic extremes of the F2 distribution displayed FPS responses that were more extreme than either of the progenitor strains. However, both baseline startle amplitude and the salience of auditory stimuli did not differ in these groups. The results of this study confirm an early report by Falls et al. (1997), and provide additional quantitative genetics information necessary for the eventual mapping of the chromosomal regions or genes associated with the FPS response in mice.

Acoustic Stimulation↗
PubMed1995

Strain and age differences in acoustic startle responses and effects of nicotine in rats.

Two experiments examined the effects of age, genetic strain, and nicotine on acoustic startle response (ASR) amplitude and prepulse inhibition (PPI) in rats. ASR amplitude measures reactivity to external stimulation, and PPI is used as an index of sensory gating related to attention. Both ASR amplitude and PPI have been previously reported to be increased by nicotine in adult rats. Experiment 1 examined effects of chronically administered nicotine and saline on ASR and PPI in Wistar, Long-Evans, and Sprague-Dawley rats (40 days of age). Experiment 2 examined the effects of chronically administered nicotine and saline in Sprague-Dawley rats of two age groups: 40 and 70 days of age at the beginning of the study. ASR amplitude differed significantly across strains with the values for Wistar > Sprague-Dawley > Long-Evans, and there were no differences in percent of PPI among the three strains. In addition, results of Experiment 2 indicated that older rats had significantly greater ASR amplitudes and PPI than younger rats. Consistent with previous reports, nicotine increased ASR and PPI in the older rats; however, there were no significant differences in the younger rats. Therefore, age and genetic strain are important variables in the analysis of nicotine's effects on startle behaviors in rats.

Aging↗
PubMed1999

Sex differences in the acoustic startle response and prepulse inhibition in Wistar rats.

The prepulse inhibition paradigm (PPI) is based on the phenomenon that the acoustic startle response (ASR) to an acoustic stimulus is reduced when the stimulus is preceded by a weak prepulse. It has been shown that PPI is dramatically disrupted in patients with schizotypic disorders. Since PPI can be easily tested in animals as well as in humans it is a widely used model to investigate the neurobiological mechanisms underlying those disorders. In humans it has been demonstrated that men show increased PPI at weak prepulses relative to women. Only very few studies have investigated PPI sex differences in rats and these report negative findings. Studies are reported on here where consistent differences have been found in ASR and PPI between adult male and female Wistar rats. Compilation of data from a series of experiments demonstrates that ASR and PPI are both greater in males than in females in this rat strain, a finding which is largely in line with the human evidence. This study therefore adds weight to the argument that PPI of the ASR provides an animal model with high validity for the study of important human disorders which are characterized by sensorimotor gating deficits.

Acoustic Stimulation↗
PubMed1995

Involvement of cyclic AMP at the level of the nucleus reticularis pontis caudalis in the acoustic startle response.

Rats were implanted with cannulas in the nucleus reticularis pontis caudalis (PnC), an obligatory part of the neural pathway that mediates the acoustic startle reflex. Following at least 1 week of recovery, rats were tested for acoustic startle amplitude before or after infusion of compounds known to alter the second messenger, adenosine cyclic 3', 5'-monophosphate (cAMP). Local infusion into the PnC of the cAMP analog, 8-bromo cAMP (0.125-1.0 micrograms), increased the amplitude of the acoustic startle response in a dose-dependent manner. In addition, local infusion of a phosphodiesterase inhibitor, rolipram (10 micrograms) or the water soluble adenylate cyclase activator, forskolin-DHA (2.5 micrograms), produced a significant enhancement of startle amplitude. These effects probably resulted from intracellular actions because cAMP itself, which does not readily penetrate lipid membranes, had no effect. Moreover, the effects seemed somewhat specific because the precursor of cAMP, ATP or 8-bromo cGMP, also failed to alter startle at doses where 8 bromo-cAMP did. The fact that a phosphodiesterase inhibitor elevated startle suggests that cAMP serves to tonically elevate startle at this level of the pathway. Hence, treatments that either increase (fear, sensitization) or decrease (habituation, pre-pulse inhibition) startle at the level of the PnC may do so via release of neurotransmitters either positively or negatively coupled to cAMP, which in turn may alter either sound evoked transmitter release, excitability of PnC neurons or both.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1988

Ontogeny of the acoustic startle response and sensitization to background noise in the rat.

The purpose of this study was to characterize the ontogeny of the acoustic startle response (ASR) and response sensitization to background noise in preweanling rats. Animals were tested daily from 11 to 21 days of age using one of four sets of background white noise levels [45-80 dB(A)]. With constant low-level (45 dB, SPL) background noise, response latency decreased steadily with age, whereas both response incidence and amplitude increased nonmonotonically with age. Two approaches were used to examine the ontogeny of sensitization to background noise: The first compared the ASR of animals tested at 75 dB background noise with ones tested at 45 dB; the second compared the ASR of animals tested at three background levels (30 dB range) within the test session. Sensitization was not evident before 15-16 days of age. By comparing these results with the results from naive animals, it was found that daily test experience does not alter ASR amplitude, latency, incidence, or the development of sensitization.

Acoustic Stimulation↗
PubMed1995

Cholecystokinin enhances the acoustic startle response in rats.

The present study examined the effects of the neuropeptide cholecystokinin (CCK) on neurones of the caudal pontine reticular nucleus (PnC), which mediates the acoustic startle response (ASR) in rats. Electrophysiological experiments revealed an excitatory effect of CCK on acoustically responsive neurones in the PnC. On the behavioural level, CCK also enhanced the ASR. Since the PnC is not only an obligatory relay station of the brain circuit mediating the ASR, but also receives modulatory input from brain areas involved in the expression of fear and anxiety, the enhancement of the ASR by CCK could be interpreted as an anxiogenic-like effect of this peptide.

Acoustic Stimulation↗
PubMed1994

Amygdaloid noradrenaline is involved in the sensitization of the acoustic startle response in rats.

The present study examined the role of noradrenaline (NA) in the central nucleus of the amygdala (cA) in the sensitization of the acoustic startle response (ASR) in rats. In the first experiment, local microinjections of 0, 0.5, 1, 2 nmol of the alpha 2-adrenergic antagonist yohimbine into the cA increased the magnitude of the ASR in a dose-dependent way. In the second experiment, foot shocks were applied to increase the ASR amplitude (sensitization). Local microinjections of 0, 4, 8, 16 nmol of the alpha 2-adrenergic agonist ST-91 into the cA dose dependently decreased the sensitizing effects of foot shocks on the amplitude of the ASR. It is conjectured that yohimbine increases and ST-91 decreases local NA release by acting at presynaptic autoreceptors. The present data suggest that the release of NA in the cA is involved in the mediation of the sensitizing effects of foot shocks on the ASR.

Acoustic Stimulation↗
PubMed2004

Attention, heart rate, and startle response during exposure to trauma-relevant pictures: a comparison of recent trauma victims and patients with posttraumatic stress disorder.

Victims of a recent trauma were compared with posttraumatic stress disorder (PTSD) patients and healthy controls to assess whether a specific anxiety response and an attentional bias were evident initially or only in chronic PTSD. Heart rate (HR) and startle response were measured, and a dot-probe task was carried out using trauma-relevant pictures. Severely affected recent trauma victims and chronic PTSD patients showed HR acceleration to trauma-related material, which was the only significant group difference. A bias away from trauma-related material was related to severity of intrusions in recent trauma victims, and the bias toward trauma-related material increased with amplitude of the HR response in PTSD patients. A specific anxiety reaction is present initially in severely affected trauma victims.

Adult↗