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PubMed1993

The use of the startle reflex measurement in patients with various types of fixation of the ossicular chain.

The results of startle and acoustic stapedius reflex measurements can be used to subclassify various types of fixation of the ossicular chain. Reflex measurements were performed on a group of subjects with normal hearing and on a group of patients with surgically verified ossicular chain fixation. In 97% of the subjects with normal hearing (n = 30), reproducible impedance changes were observed as part of a startle reaction and four different reaction patterns could be distinguished. In a subgroup of subjects with normal hearing who had a relatively, statistically significant, high acoustic reflex threshold, a characteristic response was found which was most probably caused by contraction of the tensor tympani muscle only. The same response was detected in 77% of the patients (n = 22) with otosclerosis. In the remaining 23%, no middle ear impedance changes occurred as part of a startle reaction. In five out of six patients with fixation of the malleus, no response was observed. Although the startle reflex measurement is a valuable tool for distinguishing between stapes fixation and multiple ossicular chain fixations, the results are not conclusive.

Acoustic Impedance Tests↗

PubMed2003

Startle reflex modulation, affective ratings and autonomic reactivity in incarcerated Spanish psychopaths.

Startle probe modulation during affective picture viewing was assessed in a Spanish prison population. As for North American inmates, psychopaths failed to display normal blink potentiation during unpleasant slides even though their evaluative judgments and autonomic reaction to affective stimuli paralleled those of other inmate and noninmate participants. The results suggest that diminished defense activation characterizes psychopaths despite cultural differences.

Adult↗

PubMed1990

Startle reflex modification: emotion or attention?

Alternative interpretations of startle probe modulation by a pictorial foreground were tested: Either reflex amplitude varies as a function of modality-determined attention allocation, or, regardless of probe modality, reflex amplitude varies with the emotional valence of the foreground content. Thirty-six subjects viewed a series of 54 slides, divided into two 27-slide blocks. Each block consisted of nine exemplars of three independently rated emotional content categories--pleasant, neutral, and unpleasant. Startle probes, half visual (flashgun) and half acoustic (white noise), were presented unpredictably during and between slide presentations. Eyeblink reflexes, corrugator and orbicularis oculi muscle tension, heart rate, and skin conductance were recorded during a 6-s slide interval. Subjects subsequently rated the slides for emotional valence and arousal, and interest value. Free-viewing times were also recorded. Analysis of reflex response and all ancillary measures supported the hypothesis that the primary determinant of startle modulation was the emotional valence of foreground content.

Arousal↗

PubMed1994

Nicotine increases sensory gating measured as inhibition of the acoustic startle reflex in rats.

Chronic nicotine administration has been reported to increase acoustic startle response (ASR) amplitude in rats, which has been offered as evidence that some dosages of nicotine can enhance attention. The present experiments examined effects of acutely administered nicotine on amplitude and pre-pulse inhibition (PPI) of acoustic startle in rats. PPI, the decrease in ASR amplitude by a stimulus preceding the startle-eliciting event, reflects pre-attentive neural processes underlying sensory gating. Nicotine had a biphasic dose effect on startle amplitude, with increases at lower dosages (0.01 mg/kg) and decreases at higher dosages (0.5-5.0 mg/kg SC). Lower dosages of nicotine (0.001-0.01 mg/kg) increased PPI and the increase at 0.001 mg/kg occurred independently of changes in ASR amplitude. These results confirm that increases in PPI are not dependent upon changes in ASR amplitude. Results are consistent with nicotine's enhancements of performance on cognitive tasks in humans and are the first reported use of the PPI paradigm to model such effects. These findings indicate that ASR paradigms are useful to study effects of nicotine.

Acoustic Stimulation↗

PubMed1983

[Reticular neurons with double axon projections: participation in execution of the reflex startle response in the cat].

Synaptic processes in the bulbar and pontine reticular neurons with mixed ascending descending axon projections were studied on chloralose-anesthetized cats during startle reaction to somatic stimulation (spino-bulbo-spinal reflex). Characteristics of these processes proved to be similar to those reported for genuine reticulospinal neurons. Evidence was obtained that as in case of reticulospinal neurons, about a half of the investigated cells were simultaneously involved in suprasegmental relay of the spino-bulbo-spinal reflexes.

Animals↗

PubMed1995

Startle reflex modulation during exposure to pleasant and unpleasant odors.

The eyeblink component of the startle response to acoustic probes was measured while subjects smelled pleasant odors, unpleasant odors, or no odor. Peak electromyogram (EMG) 20-90 ms after probe onset was greater during unpleasant than during no odor conditions; EMGs for pleasant odors did not differ from those for no odor. Base tension in orbicularis oculi muscles was also higher during unpleasant odors. The results for unpleasant odors parallel those found in previous studies that have used a variety of methods for producing negatively valenced experiences. The results for pleasant odors diverge from those of most previous studies, which have found startle attenuation during positively valenced experiences. However, the results may be compatible with the suggestion (Lang, Bradley, & Cuthbert, 1992) that the motivational state that modulates startle involves both valence and arousal. Pleasant odors may require appropriate contexts to produce the positive motivational state required for startle attenuation.

Acoustic Stimulation↗

PubMed1990

Emotion, attention, and the startle reflex.

This theoretical model of emotion is based on research using the startle-probe methodology. It explains inconsistencies in probe studies of attention and fear conditioning and provides a new approach to emotional perception, imagery, and memory. Emotions are organized biphasically, as appetitive or aversive (defensive). Reflexes with the same valence as an ongoing emotional state are augmented; mismatched reflexes are inhibited. Thus, the startle response (an aversive reflex) is enhanced during a fear state and is diminished in a pleasant emotional context. This affect-startle effect is not determined by general arousal, simple attention, or probe modality. The effect is found when affects are prompted by pictures or memory images, changes appropriately with aversive conditioning, and may be dependent on right-hemisphere processing. Implications for clinical, neurophysiological, and basic research in emotion are outlined.

Arousal↗

PubMed2004

Sensitization and habituation of the acoustic startle reflex in patients with schizophrenia.

Assessments of prepulse inhibition and habituation of the acoustic startle response have proved to be valuable tools for assessing deficits of sensorimotor gating and information processing in schizophrenia patients. Recent studies, however, have reported inconsistent results regarding startle habituation deficits in schizophrenia using block-to-block analyses. Some of these inconsistencies may be due to abnormal initial sensitization effects to startle-eliciting stimuli. In a longitudinal study during the course of an acute psychotic episode, 34 medicated inpatients were examined with regard to sensitization and habituation effects in a trial-by-trial analysis and compared with 18 normal control subjects. On two examinations--10 days after admission and after psychopathological improvement 2-3 weeks later--schizophrenia patients exhibited an exaggerated magnitude increment across the first few startle-eliciting stimuli and habituation deficits that were evident when the effect of sensitization was removed from analysis. In the present study, both increased sensitization and reduced habituation appeared to be trait markers of schizophrenic psychoses. The enhanced sensitization effect--presumably due to an abnormal arousal modulation--reflects abnormal stimulus processing in schizophrenia, i.e. the diminished ability to learn the irrelevance of simple identical stimuli. In addition, the present data have important implications for designing startle studies to assess sensitization, habituation and prepulse inhibition in one session.

Adult↗

PubMed1992

Human startle reflex: technique and criteria for abnormal response.

Because quantitative norms for the normal audiogenic startle response to repeated stimuli have not been previously reported, we now describe a technique for eliciting the startle response and analysing its habituation with repeated stimuli. We used binaural 105 dB tones delivered in 5 blocks of 4 tones. Successive blocks were separated by a 5 min period without tones stimuli and had progressively shorter inter-stimulus intervals (ISIs) beginning with 5 min in the first block and reducing to 1 min in the final, fifth block. We contrast the response and its habituation in a group of 8 normal subjects with that in a patient with clinically exaggerated startle. Based on the differences observed, we propose that the following criteria may be used to ascertain an abnormally increased startle response: (1) excessive duration of the myogenic response; (2) persistence of extracranial responses after the initial two blocks of stimuli; and (3) reduced habituation of the response (as measured by decreases in response duration and in the area under the curve of rectified EMG for the orbicularis oculi myogenic response). Our patient was abnormal on each of these measures. This result is consistent with past qualitative reports which have indicated that abnormal startle is associated both with excessive startle and with subnormal habituation. Study of further patients with hyperekplexia will be necessary to either confirm our data or modify our proposed criteria.

Acoustic Stimulation↗

PubMed2006

Diurnal variation of the startle reflex in relation to HPA-axis activity in humans.

Diurnal variation of baseline startle amplitude was examined in 14 normal inpatients on a research unit where behavioral activity and environmental stimuli were highly controlled. We tested a hypothesized association between diurnal variations of salivary cortisol and reflex amplitude by recording acoustic startle eyeblinks shortly before bedtime, when cortisol was near its lowest daily level, and just after awakening, when cortisol was at its peak. Results showed that startle eyeblinks were greater during evening than morning sessions, whereas the opposite was true for cortisol levels. Skin conductance levels and reaction time performance also increased from morning to evening. These findings are consistent with accumulating evidence suggesting a possible link between startle reactivity and hypothalamic-pituitary-adrenal axis activity, and an association between diurnal variations in endogenous arousal and startle amplitude.

Adult↗

PubMed2005

Effect of cefepime on startle amplitude and prepulse inhibition of startle reflex in rats: manipulation of GABAA receptor function with midazolam.

Disruption of prepulse inhibition (PPI) of startle response is manifested in schizophrenia and Huntington's disease among other neuropsychiatric disorders characterized by sensorimotor gating deficit. Antagonism of GABAA receptor function was documented to reduce PPI response. However, whether GABAA antagonism reduces PPI response is yet to be established because of contradicting reports. Cefepime is one of the fourth-generation cephalosporins documented to antagonize GABAA receptor function. This study investigated the effect of intramuscular injection of cefepime (45 and 90 mg/kg) twice daily for three consecutive days on both PPI of acoustic startle response and acoustic startle amplitude in rats. The effect of administration of the GABAA receptor agonist midazolam (1 mg/kg, i.p.) in conjunction with cefepime on PPI response and startle amplitude was also investigated. Results showed that administration of both dose levels of cefepime caused PPI deficit. Treatment of animals with midazolam in conjunction with cefepime reversed the effect of the lower dose, but not the higher one, on PPI of startle response without affecting startle amplitude in both dose levels. Results of this study, therefore, support the view that GABAA antagonism reduces PPI response. It is also concluded that antagonism of GABAergic transmission may be involved in the effect of the lower dose of cefepime on PPI response. Other mechanisms may mediate the effect of the higher dose of cefepime on PPI response. Clinical investigations are needed to determine the consequence of using cefepime in disorders of sensorimotor gating.

Animals↗

PubMed2004

The Effects of dizocilpine and phencyclidine on prepulse inhibition of the acoustic startle reflex and on prepulse-elicited reactivity in C57BL6 mice.

Prepulse inhibition (PPI) of the acoustic startle response refers to the reduction in startle reaction to a startle-eliciting stimulus when it is shortly preceded by a subthreshold prepulse stimulus. Here, we evaluated the possible effects on prepulse-elicited reactivity by dizocilpine (MK-801) and phencyclidine (PCP) in the PPI of acoustic startle paradigm in C57BL6/J mice. The aim was to ascertain whether these two drugs would affect prepulse-elicited reactivity in a manner similar to apomorphine, which enhances prepulse-elicited reactivity at doses that disrupt PPI. In two dose-response studies, we showed that both drugs exhibited a tendency to attenuate prepulse-elicited reaction at higher doses when PPI was severely disrupted. On the other hand, at lower doses when PPI was marginally disrupted, reaction to the prepulse, if anything, tended to increase. It is concluded that PPI disruption induced by noncompetitive NMDA receptor antagonists can be distinguished from apomorphine-induced PPI disruption by their concomitant effects on prepulse-elicited reactivity. Our data support the suggestion that dopamine receptor agonists and NMDA receptor antagonists disrupt PPI via interference with distinct neural pathways or neuronal systems.

Acoustic Stimulation↗

PubMed1994

Effects of acoustic prepulses on the startle reflex in rats: a parametric analysis.

Small changes in the sensory environment, called prepulses, prior to a startle-eliciting stimulus can either inhibit or facilitate the startle reaction. To investigate this apparent discrepancy, a number of characteristics of the acoustic prepulse were varied and the effects on the startle reaction were studied. The results showed that increasing the intensity of the prepulse (81-85 dB) resulted in an increased inhibition and could even turn facilitation into inhibition (at 3-13 ms prepulse-startle interval). Varying prepulse lengths (1-45 ms) did not change the observed startle modification. Only when the prepulse offset was close to the startle onset, changes could be observed. Confronting the animal with the same test session for several days resulted in increased inhibition and a change from facilitation to inhibition (at 3-13 ms prepulse-startle interval). The results demonstrate that the characteristics of the prepulse determine its effect on the startle reaction. An hypothetical model is proposed which might explain the observed data.

Acoustic Stimulation↗

PubMed1994

Effects of acoustic prepulses on the startle reflex in rats: a parametric analysis.

Acoustic Stimulation↗

PubMed1988

Comparative threshold studies of the acoustic pinna, jaw and startle reflex in the rat.

Electromyograms of M. Levator auris and M. Temporalis and movement produced by whole body startle were recorded simultaneously in awake, freely moving rats. Thresholds were 78 db SPL for the L. auris, 80 dB SPL for the ballistic and 81 dB SPL for the Temporalis. The rank ordering of the three thresholds was extremely strict, 188 suprathreshold M. L. auris responses could be observed without M. Temporalis responses, but only once was a M. Temporalis response observed without a M. L. auris response. Thresholds as well as amplitudes and latencies measured by the different methods show correlated fluctuations. While the rise in amplitude which accompanies increasing stimulus intensity is similar in the three measures, the latency decrease is not. The latency difference between M. Temporalis EMG and M. L. auris EMG is intensity dependent, increasing from 0 msec at 78 dB SPL to 1.1 msec at 115 dB SPL, with a faster response for the M. L. auris.

Animals↗

PubMed1997

Startle reflex modulation by pleasant and unpleasant odors in a between-subjects design.

Participants were presented with an acoustic startle probe while they smelled either a pleasant odor or an unpleasant odor (n = 40 per condition). Within each condition, participants were presented with four blocks in which odor was present and four in which odor was not present (no-odor control). Significant differences were found in both conditions between the odor and no-odor blocks. In the unpleasant odor condition, blink magnitude was greater during the odor blocks; in the pleasant odor condition, blink magnitude was smaller during the odor blocks.

Acoustic Stimulation↗

PubMed1997

Role of the hippocampus, the bed nucleus of the stria terminalis, and the amygdala in the excitatory effect of corticotropin-releasing hormone on the acoustic startle reflex.

Previously, we demonstrated that transection of the fimbria/fornix blocked the excitatory effect of corticotropin-releasing hormone (CRH) on startle (CRH-enhanced startle), suggesting that the hippocampus and its efferent target areas that communicate via the fimbria may be critically involved in CRH-enhanced startle. The bed nucleus of the stria terminalis (BNST) receives direct projections from the ventral hippocampus via the fimbria/fornix. Therefore, the role of the ventral hippocampus, the BNST, and the amygdala in CRH-enhanced startle was investigated. NMDA lesions of the BNST completely blocked CRH-enhanced startle, whereas chemical lesions of the ventral hippocampus and the amygdala failed to block CRH-enhanced startle. However, the same amygdala-lesioned animals showed a complete blockade of fear-potentiated startle, a conditioned fear response sensitive to manipulations of the amygdala. In contrast, BNST-lesioned rats had normal fear-potentiated startle. This indicates a double dissociation between the BNST and the amygdala in two different paradigms that enhance startle amplitude. Microinfusions of CRH into the BNST, but not into the ventral hippocampus, mimicked intracerebroventricular CRH effects. Furthermore, infusion of a CRH antagonist into the BNST blocked CRH-enhanced startle in a dose-dependent manner. Control studies showed that this blockade did not result from either leakage of the antagonist into the ventricular system or a local anesthetic effect caused by infusion of the antagonist into the BNST. The present studies strongly suggest that CRH in the CSF can activate the BNST, which could lead to activation of brainstem and hypothalamic BNST target areas involved in anxiety and stress responses.

Acoustic Stimulation↗

PubMed1998

[Effect of the maternal environment on blood pressure and startle reflex in rats with inherited hypertension].

In a long-term study comprising adolescence (6 weeks of age) and adulthood, acoustic startle response (ASR) and arterial blood pressure (ABP) were studied in the ISIAH (inherited stress-induced arterial hypertension) rats, in normotensive Wistar, and cross-fostered rats. The 6-week ISIAH rats already revealed a hypertension enhanced ASR as well as a reduced habituation as compared with the control rats. Maternal effects on the ASR and, to a lesser extent, on the ABP were revealed in cross-fostered rats. In young ISIAH rats fostered by Wistar surrogate mothers, the ASR was decrease and development of hypertension was delayed. There was no significant difference in expression of the ASR between adult ISIAH and Wistar rats whereas the ABP difference was quite obvious.

Animals↗