SEARCH · PubMed Health

Results for “Reflex, Startle”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 487 records · Page 27Linked to original sources

PubMed1997

Startle modulation in children at risk for anxiety disorders and/or alcoholism.

OBJECTIVE: To examine the startle reflex as a possible vulnerability marker among offspring of parents with anxiety disorders and/or alcoholism. METHOD: The subjects were 66 male and female offspring (aged 10 to 17 years) of proband who participated in a family study of comorbidity of alcoholism and anxiety disorders. Testing consisted of examining the startle reflex and its modulation by prepulse stimuli (prepulse facilitation and prepulse inhibition). RESULTS: Different components of the startle discriminated among children of parents with anxiety disorders, children of alcoholics, and children of normal controls. Specifically startle magnitude was elevated in children with a parental history of an anxiety disorder, whereas startle habituation and prepulse inhibition were impaired in children with a parental history of alcoholism. CONCLUSION: These findings suggest that individual differences in the startle reflex may serve as a vulnerability marker for the development of anxiety disorders and alcohol problems.

Adolescent↗

PubMed1995

Startle responses of spider phobics to masked stimuli: a pilot study.

The present study tested the hypothesis that briefly flashed and backwardly masked phobic stimuli potentiate startle reflexes in phobic subjects. Spider phobic (n = 17) and normal control (n = 12) subjects were exposed to short (30 ms) and backwardly masked presentations of phobic slides (i.e., spiders) and neutral slides (i.e., flowers, mushrooms, snakes). On half the trials, eyeblink startle reflexes were elicited with auditory probes following presentation of the slides. In spite of the degraded stimulus conditions, there were some indications that phobics exhibited a startle pattern different from control subjects. More specifically, phobic subjects tended to react with larger startles during the second block of spider trials than control subjects. No such group differences were found for the neutral trials. As the eyeblink startle reflex is closely linked to the thalamo-amygdala pathway, the present findings provide some preliminary support for the idea that the preattentive processing of phobic cues is located at the subcortical level.

Adult↗

PubMed2001

Affective startle modulation in anticipation and perception.

Startle modulation was investigated as participants first anticipated and then viewed affective pictures in order to determine whether affective modulation of the startle reflex is similar in these different task contexts. During a 6-s anticipation period, a neutral light cue signaled whether the upcoming picture would portray snakes, erotica, or household objects; at the end of the anticipatory period, a picture in the signaled category was viewed for 6 s. Male participants highly fearful of snakes were recruited to maximize emotional arousal during anticipation and perception. Results indicated that the startle reflex was potentiated when anticipating either unpleasant (phobic) or pleasant (erotic) pictures, compared to neutral stimuli, whereas during perception, reflexes were potentiated when viewing unpleasant stimuli, and reduced when viewing pleasant pictures. The startle reflex is modulated by hedonic valence in picture perception, and by emotional arousal in a task context involving picture anticipation.

Acoustic Stimulation↗

PubMed2006

Reaction time facilitation by acoustic task-irrelevant stimuli is not related to startle.

Previous research has been interpreted to suggest that the startle reflex mediates the RT facilitation observed if intense, accessory acoustic stimuli are presented coinciding with the onset of a visual imperative stimulus in a forewarned simple RT task. The present research replicated this finding as well as the facilitation of startle observed during the imperative stimulus. It failed, however, to find any relationship between the size of the blink startle reflex elicited by the accessory acoustic stimuli, which differed in intensity and rise time, and RT or RT facilitation observed on trials with accessory acoustic stimuli. This finding suggests that the RT facilitation is not mediated by the startle reflex elicited by the accessory acoustic stimuli.

Acoustic Stimulation↗

PubMed2004

Modulation of involuntary and voluntary behavior following emotional stimuli in healthy subjects.

INTRODUCTION: Alterations of behavior control are core symptoms of various psychiatric disorders. Patients present with changes in complex behavior patterns and basic motor functions. Little is known about emotional modulation of voluntary behavior. Therefore, a paradigm was developed to study simultaneously influence of emotions on voluntary and involuntary movements. METHOD: Healthy volunteers (n=30) documented aspects of their mood and personality including depression, anxiety, and impulsivity. Individuals were instructed to view color slides of different emotional content and switch off the slide after by pressing a button, which was placed in a standardized distance from the resting point. The startle reflex was elicited while looking at the slides and quantified by EMG. Kinematic measures of hand movements by infrared detection were used to analyze the patterns of voluntary movements. RESULTS: This study confirmed previous findings about the modulation of the startle reflex by emotional stimuli which may reflect activity of the amygdala and subcortical stimulus processing. Voluntary movements, which may result from cortical processing of stimuli, were not influenced by the emotional context. In individuals with higher impulsivity scores, the startle reflex amplitudes were lower and relative time to peak velocity of the movement smaller. CONCLUSION: Voluntary movements were not modulated by emotional stimuli, but time to peak velocity was shorter in individuals with greater impulsivity. The ability to generate adequate behavior as a key function of the brain is relevant for social functioning and activities of daily living. The studied paradigm could be useful to assess impulsivity and behavior control in psychiatric disorders.

Adult↗

PubMed1987

Possible role of the brainstem in the mediation of prepulse inhibition in the rat.

Bilateral stimulation of electrodes aimed at the cuneiform nucleus produced significant inhibition of the startle response produced by presentation of an 8-kHz, 110-dB tone. Stimulation of electrodes aimed at the deep mesencephalic nucleus also reduced the magnitude of the startle response, but the effect was less than that following stimulation sites near the cuneiform nucleus. Histological reconstruction of the electrode tip locations revealed a significant negative correlation between the maximum magnitude reduction of the acoustic startle response following an electrical prepulse stimulus and the distance from the cuneiform nucleus. Histological examination also indicated that some electrodes aimed at the cuneiform nucleus were located in or near the inferior colliculus or parabrachial nucleus, all of which are thought to be part of an inhibitory circuit parallel to the acoustic startle reflex arc. These experiments support the view that the prepulse inhibition of the acoustic startle reflex originates in the brainstem.

Acoustic Stimulation↗

PubMed1976

Control of ethanol withdrawal symptoms in mice by phenytoin.

Mice were made physically dependent upon ethanol using either of two methods which involved ethanol vapor inhalation. Following the cessation of exposure to ethanol, the severity of handling-induced convulsions and changes in the response to an electric foot shock (startle reflex) were recorded. Animals given isotonic saline or propylene glycol:ethanol vehicle during withdrawal exhibited handling-induced convulsions, and ethanol (2.0-4.0 g/kg) or phenytoin (5-20 mg/kg) administration during withdrawal resulted in a reduction in the severity of these convulsions. A reduced startle reflex threshold was also evident during withdrawal in mice given isotonic saline or propylene glycol:ethanol vehicle. Ethanol (0.5-4.0 g/kg) or phenytoin (10-20 mg/kg) administration during withdrawal resulted in a significant elevation of the startle reflex threshold compared to control animals. The results are discussed as they relate to others obtained in experimental and clinical studies.

Animals↗

PubMed2003

The prediction of individual differences in response to D-amphetamine in healthy adults.

Based on previous animal work, the present study investigated whether individual differences in motor activity in a novel environment predicted reinforcing and behaviorally activating effects of D-amphetamine (0, 5, 10 and 20 mg p.o.) in healthy adults. When exposed to a novel environment, 18 participants had high levels of motor activity (high responders; HR) and six had low levels (low responders; LR). These group differences were used to predict effects of D-amphetamine on drug reinforcement, salivary cortisol, motor activity, subjective effects, and acoustic startle reflex in subsequent sessions. Unlike observations in rodents, (1). dose-dependent reinforcing effects of D-amphetamine were evident but without group differences; (2). motor activity was greater in HR but did not vary with D-amphetamine dose; and (3). cortisol levels were not related to the reinforcing effects of D-amphetamine. Startle reflex amplitudes were greater in HR following placebo, but D-amphetamine 20 mg equalized this group difference. There was a trend towards less prepulse inhibition of the acoustic startle reflex in HR compared to LR. LR reported greater overall negative effect following amphetamine administration, but this was not consistently related to dose. Finally, participants with high sensation-seeking personality scores exhibited less prepulse inhibition. The results are discussed in terms of the extant literature.

Adult↗

PubMed2005

Cortisol and DHEA-S are associated with startle potentiation during aversive conditioning in humans.

RATIONALE: Fear conditioning reliably increases the startle reflex and stress hormones, yet very little is known about the effect of stress hormones on fear-potentiated startle. Cortisol and the sulfate ester of dehydroepiandrosterone (DHEA-S) are involved in stress and anxiety. Evidence suggests that low cortisol/DHEA-S ratio has a buffering effect on stress and anxiety in preclinical and clinical studies, suggesting that there may be a relationship between fear-potentiated startle and cortisol and DHEA-S activity. OBJECTIVE: The aim of the study was to examine whether there is a relationship between cortisol/DHEA-S ratio and fear-potentiated startle. METHODS: Thirty healthy subjects participated in a differential aversive conditioning experiment during which one of two stimuli (CS+) was paired with a shock, and the other was not (CS-). Conditioned responses were assessed with the startle reflex, defined as startle potentiation during CS+ compared to CS-. DHEA-S and cortisol levels were assayed from blood samples collected in both a baseline and an aversive conditioning session. Subjective state anxiety, arousal, and valence were assessed at various times during testing. RESULTS: Fear-potentiated startle was larger in individuals with high compared to low cortisol/DHEA-S ratio. Multiple regression analyses revealed that fear-potentiated startle was positively associated with cortisol and negatively associated with DHEA-S. There was no significant correlation between DHEA-S and cortisol levels. CONCLUSION: These data suggest that cortisol and DHEA-S are involved in fear conditioning.

Adult↗

PubMed1995

Startle potentiation during anticipation of a noxious stimulus: active versus passive response sets.

The startle reflex response increases during aversive stimulus processing. This study examined whether differing response sets affected startle potentiation during anticipation of an aversive event. Two groups received a noxious noise blast following a 6-s warning cue. Subjects in the active group could press a switch to stop the noise; yoked passive subjects received the same noises with no control. Subjects in a yoked control group heard a soft tone following cue offset. Acoustic startle probes were presented during some of the warning periods and during some of the intertrial intervals. The major finding was that the active and passive groups did not differ in startle potentiation. In comparison with controls, startle reactions for both groups were larger and faster during the warning cue than between trials. The results suggest that the startle reflex indexes defensive response mobilization independently of specific task demands.

Acoustic Stimulation↗

PubMed1986

Trimethyltin ototoxicity: evidence for a cochlear site of injury.

The environmental contaminant, trimethyltin (TMT), produces a profound elevation in tone intensity necessary to inhibit the acoustic startle reflex in laboratory animals which recovers over a prolonged period except at very high frequencies. The recovery that is observed does not begin until 3 to 5 weeks after a single acute administration depending upon dosage. As opposed to the very temporary threshold shifts by the salicylates and loop diuretics or the permanent and progressive ototoxicity resulting from aminoglycoside antibiotics the time course for recovery of acoustic startle reflex inhibition after TMT appears to be an anomaly for a chemical ototoxicant. In terms of the duration of loss only, this pattern appears similar to that sometimes observed after noise exposure. The current investigation replicates the finding that recovery of acoustic startle reflex inhibition after TMT is frequency related in that only the highest frequency impairment appears to be permanent. While this frequency dependence suggests a cochlear locus of injury, both the known neurotoxic effects of TMT and the time course of the behavioral impairment suggest a more central locus of injury. Compound action potential and cochlear microphonic recordings made from the round window in the current study confirm a preferential high frequency effect of TMT and demonstrate a significant cochlear component to the ototoxic effects of this agent.

Action Potentials↗

PubMed1995

[Hyperexplexia].

Hyperexplexia is a disease of neonatal onset characterized by an exaggerated startle reflex. Early diagnosis is important to rule out epilepsy. Clinical findings are mainly hypertony and generalized startle reflex which is exaggerated by tiredness and some exogenous stimuli. Electroencephalogram is normal. The expression of the disease is variable including minor forms that may be unnoticed and major forms with arthrogryposis-like symptoms, orthopedic complications, false passages, apnea and even sudden infant death (SID). The evolution is generally benign and symptoms disappear within 2 or 3 years. A neuromotor retardation is often present, without intellectual deficit. In severe forms, the risk of SID requires a multidisciplinary follow-up including monitoring and treatment with clonazepam. A low GABA level in cerebrospinal fluid has been reported. Present etiological hypotheses include neuromediator and/or receptor dysfunction.

Humans↗

PubMed2000

Animal models of deficient sensorimotor gating: what we know, what we think we know, and what we hope to know soon.

Sensorimotor gating of the startle reflex can be studied in humans and laboratory animals using measures of prepulse inhibition (PPI) of the startle reflex. PPI is reduced in patients with specific neuropsychiatric disorders and in rats after manipulation of the limbic cortex, striatum, pallidum or pontine tegmentum. Studies are rapidly identifying the neurochemical and neuroanatomical substrates regulating PPI in laboratory animals; this detailed circuit information has been used as a 'blueprint' to identify possible candidate substrates responsible for PPI deficits in psychiatrically disordered humans. In parallel, studies have also begun to assess the homology of pharmacological effects on PPI across species, as an initial step towards translating detailed neural circuit information from rats to humans. Despite this rapid progress, there is an increasing danger of overlooking important methodological and interpretative issues that could impact either positively or negatively on the ultimate utility of models based on measures of PPI. Some of these issues--ranging from the cross-species methods for quantifying specific variables to the relevance of genetic drift to animal and human studies of PPI--and their implications for future studies are the focus of this review.

Animals↗

PubMed2000

[Effect of cross-fostering on various physiological and behavioral features in Wistar and genetically cataleptic rats].

In the GC rats reared by their natural mothers the plasma corticosterone concentration and open field locomotion were lower than in Wistar rats whereas the startle-reflex amplitude was higher. Cross-fostering did not affect the plasma corticosterone concentration or the startle-reflex amplitude. A negative correlation between these parameters was found. An open field test yielded lower results in Wistar rats reared by foster mothers belonging to the GC strain whereas the reverse cross-fostering did not affect the locomotion in GC rats. The data suggest that fostering affects the open field behaviour whereas cross-fostering effects depend on the genotype of fostered litter.

Acoustic Stimulation↗

PubMed2001

Essential startle disease may not be a uniform entity.

A 25-year-old man with essential startle disease has been reported. He had a history of sudden jerks and falls in response to unexpected stimuli. Abnormal falling developed when he learned to walk. No similar cases are known in his family. Physical examination revealed hyperreflexia. Pathologic startle reflex was elicited by light touching on the patient's nose, clapping or making other noises. EEG response to startle stimuli consisted of spikes recorded from both centroparietooccipital regions immediately preceding diffuse muscle and movement artifacts. The motor responses to auditory stimuli, which are startle reflex on the orbicularis oculi, sternocleidomastoid, biceps and quadriceps femoris muscles, habituated within 2-4 trials. Electrical stimulation of the median nerve at the wrist elicited a consistent C reflex (cortical long loop reflex) but not any giant cortical somatosensory evoked potentials. Our patient showed early disease onset and habituation of motor response, which are not seen in other essential hyperekplexia cases, and clinically differs from the patients with hereditary hyperekplexia in which neonatal rigidity, epilepsy, apneic attacks, low intelligence, congenital dislocated hips and inguinal hernia can be seen in differing frequency.

Adult↗

PubMed1999

Patterned ballistic movements triggered by a startle in healthy humans.

1. The reaction time to a visual stimulus shortens significantly when an unexpected acoustic startle is delivered together with the 'go' signal in healthy human subjects. In this paper we have investigated the physiological mechanisms underlying this effect. If the commands for the startle and the voluntary reaction were superimposed at some level in the CNS, then we would expect to see alterations in the configuration of the voluntary response. Conversely, if the circuit activated by the startling stimulus is somehow involved in the execution of voluntary movements, then reaction time would be sped up but the configuration of the motor programme would be preserved. 2. Fourteen healthy male and female volunteers were instructed to react as fast as possible to a visual 'go' signal by flexing or extending their wrist, or rising onto tiptoe from a standing position. These movements generated consistent and characteristic patterns of EMG activation. In random trials, the 'go' signal was accompanied by a very loud acoustic stimulus. This stimulus was sufficient to produce a startle reflex when given unexpectedly on its own. 3. The startling stimulus almost halved the latency of the voluntary response but did not change the configuration of the EMG pattern in either the arm or the leg. In some subjects the reaction times were shorter than the calculated minimum time for processing of sensory information at the cerebral cortex. Most subjects reported that the very rapid responses were produced by something other than their own will. 4. We conclude that the very short reaction times were not produced by an early startle reflex adding on to a later voluntary response. This would have changed the form of the EMG pattern associated with the voluntary response. Instead, we suggest that such rapid reactions were triggered entirely by activity at subcortical levels, probably involving the startle circuit. 5. The implication is that instructions for voluntary movement can in some circumstances be stored and released from subcortical structures.

Acoustic Stimulation↗

PubMed2006

Anxiolytic-like properties of the anandamide transport inhibitor AM404.

The endocannabinoids anandamide and 2-arachidonoyglycerol (2-AG) may contribute to the regulation of mood and emotion. In this study, we investigated the impact of the endocannabinoid transport inhibitor AM404 on three rat models of anxiety: elevated plus maze, defensive withdrawal and separation-induced ultrasonic vocalizations. AM404 (1-5 mg kg(-1), intraperitoneal (i.p.)) exerted dose-dependent anxiolytic-like effects in the three models. These behavioral effects were associated with increased levels of anandamide, but not 2-AG, in the prefrontal cortex and were prevented by the CB(1) cannabinoid antagonist rimonabant (SR141716A), suggesting that they were dependent on anandamide-mediated activation of CB(1) cannabinoid receptors. We also evaluated whether AM404 might influence motivation (in the conditioned place preference (CPP) test), sensory reactivity (acoustic startle reflex) and sensorimotor gating (prepulse inhibition (PPI) of the startle reflex). In the CPP test, AM404 (1.25-10 mg kg(-1), i.p.) elicited rewarding effects in rats housed under enriched conditions, but not in rats kept in standard cages. Moreover, AM404 did not alter reactivity to sensory stimuli or cause overt perceptual distortion, as suggested by its lack of effect on startle or PPI of startle. These results support a role of anandamide in the regulation of emotion and point to the anandamide transport system as a potential target for anxiolytic drugs.

Animals↗

PubMed1997

The basolateral amygdala regulates sensorimotor gating of acoustic startle in the rat.

The acoustic startle reflex is a coordinated contraction of the skeletal musculature in response to a sudden, intense sound. One form of startle plasticity, "prepulse inhibition", is the normal suppression of the startle reflex when the intense startling stimulus is immediately preceded by a weak pre-stimulus. Prepulse inhibition is utilized as an operational measure of sensorimotor gating, and is significantly impaired in several neuropsychiatric disorders that are characterized by symptoms associated with central inhibitory deficits. In rats, prepulse inhibition is disrupted by central dopamine activation or by manipulations of limbic cortical structures including the prefrontal cortex and hippocampus. In the present study, we assessed prepulse inhibition in rats after surgical and pharmacologic manipulations of the basolateral amygdala. Quinolinic acid lesions of the basolateral amygdala significantly reduced prepulse inhibition without significantly changing startle amplitude. These lesions also blocked fear-potentiated startle, which is known to be regulated by the basolateral amygdala. The prepulse inhibition-disruptive effects of basolateral amygdala lesions were not reversed by systemic injection of the dopamine antagonist haloperidol at doses that totally restored prepulse inhibition in apomorphine-treated rats. In other studies, intra-amygdala infusion of the competitive N-methyl-D-aspartate antagonist DL-2-amino-5-phosphonovaleric acid (0, 0.15, 1.5, 4.5 microg) dose-dependently reduced prepulse inhibition. These data suggest that the basolateral amygdala regulates sensorimotor gating by mechanisms that are independent of central dopamine hyperactivity.

2-Amino-5-phosphonovalerate↗