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PubMed1999

Fear appears fast: temporal course of startle reflex potentiation in animal fearful subjects.

The temporal course of startle reflex modulation and autonomic response patterns to fear-relevant and fear-irrelevant pictures in subjects with high and low levels of animal fear was investigated. Thirty-eight high-fear and 48 low-fear volunteers viewed photos of snakes and spiders and pictures of neutral and pleasant content. The slides were presented for 6 s or for only 150 ms, depending on the group. Acoustic startle probes were presented at five different times after slide onset. Relative potentiation of the startle responses started 300 ms after onset of snake/spider pictures in fearful subjects. This fear-potentiated startle effect was maintained for the later probe times and was identical in the 150-ms condition. Fear-relevant pictures also prompted a sympathetically dominated autonomic response profile in fearful persons. These data support the idea that fear can be activated very rapidly, requiring only minimal stimulus input.

Adolescent↗
PubMedDate not supplied

Timing of fear expression in trace and delay conditioning measured by fear-potentiated startle in rats.

In two experiments, the time course of the expression of fear in trace (hippocampus-dependent) versus delay (hippocampus-independent) conditioning was characterized with a high degree of temporal specificity using fear-potentiated startle. In experiment 1, groups of rats were given delay fear conditioning or trace fear conditioning with a 3- or 12-sec trace interval between conditioned stimulus (CS) offset and unconditioned stimulus (US) onset. During test, the delay group showed fear-potentiated startle in the presence of the CS but not after its offset, whereas the trace groups showed fear-potentiated startle both during the CS and after its offset. Experiment 2 compared the time course of fear expression after trace conditioning with the time course in two delay conditioning groups: one matched to the trace conditioning group with respect to CS duration, and the other with respect to ISI. In all groups, fear was expressed until the scheduled occurrence of the US and returned to baseline rapidly thereafter. Thus, in both trace and delay fear conditioning, ISI is a critical determinant of the time course of fear expression. These results are informative as to the possible role of neural structures, such as the hippocampus, in memory processes related to temporal information.

Acoustic Stimulation↗
PubMedDate not supplied

Common fears and their relationship to dental fear and utilization of the dentist.

Common fears were studied by household telephone interviews and mail survey in Seattle, Washington, to determine their relationship to dental fear and to utilization of the dentist. Dental fear was either the first or second most common fear, with a prevalence estimated between 183 and 226 persons per 1000 population. Dental fear was associated with fears of heights, flying, and enclosures. Respondents with multiple common fears other than fear of dentistry were more likely to delay or cancel dental appointments, report a longer period since their last visit to the dentist, and report poorer oral health and less satisfaction with oral appearance. Over 22 percent of the dentally fearful group reported two or more accompanying common fears.

Adult↗
PubMed1995

Involvement of subcortical and cortical afferents to the lateral nucleus of the amygdala in fear conditioning measured with fear-potentiated startle in rats trained concurrently with auditory and visual conditioned stimuli.

The goal of this work was to test the involvement, in fear conditioning, of afferents to the lateral nucleus of the amygdala originating from the auditory thalamus, auditory cortex, and perirhinal area. The acoustic startle reflex was used as the behavioral index of conditioning because it is reliably enhanced in the presence of a conditioned stimulus (CS) previously paired with a footshock. Auditory and visual CSs were used to assess the modality specificity of lesions to the above brain areas. Pre- or posttraining lesions of the entire auditory thalamus including the ventral, dorsal, and medial divisions of the medial geniculate body, the posterior intralaminar nucleus, and the suprageniculate nucleus, completely blocked fear-potentiated startle to the auditory CS, but had no effect on fear-potentiated startle to the visual CS. Posttraining lesions mostly restricted to the ventral and dorsal divisions of the medial geniculate body specifically disrupted fear-potentiated startle to the auditory CS. However, retraining in rats sustaining ventral and dorsal medial geniculate body lesions led to reliable fear-potentiated startle to the auditory CS. Posttraining lesions mostly restricted to the medial division of the medial geniculate body, posterior intralaminar, and suprageniculate nuclei did not disrupt fear-potentiated startle. These results indicate that the auditory thalamus is specifically involved, through either its direct or indirect amygdaloid afferents, in fear conditioning to auditory CSs. Pre- or posttraining lesions mostly restricted to the primary auditory cortex did not reliably attenuate fear-potentiated startle to the auditory or visual CSs. Extensive posttraining lesions of the perirhinal area (including secondary auditory cortices), but not its rostral aspect alone, blocked fear-potentiated startle to both CSs. However, reliable potentiated startle was observed to both CSs following similarly extensive pretraining lesions of the perirhinal area. Because post- but not pretraining lesions of the perirhinal area blocked fear-potentiated startle nonspecifically, at least with regard to auditory and visual CSs, the results are consistent with the involvement of the perirhinal area in general memory functions such as information storage or retrieval. Alternatively, the secondary auditory and/or perirhinal cortices might function as multimodal sensory relays to the amygdala.

Acoustic Stimulation↗
PubMed1998

Dental fear with and without blood-injection fear: implications for dental health and clinical practice.

The relation between dental, blood and injection fear and oral health was examined in 936 New Zealand 18-year-olds. Of the approximately ten percent (n = 96) of the sample who reported a dental fear, 1 in 10 also reported a fear of blood and 53% a co-morbid fear of injections. Study members with dental fear alone or co-morbid dental and blood or injection fear had significantly worse oral health (i.e. greater caries experience) than a no-fear comparison group or individuals with blood-injection fear only. Further, individuals with dental and blood or injection fear had a significantly higher level of recent tooth decay than individuals with dental fear alone. Time since last dental treatment also tended to be highest in this group. Implications for dental health and practice were discussed.

Adolescent↗
PubMed1993

Fearful and non-fearful panic attacks in a student population.

The phenomenon of non-fearful panic was investigated in a sample of 83 university students who reported histories of unexpected panic attacks. Based on severity ratings of individual panic symptoms, Ss were classified as having panic attacks characterized by No Fear (N = 22), Low Fear (N = 30) or High Fear (N = 31). The three groups were similar with respect to the age-of-onset of panic attacks, the frequency with which they experienced panic and the severity of panic symptoms unrelated to fear. However, Ss reporting fear during panic attacks were more likely to engage in avoidance behaviour and to use alcohol or drugs as ways of coping with panic. Only High Fear subjects showed significant elevations on self-report measures of depression and global psychopathology. These results indicate that the experience of fear during panic attacks may be important in the transition from non-clinical panic to panic disorder, in a manner proportional to the amount of reported fear.

Adolescent↗
PubMed1996

The role of parental fearfulness and modeling in children's fear.

The present study investigated the contribution of parental modeling to the fearfulness of children. Forty children (aged 9-12) who were referred to an outpatient treatment centre filled out the trait version of the Spielberger State-Trait Anxiety Inventory for Children (STAIC) and the revised version of the Fear Survey Schedule for Children (FSSC). The parents of the children completed adult versions of the STAI-trait and the FSS. In addition, parents rated to what extent they generally expressed fears to their children. Results showed that trait anxiety in children was positively associated with trait anxiety of both the mother (r = 0.34, P < 0.05) and the father (r = 0.31, P < 0.05). Fearfulness of the children was only related to fearfulness of the mother (r = 0.56, P < 0.001). Most importantly, the data showed that modeling played a role in this relationship. A linear association between FSSC scores and mothers' rating of expressing fears to their children was found. That is to say, children of mothers who never expressed their fears had the lowest FSSC scores, children of mothers who often expressed their fears had the highest FSSC scores, whereas children of mothers who sometimes expressed their fears scored in between.

Anxiety Disorders↗
PubMed2001

Failure to overcome 'innate' fear: a developmental test of the non-associative model of fear acquisition.

The non-associative, Darwinian theory of fear acquisition proposes that some individuals fail to overcome biologically-relevant fears (e.g. height) because they (1) do not have sufficient safe exposure to the relevant stimuli early in life or (2) are poor habituators who have difficulty 'learning not to fear'. These two hypotheses were tested in a longitudinal birth cohort study. Study 1 found evidence for reduced exposure to height stimuli in childhood for individuals with a fear of heights compared to study members without fear. Study 2 found evidence for higher levels of stress reactivity (a proxy for habituation) in childhood and adolescence among 18-year-old height phobics compared to study members with dental phobia and those with no fear. The results were discussed in relation to recent findings suggesting that some evolutionary-relevant fears may appear in the absence of traumatic 'learning' experiences. The merits of adding a fourth, non-associative pathway to Rachman's [Rachman, S. (1977)]. The conditioning theory of fear acquisition: a critical examination. Behaviour Research and Therapy, 15, 375-387) three pathways model of fear acquisition were briefly considered.

Adolescent↗
PubMed2001

N-Methyl-D-aspartate receptor antagonism blocks contextual fear conditioning and differentially regulates early growth response-1 messenger RNA expression in the amygdala: implications for a functional amygdaloid circuit of fear.

N-Methyl-D-aspartate receptors in the amygdala are known to be crucial for the learning of conditioned fear, although the molecular cascades that N-methyl-D-aspartate receptors regulate are not well understood. Recent experiments from our laboratory have shown that messenger RNA expression of the immediate-early messenger gene, early growth response gene 1, increases in the lateral nucleus of the amygdala following contextual fear conditioning. However, the regulation of the increase in early growth response gene 1 expression is not known. To determine if N-methyl-D-aspartate receptors regulate both fear conditioning and the increase in early growth response gene 1 expression in the lateral nucleus of the amygdala, rats were infused i.c.v. with 2.5microg of the N-methyl-D-aspartate antagonist, DL-2-amino-5-phosphonovalerate. Most rats were killed 30min following one-trial contextual fear conditioning and their brains were processed for in situ hybridization detection of early growth response gene 1 messenger RNA expression. The remainder of the rats was tested for retention of fear conditioning 24h later. In DL-2-amino-5-phosphonovalerate-treated rats, post-shock freezing remained intact, whereas fear-conditioned freezing during the retention test was abolished. Image analysis of early growth response gene 1 messenger RNA revealed that DL-2-amino-5-phosphonovalerate blocked the fear-conditioning-associated increase in early growth response gene 1 expression in the lateral nucleus of the amygdala. In addition, DL-2-amino-5-phosphonovalerate significantly increased early growth response gene 1 expression in the central nucleus of the amygdala. The results reveal differential regulation of early growth response gene 1 messenger RNA in the amygdala by N-methyl-D-aspartate receptors and argue for a functional role of early growth response gene 1 in the formation of long-term memory for contextual fear. Furthermore, the results indicate a functional neuroanatomical circuit within the amygdala that includes dampening of excitatory and activation of inhibitory processes in distinct amygdala nuclei, resulting in the reduction of fear conditioning.

2-Amino-5-phosphonovalerate↗
PubMed2004

Major growth QTLs in fowl are related to fearful behavior: possible genetic links between fear responses and production traits in a red junglefowl x white leghorn intercross.

The aim of this work was to study fear responses and their relation to production traits in red junglefowl ( Gallus gallus spp.), White Leghorn ( Gallus domesticus ), and their F2-progeny. Quantitative trait locus (QTL) analyses were performed for behavioral traits to gain information about possible genetic links between fear-related behaviors and production. Four behavioral tests were performed that induce different levels of acute fear (open field [OF], exposure to a novel object, tonic immobility, and restraint). Production traits, that is, egg production, sexual maturity (in females), food intake, and growth, were measured individually. A genome scan using 105 microsatellite markers was carried out to identify QTLs controlling the traits studied. In the OF and novel object tests (NO), Leghorns showed less fear behavior than junglefowl, whereas junglefowl behaved less fearfully in the tonic immobility test (TI) and were more active in the restraint test. In the F2 progeny, only weak phenotypic associations were found between production traits and fear behavior. A significant QTL for TI duration was found on chromosome 1 that coincided with a QTL for egg weight and growth in the same animals. Another QTL for NO in males coincided with another major growth QTL. These two known growth QTLs affected a wide range of reactions in different tests. Several other significant and suggestive QTLs for behavioral traits related to fear were found. These QTLs did not coincide with QTLs for production traits, indicating that these fear variables may not be genetically linked to the production traits we measured here. The results show that loci affecting important production traits are located in the same chromosomal region as loci affecting different fear-related behaviors.

Animals↗
PubMed2003

Nicotine enhances contextual fear conditioning and ameliorates ethanol-induced deficits in contextual fear conditioning.

Nicotine and ethanol are 2 commonly used and abused drugs that have divergent effects on learning. The present study examined the effects of acute nicotine (0.25 mg/kg), ethanol (1.0 g/kg), and ethanol-nicotine coadministration on fear conditioning in C57BL/6 mice. Mice were assessed for contextual and cued fear conditioning at 1 day and 1 week posttraining. Ethanol disrupted acquisition but not consolidation of contextual fear conditioning; nicotine enhanced contextual fear conditioning and ameliorated ethanol-associated deficits in contextual fear conditioning. Mecamylamine antagonized this effect. Fear conditioning was reassessed 1 week after initial testing with no drug administered. At the 1-week retest, mice previously treated with nicotine continued to show enhanced contextual fear, and mice previously treated with ethanol continued to show contextual fear deficits. Thus, nicotine both produces a long-lasting enhancement of contextual fear conditioning and protects against ethanol-associated deficits.

Animals↗
PubMed1994

Fear of acquired immunodeficiency syndrome and fear of other illness in suicide.

Suicide victims with fear of acquired immunodeficiency syndrome (AIDS) or other somatic illness were compared for psychosocial and health-related characteristics, triggers and content of fear. Fear of AIDS cases (n = 28), 2% of the 1-year Finnish suicide population (n = 1397), were younger and fewer had serious somatic disease (32% vs 64%) compared with cases of fear of other somatic illness. Both groups had more depression, especially major depression (54% and 61% vs 26%), more psychotic disorders (50% and 32% vs 24%) and health care contacts during their final week (61% and 64% vs 36%) than other suicides. Suicidal fear of AIDS calls for evaluation of sexual and other risk behaviour, but fear of AIDS was largely generated by the extensive media coverage. Fear of other somatic illness was more diverse in origin and related to illness experiences. Suicidal fear of illness calls for recognition of depression and differentiation of the origin and content of fear.

Adult↗
PubMed2000

Involvement of NMDA receptors within the amygdala in short- versus long-term memory for fear conditioning as assessed with fear-potentiated startle.

Pretraining intra-amygdala infusions of the NMDA receptor antagonist. D,L-AP5, block fear-potentiated startle in rats tested 24+ hr after training. This may reflect a failure of either acquisition or retention. To evaluate these alternatives, rats were tested for fear-potentiated startle during fear conditioning (30 light-shock pairings [0.6 mA shock]), as well as 1-30 min and 48 hr after fear conditioning. Amygdala lesions abolished fear-potentiated startle at all train-test intervals. Intra-amygdala AP5 infusions (25 nmol/side) abolished fear-potentiated startle during the long-term test and had partial effects at shorter train-test intervals. When the level of fear-potentiated startle during the short-term test was lowered to that of the 48-hr test (i.e., by training rats with a lower, 0.3 mA footshock), AP5 abolished fear-potentiated startle at each timepoint. Thus, amygdala NMDA receptors appear to participate in the initial acquisition of fear memories.

Amygdala↗
PubMed2001

Neurotoxic lesions of the lateral nucleus of the amygdala decrease conditioned fear but not unconditioned fear of a predator odor: comparison with electrolytic lesions.

Considerable evidence suggests that the lateral (LA) and basal (BA) nuclei of the amygdala are sites of plasticity and storage of emotional memory. Recent arguments, however, have seriously challenged this view, suggesting that the effects of amygdala lesions are attributable to interference with performance of fear behavior and not learning and memory. One way to address this controversy is to measure the same behavioral response during both conditioned and unconditioned fear. This is done in the present study by measuring fear-related freezing behavior after electrolytic and neurotoxic lesions of the LA or LA/BA nuclei in rats in a contextual fear conditioning paradigm and unconditioned fear to a predator odor. Electrolytic LA lesions attenuated post-shock freezing, retention test freezing, and freezing to the predator odor trimethylthiazoline (TMT). In contrast, excitotoxic NMDA lesions of the LA had no effect on post-shock freezing but significantly attenuated retention test freezing. Furthermore, excitotoxic LA lesions did not diminish freezing to TMT. Larger excitotoxic lesions that included the BA significantly reduced freezing in both the post-shock and retention tests but did not appreciably decrease freezing to TMT. The results suggest that the LA is important for memory of learned fear but not for generation of freezing behavior. In addition, the BA plays a role in freezing in conditioned fear situations but not in unconditioned fear. The studies suggest that the LA and BA play different roles in fear conditioning, but neither of them has a significant role in unconditioned freezing to a predator odor.

Amygdala↗
PubMed2006

The benzodiazepine alprazolam dissociates contextual fear from cued fear in humans as assessed by fear-potentiated startle.

BACKGROUND: The startle reflex is potentiated by aversive states. It has been proposed that phasic startle potentiation to a threat cue and sustained startle potentiation to contextual stimuli reflect distinct processes mediated by different brain structures. The present study tested the hypothesis that alprazolam would reduce the sustained startle potentiation to contextual threats but not the startle potentiation to a threat cue. METHODS: Sixteen healthy subjects received each of four treatments: placebo, .5 mg of alprazolam, 1 mg of alprazolam, and 50 mg of diphenhydramine (Benadryl) in a crossover design. Participants were exposed to three conditions, including one in which predictable aversive shocks were signaled by a cue, a second in which shocks were administered unpredictably, and a third condition in which no shocks were anticipated. Acoustic startle were delivered regularly across conditions. RESULTS: Phasic startle potentiation to the threat cue in the predictable condition was not affected by alprazolam. In contrast, the sustained increase in startle in the predictable and unpredictable conditions was reduced significantly by the high dose of alprazolam. CONCLUSIONS: Startle responses to an explicit threat cue and to an aversive context are psychopharmacologically distinct, suggesting that they may represent functionally dissociable aversive states.

Acoustic Stimulation↗
PubMed2002

Quantifying fear potentiated startle using absolute versus proportional increase scoring methods: implications for the neurocircuitry of fear and anxiety.

RATIONALE: The fear-potentiated startle paradigm [increased startle in the presence of a conditioned fear stimulus (CS)] has become increasingly popular as a tool for evaluating the potential efficacy of putative anxiolytic compounds. However, when the tested compounds also influence baseline startle, it is unclear how comparisons with control groups can best be made. OBJECTIVE: To evaluate the validity of absolute difference (startle amplitude on CS minus non-CS test trials) vs. proportional increase (the absolute difference score divided by startle amplitude on non-CS test trials) scoring methods. METHODS: The effect on proportional increase and absolute difference scores of baseline shifts that occur with or without concomitant increases in fear was evaluated in rats. A reliable measure should yield similar scores across shifting baselines, provided that fear levels remain constant. RESULTS: Preexisting baseline differences, and those brought about by different startle-eliciting noise burst intensities, by strychnine injections, or by CRH infusions, each increased absolute difference scores without markedly influencing proportional change scores. These baseline differences were not associated with different fear levels. Increases in baseline startle brought about by unsignaled footshocks or by a second CS - increases which are associated with increased fear - partially occluded additional CS-induced increases using either measure. CONCLUSIONS: Across different baselines, CS-elicited fear is most accurately reflected in proportional change scores. Under certain conditions saturation effects may interfere with an accurate assessment using either measure. However, these same saturation effects may provide opportunities to explore the neural circuitry of fear and anxiety in novel ways.

Acoustic Stimulation↗
PubMed2005

Do fundamental fears differentially contribute to pain-related fear and pain catastrophizing? An evaluation of the sensitivity index.

Three fundamental fears - anxiety sensitivity (AS), injury/illness sensitivity (IS) and fear of negative evaluation (FNE) - have been proposed to underlie common fears and psychopathological conditions. In pain research, the relation between AS and (chronic) pain processes was the subject of several studies, whereas the possible role of IS has been ignored. The current research examines the role of IS with respect to various pain-related variables in two studies. In the first study, 192 healthy college students completed the Sensitivity Index (SI; a composite measure assessing the three fundamental fears) and various pain-related questionnaires. In a second study, 60 students out of the original sample took part in a pain induction procedure and completed the SI as well. We first examined the properties of the SI. Factor analysis on the SI replicated the proposed factor structure [Taylor S. The structure of fundamental fears, J Behav Ther Exp Psychiat 1993;24:289-99]. However, some items of the ASI did show problematic loadings and were therefore excluded in subsequent analyses. The main hypothesis of the current study states that IS is a stronger predictor than AS of pain catastrophizing and fear of pain as assessed by self-report measures, and of pain tolerance and anticipatory fear of pain as assessed in a pain induction study. This hypothesis could be confirmed for all variables, except for pain tolerance, which was not predicted by any of the three fundamental fears. The current study can be considered as an impetus for devoting attention to IS in future pain research.

Adolescent↗