Startle Eyeblink Reflex Research Articles

Preparatory suppression and facilitation of voluntary and involuntary responses to loud acoustic stimuli in an anticipatory timing task.

In this study, we sought to characterize the effects of intense sensory stimulation on voluntary and involuntary behaviors at different stages of preparation for an anticipated action. We presented unexpected loud acoustic stimuli (LAS) at-rest and at three critical times during active movement preparation (-1,192, -392, and 0ms relative to expected voluntary movement onset) to probe the state of the nervous system, and measured their effect on voluntary and involuntary motor actions (finger-press and eye-blink startle reflex, respectively). Voluntary responses were facilitated by LAS presented during active preparation, leading to earlier and more forceful responses compared to control and LAS at-rest. Notably, voluntary responses were significantly facilitated on trials where the LAS was presented early during preparation (-1,192ms). Eye-blink reflexes to the LAS at -392ms were significantly reduced and delayed compared to blinks elicited at other time-points, indicating suppression of sub-cortical excitability. However, voluntary responses on these trials were still facilitated by the LAS. The results provide insight into the mechanisms involved in preparing anticipatory actions. Induced activation can persist in the nervous system and can modulate subsequent actions for a longer time-period than previously thought, highlighting that movement preparation is a continuously evolving process that is susceptible to external influence throughout the preparation period. Suppression of sub-cortical excitability shortly before movement onset is consistent with previous work showing corticospinal suppression which may be a necessary step before the execution of any voluntary response.

Implicit and explicit motivational responses to high- and low-calorie food in women with disordered eating

Eating disorders and their symptoms are thought to be associated with altered motivational responding to food. Binge eating may relate to increased reward reactivity, restrictive eating may be associated with increased threat and/or decreased reward reactivity, and the combination of these symptoms within an individual may be linked to motivational conflict to food. Using both implicit (i.e., physiological) and explicit (i.e., self-reported) measures, we tested these hypotheses in 88 women with binge eating only, restrictive eating only, both binge eating and restrictive eating, or no eating pathology. Participants viewed and rated high-calorie food, low-calorie food, and emotional images while startle eye blink and postauricular reflexes were measured. Arousal and craving, but not valence, ratings were significantly greater for high- than low-calorie food. Startle blink reflexes during all food images were significantly lower than during neutral images, whereas only high-calorie foods related to greater postauricular reactivity than neutral images. Eating pathology group did not predict implicit and explicit motivational reactions to food. Exploratory dimensional analyses revealed that rating low-calorie foods as lower on craving predicted endorsement of restrictive eating, while rating low-calorie foods as lower on valence and arousal, and experiencing lower postauricular reactivity to high-calorie foods minus neutral images, predicted greater frequency of restrictive eating episodes. Decreased implicit and explicit appetitive motivation to high- and low-calorie food may relate to the presence and frequency of restrictive eating. Future longitudinal research should investigate whether decreased appetitive responding to food is a risk factor for, versus consequence of, restrictive eating.

A novel optical non-intrusive method for measuring acoustic startle reflex in humans

Objective: The development of a new non-intrusive optical system for remotely measuring acoustic startle reflex (ASR) in humans. Approach: The eye reflex movement during an acoustic stimulation session is recorded through a high-speed digital camera. The eyes region is isolated by the rest of the face by an advanced pyramid-like feature detection algorithm, which greatly reduces the number of false positives. A separate Lucas–Kanade optical flow routine is designed for the eyeblink movement detection and the startle eyeblink reflex (SEBR) curve extraction. Image masking is implemented for the elimination of unwanted artifacts caused mainly by voluntary eye movement. The proposed system was tested along with a valid EMG system on a sample of 32 healthy randomly selected adults, and the results were compared in order to measure the system’s degree of reliability. Main results: To assess the proposed method’s validity the EMG data was used as a benchmark. The results showed strong correlation between EMG and Camera acquired results, which proves the validity of the proposed method. Furthermore, by comparing the response probability and the signal to noise ratio (SNR) for the two techniques, we proved that the proposed method can surpass the traditional EMG system in terms of accuracy and reliability. Significance: The proposed technique presents a simple, robust and reliable non-intrusive means of measuring ASR in humans, with the potential of future implementation on various ASR psychophysiology experiments, such as the study of PPI.

Associations between self-report and physiological measures of emotional reactions to food among women with disordered eating

Individuals with eating disorders have exhibited both positive and negative emotional responses to food when assessed via self-report and psychophysiology. These mixed findings may be explained by a lack of association between self-report and physiological measures, and the degree of association may differ based on core eating disorder symptoms like dietary restriction and binge eating. Women from the community (N = 82) were recruited based on the presence or absence of dietary restriction and binge eating. We examined the startle eyeblink reflex, a physiological measure of defensive motivation, in relation to self-reported valence, arousal, and craving ratings of emotional (positive, neutral, negative) and food (high- and low-calorie) images. Dietary restriction and binge eating were investigated as moderators of self-report/physiology relationships. Replicating extant literature, valence ratings of emotional images were correlated with startle blink reflex magnitude, with more unpleasant ratings related to higher startle eyeblink reflex magnitudes. Increased craving, but not valence, ratings of food images were related to lower startle blink reflex magnitudes. Dietary restriction and binge eating did not moderate the relationship between self-report ratings and startle blink magnitude to food. Our findings suggest that self-reported appetitive motivation towards food relates to a decrease in physiologically measured aversion towards food. Future research should examine the extent to which self-report ratings correlate with physiological indices of positive emotion (e.g., postauricular reflex, zygomaticus major) during the viewing of food images in both patients with eating disorders and healthy controls.

Recurrent Hepatic Encephalopathy Due to Spontaneous Mesocaval Shunt

Spontaneous portosystemic shunting is a rare entity that can manifest as hepatic encephalopathy (HE) in longstanding liver disease. In cases of severe portal hypertension (pHTN) portal blood flow may reverse with shunting from the portal vein to the inferior vena cava through a portosystemic anastomosis. Shunting allows toxins to accumulate in the systemic circulation leading to encephalopathy. We present a case of spontaneous mesocaval shunting in a patient with recurrent HE. A 76 year old female with history of Hepatitis B cirrhosis, grade II varices, and multiple admissions for HE presented for acute altered mental status for 1 day. At baseline, she is functionally independent and takes lactulose, rifaxamin, nadolol, entecavir, spironolactone, furosemide, and omeprazole. On presentation, she was not alert or orientated, minimally responsive to voice, moving only to pain, eye-blink startle reflex present but without tracking. There were facial spider angiomas, but no jaundice, ascites or asterixis. She was hemodynamically stable with mild pan-elevation of liver tests, hyperammonemia, hypoalbuminemia, macrocytosis with thrombocytopenia and mild coagulopathy. Prior work-up was limited to head CT and abdominal ultrasound due to acute kidney injury, and negative infectious work-up. CT abdomen on presentation revealed stable appearance of cirrhotic liver, as well as pHTN including recanalization of the umbilical vein, esophageal and omental varices, and mesocaval shunt adjacent to the left portal vein consistent with AV shunting. Interventional radiology was consulted for closure of the shunt and after 3 days of medical therapy, her mental status improved to baseline. Initial attempt was unsuccessful in catheterizing the shunt through the inferior vena cava, while a second attempt through the transplenic portogram and embolization of mesocaval shunt was successful. Patient made a stable recovery after the intervention for discharge. Spontaneous mesocaval shunting is a rare collateral circulation that develops between the superior or inferior mesenteric veins and the inferior vena cava. Similar collateral vessels can manifest as patent paraumbical vessels arising from the left portal vein, as seen in this patient. A high index of suspicion in patients with HE with appropriate imaging is needed to make a diagnosis. Treatment of these shunts via occlusion is crucial in reducing the occurrence of recurrent HE in cirrhosis.2292_A Figure 1. Axial CT - Demonstrates large portosystemic shunt arising from the superior mesenteric vein with its confluence at the inferior vena cava. A transplenic approach was utilized to gain access into the portal system and the mesocaval shunt was subselected.2292_B Figure 2. Robust flow was noted on venograms through the shunt pre-embolization. The mesocaval shunt was embolized with multiple coils of varying sizes and with nBCA.2292_C Figure 3. Final venograms demonstrated complete occlusion of the shunt and preferential flow through to the portal vein post-procedure.

The Impact of Alcohol and Social Context on the Startle Eyeblink Reflex.

Researchers have long sought to understand how individuals respond to alcohol in social settings with the aim of elucidating pathways of risk for alcohol use disorder (AUD). But studies that incorporate a social context are still outnumbered by those that examine alcohol's subjective effects among participants drinking alcohol in isolation. Further, perhaps due to the challenges of capturing automatic affective processes in these settings, prior studies of alcohol response in social context have relied mainly on self-report measures, and so relatively little is known about alcohol's psychophysiological effects in social settings. Using a novel paradigm that integrated alcohol-administration procedures, startle methodology, and social context, this study examined the impact of alcohol and social context on startle eyeblink reflex among 40 social drinkers. Results indicated that there was a significant effect of group presence, indicating that startle magnitude was larger when people were alone than with others. There was a significant group presence-by-alcoholic beverage interaction, with the effect of alcohol being significantly larger when people were alone versus with others. These effects were found both for the startle habituation data and during the picture-viewing task. Results of this study highlight the importance of considering the presence of other individuals for understanding alcohol response and mechanisms of AUD risk. Findings are discussed in light of both emotional and cognitive correlates of startle reflex magnitude. Future research should examine these effects within larger samples of participants and further explore mechanisms that might underlie these effects.

Measuring Pavlovian appetitive conditioning in humans with the postauricular reflex.

Despite its evolutionary and clinical significance, appetitive conditioning has been rarely investigated in humans. It has been proposed that this discrepancy might stem from the difficulty in finding suitable appetitive stimuli that elicit strong physiological responses. However, this might also be due to a possible lack of sensitivity of the psychophysiological measures commonly used to index human appetitive conditioning. Here, we investigated whether the postauricular reflex—a vestigial muscle microreflex that is potentiated by pleasant stimuli relative to neutral and unpleasant stimuli—may provide a valid psychophysiological indicator of appetitive conditioning in humans. To this end, we used a delay differential appetitive conditioning procedure, in which a neutral stimulus was contingently paired with a pleasant odor (CS+), while another neutral stimulus was not associated with any odor (CS−). We measured the postauricular reflex, the startle eyeblink reflex, and skin conductance response (SCR) as learning indices. Taken together, our results indicate that the postauricular reflex was potentiated in response to the CS+ compared with the CS−, whereas this potentiation extinguished when the pleasant odor was no longer delivered. In contrast, we found no evidence for startle eyeblink reflex attenuation in response to the CS+ relative to the CS−, and no effect of appetitive conditioning was observed on SCR. These findings suggest that the postauricular reflex is a sensitive measure of human appetitive conditioning and constitutes a valuable tool for further shedding light on the basic mechanisms underlying emotional learning in humans.

Startle reflex modulation by affective face "Emoji" pictographs.

The current research was designed to assess possible differences in the emotional content of pleasant and unpleasant face emoji using acoustically evoked eyeblink startle reflex response. Stimuli were selected from Emojipedia Webpage. First, we assessed these stimuli with a previous independent sample of 190 undergraduate students (46 males and 144 females) mean age of 21.43years (SD 3.89). A principal axis method was performed using the 30 selected emoji faces, extracting two factors (15 pleasant and 15 unpleasant emoji). Second, we measured the acoustic startle reflex modulation in 53 young adult women [mean age 22.13years (SD 4.3)] during the viewing of each of the 30 emoji emotional faces in the context of the theory of motivation and emotion proposed by Lang (1995), but considering only the valence dimension. We expected to find higher acoustically evoked startle responses when viewing unpleasant emoji and lower responses for pleasant ones, similarly to the results obtained in the studies using human faces as emotional stimulus. An ANOVA was conducted to compare acoustic startle responses associated with pleasant and unpleasant emoji. Results yielded main effects for picture valence (λ = 0.80, F(1, 50) = 12.80, p = .001, η2 = 0.20). Post-hoc t test analysis indicated significant differences in the startle response between unpleasant (50.95 ± 1.75) and pleasant (49.14 ± 2.49) emoji (t (52) = 3.59, p = .001), with a Cohen's d = 0.495. Viewing affective facial emoji expressions modulates the acoustic startle reflex response according to their emotional content.

The Relationship between Insulin Resistance, Antioxidants, and Eye Blink Startle Reflex during International Affective Picture System Presentation

Approximately one in three U.S. adults have pre‐diabetes (CDC). Pre‐diabetes etiology is characterized by insulin resistance (IR), a reduced cellular response to insulin, and lower glucose uptake in the brain. IR is also related to deficits in cognitive and affective processing, particularly reactivity to psychological stress. Additional data supports a role for inflammation in the pathogenesis of IR. The goal of our analysis was to determine how IR or hyperglycemia predicted eye blink startle reflex (EBR) magnitude and amplitude, an objective index of the startle response, in response to positive, negative and neutral pictures using the International Affective Picture System (IAPS). We also assessed if specific antioxidants predicted EBR. We hypothesized that individuals with higher IR and lower levels of antioxidants would show greater EBR. The analysis consisted of healthy adults (N=331 participants), aged 36–84 years old, from the University of Wisconsin‐Madison's MIDUS (Midlife in the United States) II longitudinal study. As described in the MIDUS protocol, fasted blood samples were collected during an overnight stay. EBR in response to IAPS visual stimuli paired with acoustic startle was measured by placing two mini electrodes below the eye. Picture duration was 4,000ms. For a given trial, the acoustic startle stimuli (105 dB) was administered for 50ms during one of three phases: 1) The “early” phase at 2,900ms after picture onset while the picture was on the screen to assess reactivity; 2) the “middle” phase at 400ms after picture onset; and 3) the “late” phase at 1,900ms after picture offset and removal to assess longer‐term recovery. Data was analyzed using SPSS 23.0. Linear mixed models were used to analyze the main effect of log‐transformed homeostasis model assessment of insulin resistance (HOMA‐IR) on antioxidants and EBR, as well as its interaction with IAPS picture valence (positive, neutral, negative). Antioxidants were also used to predict EBR and its interaction with IAPS picture valence. Higher log10 HOMA‐IR predicted greater EBR amplitude during negative versus positive pictures (n=290, p<.05, r2=0.127). Higher blood lutein (n=261, p<.05, early r2=.100, late r2=.130) and E‐selectin (n=259, p<.05, early r2=.201, late r2=.053) predicted greater EBR magnitude during negative verses positive pictures in the early phase, but hypo‐responsivity in the late phase. Blood zeaxanthin predicted greater EBR magnitude during the same phase early on, but not during the late phase after the image disappeared (n=259, p<.05, early r2=.157, late r2=.013). In conclusion, higher IR and antioxidant levels (lutein, e‐selectin, zeaxanthin) may be selective biomarkers of different phases of psychological stress reactivity.Support or Funding InformationThis work was supported by Iowa State University and NIH AG047282. Neither funding source had any involvement in the report. MIDUS is funded by the National Institute on Aging (PO1‐AG020166; Carol D. Ryff, Principal Investigator). John D. Catherine and Catherine T. MacArthur of the Foundation Research Network on Successful Midlife Development were the supporters of the original project.

An Association between Nature Exposure and Physiological Measures of Emotion and Cognition

Nature environments have significant benefits for human psychological functioning, in both the cognitive and emotional domains. These positive effects have been found primarily with questionnaires, performance measures, and transient physiological measures. This study explores the long-term relationships between degree of nature exposure and physiological states. With a publically available dataset, multiple hierarchical regressions were conducted testing the relationship between reported nature exposure and two physiological measures of cognition and emotion, including alpha band EEG asymmetry and degree of eyeblink startle reflex (EBR). A significant relationship was found with nature exposure and these measures, suggesting that nature has enduring positive effects for human functioning via measured physiology.

The Relationship between Insulin Resistance, Resting EEG Alpha Wave Asymmetry, and Eye Blink Startle Reflex during International Affective Picture System Presentation

According to the CDC, it is estimated that more than one in three U.S. adults have pre‐diabetes. Pre‐diabetes etiology is characterized by insulin resistance (IR), which is a reduced cellular response to insulin and characterized by lower glucose uptake in the brain. IR is also related to deficits in cognitive and affective processing, particularly reactivity to psychological stress. The goal of our analysis was to determine how IR or hyperglycemia predict eye blink startle reflex (EBR) magnitude and amplitude, an objective index of the startle response, in response to positive, negative and neutral pictures using the International Affective Picture System (IAPS). We similarly assessed if IR predicted resting right frontal asymmetry using electroencephalography (EEG), an established biomarker of predisposition toward negative affect. We hypothesized that individuals with higher IR or hyperglycemia would show greater EBR and EEG right frontal asymmetry.The analysis incorporated healthy adults (N=331 participants), aged 36–84 years old, from the University of Wisconsin‐Madison's MIDUS (Midlife in the United States) II longitudinal study. As described in the MIDUS protocol, fasted blood samples were collected during an overnight stay. EBR in response to IAPS visual stimuli paired with acoustic startle was measured by placing two mini electrodes below the eye. Picture duration was 4,000ms. For a given trial, the acoustic startle stimulus occurred for 50ms during one of three phases: 1) The “early” phase at 2,900ms after picture onset while the picture was on the screen to assess reactivity; 2) the “middle” phase at 400ms after picture offset and removal to assess short‐term recovery; and 3) the “late” phase at 1,900ms after picture offset and removal to assess longer‐term recovery.Resting EEG right frontal asymmetry was collected prior to the IAPS presentation.Data was analyzed using SPSS 23.0. Linear mixed models were used to analyze the main effect of log‐transformed homeostasis model assessment of insulin resistance (HOMA‐IR) on EBR, as well as its interaction with IAPS picture valence (positive, neutral, negative). Higher log10 HOMA‐IR predicted greater EBR amplitude during negative versus positive pictures when paired with the startle stimulus (n=290, p<.05, r2=0.127). Resting state EEG at frontal F3/F4 alpha 1 (8–13 Hz) showed that participants with hyperglycemia had more left than right alpha power (−0.0324 +/− 0.026 vs. 0.0126 +/− 0.028) indicating greater right EEG frontal asymmetry. This result is consistent with Jackson et al. (2003) that hyperglycemia individuals are predisposed to negative emotion/affect. In conclusion, higher IR and type 2 diabetes are related to biomarkers of psychological stress reactivity.Support or Funding InformationThis work is directly supported by the National Institute on Aging (AG047282). Data collection and sharing for this project was funded by the Alzheimer's Disease Neuroimaging Initiative (ADNI) (National Institutes of Health Grant U01 AG024904). The grantee organization is the Northern California Institute for Research and Education, and the study is coordinated by the Alzheimer's Disease Cooperative Study at the University of California, San Diego. ADNI data are disseminated by the Laboratory for Neuro Imaging at the University Southern California. This research was also supported by NIH grants P30 AG010129 and K01 AG030514.

Affective Modulation of Brain and Autonomic Responses in Patients With Fibromyalgia.

Emotional dysregulation and abnormal processing of affective information are thought to play a significant role for the maintenance of pain in fibromyalgia. The motivational priming hypothesis states that negative emotions could increase pain via activation of the aversive system, thus leading to an affective modulation of defensive reflexes. Nevertheless, little is known about peripheral and central correlates of affective reflex modulation in fibromyalgia. Thirty patients with fibromyalgia and 30 healthy individuals were asked to view three video clips from a self-perspective to induce specific mood states. Video clips consisted of the same virtual walk through different locations of a park under three affective environments (unpleasant, pleasant, and neutral). Startle eyeblink reflex and heart rate response elicited by abrupt startle noises, as well as heart rate variability and electroencephalography (EEG) oscillations were recorded when participants were passively viewing the virtual environments. Patients with fibromyalgia rated all environments as more negative and arousing than did healthy controls (p values < .05). Nevertheless, startle eyeblink reflex and heart rate response were lower in patients with fibromyalgia than in healthy controls when viewing all three environments (p values < .05). Patients with fibromyalgia also displayed lower heart rate variability, as well as higher EEG power (2-22 Hz) during all environments than did healthy controls (p values < .05). Patients with fibromyalgia were characterized by relevant deficits in affective modulation of startle and cardiac responses, heart rate variability, and EEG power spectra in response to sustained induction of affective states. These findings suggest an alteration of emotional and attentional aspects of information processing at subjective, autonomic, and central nervous system levels.

Event-related potentials to acoustic startle probes during the anticipation of predictable and unpredictable threat.

The startle reflex is a robust measure of defense system activation. Startle probes also elicit ERP P300 and N100 responses that capture attentional engagement. The startle probe-elicited P300 and N100 have been primarily examined during affective picture viewing paradigms, and no study has examined these measures in the context of a threat anticipation task or in relation to threat predictability. In the present study, 131 participants completed a no (N), predictable (P), and unpredictable (U) threat-of-shock task, and the startle eye blink reflex, P300, and N100 responses to the startle probe were measured. We also examined several psychometric properties of these psychophysiological measures. Results indicated probe P300 attenuation during the P and U relative to N condition. In contrast, probe N100 enhancement was present only for the U condition. The P300 and N100 decreased (i.e., habituated) at comparable rates across the different threat conditions. The startle reflex also decreased, but only startle during the U (and not P) condition continued to differ from the N condition by the end of the task. Internal consistency of the ERP measures was acceptable and comparable to the startle reflex. Finally, the startle reflex was correlated with the probe N100, but not P300, across threat conditions. This study is one of the first to use startle probe ERPs to demonstrate that a context of potential threat also elicits attentional engagement. Furthermore, this study provides novel evidence that the probe N100 may provide a measure that is uniquely sensitive to unpredictable threat.

Greater general startle reflex is associated with greater anxiety levels: a correlational study on 111 young women.

Startle eyeblink reflex is a valid non-invasive tool for studying attention, emotion and psychiatric disorders. In the absence of any experimental manipulation, the general (or baseline) startle reflex shows a high inter-individual variability, which is often considered task-irrelevant and therefore normalized across participants. Unlike the above view, we hypothesized that greater general startle magnitude is related to participants’ higher anxiety level. 111 healthy young women, after completing the State-Trait Anxiety Inventory (STAI), were randomly administered 10 acoustic white noise probes (50 ms, 100 dBA acoustic level) while integrated EMG from left and right orbicularis oculi was recorded. Results showed that participants with greater state anxiety levels exhibited larger startle reflex magnitude from the left eye (r109 = 0.23, p < 0.05). Furthermore, individuals who perceived the acoustic probe as more aversive reported the largest anxiety scores (r109 = 0.28, p < 0.05) and had the largest eyeblinks, especially in the left eye (r109 = 0.34, p < 0.001). Results suggest that general startle may represent a valid tool for studying the neural excitability underlying anxiety and emotional dysfunction in neurological and mental disorders.

Impaired acquisition of classically conditioned fear-potentiated startle reflexes in humans with focal bilateral basolateral amygdala damage

Based on studies in rodents, the basolateral amygdala (BLA) is considered a key site for experience-dependent neural plasticity underlying the acquisition of conditioned fear responses. In humans, very few studies exist of subjects with selective amygdala lesions and those studies have only implicated the amygdala more broadly leaving the role of amygdala sub-regions underexplored. We tested a rare sample of subjects (N = 4) with unprecedented focal bilateral BLA lesions due to a genetic condition called Urbach-Wiethe disease. In a classical delay fear conditioning experiment, these subjects showed impaired acquisition of conditioned fear relative to a group of matched control subjects (N = 10) as measured by fear-potentiation of the defensive eye-blink startle reflex. After the experiment, the BLA-damaged cases showed normal declarative memory of the conditioned association. Our findings provide new evidence that the human BLA is essential to drive fast classically conditioned defensive reflexes.

The impact of cue learning, trait anxiety and genetic variation in the serotonin 1A receptor on contextual fear

In everyday life, aversive events are usually associated with certain predictive cues. Normally, the acquisition of these contingencies enables organisms to appropriately respond to threat. Presence of a threat cue clearly signals ‘danger’, whereas absence of such cues signals a period of ‘safety’. Failure to identify threat cues may lead to chronic states of anxious apprehension in the context in which the threat has been imminent, which may be instrumental in the pathogenesis of anxiety disorders.In this study, existing data from 150 healthy volunteers in a cue and context virtual reality fear conditioning paradigm were reanalyzed. The aim was to further characterize the impact of cue acquisition and trait anxiety, and of a single nucleotide polymorphism in the serotonin 1A receptor gene (5-HTR1A, rs6295), on cued fear and contextual anxiety before and after fear contingencies were explicitly introduced. Fear conditioned responding was quantified with fear potentiation of the eyeblink startle reflex and subjective fear ratings.First, we replicated previous findings that the inability to identify danger cues during acquisition leads to heightened anxious apprehension in the threat context. Second, in subjects who did not identify the danger cue initially, contextual fear was associated with trait anxiety after the contingencies were explicitly instructed. Third, genetic variability within 5-HTR1A (rs6295) was associated with contextual fear independent of awareness or trait anxiety.These findings confirm that failure to acquire cue contingencies impacts contextual fear responding, in association with trait anxiety. The observed 5-HTR1A effect is in line with models of anxiety, but needs further replication.

Personality Predicts Individual Variation in Fear Learning

Although fear-learning research has tended to focus on typical responses, there is substantial individual variation in response to threat. Here, we investigated how personality is related to variability in associative fear learning. We used multilevel growth curve modeling to examine the unique and interactive effects of Stress Reaction (SR) and Harmavoidance (HA; Multidimensional Personality Questionnaire scales) and their corresponding higher-order factors on differential fear conditioning ( n = 225) and extinction ( n = 109; 24–48 hr later). Fear was indexed by fear potentiation of the eyeblink startle reflex. Our findings demonstrated weaker discrimination between threat and safety with high levels of SR. Subsequently, both retention of differential fear acquisition and extinction were weaker with high levels of SR and HA, thereby indicating maladaptive fear learning, whereas they were stronger with low levels of SR and high levels of HA, which suggests efficient fear learning. These findings illustrate how specific personality traits may operate to confer vulnerability or resilience for anxiety disorders.

The startle paradigm in a forensic psychiatric setting: Elucidating psychopathy

Most people who meet the diagnostic criteria for anti-social personality disorder (ASPD) do not meet the criteria for psychopathy. A differentiating feature is affective-interpersonal style. Eye blink startle reflex paradigms have been used to study affect. The aim of this study is to explore an eye blink startle paradigm as a means of distinguishing between men with both ASPD and psychopathy, and men with ASPD alone. One hundred and thirty-six men were recruited as follows: 31 patients with ASPD and a Psychopathy Checklist-Revised (PCL-R) score of 26 or more, 22 patients with ASPD and a PCL-R score of 25 or less, 50 forensic hospital employees and 33 general population men, none in the latter two groups having abnormal personality traits. Each was presented with 16 pleasant, 16 unpleasant and 16 neutral pictures. Acoustic probes were presented during each category at 300, 800, 1300 and 3800 milliseconds (ms) after picture onset. Eye blink response was measured by electromyography. Overall, both patient groups showed significantly smaller eye blink responses to the startle stimuli compared with the community controls. Both the latter and the ASPD group showed the expected increase in eye blink response at longer startle latencies to unpleasant pictures than pleasant pictures, but this was not present either in the group with psychopathy or in the forensic hospital employees. With increasing startle latency onset, eye blink amplitude increased significantly in both the healthy comparison groups and the ASPD group, but not in the group with psychopathy. We replicated eye blink startle modulation deficiencies among men with psychopathy. We confirmed that the psychopathy and ASPD groups could be distinguished by startle stimulus onset asynchrony, but this pattern was also seen in one healthy group - the forensic hospital employees. This suggests a case for more research with more diverse comparison groups and more differentiation of personality traits before drawing definitive conclusions about distinctive startle response patterns among men with psychopathy.

Emotional reactivity during anticipation and perception of affective pictures.

The focus of the present study was on further exploring anticipatory responses to emotional stimuli by measuring the eyeblink startle reflex in a variation of the picture-picture affective learning procedure. Participants (113 undergraduate women) were not explicitly instructed before the experiment began. Instead, they had to learn the specific relations between cues (geometrical shapes) and emotional pictures based on pairings during the first part of the task. Plausible contingency learning effects were tested afterwards, in a parallel sequence of trials including auditory probes during cues and pictures processing during the second part of the task. Results did show the typical affective startle modulation pattern during perception, linear F(1, 200) = 52.67, p < .0001, but unexpected inhibition for both pleasant and unpleasant, compared to neutral cues, during anticipation, quadratic F(1, 200) = 7.07, p < .009. All patterns of startle modulation were independent of cue-picture contingency awareness (all interactions Fs < 1). Skin conductance changes showed the predictable quadratic trend either during picture perception or anticipatory periods (greater activity for emotional vs. neutral; overall quadratic F(1, 224) = 7.04, p < .01), only for participants fully aware of the cue-picture contingency, quadratic F(1, 158) = 5.86, p < .02. Overall, our results during anticipation (cues processing) seem to suggest that more resources were allocated to highly arousing pictures that engage attention. Differences between the present results and prior research may be attributed to procedural variations in the sample, cues, or instructions. Future studies should also explore in more detail the role of the contingency awareness during anticipation.

Hypnotizability, Hypnosis and Prepulse Inhibition of the Startle Reflex in Healthy Women: An ERP Analysis

A working model of the neurophysiology of hypnosis suggests that highly hypnotizable individuals (HHs) have more effective frontal attentional systems implementing control, monitoring performance, and inhibiting unwanted stimuli from conscious awareness, than low hypnotizable individuals (LHs). Recent studies, using prepulse inhibition (PPI) of the auditory startle reflex (ASR), suggest that HHs, in the waking condition, may show reduced sensory gating although they may selectively attend and disattend different stimuli. Using a within subject design and a strict subject selection procedure, in waking and hypnosis conditions we tested whether HHs compared to LHs showed a significantly lower inhibition of the ASR and startle-related brain activity in both time and intracerebral source localization domains. HHs, as compared to LH participants, exhibited (a) longer latency of the eyeblink startle reflex, (b) reduced N100 responses to startle stimuli, and (c) higher PPI of eyeblink startle and of the P200 and P300 waves. Hypnosis yielded smaller N100 waves to startle stimuli and greater PPI of this component than in the waking condition. sLORETA analysis revealed that, for the N100 (107 msec) elicited during startle trials, HHs had a smaller activation in the left parietal lobe (BA2/40) than LHs. Auditory pulses of pulse-with prepulse trials in HHs yielded less activity of the P300 (280 msec) wave than LHs, in the cingulate and posterior cingulate gyrus (BA23/31). The present results, on the whole, are in the opposite direction to PPI findings on hypnotizability previously reported in the literature. These results provide support to the neuropsychophysiological model that HHs have more effective sensory integration and gating (or filtering) of irrelevant stimuli than LHs.