The psychological significance of human startle eyeblink modification: a review

Affective modulation of emotional reactivity in euthymic patients with bipolar disorder

BACKGROUND

Affective modulation of startle reflex (AMSR) is a widely used experimental tool for assessing emotional reactivity. Previous research has shown inconsistent findings of emotional reactivity in amplitude in bipolar patients (BP). This study examined emotional reactivity (ER) in euthymic BP compared to healthy controls using both subjective and objective measures.

METHOD

This study compared ER between 33 euthymic BP (I and II) and 35 healthy controls. Subjective experiences, valence, and arousal scores were assessed using the Self-Assessment Manikin. Objective measures included startle reflex parameters - amplitude, area, and latency - from the orbicularis oculi muscle via electromyography. To assess the AMSR, pictures of varying emotional valences from the International Affective Picture System were used during acoustic stimulation.

RESULTS

A significant picture category effect was observed in the subjective picture evaluation; however, no substantial group effect or picture category-group interaction was detected. In the controls, picture categories exerted a significant effect on amplitude, but did not in euthymic BP. A linear pattern of startle amplitude across different picture categories was evident in the control group but not in patients. Analyses of the area did not reveal significant group differences. Onset latency was also similar between groups.

CONCLUSION

This study indicates impaired emotional processing in euthymic individuals with bipolar disorder, as shown by altered startle reflex measurements. Future research with larger samples and consideration of bipolar disorder subtypes is needed to explore these findings further.

Elevated unanticipated acoustic startle reactivity in dyslexia

People with dyslexia, a neurodevelopmental disorder of reading, are highly attuned to the emotional world. Compared with their typically developing peers, children with dyslexia exhibit greater autonomic nervous system reactivity and facial behaviour to emotion- and empathy-inducing film clips. Affective symptoms, such as anxiety, are also more common in children with dyslexia than in those without. Here, we investigated whether the startle response, an automatic reaction that lies at the interface of emotion and reflex, is elevated in dyslexia. We measured facial behaviour, electrodermal reactivity (a sympathetic nervous system measure) and emotional experience in response to a 100 ms, 105 dB unanticipated acoustic startle task in 30 children with dyslexia and 20 comparison children without dyslexia (aged 7-13) who were matched on age, sex and nonverbal reasoning. Our results indicated that the children with dyslexia had greater total facial behaviour and electrodermal reactivity to the acoustic startle task than the children without dyslexia. Across the sample, greater electrodermal reactivity during the startle predicted greater parent-reported anxiety symptoms. These findings contribute to an emerging picture of heightened emotional reactivity in dyslexia and suggest accentuated sympathetic nervous system reactivity may contribute to the elevated anxiety that is often seen in this population.

Non-dual awareness and sensory processing in meditators: Insights from startle reflex modulation

Startle modulation paradigms, namely habituation and prepulse inhibition (PPI), can offer insight into the brain's early information processing mechanisms that might be impacted by regular meditation practice. Habituation refers to decreasing response to a repeatedly-presented startle stimulus, reflecting its redundancy. PPI refers to response reduction when a startling stimulus "pulse" is preceded by a weaker sensory stimulus "prepulse" and provides an operational measure of sensorimotor gating. Here, we examined habituation and PPI of the acoustic startle response in regular meditators (n = 32), relative to meditation-naïve individuals (n = 36). Overall, there was no significant difference between meditators and non-meditators in habituation or PPI, but there was significantly greater PPI in meditators who self-reported being able to enter and sustain non-dual awareness during their meditation practice (n = 18) relative to those who could not (n = 14). Together, these findings suggest that subjective differences in meditation experience may be associated with differential sensory processing characteristics in meditators.

Affective processing in dysphoria: Evidence from startle probe modulation of ERPs

The hypoactivation of the appetitive and defensive motivational systems in the brain is a feature of depression and might also represent a vulnerability factor for the disorder. A measure that can be employed to investigate both motivational systems is the electroencephalographic response to an acoustic startle probe during affective processing. Particularly, the amplitude of auditory event-related potentials (ERPs) components to the startle probe is smaller when the emotional context is more arousing. Neural responses to an unattended startle probe during an emotional passive viewing task of pleasant, neutral, and unpleasant pictures was employed to assess the activation of the approach and defensive motivational systems in a sample of individuals with (n = 24, 23 females) vs. without (n = 24, 23 females) dysphoria. The group without dysphoria showed a reduced startle-elicited N200 only in the context of pleasant relative to neutral pictures, indicating that the affective processing of the appetitive context might reduce the attentional resources needed to orient attention toward unattended non-salient stimuli. Conversely, the N200 amplitude was not attenuated for pleasant relative to neutral and unpleasant contexts in the group with dysphoria. Moreover, no within- or between-group differences emerged in the P300 amplitude. Taken together, the results of this study showed that depression vulnerability is characterized by reduced attention to pleasant contexts, suggesting a blunted affective processing of appetitive emotional stimuli.

The photic blink reflex as an index of photophobia

Two recent studies of eye closure triggered by intense luminance increase suggest that this behavior reflects the melanopsin-based retinal activity known to underlie photophobia, the pathological aversion to light (Kardon, 2012; Kaiser et al., 2021). Early studies of the photic blink reflex (PBR) are reviewed to help guide future research on this possible objective index of photophobia. Electromyographic recordings of the lid-closure muscle, orbicularis oculi, reveal distinct bursts with typical onset latencies of 50 and 80 ms, R50 and R80, respectively. The latter component appears to be especially sensitive to visual signals from intrinsically photosensitive retinal ganglion cells (ipRGCs) and to prior trigeminal nociceptive stimuli. The authors argue that the R80's function, in addition to protecting the eyeballs from physical contact, is to shape the upper and lower eyelids into a narrow slit to restrict incoming light. This serves to prevent retinal bleaching or injury, while allowing continued visual function.

On the Automatic Nature of Threat: Physiological and Evaluative Reactions to Survival-Threats Outside Conscious Perception

A neural architecture that preferentially processes immediate survival threats relative to other negatively and positively valenced stimuli presumably evolved to facilitate survival. The empirical literature on threat superiority, however, has suffered two problems: methodologically distinguishing threatening stimuli from negative stimuli and differentiating whether responses are sped and strengthened by threat superiority or delayed and diminished by conscious processing of nonthreatening stimuli. We addressed both problems in three within-subject studies that compared responses to empirically validated sets of threating, negative, positive, and neutral stimuli, and isolated threat superiority from the opposing effect of conscious attention by presenting stimuli outside conscious perception. Consistent with threat superiority, threatening stimuli elicited stronger skin-conductance (Study 1), startle-eyeblink (Study 2), and more negative downstream evaluative responses (Study 3) relative to the undifferentiated responses to negative, positive, and neutral stimuli.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42761-021-00090-6.

Non-invasive recording from the human cerebellum during a classical conditioning paradigm using the otolith-evoked blink reflex

We studied nine normal volunteers with a classical conditioning paradigm using a mastoid tap, believed to activate otolith receptors, as an unconditional stimulus (US) and the consequent blink as the unconditioned response (UR). Both visual (alternation of stripes) and an auditory tone were used as conditional stimuli (CS). Recordings were made below the eyes at IO1 and IO2, from over the frontal eye fields (C3' and C4') and over the posterior fossa, the latter at sites we have previously reported that we were able to record an evoked climbing fibre response (CFR) at short latency. Behavioural analysis confirmed that weak conditioning did occur early, which subsequently showed extinction on repeated CS alone trials. Further, a UR was more likely to occur following a preceding CFR when preceded by a CS, supporting a correlation between the CFRs and behaviour. For further statistical analysis, the time period of interest was divided into a series of epochs, based around the events occurring at the time. Grand averages, plus analysis of variance, confirmed evidence of weak conditioning for the blink response following both modalities. The EMG associated with the eyeblink for the UR occurred at a similar time to the expected post-CFR pause in the spontaneous cerebellar activity, or electrocerebellogram (ECeG), while hypothesised conditioned pausing in the ECeG was also observed in CS alone trials. A correlation was found between the size of the CFR and the RMS amplitudes of the segments covering the ocular vestibular evoked myogenic potential oVEMP, (periocular) EMG and the EOG. The slope was greater for the non-oVEMP segments than for the oVEMP segment suggesting the correlation was not simply due to differing sizes of the vestibular volley. We suggest that these recorded events fit with the proposed role of the CFR in Purkinje neurons in classical conditioning, gating the excitability of the cerebellar nuclei, and thereby neurons in the reticular formation mediating the otolith blink reflex. This effect appears to apply to polysynaptic reflexes only as there was no evidence of changes to the oVEMP.

Therapeutic potential of TAK-071, a muscarinic M1 receptor positive allosteric modulator with low cooperativity, for the treatment of cognitive deficits and negative symptoms associated with schizophrenia

The selective activation of the muscarinic M1 receptor (M1R) may be a promising approach for treating cognitive impairment associated with cholinergic dysfunction. We previously reported that low cooperativity (α-value) is associated with a favorable cholinergic side effect profile of M1R positive allosteric modulators (M1 PAMs), as well as being a crucial factor for the cognitive improvement observed after combining M1 PAMs with donepezil, in rodents. In this study, we preclinically characterized TAK-071, a novel M1 PAM with low cooperativity (α-value = 199), as a new therapy for schizophrenia. We tested TAK-071 in the offspring of polyriboinosinic-polyribocytidylic acid-treated dams, which is a maternal immune activation model of schizophrenia. TAK-071 improved sociability deficits and working memory in this model. In a genetic mouse model of schizophrenia, miR-137 transgenic (Tg) mice, TAK-071 improved deficits in working memory, recognition memory, sociability, and sensorimotor gating. Patients with schizophrenia usually take several antipsychotics to treat positive symptoms. Thus, we also investigated the combined effects of TAK-071 with currently prescribed antipsychotics. Among the 10 antipsychotics tested, only olanzapine and quetiapine showed M1R antagonistic effects, which were counteracted by TAK-071 at possible effective concentrations for cognitive improvement in vitro. Moreover, haloperidol did not affect the ability of TAK-071 to improve working memory in miR-137 Tg mice, suggesting a low risk of losing efficacy when combined with dopamine D2 receptor antagonists. In conclusion, TAK-071 can exert beneficial effects on social behavior and cognitive function and could be a new therapy for schizophrenia.

Premovement inhibition can protect motor actions from interference by response-irrelevant sensory stimulation

KEY POINTS

Suppression of corticospinal excitability is reliably observed during preparation for a range of motor actions, leading to the belief that this preparatory inhibition is a physiologically obligatory component of motor preparation. The neurophysiological function of this suppression is uncertain. We restricted the time available for participants to engage in preparation and found no evidence for preparatory inhibition. The function of preparatory inhibition can be inferred from our findings that sensory stimulation can disrupt motor output in the absence of preparatory inhibition, but enhance motor output when inhibition is present. These findings suggest preparatory inhibition may be a strategic process which acts to protect prepared actions from external interference. Our findings have significant theoretical implications for preparatory processes. Findings may also have a pragmatic benefit in that acoustic stimulation could be used therapeutically to facilitate movement, but only if the action can be prepared well in advance.

ABSTRACT

Shortly before movement initiation, the corticospinal system undergoes a transient suppression. This phenomenon has been observed across a range of motor tasks, suggesting that it may be an obligatory component of movement preparation. We probed whether this was also the case when the urgency to perform a motor action was high, in a situation where little time was available to engage in preparatory processes. We controlled the urgency of an impending motor action by increasing or decreasing the foreperiod duration in an anticipatory timing task. Transcranial magnetic stimulation (TMS; experiment 1) or a loud acoustic stimulus (LAS; experiment 2) were used to examine how corticospinal and subcortical excitability were modulated during motor preparation. Preparatory inhibition of the corticospinal tract was absent when movement urgency was high, though motor actions were initiated on time. In contrast, subcortical circuits were progressively inhibited as the time to prepare increased. Interestingly, movement force and vigour were reduced by both TMS and the LAS when movement urgency was high, and enhanced when movement urgency was low. These findings indicate that preparatory inhibition may not be an obligatory component of motor preparation. The behavioural effects we observed in the absence of preparatory inhibition were induced by both TMS and the LAS, suggesting that accessory sensory stimulation may disrupt motor output when such stimulation is presented in the absence of preparatory inhibition. We conclude that preparatory inhibition may be an adaptive strategy which can serve to protect the prepared motor action from external interference.

Safety learning during development: Implications for development of psychopathology

Fear and safety learning are necessary adaptive behaviors that develop over the course of maturation. While there is a large body of literature regarding the neurobiology of fear and safety learning in adults, less is known regarding safety learning during development. Given developmental changes in the brain, there are corresponding changes in safety learning that are quantifiable; these may serve to predict risk and point to treatment targets for fear and anxiety-related disorders in children and adolescents. For healthy, typically developing youth, the main developmental variation observed is reduced discrimination between threat and safety cues in children compared to adolescents and adults, while lower expression of extinction learning is exhibited in adolescents compared to adults. Such distinctions may be related to faster maturation of the amygdala relative to the prefrontal cortex, as well as incompletely developed functional circuits between the two. Fear and anxiety-related disorders, childhood maltreatment, and behavioral problems are all associated with alterations in safety learning for youth, and this dysfunction may proceed into adulthood with corresponding abnormalities in brain structure and function-including amygdala hypertrophy and hyperreactivity. As impaired inhibition of fear to safety may reflect abnormalities in the developing brain and subsequent psychopathology, impaired safety learning may be considered as both a predictor of risk and a treatment target. Longitudinal neuroimaging studies over the course of development, and studies that query change with interventions are needed in order to improve outcomes for individuals and reduce long-term impact of developmental psychopathology.

Induced Positive Affect Reduces the Magnitude of the Startle Response and Prepulse Inhibition

Abstract. The startle response is a reflex that represents a form of adaptation to environmental changes potentially relevant to survival. Startle magnitude can change depending on a number of factors such as the affective state of the organism during the presentation of the startle-inducing stimulus, or the so-called Prepulse Inhibition (PPI) that occurs when the startling stimulus (or Pulse) is preceded by a low-intensity stimulus (or Prepulse). This paper describes an experiment designed to analyze the impact of an induced positive affect on the magnitude of the startle response and PPI in adult humans. Specifically, each participant received alternating exposures to a picture of a face of a loved person (positive affect condition) or to a picture of a face of an unknown person (control condition) while the startle response and PPI were recorded. The results showed a decrease in both the magnitude of the startle response and percent PPI on the positive affect trials when compared with the control trials. These results are interpreted from psychophysiological and psychological perspectives considering the role of emotions in adaptive behavior.

The Social Neuroscience of Prejudice

The social neuroscience approach to prejudice investigates the psychology of intergroup bias by integrating models and methods of neuroscience with the social psychology of prejudice, stereotyping, and discrimination. Here, we review major contemporary lines of inquiry, including current accounts of group-based categorization; formation and updating of prejudice and stereotypes; effects of prejudice on perception, emotion, and decision making; and the self-regulation of prejudice. In each section, we discuss key social neuroscience findings, consider interpretational challenges and connections with the behavioral literature, and highlight how they advance psychological theories of prejudice. We conclude by discussing the next-generation questions that will continue to guide the social neuroscience approach toward addressing major societal issues of prejudice and discrimination.

The acquisition and generalization of fear of touch

Objectives Contemporary fear-avoidance models of chronic pain posit that fear of pain, and overgeneralization of fear to non-threatening stimuli is a potential pathway to chronic pain. While increasing experimental evidence supports this hypothesis, a comprehensive investigation requires testing in multiple modalities due to the diversity of symptomatology among individuals with chronic pain. In the present study we used an established tactile fear conditioning paradigm as an experimental model of allodynia and spontaneous pain fluctuations, to investigate whether stimulus generalization occurs resulting in fear of touch spreading to new locations. Methods In our paradigm, innocuous touch is presented either paired (predictable context) or unpaired (unpredictable context) with a painful electrocutaneous stimulus (pain-US). In the predictable context, vibrotactile stimulation to the index or little finger was paired with the pain-US (CS+), whilst stimulation of the other finger was never paired with pain (CS-). In the unpredictable context, vibrotactile stimulation to the index and little fingers of the opposite hand (CS1 and CS2) was unpaired with pain, but pain-USs occurred unpredictable during the intertrial interval. During the subsequent generalization phase, we tested the spreading of conditioned responses (self-reported fear of touch and pain expectancy) to the (middle and ring) fingers between the CS+ and CS-, and between the CS1 and CS2. Results Differential fear acquisition was evident in the predictable context from increased self-reported pain expectancy and self-reported fear for the CS + compared to the CS-. However, expectancy and fear ratings to the novel generalization stimuli (GS+ and GS-) were comparable to the responses elicited by the CS-. Participants reported equal levels of pain expectancy and fear to the CS1 and CS2 in the unpredictable context. However, the acquired fear did not spread in this context either: participants reported less pain expectancy and fear to the GS1 and GS2 than to the CS1 and CS2. As in our previous study, we did not observe differential acquisition in the startle responses. Conclusions Whilst our findings for the acquisition of fear of touch replicate the results from our previous study (Biggs et al., 2017), there was no evidence of fear generalization. We discuss the limitations of the present study, with a primary focus on procedural issues that were further investigated with post-hoc analyses, concluding that the present results do not show support for the hypothesis that stimulus generalization underlies spreading of fear of touch to new locations, and discuss how this may be the consequence of a context change that prevented transfer of acquisition.

Do Varying Levels of Exposure to Pornography and Violence Have an Effect on Non-Conscious Emotion in Men?

As we are often inundated with images of violence and pornography in modern times with the aid of mobile devices and unrestricted online access and content, the non-conscious effect of such exposure is an area of concern. To date, many clinicians and researchers in behavioral sciences rely on conscious responses from their clients to determine affective content. In doing so, they overlook the effect the non-conscious has on an individual's emotions. The present study aimed to examine variations in conscious and non-conscious responses to emotion-inducing images following varying amounts of exposure to violent and pornographic images. Eighteen participants who self-reported as being low pornography users were presented with emotion-inducing images after no exposure (Session 1), after one round of exposure to 50 pornographic and 50 violent images (Session 2) and after a further nine rounds of exposure to 50 pornographic and 50 violent images (Session 3). Sessions were temporally separated by at least 2 days while startle reflex modulation (SRM) and scalp-recorded event-related potentials (ERPs) were used to determine non-conscious emotion-related responses to pre-evaluated emotion pictures. Explicit valence and arousal ratings were assessed for each of those emotion pictures to determine conscious emotion effects potentially changing as a function of increasing controlled exposure to pornographic and violent visual material. Conscious explicit ratings and SRM amplitudes revealed no significant difference between the sessions. However, frontal ERP analysis revealed significant changes between processing of "violent" and "unpleasant" images at later ERP time windows, further supporting the growing body of research which shows that relying on self-report data does not result in a full understanding of emotional responses.

A systematic and methodological review of attentional biases in eating disorders: Food, body, and perfectionism

OBJECTIVE

The current systematic and methodological review aimed to critically review existing literature utilizing implicit processing, or automatic approach- and/or avoidance-related attentional biases between eating disorder (ED) and nonclinical samples, which (a) highlights how psychophysiological methods advance knowledge of ED implicit bias; (b) explains how findings fit into transdiagnostic versus disorder-specific ED frameworks; and (c) suggests how research can address perfectionism-related ED biases.

METHOD

Three databases were systematically searched to identify studies: PubMed, Scopus, and PsychInfo electronic databases. Peer-reviewed studies of 18- to 39-year-olds with both clinical ED and healthy samples assessing visual attentional biases using pictorial and/or linguistic stimuli related to food, body, and/or perfectionism were included.

RESULTS

Forty-six studies were included. While behavioral results were often similar across ED diagnoses, studies incorporating psychophysiological measures often revealed disease-specific attentional biases. Specifically, women with bulimia nervosa (BN) tend to approach food and other body types, whereas women with anorexia nervosa (AN) tend to avoid food as well as overweight bodies.

CONCLUSIONS

Further integration of psychophysiological and behavioral methods may identify subtle processing variations in ED, which may guide prevention strategies and interventions, and provide important clinical implications. Few implicit bias studies include male participants, investigate binge-eating disorder, or evaluate perfectionism-relevant stimuli, despite the fact that perfectionism is implicated in models of ED.

The relationship between fear generalization and pain modulation: an investigation in healthy participants

Background and aims

Pain-related fear and its subsequent generalization is key to the development and maintenance of chronic pain disability. Research has shown that pain-related fear acquired through classical conditioning generalizes following a gradient, that is, novel movements that are proprioceptively similar to the original pain-associated movement elicit more fear. Studies suggest that classical conditioning can also modulate pain and conditioned fear seems to mediate this effect. However, it remains uninvestigated whether this is also the case for generalized fear.

Methods

In a voluntary joystick movement paradigm, one movement (conditioned stimulus; CS+) was followed by pain (pain-US), and another was not (CS−). Generalization to five novel movements (generalization stimuli; GSs) with varying levels of similarity to the CSs was tested when paired with an at-pain-threshold intensity stimulus (threshold-USs). We collected self-reported fear and pain, as well as eyeblink startle responses as an additional index of conditioned fear.

Results

Results showed a fear generalization gradient in the ratings, but not in the startle measures. The data did not support the idea that fear generalization mediates spreading of pain.

Conclusions

Despite the lack of effects in the current study, this is a promising novel approach to investigate pain modulation in the context of chronic pain.

Implications

This study replicates the finding that pain-related fear spreads selectively towards movements that are proprioceptively more similar to the original pain-eliciting movement. Although results did not support the idea that such generalized fear mediates spreading of pain, the study provides a promising approach to investigate pain modulation by pain-associated movements.

Affective startle modulation and psychopathology: Implications for appetitive and defensive brain systems

Startle reflex potentiation versus startle attenuation to unpleasant versus pleasant stimuli likely reflect priming of the defensive versus appetitive motivational systems, respectively. This review summarizes and systemizes the literature on affective startle modulation related to psychopathologies with the aim to reveal underlying mechanisms across psychopathologies. We found evidence for psychopathologies characterized by increased startle potentiation to unpleasant stimuli (anxiety disorders), decreased startle potentiation to unpleasant stimuli (psychopathy), decreased startle attenuation to pleasant stimuli (ADHD), as well as a general hyporeactivity to affective stimuli (depression). Increased versus decreased startle responses to disorder-specific stimuli characterize specific phobia and drug dependence. No psychopathology is characterized by increased startle attenuation to standard pleasant stimuli or a general hyperreactivity to affective stimuli. This review indicates that the defensive and the appetitive systems operate independently mostly in accordance with the motivational priming hypothesis and that affective startle modulation is a highly valuable paradigm to unraveling dysfunctions of the defensive and appetitive systems in psychopathologies as requested by the Research Domain Criteria initiative.

Video-Based Analysis of Bodily Startle and Subsequent Emotional Facial Expression in Posttraumatic Stress Disorder

Exaggerated startle is a core hyperarousal symptom of Posttraumatic Stress Disorder (PTSD). Observational studies on the characteristics of this response are strikingly lacking. Previous research has demonstrated that detailed video analysis of facial and bodily responses to startling stimuli enables the differentiation of an initial, primarily reflexive response and a secondary, primary emotional response. We exposed PTSD patients (n = 34) and trauma-exposed but healthy participants (TE group, n = 26) to startling electric stimuli while acquiring observational behavioral, psychophysiological, and experiential measures. Videographic results indicate that PTSD patients' initial bodily startle response was stronger than in the TE group, and their secondary facial expression was more negatively valenced, largely due to elevated anger expression. Videographic assessment of primary and secondary startle responses provides a new window into reflexive and emotional functioning of PTSD and may therefore complement existing startle measures. PTSD treatments should address bodily startle, negative symptom appraisals, and anger more specifically.

Exposure to an obesogenic diet during adolescence leads to abnormal maturation of neural and behavioral substrates underpinning fear and anxiety

BACKGROUND

Post-traumatic stress disorder (PTSD) and obesity are highly prevalent in adolescents. Emerging findings from our laboratory and others are consistent with the novel hypothesis that obese individuals may be predisposed to developing PTSD. Given that aberrant fear responses are pivotal in the pathogenesis of PTSD, the objective of this study was to determine the impact of an obesogenic Western-like high-fat diet (WD) on neural substrates associated with fear.

METHODS

Adolescent Lewis rats (n = 72) were fed with either the experimental WD (41.4% kcal from fat) or the control diet. The fear-potentiated startle paradigm was used to determine sustained and phasic fear responses. Diffusion tensor imaging metrics and T2 relaxation times were used to determine the structural integrity of the fear circuitry including the medial prefrontal cortex (mPFC) and the basolateral complex of the amygdala (BLA).

RESULTS

The rats that consumed the WD exhibited attenuated fear learning and fear extinction. These behavioral impairments were associated with oversaturation of the fear circuitry and astrogliosis. The BLA T2 relaxation times were significantly decreased in the WD rats relative to the controls. We found elevated fractional anisotropy in the mPFC of the rats that consumed the WD. We show that consumption of a WD may lead to long-lasting damage to components of the fear circuitry.

CONCLUSIONS

Our findings demonstrate that consumption of an obesogenic diet during adolescence has a profound impact in the maturation of the fear neurocircuitry. The implications of this research are significant as they identify potential biomarkers of risk for psychopathology in the growing obese population.

Trauma, Pain, and Psychological Distress

Abstract. Posttraumatic stress disorder (PTSD) and chronic musculoskeletal pain (CMP) are highly prevalent ( Breslau, 2002 ) and comorbid disorders ( Otis, Keane, & Kerns, 2003 ). The shared vulnerability model explains this overlap in part through a common attentional bias toward threat ( Asmundson, Coons, Taylor, & Katz, 2002 ). The current study made use of the acoustic startle to assess cognitive bias to threat in participants (n = 106; 64% women) who reported experiencing a motor vehicle accident (MVA). Participants were divided into five groups based on their diagnoses: PTSD, CMP, both PTSD and CMP, any general (i.e., non-PTSD) anxiety disorder with no CMP, and a no-disorder Control group. Self-report measures were used to assess psychological symptoms, trauma response, and pain-related factors. Word stimuli (i.e., trauma, sensory pain, health, pleasant, neutral) were presented visually prior to onset of the acoustic startle probe to assess for diagnosis-congruent attentional biases (e.g., persons with PTSD respond differently to trauma words). Relative to the general anxiety and control group, persons with PTSD or chronic pain demonstrated delayed startle peak and greater startle intensity across all word stimuli types; the results suggest there may be psychophysiologically measurable differences associated with PTSD and pain. The startle probe paradigm remains relatively nascent for such research, but has potential utility for assessment and treatment monitoring. Comprehensive results, discussion, and implications are analyzed.

The Acquisition and Extinction of Fear of Painful Touch: A Novel Tactile Fear Conditioning Paradigm

Fear of touch, due to allodynia and spontaneous pain, is not well understood. Experimental methods to advance this topic are lacking, and therefore we propose a novel tactile conditioning paradigm. Seventy-six pain-free participants underwent acquisition in a predictable as well as an unpredictable pain context. In the predictable context, vibrotactile stimulation was paired with painful electrocutaneous stimulation (simulating allodynia). In the unpredictable context, vibrotactile stimulation was unpaired with pain (simulating spontaneous pain). During an extinction phase, a cue exposure and context exposure group continued in the predictable and unpredictable context, respectively, without pain. A control group received continued acquisition in both contexts. Self-reported fear and skin conductance responses, but not startle responses, showed fear of touch was acquired in the predictable context. Context-related startle responses showed contextual fear emerged in the unpredictable context, together with elevated self-reported fear and skin conductance responses evoked by the unpaired vibrotactile stimulations. Cue exposure reduced fear of touch, whereas context exposure reduced contextual fear. Thus, painful touch leads to increased fear, as does touch in the same context as unpredictable pain, and extinction protocols can reduce this fear. We conclude that tactile conditioning is valuable for investigating fear of touch and can advance our understanding of chronic pain.

PERSPECTIVES

The acquisition and extinction of fear of touch was investigated in a clinical analog study using a novel tactile fear conditioning paradigm. The results have implications for research on the development and treatment of chronic pain conditions characterized by allodynia and spontaneous pain fluctuations.

In Harm’s Way: On Preferential Response to Threatening Stimuli

Given the evolutionary significance of survival, the mind might be particularly sensitive (in terms of strength and speed of reaction) to stimuli that pose an immediate threat to physical harm. To rectify limitations in past research, we pilot-tested stimuli to obtain images that are threatening, nonthreatening-negative, positive, or neutral. Three studies revealed that participants (a) were faster to detect a threatening than nonthreatening-negative image when each was embedded among positive or neutral images, (b) oriented their initial gaze more frequently toward threatening than nonthreatening-negative, positive, or neutral images, and (c) evidenced larger startle-eyeblinks to threatening than to nonthreatening-negative, positive, or neutral images. Social-psychological implications for the mind’s sensitivity to threat are discussed.

The effects of multiphasic prepulses on automatic and attention-modulated prepulse inhibition

Prepulse inhibition (PPI) is widely viewed as an operational measure of sensorimotor gating. Previous research has shown that sensorimotor gating can occur automatically and also can be influenced by selective attention. The present research investigated the relationship of the transient detection response (TDR) with automatic and attention-modulated PPI using a novel "multiphasic" prepulse stimulus. Experiment 1 compared discrete versus multiphasic prepulse types in a no-task PPI protocol to validate multiphasic prepulses as effective elicitors of automatic sensorimotor gating. Results revealed that the two prepulse types elicited equivalent levels of PPI. Experiment 2 compared the effectiveness of continuous monophasic versus continuous multiphasic prepulses within a task-based PPI protocol using a lead interval of 120 ms. Results revealed a significant attention effect for monophasic prepulses only. However, robust PPI was produced by the multiphasic prepulses independent of attention as well as over time. These results suggest that multiple influences on PPI can be assessed concurrently depending on prepulse parameters designed to activate the TDR when used in a PPI protocol capable of assessing the effects of selective attention on prepulse processing [corrected]

Prepulse inhibition and facilitation of the postauricular reflex, a vestigial remnant of pinna startle

If the postauricular reflex (PAR) is to be used effectively in studies of emotion and attention, its sensitivity to basic modulatory effects such as prepulse inhibition and facilitation must be determined. Two experiments were carried out with healthy young adults to assess the effects of transient and sustained visual prestimuli on the pinna-flexion response to trains of startle probes. In the first experiment, participants passively viewed a small white square. It was displayed from 1,000 ms prior to onset of a train of noise bursts until the end of that train. Relative to no-prepulse control trials, PAR amplitude was inhibited, possibly due to the withdrawal of attentional resources from the auditory modality. In the second experiment, participants performed a visual oddball task in which irrelevant trains of startle probes followed most briefly displayed task stimuli (checkerboards). Prepulse inhibition was observed when a transient stimulus preceded the first probe at a lead time of 100 ms. Amplitude facilitation was observed at longer lead times. In addition to documenting the existence of prepulse inhibition and facilitation, the data suggest that the PAR is not elicited by visual stimuli, that temporal expectancy does not influence its amplitude or latency, and that this vestigial microreflex is resistant to habituation. Results are interpreted in light of a recent theory that the human PAR is a highly degraded pinna startle, in which the reflex arc no longer includes the startle center (nucleus reticularis pontis caudalis).

The Malleability of Automatic Stereotypes and Prejudice

The present article reviews evidence for the malleability of automatic stereotypes and prejudice. In contrast to assumptions that such responses are fixed and inescapable, it is shown that automatic stereotypes and prejudice are influenced by, (a) self- and social motives, (b) specific strategies, (c) the perceiver's focus of attention, and (d) the configuration of stimulus cues. In addition, group members' individual characteristics are shown to influence the extent to which (global) stereotypes and prejudice are automatically activated. This evidence has significant implications for conceptions of automaticity, models of stereotyping and prejudice, and attitude representation. The review concludes with the description of an initial model of early social information processing.

Sensory Gating Deficits in First-Episode Psychosis: Evidence From Neurophysiology, Psychophysiology, and Neuropsychology

Sensory gating deficits are commonly found in patients with schizophrenia. However, there is still scarce research on this issue. Thirty-eight patients with first-episode psychosis (FEP) were compared to thirty-eight controls. A condition-test paradigm of event-related potentials (ERP), prepulse inhibition (PPI), and some specific tasks of the MATRICS Consensus Cognitive Battery (MCCB) were used (i.e., TMT, BACS-SC, and Fluency for processing speed and CPT-IP for attention and vigilance). The ERP components measured were P50, N1, and P2. The PPI intervals examined were 30, 60, and 120 msec. Regarding the MCCB, processing speed and attention/vigilance cognitive domains were selected. FEP patients showed significant deficits in N1 and P2 components, at 30 and 60 PPI levels and in all the MCCB subtests selected. We obtained significant relationships in N1 with PPI-60, and with one MCCB subtest for processing speed. In addition, this same subtest showed significant association with P2. Therefore, sensory gating functioning is widely impaired since the very early stages of schizophrenia.

Heritability of startle reactivity and affect modified startle

Startle reflex and affect-modified startle reflex are used as indicators of defensive reactivity and emotional processing, respectively. The present study investigated the heritability of both the startle blink reflex and affect modification of this reflex in a community sample of 772 twins ages 14-15years old. Subjects were shown affective picture slides falling in three valence categories: negative, positive and neutral; crossed with two arousal categories: high arousal and low arousal. Some of these slides were accompanied with a loud startling noise. Results suggested sex differences in mean levels of startle reflex as well as in proportions of variance explained by genetic and environmental factors. Females had higher mean startle blink amplitudes for each valence-arousal slide category, indicating greater baseline defensive reactivity compared to males. Startle blink reflex in males was significantly heritable (49%), whereas in females, variance was explained primarily by shared environmental factors (53%) and non-shared environmental factors (41%). Heritability of affect modified startle (AMS) was found to be negligible in both males and females. These results suggest sex differences in the etiology of startle reactivity, while questioning the utility of the startle paradigm for understanding the genetic basis of emotional processing.

Hypnotizability and Placebo Analgesia in Waking and Hypnosis as Modulators of Auditory Startle Responses in Healthy Women: An ERP Study

We evaluated the influence of hypnotizability, pain expectation, placebo analgesia in waking and hypnosis on tonic pain relief. We also investigated how placebo analgesia affects somatic responses (eye blink) and N100 and P200 waves of event-related potentials (ERPs) elicited by auditory startle probes. Although expectation plays an important role in placebo and hypnotic analgesia, the neural mechanisms underlying these treatments are still poorly understood. We used the cold cup test (CCT) to induce tonic pain in 53 healthy women. Placebo analgesia was initially produced by manipulation, in which the intensity of pain induced by the CCT was surreptitiously reduced after the administration of a sham analgesic cream. Participants were then tested in waking and hypnosis under three treatments: (1) resting (Baseline); (2) CCT-alone (Pain); and (3) CCT plus placebo cream for pain relief (Placebo). For each painful treatment, we assessed pain and distress ratings, eye blink responses, N100 and P200 amplitudes. We used LORETA analysis of N100 and P200 waves, as elicited by auditory startle, to identify cortical regions sensitive to pain reduction through placebo and hypnotic analgesia. Higher pain expectation was associated with higher pain reductions. In highly hypnotizable participants placebo treatment produced significant reductions of pain and distress perception in both waking and hypnosis condition. P200 wave, during placebo analgesia, was larger in the frontal left hemisphere while placebo analgesia, during hypnosis, involved the activity of the left hemisphere including the occipital region. These findings demonstrate that hypnosis and placebo analgesia are different processes of top-down regulation. Pain reduction was associated with larger EMG startle amplitudes, N100 and P200 responses, and enhanced activity within the frontal, parietal, and anterior and posterior cingulate gyres. LORETA results showed that placebo analgesia modulated pain-responsive areas known to reflect the ongoing pain experience.

Classical Conditioning and Modification of the Rabbit's (Oryctolagus Cuniculus) Unconditioned Nictitating Membrane Response

A fundamental tenet of behavior is that a reflex is automatic, unconscious, involuntary, and relatively invariant. However, we have discovered that a reflex can change dramatically as a function of classical conditioning, and this change can be demonstrated independently of the conditioned stimulus. We have termed this phenomenon conditioning-specific reflex modification (CRM). Although the behavioral laws and neural substrates of nonassociative reflex changes have been identified, the behavioral laws and neural substrates of CRM are only now being revealed. For example, CRM is similar to classical conditioning in that (a) it is a function of both the strength of conditioning and (b) the strength of the unconditioned stimulus, (c) it can be extinguished, and (d) it can be generalized from one unconditioned stimulus to another. Preliminary analysis suggests that CRM may have some features in common with post-traumatic stress disorder and may provide insights into treatment of the disorder.

Deep Assessment: A Novel Framework for Improving the Care of People with Very Advanced Alzheimer's Disease

Best practice in understanding and caring for people with advanced Alzheimer's disease presents extraordinary challenges. Their severe and deteriorating cognitive impairments are such that carers find progressive difficulty in authentically ascertaining and responding to interests, preferences, and needs. Deep assessment, a novel multifaceted framework drawn from research into the experiences of others with severe cognitive impairments, has potential to empower carers and other support professionals to develop an enhanced understanding of people with advanced Alzheimer's disease and so deliver better calibrated care in attempts to maximize quality of life. Deep assessment uses a combination of techniques, namely, Behaviour State Observation, Triangulated Proxy Reporting, and Startle Reflex Modulation Measurement, to deliver a comprehensive and deep assessment of the inner states (awareness, preferences, likes, and dislikes) of people who cannot reliably self-report. This paper explains deep assessment and its current applications. It then suggests how it can be applied to people with advanced Alzheimer's disease to develop others' understanding of their inner states and to help improve their quality of life. An illustrative hypothetical vignette is used to amplify this framework. We discuss the potential utility and efficacy of this technique for this population and we also propose other human conditions that may benefit from research using a deep assessment approach.

Variants Near CCK Receptors are Associated With Electrophysiological Responses to Pre-pulse Startle Stimuli in a Mexican American Cohort

Neurophysiological measurements of the response to pre-pulse and startle stimuli have been suggested to represent an important endophenotype for both substance dependence and other select psychiatric disorders. We have previously shown, in young adult Mexican Americans (MA), that presentation of a short delay acoustic pre-pulse, prior to the startle stimuli can elicit a late negative component at about 400 msec (N4S), in the event-related potential (ERP), recorded from frontal cortical areas. In the present study, we investigated whether genetic factors associated with this endophenotype could be identified. The study included 420 (age 18-30 years) MA men (n = 170), and women (n = 250). DNA was genotyped using an Affymetrix Axiom Exome1A chip. An association analysis revealed that the CCKAR and CCKBR (cholecystokinin A and B receptor) genes each had a nearby variant that showed suggestive significance with the amplitude of the N4S component to pre-pulse stimuli. The neurotransmitter cholecystokinin (CCK), along with its receptors, CCKAR and CCKBR, have been previously associated with psychiatric disorders, suggesting that variants near these genes may play a role in the pre-pulse/startle response in this cohort.

Presidential Address 2014: The more-or-less interrupting effects of the startle response

The startle response can be used to assess differences in a variety of ongoing processes across species, sensory modalities, ages, clinical conditions, and task conditions. Startle serves defensive functions, but it may also interrupt ongoing processes, allowing for a reorientation of resources to potential danger. A wealth of research suggests that prepulse inhibition of startle (PPI) is an indicator of the protection of the processing of the prepulse from interruption by the startle response. However, protection against interruption by suppressing the startle response may extend to many other ongoing processes, including the higher processing of the startle stimulus itself. Proof of protection would require measuring ongoing processing, which has very rarely been reported. The idea that PPI represents the protection of the earliest stages of prepulse processing can be challenged, since those earliest stages are completed by the time the startle response occurs, so they are not threatened by interruption and need not be protected. The conception of low PPI as indicative of a "gating deficit" in schizophrenia should be made with caution, since low PPI is seen in some, but not all studies of schizophrenia, but also in a range of other disorders and conditions. Finally, startle is often used to probe ongoing processes, but the response also modifies those processes, interrupting some processes but perhaps facilitating others. A deeper understanding of the function of startle and PPI might improve the precision of application of these measures in the investigation of a range of research topics.

Affective Modulation of Brain and Autonomic Responses in Patients With Fibromyalgia

OBJECTIVES

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.

METHODS

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.

RESULTS

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).

CONCLUSIONS

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.

Effects of anxiety sensitivity and expectations on the modulation of the startle eyeblink response during a caffeine challenge

RATIONALE

The way in which the tendency to fear somatic arousal sensations (anxiety sensitivity), in interaction with the created expectations regarding arousal induction, might affect defensive responding to a symptom provocation challenge is not yet understood.

OBJECTIVES

The present study investigated the effect of anxiety sensitivity on autonomic arousal, startle eyeblink responses, and reported arousal and alertness to expected vs. unexpected caffeine consumption.

METHODS

To create a match/mismatch of expected and experienced arousal, high and low anxiety sensitive participants received caffeine vs. no drug either mixed in coffee (expectation of arousal induction) or in bitter lemon soda (no expectation of arousal induction) on four separate occasions. Autonomic arousal (heart rate, skin conductance level), respiration (end-tidal CO2, minute ventilation), defensive reflex responses (startle eyeblink), and reported arousal and alertness were recorded prior to, immediately and 30 min after beverage ingestion.

RESULTS

Caffeine increased ventilation, autonomic arousal, and startle response magnitudes. Both groups showed comparable levels of autonomic and respiratory responses. The startle eyeblink responses were decreased when caffeine-induced arousal occurred unexpectedly, e.g., after administering caffeine in bitter lemon. This effect was more accentuated in high anxiety sensitive persons. Moreover, in high anxiety sensitive persons, the expectation of arousal (coffee consumption) led to higher subjective alertness when administering caffeine and increased arousal even if no drug was consumed.

CONCLUSIONS

Unexpected symptom provocation leads to increased attention allocation toward feared arousal sensations in high anxiety sensitive persons. This finding broadens our understanding of modulatory mechanisms in defensive responding to bodily symptoms.

Contrasting effect of prepulse signals on performance of Toxoplasma-infected and Toxoplasma-free subjects in an acoustic reaction times test

Background

About 30% of people on Earth have latent toxoplasmosis. Infected subjects do not express any clinical symptoms, however, they carry dormant stages of parasite Toxoplasma for the rest of their life. This form of toxoplasmosis is mostly considered harmless, however, recent studies showed its specific effects on physiology, behaviour and its associations with various diseases, including psychiatric disorders such as schizophrenia. Individuals who suffer from schizophrenia have about 2.7 times higher prevalence of Toxoplasma-seropositivity than controls, which suggests that some traits characteristic of schizophrenic patients, including the sex difference in schizophrenia onset, decrease of grey matter density in specific brain areas and modification of prepulse inhibition of startle reaction could in fact be caused by toxoplasmosis for those patients who are Toxoplasma-seropositive.

Methodology/Principal Findings

We measured the effect of prepulse inhibition/facilitation of the startle reaction on reaction times. The students, 170 women and 66 men, were asked to react as quickly as possible to a startling acoustic signal by pressing a computer mouse button. Some of the startling signals were without the prepulse, some were 20 msec. preceded by a short (20 msec.) prepulse signal of lower intensity. Toxoplasma-seropositive subjects had longer reaction times than the controls. Acoustic prepulse shorted the reaction times in all subjects. This effect of prepulse on reaction times was stronger in male subjects and increased with the duration of infection, suggesting that it represented a cumulative effect of latent toxoplasmosis, rather than a fading out after effect of past acute toxoplasmosis.

Conclusions

Different sensitivity of Toxoplasma-seropositive and Toxoplasma-seronegative subjects on effect of prepulses on reaction times (the toxoplasmosis-prepulse interaction) suggested, but of course did not prove, that the alternations of prepulse inhibition of startle reaction observed in schizophrenia patients probably joined the list of schizophrenia symptoms that are in fact caused by latent toxoplasmosis.

Methylphenidate and desipramine combined treatment improves PTSD symptomatology in a rat model

Antidepressant medication constitutes the first line pharmacological treatment for posttraumatic stress disorder (PTSD), however, because many patients display no beneficial drug effects it has been suggested that combinations of antidepressants with additional drugs may be necessary. The defining symptoms of PTSD include re-experiencing, avoidance and hyperarousal. In addition, PTSD patients were shown to become easily distracted and often suffer from poor concentration together with indications of comorbidity with attention-deficit hyperactivity disorder (ADHD). Methylphenidate (MPH) is the most common and effective drug treatment for ADHD, thus we aimed to investigate the effects of MPH treatment, by itself or in combination with the antidepressants fluoxetine (FLU) or desipramine (DES). We modified an animal model of PTSD by exposing rats to chronic stress and evaluating the subsequent development of behavioral PTSD-like symptoms, as well as the effects on proinflammatory cytokines, which were implicated in PTSD. We report that while FLU or DES had a beneficial effect on avoidance and hyperarousal symptoms, MPH improved all three symptoms. Moreover, the combination of MPH with DES produced the most dramatic beneficial effects. Serum levels of interleukin-1β (IL-1β) and IL-6 were elevated in the PTSD-like group compared with the control group, and were decreased by MPH, FLU, DES or the combination drug treatments, with the combination of DES+MPH producing the most complete rescue of the inflammatory response. Considering the versatile symptoms of PTSD, our results suggest a new combined treatment for PTSD comprising the antidepressant DES and the psychostimulant MPH.

The impact of sex and menstrual cycle on the acoustic startle response

Sex differences in fear and anxiety have been widely reported although results are not entirely consistent depending on measures used. Also, a possible influence of the menstrual cycle is often not taken into account, and effect sizes are not always discussed. In a sample of healthy young adults (n=111 women without hormonal contraceptives and n=107 men) the acoustic startle response (ASR) and emotional ASR modulation were analysed. We found no significant effect of sex on ASR (p=.269) but a significant effect of menstrual cycle (p=.027, η(2)=0.105). Compared to men, women showed increased ASR during the late luteal phase probably reflecting elevated negative emotionality, and during ovulation which, however, might be due to increased auditory sensitivity and changes in general CNS arousal. Neither sex nor menstrual cycle affected startle modulation. Thus, at least in young adults, menstrual cycle but not sex per se appears to contribute significantly to ASR variance.

Relations between trait impulsivity, behavioral impulsivity, physiological arousal, and risky sexual behavior among young men

The current study examined how impulsivity-related traits (negative urgency, sensation seeking, and positive urgency), behavioral measures of risk taking and reward seeking, and physiological reactivity related to three different risky sexual behaviors in sexually active undergraduate men (N = 135). Regression analyses indicated that sensation seeking and behavioral risk-taking predicted unique variance in number of sexual partners. These findings suggest that, for young men, acquisition of new partners is associated with need for excitement and reward and willingness to take risks to meet those needs. Sensation seeking, behavioral risk-taking, and skin conductance reactivity to arousing stimuli was related to ever having engaged in sex with a stranger, indicating that, for men, willingness to have sex with a stranger is related not only to the need for excitement and risk-taking but also with innate responsiveness to arousing environmental triggers. In contrast, regression analyses indicated that young men who were impulsive in the context of negative emotions were less likely to use condoms, suggesting that emotion-based impulsivity may be an important factor in negligent prophylactic use. This study adds to the current understanding of the divergence between the correlates of risky sexual behaviors and may lend utility to the development of individualized HIV prevention programming.

The emotional and attentional impact of exposure to one's own body in bulimia nervosa: a physiological view

Background

Body dissatisfaction is the most relevant body image disturbance in bulimia nervosa (BN). Research has shown that viewing one's own body evokes negative thoughts and emotions in individuals with BN. However, the psychophysiological mechanisms involved in this negative reaction have not yet been clearly established. Our aim was to examine the emotional and attentional processes that are activated when patients with BN view their own bodies.

Method

We examined the effects of viewing a video of one's own body on the physiological (eye-blink startle, cardiac defense, and skin conductance) and subjective (pleasure, arousal, and control ratings) responses elicited by a burst of 110 dB white noise of 500 ms duration. The participants were 30 women with BN and 30 healthy control women. The experimental task consisted of two consecutive and counterbalanced presentations of the auditory stimulus preceded, alternatively, by a video of the participant's own body versus no such video.

Results

The results showed that, when viewing their own bodies, women with BN experienced (a) greater inhibition of the startle reflex, (b) greater cardiac acceleration in the first component of the defense reaction, (c) greater skin conductance response, and (d) less subjective pleasure and control combined with greater arousal, compared with the control participants.

Conclusion

Our findings suggest that, for women with BN, peripheral-physiological responses to self-images are dominated by attentional processes, which provoke an immobility reaction caused by a dysfunctional negative response to their own body.

Prepulse inhibition of the acoustic startle reflex in high functioning autism

Background

High functioning autism is an autism spectrum disorder that is characterized by deficits in social interaction and communication as well as repetitive and restrictive behavior while intelligence and general cognitive functioning are preserved. According to the weak central coherence account, individuals with autism tend to process information detail-focused at the expense of global form. This processing bias might be reflected by deficits in sensorimotor gating, a mechanism that prevents overstimulation during the transformation of sensory input into motor action. Prepulse inhibition is an operational measure of sensorimotor gating, which indicates an extensive attenuation of the startle reflex that occurs when a startling pulse is preceded by a weaker stimulus, the prepulse.

Methods

In the present study, prepulse inhibition of acoustic startle was compared between 17 adults with high functioning autism and 17 sex-, age-, and intelligence-matched controls by means of electromyography.

Results

Results indicate that participants with high functioning autism exhibited significantly higher startle amplitudes than the control group. However, groups did not differ with regard to PPI or habituation of startle.

Discussion

These findings challenge the results of two previous studies that reported prepulse inhibition deficits in high-functioning autism and suggest that sensorimotor gating is only impaired in certain subgroups with autism spectrum disorder.

Effect of seated trunk posture on eye blink startle and subjective experience: comparing flexion, neutral upright posture, and extension of spine

Postures are known to be able to affect emotion and motivation. Much less is known about whether (affective) modulation of eye blink startle occurs following specific postures. The objective of the current study was to explore this. Participants in the present study were requested to assume three different sitting postures: with the spine flexed (slouched), neutral upright, and extended. Each posture was assumed for four minutes, and was followed by the administration of brief self-report questionnaires before proceeding to the next posture. The same series of postures and measures were repeated prior to ending the experiment. Results indicate that, relative to the other postures, the extended sitting posture was associated with an increased startle, was more unpleasant, arousing, had smaller levels of dominance, induced more discomfort, and was perceived as more difficult. The upright and flexed sitting postures differed in the level of self-reported positive affect, but not in eye blink startle amplitudes.

Habituation in acoustic startle reflex: individual differences in personality

This study analyzed the relationship of individual differences in personality with habituation in the acoustic startle response (ASR). Data from nine trials in ASR to white noise bursts and a personality questionnaire based on the alternative big five personality approach were modelled with a latent growth curve (LCM) including intercept and slope habituation growth factors. There was a negative correlation between the intercept and slope, indicating that individuals with higher initial ASR levels had also a more pronounced and faster decrease in the ASR. Contrary to expectations, Extraversion and Sensation Seeking did not relate with habituation in ASR. Neuroticism and Aggressiveness related asymmetrically with the habituation rate in ASR. Higher levels of Neuroticism were related with faster habituation, whereas higher levels of Aggressiveness were related with slower habituation. Further studies with the LCM should be undertaken to clarify in a greater extent the association of personality with habituation in ASR.

Arousal and Habituation Effects (Excitability) on Startle Responses to the International Affective Picture Systems (IAPS)

The magnitude and habituation of startle reflex responses have been used to evaluate the excitability of the neural structures involved in this psychophysiological response. We analyzed the magnitude and habituation responses to startle reflex probes in 112 women. Results confirmed the modulation of eyeblink reflex by affective valence for arousing (F = 34.79, p < .001), but not for nonarousing pictures (F = 1.08, ns). Our results indicate that there is a linear adjustment for habituation in all picture groups, except for arousing unpleasant pictures where there is a quadratic adjustment that could be due to initial sensitization followed by the subsequent habituation. Multiple linear regression analysis revealed that the startle magnitude was partially determined by arousal and startle presentation order. In conclusion, our results emphasize the usefulness of arousing pictures to study startle reflex response and show evidence of different response mechanisms for pleasant and unpleasant pictures conditions.