The effects of contextual threat and anxiety on affective startle modulation

Effects of startle on cognitive performance and physiological activity revealed by fNIRS and thermal imaging

Sudden and threatening stimuli can trigger a startle reflex, a stereotyped physiological response that may lead to a brief cognitive incapacitation. Better understanding this reaction would be beneficial to safety-critical occupational domains. We characterized some physiological correlates of the startle response while participants completed a difficult task (Toulouse N-back task) tapping executive functions. During the task, loud and threatening sounds were presented unpredictably to trigger a startle reflex. Brain activity and facial skin temperature were measured in 34 participants using functional near-infrared spectroscopy (fNIRS) and functional infrared thermal imaging (fITI), respectively. In the high difficulty condition, participants were generally less efficient, but their performance improved slightly following startle in the high difficulty condition. Brain activity in the right prefrontal cortex was also higher following startle, potentially reflecting a compensatory overactivation to sustain performance. Interestingly, higher trait-anxiety was associated with lower task performance, still following startle in the high difficulty condition. Finally, we found a decrease in temperature of the right eye and right cheek as well as an increase in the nose temperature following startle. These results underscore the complexity of startle-induced cognitive and physiological dynamics, which may have implications for occupational settings where managing sudden stressors is crucial.

Threat of shock increases distractor susceptibility during the short-term maintenance of visual information

Elevated arousal in anxiety is thought to affect attention control. To test this, we designed a visual short-term memory (VSTM) task to examine distractor suppression during periods of threat and no-threat. We hypothesized that threat would impair performance when subjects had to filter out large numbers of distractors. The VSTM task required subjects to attend to one array of squares while ignoring a separate array. The number of target and distractor squares varied systematically, with high (four squares) and low (two squares) target and distractor conditions. This study comprised two separate experiments. Experiment 1 used startle responses and white noise as to directly measure threat-induced anxiety. Experiment 2 used BOLD to measure brain responses. For Experiment 1, subjects showed significantly larger startle responses during threat compared to safe period, supporting the validity of the threat manipulation. For Experiment 2, we found that accuracy was affected by threat, such that the distractor load negatively impacted accuracy only in the threat condition. We also found threat-related differences in parietal cortex activity. Overall, these findings suggest that threat affects distractor susceptibility, impairing filtering of distracting information. This effect is possibly mediated by hyperarousal of parietal cortex during threat.

Threat of shock increases distractor susceptibility during the short-term maintenance of visual information

BACKGROUND

Work on anxiety related attention control deficits suggests that elevated arousal impacts the ability to filter out distractors. To test this, we designed a task to look at distractor suppression during periods of threat. We administered trials of a visual short-term memory (VSTM) task, during periods of unpredictable threat, and hypothesized that threat would impair performance during trials where subjects were required to filter out large numbers of distractors.

METHOD

Experiment 1 involved fifteen healthy participants who completed one study visit. They performed four runs of a VSTM task comprising 32 trials each. Participants were presented with an arrow indicating left or right, followed by an array of squares. They were instructed to remember the target side and disregard the distractors on the off-target side. A subsequent target square was shown, and participants indicated whether it matched one of the previously presented target squares. The trial conditions included 50% matches and 50% mismatches, with an equal distribution of left and right targets. The number of target and distractor squares varied systematically, with high (4 squares) and low (2 squares) target and distractor conditions. Trials alternated between periods of safety and threat, with startle responses recorded using electromyography (EMG) following white noise presentations. Experiment 2 involved twenty-seven healthy participants who completed the same VSTM task inside an MRI scanner during a single study visit. The procedure mirrored that of Experiment 1, except for the absence of white noise presentations.

RESULTS

For Experiment 1, subjects showed significantly larger startle responses during threat compared to safe period, supporting the validity of the threat manipulation. However, results suggested that the white noise probes interfered with performance. For Experiment 2, we found that both accuracy was affected by threat, such that distractor load negatively impacted accuracy only in the threat condition.

CONCLUSION

Overall, these findings suggest that threat affects distractor susceptibility during the short-term maintenance of visual information. The presence of threat makes it more difficult to filter out distracting information. We believe that this is related to hyperarousal of parietal cortex, which has been observed during unpredictable threat.

Incidental learning of faces during threat: No evidence for enhanced physiological responses to former threat identities

Remembering an unfamiliar person and the contextual conditions of that encounter is important for adaptive future behavior, especially in a potentially dangerous situation. Initiating defensive behavior in the presence of former dangerous circumstances can be crucial. Recent studies showed selective electrocortical processing of faces that were previously seen in a threat context compared to a safety context, however, this was not reflected in conscious recognition performance. Here, we investigated whether previously seen threat-faces, that could not be remembered, were capable to activate defensive psychophysiological response systems. During an encoding phase, 50 participants with low to moderate levels of anxiety viewed 40 face pictures with neutral expressions (6 s each), without an explicit learning instruction (incidental learning task). Each half of the faces were presented with contextual background colors that signaled either threat-of-shock or safety. In the recognition phase, all old and additional new faces (total of 60) were presented intermixed without context information. Participants had to decide whether a face was new or had been presented previously in a threatening or a safe context. Results show moderate face recognition independent of context conditions. Startle reflex and skin conductance responses (SCR) were more pronounced for threat compared to safety during encoding. For SCR, this differentiation was enhanced with higher levels of depression and anxiety. There were no differential startle reflex or SCR effects during recognition. From a clinical perspective, these findings do not support the notion that perceptual biases and physiological arousal directly relate to threat-associated identity recognition deficits in healthy and clinical participants with anxiety and trauma-related disorders.

Assessing the role of the amygdala in fear of pain: Neural activation under threat of shock

INTRODUCTION

The DSM-5 explicitly states that the neural system model of specific phobia is centered on the amygdala. However, this hypothesis is predominantly supported by human studies on animal phobia, whereas visual cuing of other specific phobias, such as dental fear, do not consistently show amygdala activation. Considering that fear of anticipated pain is one of the best predictors of dental phobia, the current study investigated neural and autonomic activity of pain anticipation in individuals varying in the degree of fear of dental pain.

METHOD

Functional brain activity (fMRI) was measured in women (n = 31) selected to vary in the degree of self-reported fear of dental pain when under the threat of shock, in which one color signaled the possibility of receiving a painful electric shock and another color signaled safety.

RESULTS

Enhanced functional activity during threat, compared to safety, was found in regions including anterior insula and anterior/mid cingulate cortex. Importantly, threat reactivity in the anterior insula increased as reported fear of pain increased and further predicted skin conductance changes during pain anticipation.

LIMITATIONS

The sample was comprised of women.

CONCLUSIONS

Individual differences in fear of pain vary with activation in the anterior insula, rather than with the amygdala, indicating that fear is not uniquely associated with amygdala activation. Whereas coping techniques such as emotion regulation have been found to vary with activation in a frontal-amygdala circuit when confronted with visual cues, precision psychiatry may need to target specific brain circuits to diagnose and treat different types of specific phobia.

Aversive perception in a threat context: Separate and independent neural activation

Unpleasant, compared to neutral, scenes reliably prompt enhanced functional brain activity in the amygdala and inferotemporal cortex. Considering data from psychophysiological studies in which defensive reactivity is further enhanced when viewing unpleasant scenes under threat of shock (compared to safety), the current study investigates functional activation in the amygdala-inferotemporal circuit when unpleasant (or neutral) scenes are viewed under threat of shock or safety. In this paradigm, a cue signaling threat or safety was presented in conjunction with either an unpleasant or neutral picture. Replicating previous studies, unpleasant, compared to neutral, scenes reliably enhanced activation in the amygdala and inferotemporal cortex. Functional activity in these regions, however, did not differ whether scenes were presented in a context threatening shock exposure, compared to safety, which instead activated regions of the anterior insula and cingulate cortex. Taken together, the data support a view in which neural regions activated in different defensive situations act independently.

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.

Verbal instructions override the meaning of facial expressions

Psychological research has long acknowledged that facial expressions can implicitly trigger affective psychophysiological responses. However, whether verbal information can alter the meaning of facial emotions and corresponding response patterns has not been tested. This study examined emotional facial expressions as cues for instructed threat-of-shock or safety, with a focus on defensive responding. In addition, reversal instructions were introduced to test the impact of explicit safety instructions on fear extinction. Forty participants were instructed that they would receive unpleasant electric shocks, for instance, when viewing happy but not angry faces. In a second block, instructions were reversed (e.g., now angry faces cued shock). Happy, neutral, and angry faces were repeatedly presented, and auditory startle probes were delivered in half of the trials. The defensive startle reflex was potentiated for threat compared to safety cues. Importantly, this effect occurred regardless of whether threat was cued by happy or angry expressions. Although the typical pattern of response habituation was observed, defense activation to newly instructed threat cues remained significantly enhanced in the second part of the experiment, and it was more pronounced in more socially anxious participants. Thus, anxious individuals did not exhibit more pronounced defense activation compared to less anxious participants, but their defense activation was more persistent.

Startle reflex modulation during threat of shock and "threat" of reward

During threat of shock, the startle reflex is potentiated, suggesting modulation by defensive mobilization. To determine whether startle potentiation is specific to aversive anticipation, startle reflexes were measured in the context of either aversive or appetitive anticipation in a between-subject study. Participants wore a device on the wrist that could deliver electrical shock (n = 49), or vibrotactile stimulation indicating monetary reward (n = 48). Cues signaling "threat" or "safe" periods were presented alone, or accompanied by presentation of affective and neutral pictures on half of the trials. Results indicated that the startle reflex was significantly potentiated when anticipating either shock or reward, compared to safe periods, both when no picture was presented, as well as during picture viewing. The difference between threat and safety in both reflex magnitude and skin conductance changes was larger for those anticipating shock, suggesting that the aversive context was more motivationally engaging. The pattern of reflex modulation as a function of picture valence varied under threat and safety, but was identical in the shock and reward groups, consistent with a hypothesis that anticipation of either aversive or appetitive events prompts heightened perceptual vigilance, potentiating the acoustic startle reflex.

Reducing State Anxiety Using Working Memory Maintenance

The purpose of this protocol is to explain how to examine the relationship between working memory processes and anxiety by combining the Sternberg Working Memory (WM) and the threat of shock paradigms. In the Sternberg WM paradigm, subjects are required to maintain a series of letters in the WM for a brief interval and respond by identifying whether the position of a given letter in the series matches a numerical prompt. In the threat of shock paradigm, subjects are exposed to alternating blocks where they are either at risk of receiving unpredictable presentations of a mild electric shock or are safe from the shock. Anxiety is probed throughout the safe and threat blocks using the acoustic startle reflex, which is potentiated under threat (Anxiety-Potentiated Startle (APS)). By conducting the Sternberg WM paradigm during the threat of shock and probing the startle response during either the WM maintenance interval or the intertrial interval, it is possible to determine the effect of WM maintenance on APS.

Fear Spreading Across Senses: Visual Emotional Events Alter Cortical Responses to Touch, Audition, and Vision

Attention and perception are potentiated for emotionally significant stimuli, promoting efficient reactivity and survival. But does such enhancement extend to stimuli simultaneously presented across different sensory modalities? We used functional magnetic resonance imaging in humans to examine the effects of visual emotional signals on concomitant sensory inputs in auditory, somatosensory, and visual modalities. First, we identified sensory areas responsive to task-irrelevant tones, touches, or flickers, presented bilaterally while participants attended to either a neutral or a fearful face. Then, we measured whether these responses were modulated by the emotional content of the face. Sensory responses in primary cortices were enhanced for auditory and tactile stimuli when these appeared with fearful faces, compared with neutral, but striate cortex responses to the visual stimuli were reduced in the left hemisphere, plausibly as a consequence of sensory competition. Finally, conjunction and functional connectivity analyses identified 2 distinct networks presumably responsible for these emotional modulatory processes, involving cingulate, insular, and orbitofrontal cortices for the increased sensory responses, and ventrolateral prefrontal cortex for the decreased sensory responses. These results suggest that emotion tunes the excitability of sensory systems across multiple modalities simultaneously, allowing the individual to adaptively process incoming inputs in a potentially threatening environment.

Anxiety Patients Show Reduced Working Memory Related dlPFC Activation During Safety and Threat

BACKGROUND

Anxiety patients exhibit deficits in cognitive tasks that require prefrontal control of attention, including those that tap working memory (WM). However, it is unclear whether these deficits reflect threat-related processes or symptoms of the disorder. Here, we distinguish between these hypotheses by determining the effect of shock threat versus safety on the neural substrates of WM performance in anxiety patients and healthy controls.

METHODS

Patients, diagnosed with generalized and/or social anxiety disorder, and controls performed blocks of an N-back WM task during periods of safety and threat of shock. We recorded blood-oxygen-level dependent (BOLD) activity during the task, and investigated the effect of clinical anxiety (patients vs. controls) and threat on WM load-related BOLD activation.

RESULTS

Behaviorally, patients showed an overall impairment in both accuracy and reaction time compared to controls, independent of threat. At the neural level, patients showed less WM load-related activation in the dorsolateral prefrontal cortex, a region critical for cognitive control. In addition, patients showed less WM load-related deactivation in the ventromedial prefrontal cortex and posterior cingulate cortex, which are regions of the default mode network. Most importantly, these effects were not modulated by threat.

CONCLUSIONS

This work suggests that the cognitive deficits seen in anxiety patients may represent a key component of clinical anxiety, rather than a consequence of threat.

Effect of trait anxiety on cognitive test performance in adolescents with and without attention-deficit/hyperactivity disorder

INTRODUCTION

Attention-deficit/hyperactivity disorder (ADHD) and anxiety are frequently comorbid disorders associated with different types of abnormal performance on neuropsychological tests. Although some studies have shown that comorbid anxiety alters ADHD test performance, results inconsistently show both improvements and worsening of different abilities, with failures to replicate across different anxiety disorders. Alternatively, trait anxiety may reflect a more stable influence on ADHD test performance than various diagnosable anxiety disorders.

METHOD

To better understand the possible enhancing or deleterious effects of anxiety on ADHD cognitive impairments, this study examined the effect of individual differences in trait anxiety measured by the Multidimensional Anxiety Scale for Children (MASC) on a battery of computerized, rapid-performance tests measuring attention and impulsivity-related performance in 98 Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition (DSM-IV) Combined-Subtype ADHD adolescents and 123 healthy controls. It was hypothesized that trait anxiety would attenuate response inhibition and attention deficits in ADHD.

RESULTS

ADHD-diagnosed adolescents with higher trait anxiety performed better on indices of sustained attention, reaction time, and motor variability, and had altered overall test-performance strategy, while response inhibition was affected in both ADHD and non-ADHD.

CONCLUSIONS

This study provides the first evidence that pathological levels of anxiety are not needed to see differences in ADHD neuropsychological test performance. Instead, mildly elevated trait anxiety confers a protective influence by reducing the degree of impairment seen in ADHD. These findings suggest that better performing ADHD adolescents might have optimized levels of cortical arousal, and raise new questions about how best to identify the neurobiological substrates responsible for the beneficial effects.

Sustained attention in context conditioning: Evidence from steady-state VEPs

In classical fear conditioning an aversive event is paired repeatedly with a predictive stimulus, which later elicits fear. Repeated presentation of an aversive event in the absence of a predictive cue however may induce anxiety, and the context may gain a threatening value. As such conditioned anxiety can be considered a sustained reaction compared to phasic fear, it would be interesting to track continuous cortical responses during context conditioning. The present study realized a differential context conditioning paradigm and assessed sustained cortical activations to the threatening and the safe context and how neutral cues are processed within both contexts. Two pictures of different office rooms presented for 20s served as contexts. One room became associated with an unpleasant noise that was presented unpredictably (CTX+) while the other office (CTX-) was never associated with this unpleasant noise. After acquisition, a social agent or an object was presented as a distractor in both contexts. Cortical activations in response to contexts and distractors were assessed separately by steady-state visually evoked potentials (ssVEPs) using frequency tagging. Results revealed enhanced ssVEP-amplitudes for CTX+ compared to CTX- in a lateral occipital cluster during acquisition. Similarly, CTX+ elicited higher ssVEP-amplitudes during the test phase, and these context conditioning effects were not reduced by the simultaneous presentation of novel distractors. These results indicate that context conditioning was successfully implemented and that the anxiety context received facilitated cortical processing across the whole viewing time. We conclude that threatening contexts capture attention over a longer period of time, and are immune to distraction by new objects.

BDNFval66met affects neural activation pattern during fear conditioning and 24 h delayed fear recall

Brain-derived neurotrophic factor (BDNF), the most abundant neutrophin in the mammalian central nervous system, is critically involved in synaptic plasticity. In both rodents and humans, BDNF has been implicated in hippocampus- and amygdala-dependent learning and memory and has more recently been linked to fear extinction processes. Fifty-nine healthy participants, genotyped for the functional BDNFval66met polymorphism, underwent a fear conditioning and 24h-delayed extinction protocol while skin conductance and blood oxygenation level dependent (BOLD) responses (functional magnetic resonance imaging) were acquired. We present the first report of neural activation pattern during fear acquisition 'and' extinction for the BDNFval66met polymorphism using a differential conditioned stimulus (CS)+ > CS- comparison. During conditioning, we observed heightened allele dose-dependent responses in the amygdala and reduced responses in the subgenual anterior cingulate cortex in BDNFval66met met-carriers. During early extinction, 24h later, we again observed heightened responses in several regions ascribed to the fear network in met-carriers as opposed to val-carriers (insula, amygdala, hippocampus), which likely reflects fear memory recall. No differences were observed during late extinction, which likely reflects learned extinction. Our data thus support previous associations of the BDNFval66met polymorphism with neural activation in the fear and extinction network, but speak against a specific association with fear extinction processes.