Neural correlates of fear: insights from neuroimaging

Fear anticipates a challenge to one's well-being and is a reaction to the risk of harm. The expression of fear in the individual is a constellation of physiological, behavioral, cognitive, and experiential responses. Fear indicates risk and will guide adaptive behavior, yet fear is also fundamental to the symptomatology of most psychiatric disorders. Neuroimaging studies of normal and abnormal fear in humans extend knowledge gained from animal experiments. Neuroimaging permits the empirical evaluation of theory (emotions as response tendencies, mental states, and valence and arousal dimensions), and improves our understanding of the mechanisms of how fear is controlled by both cognitive processes and bodily states. Within the human brain, fear engages a set of regions that include insula and anterior cingulate cortices, the amygdala, and dorsal brain-stem centers, such as periaqueductal gray matter. This same fear matrix is also implicated in attentional orienting, mental planning, interoceptive mapping, bodily feelings, novelty and motivational learning, behavioral prioritization, and the control of autonomic arousal. The stereotyped expression of fear can thus be viewed as a special construction from combinations of these processes. An important motivator for understanding neural fear mechanisms is the debilitating clinical expression of anxiety. Neuroimaging studies of anxiety patients highlight the role of learning and memory in pathological fear. Posttraumatic stress disorder is further distinguished by impairment in cognitive control and contextual memory. These processes ultimately need to be targeted for symptomatic recovery. Neuroscientific knowledge of fear has broader relevance to understanding human and societal behavior. As yet, only some of the insights into fear, anxiety, and avoidance at the individual level extrapolate to groups and populations and can be meaningfully applied to economics, prejudice, and politics. Fear is ultimately a contagious social emotion

Preliminary report: parasympathetic tone links to functional brain networks during the anticipation and experience of visceral pain

Medical Research Council project grant - Medical Research Council Grant Number - MGAB1A1

Assessment of threat and negativity bias in virtual reality

Negativity bias, i.e., tendency to respond strongly to negative stimuli, can be captured via behavioural and psychophysiological responses to potential threat. A virtual environment (VE) was created at room-scale wherein participants traversed a grid of ice blocks placed 200 m above the ground. Threat was manipulated by increasing the probability of encountering ice blocks that disintegrated and led to a virtual fall. Participants interacted with the ice blocks via sensors placed on their feet. Thirty-four people were recruited for the study, who were divided into High (HN) and Low (LN) Neuroticism groups. Movement data were recorded alongside skin conductance level and facial electromyography from the corrugator supercilii and zygomaticus major. Risk-averse behaviours, such as standing on ‘safe’ blocks and testing blocks prior to movement, increased when threat was highest. HN individuals exhibited more risk-averse behaviour than the LN group, especially in the presence of high threat. In addition, activation of the corrugator muscle was higher for HN individuals in the period following a movement to an ice block. These findings are discussed with respect to the use of room-scale VE as a protocol for emotion induction and measuring trait differences in negativity bias within VR

Inferences of Others' Competence Reduces Anticipation of Pain When under Threat

On a daily basis, we place our lives in the hands of strangers. From dentists to pilots, we make inferences about their competence to perform their jobs and consequently to keep us from harm. Here we explore whether the perceived competence of others can alter one's anticipation of pain. In two studies, participants (Receivers) believed their chances of experiencing an aversive stimulus were directly dependent on the performance of another person (Players). We predicted that perceiving the Players as highly competent would reduce Receivers' anxiety when anticipating the possibility of an electric shock. Results confirmed that high competence ratings consistently corresponded with lower reported anxiety, and complementary fMRI data showed that increased competence perception was further expressed as decreased activity in the bilateral posterior insula, a region localized to actual pain stimulation. These studies suggest that inferences of competence act as predictors of protection and reduce the expectation of negative outcomes

Inferences of Others' Competence Reduces Anticipation of Pain When under Threat

On a daily basis, we place our lives in the hands of strangers. From dentists to pilots, we make inferences about their competence to perform their jobs and consequently to keep us from harm. Here we explore whether the perceived competence of others can alter one's anticipation of pain. In two studies, participants (Receivers) believed their chances of experiencing an aversive stimulus were directly dependent on the performance of another person (Players). We predicted that perceiving the Players as highly competent would reduce Receivers' anxiety when anticipating the possibility of an electric shock. Results confirmed that high competence ratings consistently corresponded with lower reported anxiety, and complementary fMRI data showed that increased competence perception was further expressed as decreased activity in the bilateral posterior insula, a region localized to actual pain stimulation. These studies suggest that inferences of competence act as predictors of protection and reduce the expectation of negative outcomes

The uncertain brain: a co-ordinate based meta-analysis of the neural signatures supporting uncertainty during different contexts

Uncertainty is often inevitable in everyday life and can be both stressful and exciting. Given its relevance to psychopathology and wellbeing, recent research has begun to address the brain basis of uncertainty. In the current review we examined whether there are discrete and shared neural signatures for different uncertain contexts. From the literature we identified three broad categories of uncertainty currently empirically studied using functional MRI (fMRI): basic threat and reward uncertainty, decision-making under uncertainty, and associative learning under uncertainty. We examined the neural basis of each category by using a coordinate based metaanalysis, where brain activation foci from previously published fMRI experiments were drawn together (1998-2017; 87 studies). The analyses revealed shared and discrete patterns of neural activation for uncertainty, such as the insula and amygdala, depending on the category. Such findings will have relevance for researchers attempting to conceptualise uncertainty, as well as clinical researchers examining the neural basis of uncertainty in relation to psychopathology

Anticipation of Uncertain Threat Modulates Subsequent Affective Responses and Covariation Bias

Uncertainty contributes to stress and anxiety-like behaviors by impairing the ability of participants to objectively estimate threat. Our study used the cue-picture paradigm in conjunction with the event-related potential (ERP) technique to explore the temporal dynamics of anticipation for and response to uncertain threat in healthy individuals. This task used two types of cue. While ‘certain’ cues precisely forecasted the valence of the subsequent pictures (negative or neutral), the valence of pictures following ‘uncertain’ cues was not predictable. ERP data showed that, during anticipation, uncertain cues elicited similar Stimulus-Preceding Negativity (SPN) to certain-negative cues, while both of them elicited larger SPN than certain-neutral cues. During affective processing, uncertainty enlarged the mean amplitude of late positive potential (LPP) for both negative and neutral pictures. Behavioral data showed that participants reported more negative mood ratings of uncertain-neutral pictures relative to certain-neutral pictures and overestimated the probability of negative pictures following uncertain cues. Importantly, the enlarged anticipatory activity evoked by uncertain cues relative to that evoked by certain-neutral cues positively modulated the more negative mood ratings of uncertain-neutral pictures relative to certain-neutral pictures. Further, this more negative mood ratings and the general arousal anticipation during anticipatory stage contributed to the covariation bias. These results can provide a novel insight into understanding the neural mechanism and pathological basis of anxiety

An fMRI study of unconditioned responses in post-traumatic stress disorder

BACKGROUND: Both fear and pain processing are altered in post-traumatic stress disorder (PTSD), as evidenced by functional neuroimaging studies showing increased amygdala responses to threats, and increased insula, putamen and caudate activity in response to heat pain. Using psychophysiology and functional magnetic resonance imaging, we studied conditioned and unconditioned autonomic and neuronal responses in subjects with PTSD versus trauma-exposed non-PTSD control (TENC) subjects. A design using an electric shock selected by subjects to be 'highly annoying but not painful' as an unconditioned stimulus (US) with partially reinforced cues allowed us to partly disentangle the expectancy- and prediction-error components from sensory components of the unconditioned response. RESULTS: Whereas responses to the conditioned stimulus (CS) were similar in PTSD and TENC, the former displayed higher putamen, insula, caudate and amygdala responses to the US. Reactivity to the US in the anterior insula correlated with PTSD symptom severity. Functional connectivity analyses using the putamen as a seed region indicated that TENC subjects had increased amygdala-putamen connectivity during US delivery; this connection was disengaged in PTSD. CONCLUSIONS: Our results indicate that although neural processing of fear learning in people with PTSD seems to be comparable with controls, neural responses to unconditioned aversive stimuli in PTSD seem to be increased

The depersonalized brain:New evidence supporting a distinction between depersonalization and derealization from discrete patterns of autonomic suppression observed in a non-clinical sample

Depersonalization and Derealization are characterised by feelings of detachment from one’s bodily self/surroundings and a general emotional numbness. We explored predisposition to trait-based experiences of depersonalization/derealization-type experiences and autonomic arousal toward simulated body-threats, which were delivered to the participant’s own body (i.e. Self) and when observed being delivered to another individual (i.e. Other). Ninety participants took part in an “Implied Body-Threat Illusion” task (Dewe, Watson, & Braithwaite, 2016) and autonomic arousal was recorded via standardised skin conductance responses and finger temperature. Autonomic suppression in response to threats delivered to the Self correlated with increases in trait-based depersonalization-type experiences. In contrast, autonomic suppression for threats delivered to Others correlated with trait-based derealization-like experiences. Body-temperature and anticipatory arousal did not correlate reliably with predisposition to depersonalization- or derealization-type experiences. The theoretical implications of these findings are discussed in terms of a fronto-limbic autonomic suppression mechanism