Neurophysiological responses to safety signals and the role of cardiac vagal control

Late positive potential reveals sustained threat contingencies despite extinction in adolescents but not adults

BACKGROUND

Major theories link threat learning processes to anxiety symptoms, which typically emerge during adolescence. While this developmental stage is marked by substantial maturation of the neural circuity involved in threat learning, research directly examining adolescence-specific patterns of neural responding during threat learning is scarce. This study compared adolescents and adults in acquisition and extinction of conditioned threat responses assessed at the cognitive, psychophysiological, and neural levels, focusing on the late positive potential (LPP), an event-related potential (ERP) component indexing emotional valence.

METHOD

Sixty-five adults and 63 adolescents completed threat acquisition and extinction, 24 h apart, using the bell conditioning paradigm. Self-reported fear, skin conductance responses (SCR), and ERPs were measured.

RESULTS

Developmental differences emerged in neural and psychophysiological responses during threat acquisition, with adolescents displaying heightened LPP responses to threat and safety cues as well as heightened threat-specific SCR compared to adults. During extinction, SCR suggested comparable reduction in conditioned threat responses across groups, while LPP revealed incomplete extinction only among adolescents. Finally, age moderated the link between anxiety severity and LPP-assessed extinction, whereby greater anxiety severity was associated with reduced extinction among younger participants.

CONCLUSIONS

In line with developmental theories, adolescence is characterized by a specific age-related difficulty adapting to diminishing emotional significance of prior threats, contributing to heightened vulnerability to anxiety symptoms. Further, LPP appears to be sensitive to developmental differences in threat learning and may thus potentially serve as a useful biomarker in research on adolescents, threat learning, and anxiety.

Cardio-audio synchronization elicits neural and cardiac surprise responses in human wakefulness and sleep

The human brain can encode auditory regularities with fixed sound-to-sound intervals and with sound onsets locked to cardiac inputs. Here, we investigated auditory and cardio-audio regularity encoding during sleep, when bodily and environmental stimulus processing may be altered. Using electroencephalography and electrocardiography in healthy volunteers (N = 26) during wakefulness and sleep, we measured the response to unexpected sound omissions within three regularity conditions: synchronous, where sound and heartbeat are temporally coupled, isochronous, with fixed sound-to-sound intervals, and a control condition without regularity. Cardio-audio regularity encoding manifested as a heartbeat deceleration upon omissions across vigilance states. The synchronous and isochronous sequences induced a modulation of the omission-evoked neural response in wakefulness and N2 sleep, the former accompanied by background oscillatory activity reorganization. The violation of cardio-audio and auditory regularity elicits cardiac and neural responses across vigilance states, laying the ground for similar investigations in altered consciousness states such as coma and anaesthesia.

Beliefs in Regulating Negative Emotions and Vagally Mediated Heart Rate Variability: Does Sex Make a Difference?

OBJECTIVE

This ecological study explored the association between regulatory emotional self-efficacy beliefs in managing negative emotions (RESE-NE) and heart rate variability (HRV), a measure of parasympathetic modulation of the heart that has been positively associated with a better ability to flexibly adjust to a changing environment and regulate emotions.

METHOD

To test these associations, we used data from 161 adults working in relational professions (about 40% men; mean [standard deviation] age = 40.45 [14.17] years) whose HRV was assessed continuously for 24 hours.

RESULTS

Individuals high in RESE-NE showed increased HRV levels ( β = -0.05, p = .011). However, this effect was moderated by biological sex ( β = -0.18, p = .0001) such that RESE-NE positively and significantly predicted HRV for men ( β = 0.18, p < .0001) but not for women ( β = -0.001, p = .989).

CONCLUSIONS

All in all, our study provides initial empirical support for the theoretical expectation derived from social cognitive theory that RESE-NE is positively correlated with a physiological indicator of adaptability to the environmental demands. This was true only for men, likely because of sex differences in physiological stress reactivity and regulation.

Involvement of the brain-heart axis in the link between PTSD and cardiovascular disease

Posttraumatic stress disorder (PTSD) has long been associated with a heightened risk of cardiovascular disease (CVD). A number of mechanisms have been implicated to underlie this brain-heart axis relationship, such as altered functioning of the autonomic nervous system and increased systemic inflammation. While neural alterations have repeatedly been observed in PTSD, they are rarely considered in the PTSD-CVD link. The brain-heart axis is a pathway connecting frontal and limbic brain regions to the brainstem and periphery via the autonomic nervous system and it may be a promising model for understanding CVD risk in PTSD given its overlap with PTSD neural deficits. We first provide a summary of the primary mechanisms implicated in the association between PTSD and CVD. We then review the brain-heart axis and its relevance to PTSD, as well as findings from PTSD trials demonstrating that a number of PTSD treatments have effects on areas of the brain-heart axis. Finally, we discuss sex considerations in the PTSD-CVD link. A critical next step in this study is to determine if PTSD treatments that affect the brain-heart axis (e.g., brain stimulation that improves autonomic function) also reduce the risk of CVD.

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.

Influence of Perceptual and Conceptual Information on Fear Generalization: A Behavioral and Event-Related Potential Study

Learned fear can be generalized through both perceptual and conceptual information. This study investigated how perceptual and conceptual similarities influence this generalization process. Twenty-three healthy volunteers completed a fear-generalization test as brain activity was recorded in the form of event-related potentials (ERPs). Participants were exposed to a de novo fear acquisition paradigm with four categories of conditioned stimuli (CS): two conceptual cues (animals and furniture); and two perceptual cues (blue and purple shapes). Animals (C+) and purple shapes (P+) were paired with the unconditioned stimulus (US), whereas furniture (C-) and blue shapes (P-) never were. The generalized stimuli were thus blue animals (C+P+, determined danger), blue furniture (C-P+, perceptual danger), purple animals (C+P-, conceptual danger), and purple furniture (C-P-, determined safe). We found that perceptual cues elicited larger fear responses and shorter reaction times than did conceptual cues during fear acquisition. This suggests that a perceptually related pathway might evoke greater fear than a conceptually based route. During generalization, participants were more afraid of C+ exemplars than of C- exemplars. Furthermore, C+ trials elicited greater N400 amplitudes. Thus, participants appear able to use conceptually based cues to infer the value of the current stimuli. Additionally, compared with C+ exemplars, we found an enhanced late positive potential effect in response to C- exemplars, which seems to reflect a late inhibitory process and might index safety learning. These findings may offer new insights into the pathological mechanism of anxiety disorders.

Safety learning and the Pavlovian conditioned inhibition of fear in humans: Current state and future directions

Safety learning occurs when an otherwise neutral stimulus comes to signal the absence of threat, allowing organisms to use safety information to inhibit fear and anxiety in nonthreatening environments. Although it continues to emerge as a topic of relevance in biological and clinical psychology, safety learning remains inconsistently defined and under-researched. Here, we analyse the Pavlovian conditioned inhibition paradigm and its application to the study of safety learning in humans. We discuss existing studies; address outstanding theoretical considerations; and identify prospects for its further application. Though Pavlovian conditioned inhibition presents a theoretically sound model of safety learning, it has been investigated infrequently, with decade-long interims between some studies, and notable methodological variability. Consequently, we argue that the full potential of conditioned inhibition as a model for human safety learning remains untapped, and propose that it could be revisited as a framework for addressing timely questions in the behavioural and clinical sciences.