Interoception refers to the signaling of internal bodily commands. Here, we explore repetition suppression of intero- and exteroceptive neural markers to test whether the perception and predictability of exteroceptive stimulus material affects their expression. Participants completed a repetition suppression paradigm in which angry or neutral facial expressions repeated or alternated. Participants received either an implicit (experiment 1) or explicit (experiment 2) cue enabling the formation of expectations regarding the upcoming facial expression. We measured the heartbeat-evoked potential (HEP) indexing cardiac processing and visual evoked potentials (VEP) in response to viewing the second (repeated or alternated) face. Repeating angry facial expressions produced repetition suppression of both HEP and VEP amplitude while repeating neutral expressions led to repetition enhancement of HEP amplitude. This effect was magnified when participants were explicitly aware of predictive cues. Furthermore, repetition suppression of HEP amplitude correlated with neural attenuation of VEP activity. Results highlight repetition effects for interoceptive as well as exteroceptive neural markers and support top-down, expectation-based accounts of the phenomenon. Furthermore, results demonstrate that the perception of exteroceptive stimulus information has an effect on the processing of interoceptive signals and suggest a direct neural connection between the processing of external and internal sensory information.
Interoception refers to the perception of the internal bodily states. Recent accounts highlight the role of the insula in both interoception and the subjective experience of anxiety. The current study aimed to delve deeper into the neural correlates of cardiac interoception; more specifically, the relationship between interoception-related insular activity, interoceptive accuracy, and anxiety. This was done using functional magnetic resonance imaging (fMRI) in an experimental design in which 40 healthy volunteers focused on their heartbeat and anxious events. Interoceptive accuracy and anxiety levels were measured using the Heartbeat Perception Task and State Trait Anxiety Inventory, respectively. The results showed posterior, mid and anterior insular activity during cardiac interoception, whereas anxiety-related activation showed only anterior insular activity. Activation of the anterior insula when focused on cardiac interoception was positively correlated to state and trait anxiety levels, respectively. Moreover, the mid-insular activity during the cardiac attention condition not only related to individuals’ interoceptive accuracy but also to their levels of state and trait anxiety, respectively. These findings confirm that there are distinct neural representations of heartbeat attention and anxious experience across the insular regions, and suggest the mid-insula as a crucial link between cardiac interoception and anxiety.
Dyspnea is a debilitating and threatening symptom in various diseases. Affected patients often report the unpredictability of dyspnea episodes being particularly anxiety-provoking and amplifying the perception of dyspnea. Experimental studies testing dyspnea unpredictability together with related neural processes, physiological fear responses, and dyspnea-related personality traits are sparse. Therefore, we investigated the impact of unpredictability of dyspnea offset on dyspnea perception and fear ratings, respiratory neural gating and physiological fear indices, as well as the influence of interindividual differences in fear of suffocation (FoS). Forty healthy participants underwent a task manipulating the offset predictability of resistive load-induced dyspnea including one unloaded safety condition. Respiratory variables, self-reports of dyspnea intensity, dyspnea unpleasantness, and fear were recorded. Moreover, respiratory neural gating was measured in a paired inspiratory occlusion paradigm using electroencephalography, while electrodermal activity, startle eyeblink, and startle probe N100 were assessed as physiological fear indices.Participants reported higher dyspnea unpleasantness and fear when dyspnea offset was unpredictable compared to being predictable. Individuals with high levels of FoS showed the greatest increase in fear and overall higher levels of fear and physiological arousal across all conditions. Respiratory neural gating, startle eyeblink, and startle probe N100 showed general reductions during dyspnea conditions but no difference between unpredictable and predictable dyspnea conditions. Together, the current results suggest that the unpredictable offset of dyspnea amplifies dyspnea perception and fear, especially in individuals with high levels of FoS. These effects were unrelated to respiratory neural gating or physiological fear responses, requiring future studies on underlying mechanisms.
Dyspnea or breathlessness is a symptom occurring in multiple acute and chronic illnesses, however, the understanding of the neural mechanisms underlying its subjective experience is limited. In this topical review, we propose neural oscillatory dynamics and cross‐frequency coupling as viable candidates for a neural mechanism underlying respiratory perception, and a technique warranting more attention in respiration research. With the evidence for the potential of neural oscillations in the study of normal and disordered breathing coming from disparate research fields with a limited history of interdisciplinary collaboration, the main objective of the review was to converge the existing research and suggest future directions. The existing findings show that distinct limbic and cortical activations, as measured by hemodynamic responses, underlie dyspnea, however, the time‐scale of these activations is not well understood. The recent findings of oscillatory neural activity coupled with the respiratory rhythm could provide the solution to this problem, however, more research with a focus on dyspnea is needed. We also touch on the findings of distinct spectral patterns underlying the changes in breathing due to experimental manipulations, meditation and disease. Subsequently, we suggest general research directions and specific research designs to supplement the current knowledge using neural oscillation techniques. We argue for the benefits of interdisciplinary collaboration and the converging of neuroimaging and behavioral methods to best explain the emergence of the subjective and aversive individual experience of dyspnea.
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