Longitudinal changes of resting-state functional connectivity of amygdala following fear learning and extinction

An externally validated resting-state brain connectivity signature of pain-related learning

Pain can be conceptualized as a precision signal for reinforcement learning in the brain and alterations in these processes are a hallmark of chronic pain conditions. Investigating individual differences in pain-related learning therefore holds important clinical and translational relevance. Here, we developed and externally validated a novel resting-state brain connectivity-based predictive model of pain-related learning. The pre-registered external validation indicates that the proposed model explains 8-12% of the inter-individual variance in pain-related learning. Model predictions are driven by connections of the amygdala, posterior insula, sensorimotor, frontoparietal, and cerebellar regions, outlining a network commonly described in aversive learning and pain. We propose the resulting model as a robust and highly accessible biomarker candidate for clinical and translational pain research, with promising implications for personalized treatment approaches and with a high potential to advance our understanding of the neural mechanisms of pain-related learning.

Trait anxiety is associated with attentional brain networks

Trait anxiety is a well-established risk factor for anxiety and depressive disorders, yet its neural correlates are not clearly understood. In this study, we investigated the neural correlates of trait anxiety in a large sample (n = 179) of individuals who completed the trait and state versions of the State-Trait Anxiety Inventory and underwent resting-state functional magnetic resonance imaging. We used independent component analysis to characterize individual resting-state networks (RSNs), and multiple regression analyses to assess the relationship between trait anxiety and intrinsic connectivity. Trait anxiety was significantly associated with intrinsic connectivity in different regions of three RSNs (dorsal attention network, default mode network, and auditory network) when controlling for state anxiety. These RSNs primarily support attentional processes. Notably, when state anxiety was not controlled for, a different pattern of results emerged, highlighting the importance of considering this factor in assessing the neural correlates of trait anxiety. Our findings suggest that trait anxiety is uniquely associated with resting-state brain connectivity in networks mainly supporting attentional processes. Moreover, controlling for state anxiety is crucial when assessing the neural correlates of trait anxiety. These insights may help refine current neurobiological models of anxiety and identify potential targets for neurobiologically-based interventions.

Analysis of brain signal change response in amygdala evoked by skin pressure stimulus

BACKGROUND

It was well known that the human body would produce an uncomfortable sensation when the fabric exerted a certain amount of pressure irritation on the skin. The amygdala had long been thought to be the source of negative emotion perception. However, up to now, the brain signal changes in the amygdala evoked by skin exposure pressure had not been known.

MATERIALS AND METHODS

In this work, a series of gradually increasing contact pressure stimulus from boneless corsets was repeatedly applied to the body's waist and abdomen, and the technology of functional magnetic resonance imaging (fMRI) was adopted to detect the brain response synchronously.

RESULTS

The results shown that both subjective comfort score and percent signal changes (PSCs) of amygdala decreased with the increase of skin contact pressure. When the skin pressure applied to the waist and abdomen of the human body exceeded about 1 kPa, blood oxygen level dependent signal in the amygdala was negatively activated. Besides, the degree of response of PSCs was intense than subjective evaluation, and the standard deviations of PSCs between individuals were much smaller than subjective evaluations.

CONCLUSION

It was suggested that skin contact pressure stimulus caused the attention of the amygdala brain area. The greater the stimulus, the higher the attention, but such attention was caused by negative activation of the amygdala induced by skin discomfort. In addition, skin comfort representation based on brain perception was superior to subjective representation due to its higher response sensitivity and antipsychological interference ability.

Higher functional connectivity between prefrontal regions and the dorsal attention network predicts absence of renewal

Renewal describes the recovery of an extinguished response when extinction and recall contexts differ, demonstrating the context-dependency of extinction. The unexpected outcome change during extinction presumably directs attention to the context and promotes renewal. Accordingly, studies show that context processing for renewal is modulated by salience of and attention to context. Besides context-processing hippocampus, renewal involves ventromedial prefrontal cortex, orbitofrontal cortex and inferior frontal gyrus, which mediate response processing. Since showing renewal is a trait-like processing tendency, individuals with and without renewal may differ in resting-state functional connectivity of prefrontal regions with networks mediating attentional and salience processing. We analyzed resting-state functional MRI data from healthy participants (n = 70) of a non-fear-related contextual extinction task particularly suited for investigation of renewal. Participants without renewal exhibited significantly higher functional connectivity between prefrontal regions and bilateral intraparietal sulcus of the dorsal attention network. Functional connectivity between these regions correlated negatively with renewal level. Only in participants with renewal, the renewal level correlated positively with connectivity between left frontal eye field and several prefrontal regions. In contrast, functional connectivity of prefrontal regions with the salience network did not differ between groups. The results deliver first-time evidence for differences in resting-state functional connectivity between participants with and without renewal in non-fear-related extinction. Intraparietal-sulcus-guided top-down attentional control appears more strongly related to prefrontal activity in participants without renewal, and thus may have a role in their default processing mode of focusing on the stimulus and disregarding the context.

Variance and Scale-Free Properties of Resting-State Blood Oxygenation Level-Dependent Signal After Fear Memory Acquisition and Extinction

Recently, the dynamic properties of brain activity rather than its stationary values have attracted more interest in clinical applications. It has been shown that brain signals exhibit scale-free dynamics or long-range temporal correlations (LRTC) that differ between rest and cognitive tasks in healthy controls and clinical groups. Little is known about how fear-inducing tasks may influence dispersion and the LRTC of subsequent resting-state brain activity. In this study, we aimed to explore the changes in the variance and scale-free properties of the brain’s blood oxygenation level-dependent (BOLD) signal during the resting-state sessions before and after fear learning and fear memory extinction. During a 1-h break between magnetic resonance imaging (MRI) scanning, 23 healthy, right-handed volunteers experienced a fear extinction procedure, followed by Pavlovian fear conditioning that included partial reinforcement using mild electrical stimulation. We extracted the average time course of the BOLD signal from 245 regions of interest (ROIs) taken from the resting-state functional atlas. The variance of the BOLD signal and the Hurst exponent (H), which reflects the scale-free dynamic, were compared in the resting states before and after fear learning and fear memory extinction. After fear extinction, six ROIs showed a difference in H at the uncorrected level of significance, including areas associated with fear processing. H decreased during fear extinction but then became higher than before fear learning, specifically in areas related to the fear extinction network (FEN). However, activity in the other ROIs restored the H to its initial level. The variance of the BOLD signal in six ROIs demonstrated a significant increase from initial rest to the post-task rest. A limited number of ROIs showed changes in both H and variance. Our results imply that the variability and scale-free properties of the BOLD signal might serve as additional indicators of changes in spontaneous brain activity related to recent experience.