Inter-relationships between changes in stress, mindfulness, and dynamic functional connectivity in response to a social stressor

Dynamic functional connectivity signatures of focused attention on the breath in adolescents

Breathing meditation typically consists of directing attention toward breathing and redirecting attention when the mind wanders. As yet, we do not have a full understanding of the neural mechanisms of breath attention, in particular, how large-scale network interactions may be different between breath attention and rest and how these interactions may be modulated during periods of on-task and off-task attention to the breath. One promising approach may be examining fMRI measures including static connectivity between brain regions as well as dynamic, time-varying brain states. In this study, we analyzed static and dynamic functional connectivity in 72 adolescents during a breath-counting task (BCT), leveraging physiological respiration data to detect objective on-task and off-task periods. During the BCT relative to rest, we identified increases in static connectivity within attention-direction and orienting networks and anticorrelations between attention networks and the DMN. Dynamic connectivity analysis revealed four distinct brain states, including a DMN-anticorrelated brain state, proportionally more present during the BCT than the rest. We found there were distinct brain state markers of (i) breathing tasks vs rest and (ii) momentary on-task vs off-task attention within the BCT, yet in this analysis, no identifiable brain states reflecting between-individual behavioral variability.

Long-term mindfulness meditation increases occurrence of sensory and attention brain states

Interest has been growing in the use of mindfulness meditation (MM) as a therapeutic practice, as accumulating evidence highlights its potential to effectively address a range of mental conditions. While many fMRI studies focused on neural activation and functional connectivity during meditation, the impact of long-term MM practice on spontaneous brain activity, and on the expression of resting state networks over time, remains unclear. Here, intrinsic functional network dynamics were compared between experienced meditators and meditation-naïve participants during rest. Our analysis revealed that meditators tend to spend more time in two brain states that involve synchrony among cortical regions associated with sensory perception. Conversely, a brain state involving frontal areas associated with higher cognitive functions was detected less frequently in experienced meditators. These findings suggest that, by shifting attention toward enhanced sensory and embodied processing, MM effectively modulates the expression of functional network states at rest. These results support the suggested lasting effect of long-term MM on the modulation of resting-state networks, reinforcing its therapeutic potential for disorders characterized by imbalanced network dynamics. Moreover, this study reinforces the utility of analytic approaches from dynamical systems theory to extend current knowledge regarding brain activity and evaluate its response to interventions.

Functional MRI Techniques Suggesting that the Stress System Interacts with Three Large Scale Core Brain Networks to Help Coordinate the Adaptive Response: A Systematic Review

OBJECTIVE

Synthesis of functional MRI (fMRI) and functional connectivity (FC) analysis data on human stress system (SS) function, as it relates to the dynamic function of the Salience (SN), Default Mode (DMN) and Central Executive (CEN) networks.

METHODS

Systematic search of Medline, Scopus, Clinical Trials.gov, and Google Scholar databases of studies published prior to September 2022 resulted in 28 full-text articles included for qualitative synthesis.

RESULTS

Acute stress changes the states of intra-/inter- neural network FCs and activities from those of resting, low arousal state in the SN, DMN and CEN, during which intra- and inter-network FCs and activities of all three networks are low. SS activation is positively linked to the activity of the SN and negatively to that of the DMN, while, in parallel, it is associated with an initial decrease and a subsequent increase of the intra- network FC and activity of the CEN. The FC between the DMN and the CEN increases, while those between the SN and the CEN decrease, allowing time for frontal lobe strategy input and "proper" CEN activity and task decision. SN activation is linked to sensory hypersensitivity, "impaired" memory, and a switch from serial to parallel processing, while trait mindfulness is associated with FC changes promoting CEN activity and producing a "task-ready state".

CONCLUSION

SS activation is tightly connected to that of the SN, with stress hormones likely potentiating the intra-network FC of the latter, attenuating that of the DMN, and causing a biphasic suppression- to-activation response of the CEN, all adaptive changes favoring proper decisions and survival.