Meditation-related changes in brain dynamics and structure were investigated by scanning experienced meditators and naive controls with MRI during rest and focused-attention meditation. A machine-learning approach showed that effective connectivity (causal relationships between brain regions) was more informative than functional or structural connectivity alone for distinguishing meditators from controls. The most informative effective-connectivity links involved several large-scale networks, predominantly in the left hemisphere. Anatomical differences were smaller but present: meditators had stronger structural connectivity between four left-hemisphere areas belonging to somatomotor, dorsal attention, subcortical, and visual networks. The findings suggest a mechanism linking brain structure and function underlying meditation.
A world champion free diver's brain activity and connectivity shift markedly during a 6.5-minute breath-hold. EEG shows increased alpha wave power and connectivity, with decreased delta band connectivity. fMRI reveals heightened connectivity within the default mode network and visual areas, but reduced connectivity in sensorimotor cortices. These changes overlap with some meditation-related brain signatures but also include unique features suggesting altered somatosensory integration. Self-reports indicate that elite free divers may achieve a state of sensory dissociation during prolonged apnea, reflecting their ability to adapt psychologically and physiologically to extreme breath-holding.
During a bistable visual illusion where motion perception alternates despite constant input, the primary visual area (V1) and the motion-sensitive area hMT+ show distinct patterns of activity. Using high-resolution 7 Tesla fMRI, researchers found that hMT+ activity correlates with conscious perception equally for both ambiguous and physical motion stimuli, with no difference in its laminar profiles. In contrast, V1 shows reduced functional response to ambiguous stimuli, reflecting feedback signals rather than feedforward input, and its laminar profiles differ between conditions. Temporal coupling between V1 and hMT+ increases during ambiguous perception, suggesting feedback from hMT+ to V1 helps stabilize the vivid perception of directed motion.
The default mode network (DMN), traditionally viewed as a single network active during rest and deactivated during tasks, may actually consist of multiple subsystems supporting a broader range of functions than previously thought. This meta-analysis of neuroimaging studies found that DMN activation patterns can be arranged along a continuous gradient from core midline regions linked to internal mental processes to lateral cortices involved in external tasks such as reward, semantic processing, and emotion. Importantly, many task-related activation maps differed from the canonical resting-state DMN, sometimes overlapping only in peripheral nodes and including regions like the insula. These results suggest that the distinction between intrinsic and extrinsic brain functions is better conceptualized as a continuum rather than a strict dichotomy.