In a study involving 27 long-term meditation practitioners (average age 52 years, experience ranging from 5 to 46 years) and 27 control participants of the same sex and age, scientists from UCLA used diffusion tensor imaging. They found more pronounced structural connections throughout the brain in the meditators — from the frontal and temporal lobes to the brainstem and the anterior part of the corpus callosum.
The differences are especially noticeable in the corticospinal tract, the superior longitudinal fasciculus, and the uncinate fasciculus. These pathways ensure rapid transmission of signals between the cortex and the spinal cord, between the anterior and posterior parts of the hemispheres, and also between the limbic system and the frontal cortex. The normal age-related decline in white matter density in the practitioners turned out to be significantly smaller.
The results were published in NeuroImage. The authors — Eileen Luders and colleagues — note that meditation may not only stimulate growth but also prevent atrophy, possibly through an effect on the immune system. However, the study does not allow distinguishing cause and effect from predisposition: people with initially denser connections may have been more likely to choose and maintain the practice.
Such changes affect global networks rather than individual zones. For theories of consciousness, this means that the structural integrity of white matter may influence the integration of information and the widespread propagation of signals. Within the framework of global workspace theory, strengthened connections could facilitate the "ignition" and broadcasting of the contents of consciousness, whereas in integrated information theory they could increase Φ through denser causal connections.
Imagine a network of roads between cities: if the highways become wider, denser, and better insulated, messages arrive faster and more reliably, and the aging of the infrastructure slows down. So too is white matter — not merely "wiring," but a condition on which depends how stably consciousness retains its coherence amid the natural aging of the brain.
The study remains a single one and does not control for all variables, so its conclusions require caution. Nevertheless, it points to the plasticity of structures traditionally considered relatively stable, and raises the question of how much conscious experience depends on trainable anatomy, and not only on functional activity.
This forces a reconsideration of ideas about the immutability of the neural correlates of consciousness and about the boundaries between the biological substrate and practices capable of modifying it.
