The rostrolateral prefrontal cortex becomes more active at the start of the meditative practice. It also is more active during focused attention, open awareness, and Zen meditations.  The meditation practices of the individuals that had structural differences in the rostrolateral prefrontal cortex were Insight, Tibetan Buddist, and Brain Wave Vibration (BMV) meditation.

The rostrolateral prefrontal cortex in meditation

 The processes that the anterior cingulate cortex and mid-cingulate cortex, such as self-control, emotion regulation, and behavioral flexibility; are emphasized in meditation. Behavioral evidence shows improvements in pain regulation , emotional awareness, emotion regulation , and insightful problem solviging in meditation practitioners.  Meditation practice may lead to more conscious action selection, greater attention to thoughts and information in the decision-making process, and increased attention to the movement of the body during action execution, which are all processes that the anterior cingulate cortex and mid-cingulate cortex are focused on. Frequent recruitment of the anterior cingulate cortex and mid-cingulate cortex for conscious action control might relate to the consistently observed differences in the structure of these regions.

The anterior cingulate cortex and the 
mid-cingulate cortex in meditation

The orbitofrontal cortex in meditation

Somatomotor cortices

Anterior precuneus

Insular cortex

Sensory Cortices and Insula in meditation

Meditation training may enhance stress resilience via hippocampal structure alterations. This notion comes from the idea that hippocampal atrophy is associated with clinical disorders that involve stress, anxiety, and depression. These clinical disorders may also be associated with problems of concentration and memory. Thus, structural increase in the hippocampus relate to meditation's potential betterment of these clinical conditions.  There may also be structural differences in the hippocampus because of memory reconsolidation.  Many meditative practices place a strong emphasis on re-evaluating past behavioral patterns and default emotional reactions to events. 
The differences in the hippocampus may be due to the region playing a role in seeing past experiences in a new light and allowing for greater flexibility in present behavior.  Structural differences in the hippocampus may be related to the effort involved in re-contextualizing spontaneous thought processes, memories, and simulations during meditation practice.

Hippocampus in meditation

Morphometric differences observed in the corpus callosum are mostly localized to the anterior regions, which are thought to preferentially connect to the prefrontal brain regions.  These prefrontal brain regions include the frontopolar cortex, anterior insula, orbitofrontal cortex, and anterior and mid-cingulate cortices. Therefore, prefrontal structural increases may follow structural changes of particular corpus callosum areas that reciprocally connect bilateral prefrontal gray matter regions. 

Corpus Callosum in meditation

The posterior projection areas of the superior longitudinal fasciculus  are implicated in higher-order spatial processing, which includes the representation of the body in three-dimensional space and the directing of attentional focus in space Structual changes in the superior longitudinal fasciculus are consistent with findings in the anterior precuneus, insular and somatomotor cortices, the rostrolateral prefrontal coprtex and the anterior cingulate cortex. 

Superior longitudinal fasciculus in  meditation

Eight regions of the brain are consistently altered in long and short-term  meditators. These regions include:

The frontopolar cortex ( also known as the Brodmann's area 10 or the rostrolateral prefrontal cortex)

The sensory cortices and insula

The hippocampus

The anterior cingulate cortex

The mid-cingulate cortex

The orbitofrontal cortex

The superior longitudinal fasciculus

The corpus callosum

University of Georgia

There is limited evidence as to whether meditation is the causative factor for altered brain structure. However, there is a possibility that pre-existing brain heterogeneities could explain these differences. Examinations of meditation-naive persons before and after undergoing brief meditation training in comparison to control groups bare on the edge of causality and indicate that only a few hours of meditation training are necessary to induce neuroplastic changes. The changes in the brain exhibited by those given a brief training have also been observed in almost all the same regions as long-term practitioners. 

 Is meditation a causative factor in altered brain structure?

Wang, P. P., & Jernigan, T. L. (1994). Morphometric studies using neuroimaging. Neurologic clinics, 12(4), 789–802.

Morphometric studies using neuroimaging. 

Tang, YY., Hölzel, B. & Posner, M. The neuroscience of mindfulness meditation. Nat Rev Neurosci 16, 213–225 (2015). https://doi.org/10.1038/nrn3916.

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