How does Yoga affect the brain?

Yoga aims to attain a union of mind and body and reach extreme tranquility. Positron emission tomography (PET) was used to understand this state of mind with the collaboration of seven Yoga practitioners having more than eight years of Yoga practice. After the ingestion of a radioactive glucose analogue(FDG), subjects performed 14 Yoga postures(Assannas)consecutively for one hour. The brain was imaged using a PET tomograph to identify the brain regions altered by Yoga. A statistical parametric mapping technique (SPM96) was applied to anatomically standardize the brain images to match a standard brain template. Analysis revealed widespread changes in glucose metabolism, mainly in the motor and association motor areas as activation sites and fronto-temporal, limbic, and brainstem regions as deactivation sites. The results support that Yoga induces tonic reductions in deep brain areas, including the limbic system and brain stem. If MacLean’s triune brain theory is adopted, meditation seems to be a way for the rational brain to obtain control of the diencephalons and brain stem through the limbic brain.