Cerebral blood flow effects in long-term meditators

Abstract

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Objectives: We have studied a number of subjects who are long term practitioners of various meditation practices. The purpose of this study was to determine if there are differences in the baseline brain function of experienced meditators compared to a similar control group of non-meditators. Methods: All subjects were recruited as part of an ongoing study of different meditation practices. Subjects received a baseline scan with their eyes closed and ears unoccluded. We evaluated 12 advanced meditation subjects and 21 non-meditators with cerebral blood flow(CBF) SPECT imaging. After approximately 10 minutes at rest, they were injected with 250MBq of Tc-99m ECD or HMPAO, rested quietly for another 10 minutes, and then were scanned on a Picker 3000XP triple head camera for 40 minutes. All scans were resliced and aligned in the same plane. A previously validated region of interest (ROI) analysis was used to measure the counts in various cortical and subcortical regions, which were normalized to the whole brain activity to calculate a CBF ratio. A laterality index was calculated using the formula: [100x(R-L)]/[(1/2)(R+L)]. The meditator and non-meditator scans were compared using unpaired t-tests. Results: The CBF ratios of meditators was significantly higher (p<0.05) compared to non-meditators in the following regions (results presented as mean±standard deviation for meditators and non-meditators respectively): prefrontal cortex (1.30±0.08; 1.15±0.13), parietal cortex (1.27±0.07; 1.13±0.04), thalamus (1.35±0.18; 1.25±0.08), putamen (1.37±0.13; 1.26±0.10), caudate (1.27±0.12; 1.16±0.12), cerebellum (1.22±0.06; 1.08±0.10), and midbrain (1.07±0.21; 0.93±0.11). There was also a significant difference in the thalamic laterality index with the mean LI in meditators 9.0±6.5 and that in the non-meditators 5.5±4.4 (p=0.03). Conclusions: We observed higher CBF ratios in a number of brain structures in long-term meditators compared to non-meditators. Some of the structures underlie the attention network such as the prefrontal cortex and thalamus, but include some that relate to emotion and autonomic function. The higher thalamic asymmetry may reflect differences in sensory processing. Thus, meditation appears to be associated with significant changes in the brain and longitudinal studies will be required to determine the causal relationship.