Eugene G. D'Aquili

The measurement of regional cerebral blood flow during the complex cognitive task of meditation: a preliminary SPECT study

This study measured changes in regional cerebral blood flow (rCBF) during the complex cognitive task of meditation using single photon emission computed tomography. Eight experienced Tibetan Buddhist meditators were injected at baseline with 7 mCi HMPAO and scanned 20 min later for 45 min. The subjects then meditated for 1 h at which time they were injected with 25 mCi HMPAO and scanned 20 min later for 30 min. Values were obtained for regions of interest in major brain structures and normalized to whole brain activity. The percentage change between meditation and baseline was compared. Correlations between structures were also determined. Significantly increased rCBF (P<0.05) was observed in the cingulate gyrus, inferior and orbital frontal cortex, dorsolateral prefrontal cortex (DLPFC), and thalamus. The change in rCBF in the left DLPFC correlated negatively (P<0.05) with that in the left superior parietal lobe. Increased frontal rCBF may reflect focused concentration and thalamic increases overall increased cortical activity during meditation. The correlation between the DLPFC and the superior parietal lobe may reflect an altered sense of space experienced during meditation. These results suggest a complex rCBF pattern during the task of meditation.

Cerebral Blood Flow during Meditative Prayer: Preliminary Findings and Methodological Issues:

Meditative practices typically require several coordinated cognitive activities. This study measured changes in cerebral blood flow during “verbal” based meditation by Franciscan nuns involving the internal repetition of a particular phrase. These results are compared with those we previously described in eight Buddhist meditators who use a type of “visualization” technique. Three experienced practitioners of verbal meditation were injected via IV at rest with 260MBq of Tc-99m HMPAO and scanned 30 min. later on a triple head SPECT camera for 45 min. Following the baseline scan, subjects meditated for approximately 40 min. at which time they were injected with 925MBq of HMPAO while they continued to meditate for 10 min. more (total of 50 min. of meditation). The injection during meditation was designed not to disturb practice. Subjects were scanned 20 min. later for 30 min. Counts were obtained for regions of interest for major brain structures and normalized to whole-brain blood flow Compared to baseline, mean verbal meditation scans showed increased blood flow in the prefrontal cortex (7.1%), inferior parietal lobes (6.8%), and inferior frontal lobes (9.0%). There was a strong inverse correlation between the blood flow change in the prefrontal cortex and in the ipsilateral superior parietal lobe (p<.01). This study on a limited number of subjects demonstrated the feasibility of studying different types of meditation with neuroimaging techniques, suggested that several coordinated cognitive processes occur during meditation, and also raised important methodological issues.