title: Neurohemodynamic correlates of 'OM' chanting: A pilot functional magnetic resonance imaging study.
abstract: BACKGROUND
  A sensation of vibration is experienced during audible 'OM' chanting. This has the potential for vagus nerve stimulation through its auricular branches and the effects on the brain thereof. The neurohemodynamic correlates of 'OM' chanting are yet to be explored.
  
  
  METHODS
  Using functional Magnetic Resonance Imaging (fMRI), the neurohemodynamic correlates of audible 'OM' chanting were examined in right-handed healthy volunteers (n=12; nine men). The 'OM' chanting condition was compared with pronunciation of "ssss" as well as a rest state. fMRI analysis was done using Statistical Parametric Mapping 5 (SPM5).
  
  
  RESULTS
  In this study, significant deactivation was observed bilaterally during 'OM' chanting in comparison to the resting brain state in bilateral orbitofrontal, anterior cingulate, parahippocampal gyri, thalami and hippocampi. The right amygdala too demonstrated significant deactivation. No significant activation was observed during 'OM' chanting. In contrast, neither activation nor deactivation occurred in these brain regions during the comparative task - namely the 'ssss' pronunciation condition.
  
  
  CONCLUSIONS
  The neurohemodynamic correlates of 'OM' chanting indicate limbic deactivation. As similar observations have been recorded with vagus nerve stimulation treatment used in depression and epilepsy, the study findings argue for a potential role of this 'OM' chanting in clinical practice.
authors.affiliation: Department of Psychiatry, Advanced Center for Yoga, National Institute of Mental Health and Neurosciences, Bangalore - 560 029, India.
authors.forename: Bangalore G
authors.initials: BG
authors.lastname: Kalyani
authors.forename: Ganesan
authors.initials: G
authors.lastname: Venkatasubramanian
authors.forename: Rashmi
authors.initials: R
authors.lastname: Arasappa
authors.forename: Naren P
authors.initials: NP
authors.lastname: Rao
authors.forename: Sunil V
authors.initials: SV
authors.lastname: Kalmady
authors.forename: Rishikesh V
authors.initials: RV
authors.lastname: Behere
authors.forename: Hariprasad
authors.initials: H
authors.lastname: Rao
authors.forename: Mandapati K
authors.initials: MK
authors.lastname: Vasudev
authors.forename: Bangalore N
authors.initials: BN
authors.lastname: Gangadhar