Electrophysiological studies (EEG) measure the electrical activity from groups of neurons on the surface of the scalp. EEG studies comparing the brain activation of long-term Sahaja Yoga practitioners (11) to short-term Sahaja Yoga meditators (16) found specific brain activation patterns corresponding to the subjective feelings of thoughtless awareness and happiness experienced by the Meditators (Aftanas and Golocheikine, 2001, 2002, 2000). In their EEG measures, the long-term meditators showed increased power in low band frequency EEG activity of theta and alpha, which was particularly pronounced over the left frontal regions.
Brain activation correlating with thoughtless awareness and happiness
During the Meditation, the long-term meditators showed less mental activity, i.e. less thoughts (IV) and more feelings of happiness (VI) according to their subjective ratings.
In their EEG measures, the long-term meditators showed increased power in low band frequency EEG activity of theta, which was particularly pronounced over the left frontal regions. The intensity of mental activity correlated negatively with theta activity over frontal and central brain regions, suggesting that less internal dialogue is related to more activation. Frontal theta activity is thought to originate from limbic and frontal regions regions such as the anterior cingulate and prefrontal cortex and has shown to be increased during both affective and attentional states such as emotion processing and sustained attention
The intensity of the feelings of happiness was positively correlated with the theta activity over left frontal regions. This is in line with the evidence for a role of the left frontal lobe in positive emotions whereas the right prefrontal lobe plays a greater role in negative ones.
There was also increased activation in the alpha power range over the same regions, which is thought to reflect a reduction in brain regions that mediate mental effort and external attention. Increased activation in alpha activity has commonly been observed in Meditators of different traditions and been found to correlate with reduced levels of anxiety.
In addition to enhanced fronto-parietal theta activation, the authors also found enhanced connectivity of fronto-parietal theta bands – suggesting the enforcement of attentional networks.
A reduction in the chaotic dimensional complexity was also observed suggestive of the inhibition of task-irrelevant processes.
Taken together, the findings suggest that during Meditation, the reduced mental activity is mediated by increased activation of networks of internalised attention which seem to trigger the activity in regions that mediate positive emotions (left frontal cortex) while decreasing networks related to external attention and irrelevant processes.
The enhanced connection between frontal and parietal regions is probably the prerequisite for the general intensification of internalised attention necessary for the induction of the altered state of mental silence.
In conclusion, this ground-breaking study shows that the subjective experiences of mental silence and positive emotions during Meditation have very specific neurophysiological correlates in the activation and connectivity of regions that mediate internalised attention and positive affect.
Aftanas LI, Golocheikine SA. (2001): Human anterior and frontal midline theta and lower alpha reflect emotionally positive state and internalized attention: high-resolution EEG investigation of meditation. Neuroscience Letters 310(1):57-60.
Aftanas LI, Golocheikine SA. (2002): Non-linear dynamic complexity of teh human EEG during meditation. Neuroscience Letters 330: 143-146.
Aftanas LI, Golosheikin S.A. (2003): Changes in cortical activity in altered states of consciousness: the study of meditation by high-resolution EEG. Human Physiology 29(2):143-151