"As the Christian nuns focused on God - on a word like Jesus or Elohim that helped them connect to the divine - their frontal lobes shifted into overdrive. Similarly, as the Buddhist monks meditated on an image that allowed them to connect with the ground of being, their scans showed their frontal lobes as a red glow of activity. Newberg found another peculiar similarity. With both the [Catholic] nuns and the [Buddhist] monks, the parietal lobes went dark during deep prayer and meditation. Newberg calls this the "orientation area" because it orients you in space and time: those lobes tell you where your body ends and the rest of the world begins.
That is why Sister Celeste (and countless other mystics) described a unity with God 'permeating my being'. It was the neurological reason that [Buddhist] Michael Blaine felt a 'deep and profound sense of connection to everything, recognizing that there never was a true separation at all.' And I might add, it was what those who enjoyed psychedelic drugs and natural mystical experiences reported ...
In The Doors Of Perception, Aldous Huxley proposed that the brain is a 'reducing valve.' He suggested that all around us is what he called "Mind At Large". This mind comprises everything - all of reality, all ideas, all images, seen and unseen, in the universe ... [The brain] narrows this information to a 'measly trickle,' only that information required for survival. And so we ignore thoughts of the cosmos to focus on the lion crouching behind the bush. We turn from the stirrings of transcendence to the email on the screen. We nudge aside insights about the universe in favor of dinner. Most of us live on that level of reality, satisfied we are missing nothing."
- Barbara Bradley Hagerty, Fingerprints Of God.