I am currently reading Selfless Insight: Zen and the Meditative Transformations of Consciousness by fellow neurologist James Austin, M.D. In this remarkable work, Dr. Austin sifts through the burgeoning neuroscience of mindfulness and cuts through opaque layers of contemplative traditions to reveal both the highest order functions of our brains and the potential of these ancient meditative practices to expand our consciousness.
Our fundamental human condition is self-centered, or ego-centric, supported by a default network of mainly midline structures in the brain. A outwardly focused or allocentric network exists along the outer convexities of the brain but is normally trapped and subservient to the egocentric default network. The balance between these networks, revealed by fMRI (functional MRI) demonstrates slow reciprocal fluctuations at rest. Sometmes it tilts in a more ego-centric direction, and sometimes more allocentric, but with a set-point that is ego-centric.
Top-down influences originating in the dorsolateral prefrontal cortex also help modulate the balance, tipping away from the self. Development of this is the often hard work of the meditator: to inhibit the default network, allowing the him/her to step through the self and into the world selfless.
Bottom-up influences on both the default network and its allocentric sibling also exist and are exerted through a uniquely human (in its oversized importance)thalamic master relay nucleus, the pulvinar. The pulvinar acts as a doorway through which self-referential sensory information flows and which is, itself gated by powerful inhibitory neurons. The actions of these inhibitory neurons may also be cultivated in contemplative practice. In addition, these inhibitatoty influences may be affected by sudden, strong emotional stimuli such as a beautiful sunset, a clear star-filled winter night sky or even the stress of a battlefield. When the natural oscillation, top-down and bottom-up influences converge a sudden flip in the ego- and allocentric power dynamic can occur delivering us into a state of bare awareness, where our experience of the our world and those in it is suddenly shifted. In the Zen tradition this state is termed kensho.
States of altered consciousness like kensho are experienced as markedly heightened unfiltered awareness. I think I have experienced this once. I remember it like it was yesterday…