Saturday, February 07, 2015


In an interesting article in the current New Yorker, Michael Pollan writes about current research on the use of psychedelics to treat end-of-life anxiety. 

The part of the article that really grabbed my attention (all of it was interesting, and some parts more than others) discussed a portion of the human brain called the "default-mode network." According to Pollan, the default-mode network comprises a critical and centrally situated hub of brain activity that links parts of the cerebral cortex to deeper, older structures in the brain, such as the limbic system and the hippocampus.
"The network, which consumes a significant portion of the brain’s energy, appears to be most active when we are least engaged in attending to the world or to a task. It lights up when we are daydreaming, removed from sensory processing, and engaging in higher-level 'meta-cognitive' processes such as self-reflection, mental time travel, rumination, and 'theory of mind'—the ability to attribute mental states to others."
The default-mode network has variously been described as the brain’s "orchestra conductor" or "corporate executive" or "capital city," charged with managing and holding the entire system together.  It is thought to be the physical counterpart of the autobiographical self, or ego.  The fact that it is least active when we are concentrating on a task may help explain, in part, the sense of "losing oneself" experienced during concentrated attention on a task, or even reading a book.  I know that when I'm performing intense, complicated calculations, I become extremely withdrawn and asocial, an effect that I once attributed to "left brain/right brain" theory, but might better be ascribed to quieting of the default-mode network.

Pollan goes on to discuss Dr. Robin Carhart-Harris, who has been using a variety of scanning tools—including fMRI and magnetoencephalography (MEG)—to observe what happens in the brains of healthy volunteers injected with psilocybin and LSD.  Carhart-Harris discovered that blood flow and electrical activity in the default-mode network dropped off precipitously under the influence of psychedelics, a finding that may help to explain the loss of the sense of self that volunteers reported. The biggest dropoffs in default-mode-network activity correlated with volunteers’ reports of ego dissolution. Carhart-Harris published his results in a 2012 paper in Proceedings of the National Academy of Sciences.

At about the same time, Judson Brewer, a researcher at Yale, was using fMRI to study the brains of experienced meditators, and noticed that their default-mode networks had also been quieted relative to those of novice meditators. It appears that, with the ego temporarily out of commission, the boundaries between self and world, subject and object, all dissolve. These are hallmarks of the mystical experience, what Zen Master Dogen called "mind and body dropping away."

To connect the dots, the therapeutic value of psychedelic drugs for end-of-life patients lies in their ability to free the patient from clinging to the ego-self, increasing the acceptance of death.  But since this effect appears to be achieved by quieting the brain's default-mode network, and the same quieting apparently happens in meditation, perhaps we don't need to inject the dying with psilocybin or LSD, but instead teach them to practice meditation.  Those who can't meditate due to physical or mental ailments might benefit from psychedelic drugs, but those who can don't need to rely on pharmaceutical chemistry to resolve the end of their lives.      

1 comment:

Blue Nosed Mule said...

fascinating. Before I got to the paragraphs that tied in meditation, I expected that, since I considered meditation to be a highly integrated activity, ego is present but being watched by a higher state, that default mode would be very active. I definitely have the wrong model.