In Buddhist Meditation and Depth Psychology Douglas M. Burns writes
In 1963 a fascinating and unique report on Zen meditation was presented by Dr. Akira Kasamatsu and Dr. Tomio Hirai of the Department of Neuro-Psychiatry, Tokyo University. It contained the results of a ten-year study of the brain wave or electroencephalographic (EEG) tracings of Zen masters.[66,67]…
Another finding of the same study concerned what is called alpha blocking and habituation. To understand these phenomena let us imagine that a person who is reading quietly is suddenly interrupted by a loud noise. For a few seconds his attention is diverted from the reading to the noise. If the same sound is then repeated a few seconds later his attention will again be diverted, only not as strongly nor for as long a time. If the sound is then repeated at regular intervals, the person will continue reading and become oblivious to the sound. A normal subject with closed eyes produces alpha waves on an EEG tracing. An auditory stimulation, such as a loud noise, normally obliterates alpha waves for seven seconds or more; this is termed alpha blocking. In a Zen master the alpha blocking produced by the first noise lasts only two seconds. If the noise is repeated at 15 second intervals, we find that in the normal subject there is virtually no alpha blocking remaining by the fifth successive noise. This diminution of alpha blocking is termed habituation and persists in normal subjects for as long as the noise continues at regular and frequent intervals. In the Zen master, however, no habituation is seen. His alpha blocking lasts two seconds with the first sound, two seconds with the fifth sound, and two seconds with the twentieth sound. This implies that the Zen master has a greater awareness of his environment as the paradoxical result of meditative concentration. One master described such a state of mind as that of noticing every person he sees on the street but of not looking back with emotional lingering.
It’s interesting in that Zen, however, you want to put it, is about seeing all things anew, to reference the West’s beloved. No habituation, seeing things deeply, no mind.
But relatedly and equally fascinating is this article: Zen Training Speeds The Mind’s Return After Distraction, Brain Scans Reveal.
Now just think for a moment, if there is no distraction and no coming and going, with everything just being what it is, the bell sound is no distraction, just the universe at this moment in time, requiring full attention.