"this Is Your Brain On Silence" (article)

[ChimpBrain]

http://nautil.us/issue/16/nothingness/this-is-your-brain-on-silence

Key points.......

One of the researchers who’s examined this question is a Duke University regenerative biologist, Imke Kirste. Like Bernardi, Kirste wasn’t trying to study silence at all. In 2013, she was examining the effects of sounds in the brains of adult mice. Her experiment exposed four groups of mice to various auditory stimuli: music, baby mouse calls, white noise, and silence. She expected that baby mouse calls, as a form of communication, might prompt the development of new brain cells. Like Bernardi, she thought of silence as a control that wouldn’t produce an effect.

As it turned out, even though all the sounds had short-term neurological effects, not one of them had a lasting impact. Yet to her great surprise, Kirste found that two hours of silence per day prompted cell development in the hippocampus, the brain region related to the formation of memory, involving the senses. This was deeply puzzling: The total absence of input was having a more pronounced effect than any sort of input tested.

Here’s how Kirste made sense of the results. She knew that “environmental enrichment,” like the introduction of toys or fellow mice, encouraged the development of neurons because they challenged the brains of mice. Perhaps the total absence of sound may have been so artificial, she reasoned—so alarming, even—that it prompted a higher level of sensitivity or alertness in the mice. Neurogenesis could be an adaptive response to uncanny quiet.

The growth of new cells in the brain doesn’t always have health benefits. But in this case, Kirste says that the cells seemed to become functioning neurons. “We saw that silence is really helping the new generated cells to differentiate into neurons, and integrate into the system.”

------

In 2001, Raichle and his colleagues published a seminal paper that defined a “default mode” of brain function—situated in the prefrontal cortex, active in cognitive actions—implying a “resting” brain is perpetually active, gathering and evaluating information. Focused attention, in fact, curtails this scanning activity. The default mode, Raichle and company argued, has “rather obvious evolutionary significance.” Detecting predators, for example, should happen automatically, and not require additional intention and energy.

Follow-up research has shown the default mode is also enlisted in self-reflection. In 2013, in Frontiers in Human Neuroscience, Joseph Moran and colleagues wrote the brain’s default mode network “is observed most closely during the psychological task of reflecting on one’s personalities and characteristics (self-reflection), rather than during self-recognition, thinking of the self-concept, or thinking about self-esteem, for example.” During this time when the brain rests quietly, wrote Moran and colleagues, our brains integrate external and internal information into “a conscious workspace.”

Freedom from noise and goal-directed tasks, it appears, unites the quiet without and within, allowing our conscious workspace to do its thing, to weave ourselves into the world, to discover where we fit in. That’s the power of silence.