Mice do not, so far as we know, practice meditation. But in order to study how that activity affects human brains at the cellular level, researchers at the University of Oregon managed to put murine brains into a somewhat equivalent state. Their experiments, reported in March in the Proceedings of the National Academy of Sciences, suggest new ways of investigating how a person’s brain can constantly reshape itself.
Past studies have suggested that people who meditate tend to have more white matter in and around the anterior cingulate cortex, a part of the brain involved in regulating emotions. Meditation also seems to intensify theta-wave activity, a type of rhythmic electrical pulsation often associated with a state of calm. Psychologists at Oregon speculated that the surge in theta waves stimulated the production of cells in the white matter. But they needed to develop an animal model of this activity; they obviously couldn’t examine the living brain tissue in meditating humans.
So the psychologists asked colleagues in the university’s neuroscience department if they could increase theta-wave activity in mice, which were already being used to study brain states and neural plasticity, or the brain’s ability to rewire itself. Could the neuroscientists create a comparable effect in mice?
Yes, it turned out, using a brain-research technique known as optogenetics, which uses light to turn on and off neurons, and mice that have been bred with specific genes responsive to light. The Oregon group, by pulsing the light at the same frequency found in human theta waves (eight hertz), were able to switch on the neurons in the anterior cingulate cortexes of the mice. They also exposed some mice to light at higher and lower frequencies and left others alone. Each treated mouse received 30 minutes of light therapy for 20 days, in an attempt to mimic the amount of meditation done in earlier human studies. Afterward, those mice exposed to the eight-hertz, thetalike light waves proved to be relatively calm in behavioral tests: they lingered in lighted portions of a special cage, while their twitchier counterparts ran for the shadows.
In future studies, the researchers plan to measure whether white matter increases in mice made to “meditate” and to track what’s going on biologically in that process. Cristopher Niell, a neuroscientist at the University of Oregon who was involved in this study, says they want to quantify precisely how meditation can alter the physical structure of the brain. The work might eventually enable clinicians to develop alternative therapies that tap into the same mechanism used in the mice study for those who suffer from anxiety or other nervous disorders and do not easily take to meditation, he says.
The research has broader implications as well, Niell adds. Other related studies in his lab and elsewhere will look at how exercise, sex, hunger and other mental and physical states including meditation rebuild the brain. “We want,” he says, “to understand the biological underpinnings of brain states and plasticity itself.”