Meditation may affect more of the brain than supposed

Meditation_concentrationIn recent years, much ado has been made about mindfulness meditation. Researchers and psychologists have found strong, persistent connections between meditation and enhanced executive cognitive functions – that is, high-level brain processes, like attention switching, planning, and impulse control, that depend on the frontal cortex region of the brain. But now investigators are finding that meditation may help develop bottom-up cognitive processes as well. In fact, new research from the Netherlands shows that people with experience in meditation may be better at automatic information processing, which depends on some of the oldest parts of the brain.

Top-down information processing is something we all do every day. Every time we tune out a blaring television set to focus on paying bills, or tamp down the impulse to say something nasty to our boss, we’re using top-down control. These top-down functions, also known as executive cognitive functions, are presumed to arise in the frontal cortex, the portion of the brain that is most highly developed in humans compared to other animals. Top-down cognitive processes depend on quickly assimilating new information and placing it in context. This means that we’re constantly using mental models as we operate in real time, comparing new information with previous knowledge and – hopefully – adjusting our behavior accordingly.

Bottom-up processing, on the other hand, is less complex and doesn’t deal as much in context. It simply sorts and relays information up to the higher levels of the brain. This form of processing depends more on the older, more fundamental regions of the brain that are involved in senses such as hearing, sight, and touch. In other words, bottom-up processing might tell you that you’re looking at a red metal thing with wheels; top-down processing tells you that the metal thing is a wheelbarrow, that there are bricks next to it, and that you can use the wheelbarrow to haul bricks from one place to another.

Plenty of studies have been published over the past decade or so showing that meditation, specifically the type known as “mindfulness meditation,” seems to increase people’s top-down cognitive control. People who meditate are, on average, better at controlling impulses, switching their attention from one task to another, and responding effectively to complex, rapidly shifting circumstances. These effects may combine to give rise to the general calmness that many meditators report: since they’re more able to easily deal with demanding cognitive and perceptual tasks, experienced meditators are less likely to become stressed in the face of everyday challenges.

But Paul A.M. van den Hurk and colleagues at Radboud University Nijmegen (the Netherlands) recently published research showing that meditation appears to benefit bottom-up processing as well. The researchers paired meditators with non-meditators and measured their response times as the subjects moved their heads to look at targets on a screen. The investigators also measured electrical activity in the subjects’ neck muscles, as well as the speed with which they moved their necks in response to stimuli. In some tests, warning lights were given just before subjects were shown which target to look at. Likewise, some tests featured medium-intensity noises alongside the visual stimuli, while others blasted the subjects with high-decibel noises.

Van den Hurk and his colleagues were testing for intersensory processing (IF), which describes how people show quicker reaction times when stimuli are presented in two formats rather than just one. In other words, subjects with high intersensory processing will be quicker to react when a target flashes on a screen and a loud noise sounds right behind them. Intersensory processing is usually thought to be a product of involuntary, base-level brain functions – that is, bottom-up rather than top-down processing. If meditation affected IF, the researchers reasoned, then that would be evidence that practicing mindfulness developed not only executive functions but lower-level ones as well.

As it turned out, the results of their study showed that meditators exhibited significantly slower reaction times to startling noises and visual stimuli than non-meditators. This meant that people with meditation experience had weaker “start react effect,” with reduced reactions in the face of sudden, moderately loud or loud noises. Somehow, meditation (the average amount of experience among the meditation group was 11 years) appeared to have weakened intersensory processing in practitioners.

Van den Hurk et al.’s findings dovetail with other recent research showing that meditation is correlated with increased density of gray matter in the medulla oblongata, a fundamental brain structure that helps mediate basic biological and sensory functions.

It’s old news that meditation enhances the upper-level, top-down processing functions that are associated with the advanced frontal cortex. But if practicing mindfulness meditation such as Vipassana can also physically change low-level brain structures and affect bottom-up processing, the scope of research in meditation studies may be greatly expanded. For example, meditation has often been tested as a remedy for depressive rumination, a process that depends heavily on executive cognitive functions. But what if meditation can also help with disorders that were previously considered out of the realm of psychology and behavioral treatments, such as sensory disabilities?

This is, it should be stressed, very much conjecture. Research into meditation’s effects on bottom-up processing is just beginning, and many suppositions will undoubtedly be challenged as new studies appear. But the suggestion that meditation’s positive effects may extend throughout the brain is an exciting one indeed.

See here for van den Hurk et al.'s article, "Mindfulness meditation associated with alterations in bottom-up processing: Psychophysiological evidence for reduced reactivity," in the International Journal of Psychophysiology.