The neuroscience of meditation

I recently had the chance to read The Neuroscience of Mindfulness Meditation by Tang, Hölzel and Posner. It is effectively a summary of all the research that has been done on the neuroscience of mindfulness meditation, and comments on how a lot of those studies suffer from design flaws, that make their conclusions questionable. In the process of pointing out design flaws in these research papers, the paper fleshes out some clear overarching benefits of meditation that have consistently been seen in research and self-reported experience. I intend to mainly focus on these in this blogpost.

Note that in this paper, the authors consider only mindfulness meditation. Other types of meditation like mantra meditation, chi gong, etc have been ignored. The aim of this paper is to investigate the effects of mindfulness meditation on attention control, emotion regulation and self-awareness.

Main takeaway: Mindfulness meditation helps in accepting the past in an objective light, and moving on. It also improves alertness, helps in dealing with addiction, and obviously reduces stress. Although more evidence is needed for other benefits that people attach with meditation, those mentioned above have ample scientific evidence backing them up.

Challenges in meditation research

Like in other areas of social science, there seems to be a strong bias towards the publication of positive results in the realm of meditation. In addition to this, research on meditation suffers from small samples and post hoc interpretation of results. In other words, researchers collect a bunch of data, and then say “this data probably points to the fact that meditation is beneficial for x”. Their experiment design and hypothesis don’t come from a larger overarching theory that they’re trying to verify or disprove. I will now go into specifics of some of the shortcomings that research into meditation faces:

  1. Cross-sectional versus longitudinal studies: Early research into meditation tended to be cross-sectional: this means that a control group of non-meditators was compared to a group of seasoned and experienced meditators. Differences in their brain structures and neurology would be examined, and many such differences would generally be found. The authors of this paper contend that these neurological differences need not solely be a result of meditation. Maybe people with this particular neurological structure are more likely to meditate, and become seasoned meditators. Hence, the authors propose that scientists perform longitudinal studies. These are studies in which persons are randomly sorted into a meditation group or a general “wellness” group. They’re both made to live a healthy lifestyle. The only difference between them is that one group meditates while another doesn’t. Scientists should then track neurological changes in their brains at regular time intervals. Some researchers have indeed conducted these longitudinal studies, and found that there generally are significant neurological differences between people who meditate and those who don’t. A lot of the evidence presented in this paper will come from longitudinal studies.
  2. Control conditions in functional imaging: How does one find neurological differences between two people? By taking their brain scans of course. However, taking these scans can be tricky. We want to take brain scans in which people are not actively meditating, so that we detect only those neurological features that have been permanently altered, and are not temporarily altered only when a person is meditating. However, if you ask a meditator to enter a “rest state”, they automatically enter a meditative state, or are likely to enter that state at least once. And if we engross our subjects in some other mental activity so that they don’t enter a meditative state, blood flow to their brains increases, causing their brain scans to change. Hence, imaging protocols that do not rely on blood-oxygen-level-dependent contrasts (BOLD contrasts) should be used.

Changes in brain structure

The following areas have consistently been shown to be affected by meditation. Note that other kinds of meditation like Zen, IBMT, etc have also been included in these studies.

  1. Frontopolar cortex: related to meta-awareness (awareness of your attention, and not just the object of your attention)
  2. Sensory cortices and insula: related to body awareness
  3. Hippocampus: related to memory processes
  4. Anterior cingulate cortex (ACC), mid-cingulate cortex and orbitofrontal cortex: related to self and emotion regulation
  5. Superior longitudinal fascicles and corpus callous: involved in intra and inter-hemispherical communication

Although these physical changes in the brain have been consistently found, how these physical changes impact behavior and function are less well understood. Moreover, most studies suffer from treating different regions of the brain as distinct, unrelated entities. It is possible that all of these different regions are parts of a single brain network or pathway. Hence, the neurological structure of the brain needs to be better understood before we can fully understand how meditation is impacting the brain.

Mindfulness and attention

Attention is subdivided into three different components:

  1. Alerting: This can further be subdivided into tonic and phasic effects. This paper does a good job of explaining what those are. Imagine that you’re first given a signal that someone will throw a ball at you, and then after some time a ball is indeed thrown at you. Phasic effects deal with the amount of time it takes for you to get into a suitable fielding position to be ready to catch a ball, and tonic effects deal with fatigue: how much time can you spend catching balls before you start losing your alertness and readiness.
  2. Orienting– This deals with the selection of specific information from multiple sensory stimuli. For instance, imagine that balls of different colors are thrown at you, and you’re told to only catch the red ball. Then you have to be able to ignore the other balls and only go after the red one.
  3. Conflict monitoring– Imagine a timed setting in which you’re asked to pick crayons of colors that are written on a piece of paper. If the word “green” is written in red, the brain will be tempted to pick up the red crayon, although you’re supposed to pick up green. The process of ignoring your initial reaction and going for the green crayon instead of a red one is called conflict monitoring.

Studies have found that early phases of mindfulness meditation might be associated with improvements in conflict monitoring and orienting, whereas later phases might be associated with improved alerting.

Which part of the brain does mindfulness meditation affect though, which causes these changes in attention? The part of the brain that has been most consistently linked to meditation is the anterior cingulate cortex, which will henceforth be abbreviated as ACC. The ACC allows a person to ignore thoughts that keep running in the back of their mind, and focus on the present and the task at hand. This seems pretty useful for people dealing with trauma, who find it difficult to carry on with their daily lives. However, although ACC activation may be enhanced in the early stages of mindfulness meditation, it actually decreases with higher levels of meditation. Does that mean that meditation makes people less capable of dealing with past trauma in the long run? No. Meditation over the long term helps people accept the past and move on. Hence, the suppression of trauma is no longer as important for seasoned meditators. This will be elaborated in a later section of this blogpost.

Mindfulness and emotion regulation

Emotion regulation deals with choosing which emotions rise to the surface, how long those are experienced, and how these emotions may be expressed (in action, for example). Experiments have shown that mindfulness meditation helps in reducing emotional interference by unpleasant stimuli, decreases physiological reactivity, facilitates a return to emotional baseline after stressor films, and decreases self-reported difficulties in emotion regulation. Essentially, it reduces the intensity of negative emotion, and improves overall mood.

What is the neuroscience behind this? Studies have consistently shown that mindfulness practice reduces the activation of the amygdala during stressful situations, along with the activation of the orbitofrontal cortex. Simplistically speaking, the amygdala makes us “sad” and brings up bad memories in stressful situations, and the orbitofrontal cortex helps a person re-frame past traumatic memories in a more positive light. Hence, a reduction in the activation of the amygdala implies a successful suppression of such thoughts and memories, and an activation of the orbitofrontal cortex helps one interpret painful memories in a less traumatic manner. These changes have consistently been shown in less experienced meditators. However, these changes have not been seen in seasoned meditators. Why? Aren’t things supposed to be even better for seasoned meditators? Consider the quote below:

These findings are in line with the assumption that the process of mindfulness meditation is characterized as an active cognitive regulation in meditation beginners, who need to overcome habitual ways of internally reacting to one’s emotions and might therefore show greater prefrontal activation. Expert meditators might not use this prefrontal control. Rather, they might have automated an accepting stance towards their experience and thus no longer engage in top-down control efforts but instead show enhanced bottom-up processing.

In other words, the early stages of meditation help in suppressing negative thoughts. However, the later stages promote acceptance of the past. In a sense, meditation prepares a person to accept the events of the past, and then hopefully move on.

In addition to this, a cross-sectional study has also found that meditation reduces connectivity between the pain-related brain regions and the executive regions. For instance, meditation might help a chain smoker experience the withdrawal pains of giving up nicotine, and still not succumb to start smoking again. Another longitudinal study showed an increased connectivity between the frontal regions of the brain and the amygdala. Hence, the frontal regions of the brain, responsible for modulating thoughts, could more easily modulate the amygdala, which could be thought of as a source of negativity in the brain.

Another area that meditation has been shown to help in is motivation and reward processing. A stronger activity of the putamen and the caudate following mediation suggests a stronger motivation to keep working towards one’s goals, while a lower activation in the caudate nucleus during reward anticipation suggests a heightened ability to not succumb to short-term incentives and rewards. Hence, meditation might help you keep slogging towards your life goals in a fairly stoic manner, without being overly concerned with winning and other “rewards” that you expect to get when you achieve those goals.

Mindfulness and self-awareness

Buddhist philosophy asserts that one should make awareness itself an object at one’s attention. If I’m looking at an orange, I should also be aware of how I’m looking at an orange, and whether other ways of looking at it exist. My thoughts should also go to the nature and limits of my perception. If we can recognize that our limited perception is a major source of misery to us, we may have some hope of seeing our surroundings and circumstances more objectively.

Cue the underlying neuroscience: the default mode network or DMN is considered to be the part of the brain involved in subjective (as opposed to objective) self-referential processing. The DMN shows high activity when one’s mind is wandering or not at peace, and also helps in projecting oneself into another perspective. For instance, if I was bullied as a kid in school, the DMN will help me project myself into my bully’s psyche. I will be able to see exactly how little my bully thought of me (at least according to me. Maybe he was actually bullying me out of insecurity), and the shock of that injustice will lead to trauma and repeated re-processing of that event, causing me greater and greater mental stress. Through fMRI scans, mindfulness meditation has been shown to decrease DMN activity.

The overall findings from multiple studies on mindfulness meditation are that it might alter the self-referential mode so that a previous narrative, evaluative form of self-referential processing is replaced by greater awareness and greater objectivity. Because this is my blog, I am now going to write my personal interpretation of this (plagiarized in part from multiple sources like Sam Harris, Kurt Vonnegut, etc), because I think that this is the main takeaway of the whole paper.

We are often taught to classify things as “good” or “bad”. This is the evaluative narrative that they talk about above. If someone has done something bad to us in the past, we can never get over the injustice of it: how could that person do it? If we have done something bad to someone, and this generally tends to be more traumatic than the former, we can’t get over that either. How could we possibly have wronged this person?! And these thoughts keep gnawing at us day in and out. Mediation helps in destroying this erroneous dichotomy of good and bad. Nothing really is good and bad. It is now a well-established fact that free will doesn’t really exist (I can try and establish this more scientifically in a future blogpost if you’re not convinced by this statement, but Sam Harris has many intelligent things to say about it). We are all Turing machines that have been pre-programmed to do certain tasks in certain situations, with only the illusion that we’re choosing to do these particular things. The person who wronged you was in a state of mind that prompted him to act in that manner in that particular situation. It was inevitable. If you’ve wronged someone, it is because you were in a state of mind that led you to do that thing in that particular situation. We’re not really free agents. We’re just robots gifted/cursed with consciousness. We get to experience our actions, and not really “choose” them. We’re not here to change the world based on our choices. We’re here just to enjoy the show that we put on with other actors. If one can accept this narrative, the acceptance of past and future wrongdoings becomes easier. And this is the acceptance of the past that meditation helps one attain.

References

  1. The Neuroscience of Mindfulness Meditation by Tang, Hölzel and Posner

Published by ayushkhaitan3437

Hello! My name is Ayush Khaitan, and I'm a graduate student in Mathematics. I am always excited about talking to people about their research. Please please set up a meeting with me if you feel that I might have an interesting perspective to offer- https://calendly.com/ayushkhaitan/meeting-with-ayush

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: