Blog #4: This is your Brain on Yoga
Hi friends!
I was debating on writing this next blog about Immunizations, specifically those being developed for the COVID19 pandemic, but decided on a very different topic instead. (Though if there’s interest I can write about that at some point too :]). One big reason I deferred from this topic was because infectious diseases/immunology are not my forte. Far from it, actually. So today, I wanted to go to my roots and explore an old (yet still very current) passion of mine—brain imaging—and see how it’s been used to learn more about a new hobby of mine – yoga.
If you know me personally, you might laugh at the mental image of me doing yoga. I know I laugh at myself every time I do it (or rather, attempt to do it). If you don’t know me – allow me to explain. I am not graceful. I’m clumsy. I have crappy balance. Some (read: I) would say I am lacking in “inner peace” (my initial reaction to hearing others talk about their inner peace was reminiscent of Pierce here). But I am comfy as hell in yoga pants, so here we are.
I started doing yoga because I wanted to move my body more while also putting in minimal effort. I figured yoga would be a really easy thing to do in my apartment, that doesn’t involve jumping or banging weights around or anything that might annoy my neighbors. Also one time in high school, my gym class had a yoga unit and we practiced deep breathing in corpse pose for 30 mins straight, and I remember being a biiig fan of that. So, I tried yoga!
To start, I’ve been doing yoga on YouTube (specifically starting out with Yoga with Adriene’s 30 Days of Yoga – I finished all 30 days, and have moved on to her hundreds of other videos now. She’s an absolute joy and I highly recommend!). Because of that, thanks to the algorithm, a lot of my suggested videos have been about yoga; specifically, TEDTalks/segments from documentaries about how yoga is ~good for the soul~, can build strength, and can even help with anxiety and depression! But, as I cannot turn off my scientist brain (it’s a blessing and a curse), my response to these videos is usually, “okay, sure, but can u prove it?”. This sent me on a search through the scientific literature to see what, if anything, has been done to explore the effects of yoga on the brain.
Before we get into the science, I want acknowledge the history and origins of yoga! At a point around the 1st century CE, Patanjali, a Hindu sage, began to record different meditative traditions that were practiced throughout India in 196 manuals, called the Yoga-Sutra. In these manuals, yoga was defined as the “retraining of the mind from focusing on external objects to reach a state of pure consciousness”. Over time, yoga developed to incorporate postures from influences like gymnastics and wrestling. Today, most yoga practices still use three fundamental components that Patanjali discussed: physical poses, breathing exercises, and spiritual contemplation. Those who practice yoga claim that these techniques can boost mood, improve lung and heart health, increase flexibility and more! However, these claims can be difficult to explore in a scientific setting, as things like feelings and moods are often self-reported and are subjective, and most sample sizes in studies of yoga are small and not diverse enough to make general claims about the practice.
Personally, I am interested in the claims regarding psychological benefits in yoga. My thesis research uses brain imaging technologies (PET and MRI) in various applications ranging from brain development and aging to exploring neurological and neuropsychiatric conditions. I was curious to see if anyone out there in the science sphere has used these imaging technologies to look at how brains are different with and without (or before/after) yoga and meditation practices!
Before discussing how these practices affect different parts of the brain, it might make sense to review a few important brain structures. The brain can be divided in a few different ways – firstly by hemisphere. If you were to chop your head in half, right between your eyebrows, front to back, you’d die. (lol sorry I had to). But also, you’d have two halves of your brain – the left and right hemisphere – which both have structures that are mirrored/opposite one another. The left hemisphere more frequently processes detailed oriented processes, while the right brain processes more emotional information processing. Within/across both hemispheres, there are four sub-sections of the cerebral brain, which are the frontal cortex (as the name implies, is at the front of the brain, and is in charge of cognitive processes and making executive decisions), the parietal cortex (in charge of spatial, somatosensory and motor processing), the temporal cortex (in charge of processing auditory stimuli, and memory), and the occipital cortex (in charge of processing visual stimuli). Even though these regions are functionally distinct, they are still very much connected; nerve signals can be transmitted both across regions and across hemispheres. For example, during active listening, both your temporal cortex and your frontal cortex will be activated; whereas, during passive listening, when you’re not really “paying attention” to the spotify playlist in the background, there is less activation of your frontal cortex. We can visualize which areas of the brain are activated using tools such as functional magnetic resonance imaging (fMRI), which detects changes in blood oxygenation levels in brain regions of interest during a task – where more oxygen is delivered to regions that are active. We can also look at brain activation using positron emission tomography (PET) imaging, in which radioactive ligands are administered into a subject and can be traced throughout the body, and can be used to measure blood flow to the brain – where the same concept applies, more oxygenated blood will flow to regions that are active.
A thorough review article by Roy King M.D., Ph.D. and Ann Brownstone M.S., O.T.R., published in International Journal of Yoga Therapy in 1999, summarizes the origins of yoga, various types of yoga, and reviews a few brain imaging studies that look at how different types of yoga affect the brain. Specifically, they highlighted a study that used PET imaging to look at the effect of Yoga Nidra, a relaxation meditation where you disengage from external sensations and focus attention on the body, on the cerebral blood flow to different parts of the frontal cortex (Lou, HC et al., 1999). Specifically, each subject observed four separate Yoga Nidra states during a PET scan:
1) experiencing heaviness sequentially in various body locations
2) the abstract (i.e. not related to external facts or experiences) experience of joy and happiness
3) visualizing a summer landscape
4) imagining the self as a golden egg.
The PET data showed that overall the global cerebral blood flow, or blood flow to the entire brain, did not change during meditation. However, depending on the phase of meditation, there were regional changes in blood flow! During the meditation that focused on the heaviness of body parts, blood flow in the parietal and frontal cortices were observed. Visual imagery of the summer landscape appeared to increase blood flow to the occipital lobe and the parietal lobe. So, in the act of yoga and meditation, things (i.e. blood flow) are definitely changing in your brain! Specific types of yoga, like visualization or somatic-sensualization, can activate relevant regions of your brain on command! But - as is typical in our field of PET imaging - sample size is our downfall, and this study only incorporated data from 2 subjects. Still pretty cool though!
But what about longer term effects? Can repeated yoga practicing alter the structure or function of your brain? Can it really help by reducing anxiety and alleviating depression? In the current literature that’s out there, it looks like it might be helpful! One study in particular by Streeter, CC, et al., published in 2007 (source) looked at levels of GABA, the principal inhibitory neurotransmitter in the brain, of well-practiced yoga practitioners vs. subjects who did not do yoga. GABA, or gamma-aminobutyric acid, is a neurochemical that inhibits or lowers the activity of certain brain functions. Many studies support the hypothesis that in psychiatric disorders, especially in anxiety and depression, there is a disruption in the GABA-ergic system; more specifically, there are low GABA levels in those with anxiety and/or depression. This study measured GABA levels in the brain before and after a yoga session in people who had regularly practice yoga, and before and after a reading session in people who did not practice yoga regularly. This study found that in yoga practitioners, GABA levels increased after a yoga practice, and that in control subjects with no yoga experience, GABA levels stayed the same after a reading period. So, the conclusion from this is that, for those who regularly practice yoga, the act of yoga can increase GABA levels, which can improve mood and decrease anxiety. So, for those who regularly practice yoga, it might have an anti-depressant, anxiety reducing effect! However, one thing to consider here is the lack of physical activity in the reading group. Is this increase in brain GABA level specific to just yoga practice? Or could it be a result of exercise/physical activity in general? You know, like how exercise releases endorphins and stuff! (Endorphins make people happy! Happy people don’t kill their husbands! – extra credit points if you got that reference). I’m sure there have been more studies looking into the effects of different types of exercise on the brain – I’ll look into this, but it will no doubt send me down a new rabbit hole. I have to set boundaries somewhere so for now I’ll just file it under ongoing/future topics to think about for future blogs :]
I really was pleasantly surprised to see the number of studies using brain imaging to explore the effects of yoga and meditation practices on brain function. A few other points I thought were interesting include this study using fMRI to explore hippocampal activation during silent mantra meditation (source). Some studies have even argued that yoga has neuroprotective effects on the brain (source)!
Overall, it’s pretty cool to see that a practice that uses physical, mental, emotional, and spiritual focus may have a significant impact on your brain function, your body, and your life! And, even more exciting, that we can use science to try to prove it!
Thanks for reading!
Take care and stay well,
Or, as my new Yogi friends say,
Namaste,
-s
