Earlier blogs “Folk Who Meditate Decrease Mind Wandering” and “Magic mushrooms work like meditation? The latest science.” demonstrated how dramatically long term meditation and psilocybin can alter the functioning of the default mode network (DMN). The DMN is the selfing/I-ing/me-ing/my-ing neural network (”Three Neural Networks Dancing…“blah, blah”, tasking and control”).
Two new research studies demonstrate that aging and ayahuasca, an increasingly-used psychedelic/entheogen, can also change the functioning of the DMN, as does an earlier study on autism.
Studies have shown that DMN activity varies with many tasks, states of consciousness and physical maladies. DMN activity is increased in schizophrenia, depression, Parkinson’s disease, social anxiety disorder, and by tetrahydrocannabinol (THC – marijuana). However, DMN activity is reduced in autism, Alzheimer’s disease, hypnosis, meditation and by psilocybin. (References available for all.)
AYAHUASCA and DMN
The ayahuasca research is “The Psychedelic State Induced by Ayahuasca Modulates the Activity and Connectivity of the Default Mode Network” by Palhano-Fontes, et al. in PLOS ONE. As i’m sure your friends/frenemies have told you, psychedelics produce complex changes in perception and cognition, altered states of consciousness and in some cases, a remarkable increase in introspection. This can be useful in nondual awakening to demonstrate that the reality you typically see is not the only one the brain can manufacture.
Palhano-Fontes and his Brazilian colleagues used fMRI to see what changes occur in the DMN and between it and the task-positive (TPN) network (which it competes with) during the state induced by ayahuasca in ten experienced subjects.
Experienced subjects were selected to avoid vomiting and diarrhea inside the scanner, two effects of ayahuasca frequently observed in inexperienced subjects. This does, however, introduce the distorting effect of “conditioning” in the study.
As you likely know, ayahuasca is the core of some Brazilian syncretic religions, most notably the Santo Daime church which began in the 1920s in western Brazil. It is typically made into a brew from the decoction of two different plants: the Psychotria viridis and the Banisteriopsis caapi (this will be on the quiz).
The first contains tryptamine N,N-dimethyltryptamine (DMT) that binds to serotonin and sigma-1 receptors. The second is rich in beta-carboline alkaloids, particularly harmine, tetrahydroharmine (THH), and harmaline.
Harmine and harmaline are potent monoamine oxidase inhibitors (MAOi) and THH acts as a serotonin reuptake inhibitor and a weak MAOi to prevent the degradation of monoamine neurotransmitters to maintain/increase their levels.
This complexity matters – it yields a more complex experience with more bodily experience and sedation than does psilocybin/‘shrooms.
The researchers found that ayahuasca caused a significant decrease in activity in most parts of the DMN, including its two central hubs, the posterior cingulate cortex (PCC) and the medial prefrontal cortex (mPFC). Surprisingly, functional connectivity within the PCC decreased after ayahuasca intake, but not between the PCC and the mPFC as we saw with psilocybin.
No significant change was observed in the relationship between the DMN (blah, blah) and TPN (tasking) networks.
While performing mental imagery tasks, the researchers found that ayahuasca “selectively modulates frontal, temporal and occipital brain networks associated with intention, memory and vision.”
The effects include significantly increased and coupled activity in the primary visual cortex.
In addition to the mental imagery, ayahuasca generates gastrointestinal distress, changes of space and time scaling, dissociation, sense of well-being, insights, feelings of apprehension, and, importantly, increased introspection into one’s thoughts and feelings.
AGING and DMN
The aging effects on DMN study is “Decreased Default Mode Network connectivity correlates with age-associated structural and cognitive changes” by Vidal-Piñeiro, et al. in Frontiers in Aging Neuroscience.
Grey matter – dark pink w/cells
White matter –
light pink w/meshwork
As is well known, aging entails cognitive and motor decline as well as brain changes such as loss of grey matter and white matter integrity and cerebral blood flow. Reduced resting-state fMRI connectivity
between the principal nodes of the DMN (mPFC, PCC, inferior parietal lobe, and middle and medial temporal cortex) is also an indicator of aging.
Vidal-Piñeiro and his 9 colleagues assessed these factors in aging by using two independent groups of subjects: a) 116 healthy elder subjects (age = 68.25, range: 63–78, 37 males) and b) 25 young (8 males) and 25 elder (8 males) healthy subjects (ages = 23.08 (range 19–28) and 68.92 (range 64–76) for age-related comparisons. fMRI imaging was the same.
The principal results were:
with mPCF –
(1) mPFC-PCC connectivity is highly reduced in aging
for young (black)
and old (gray)
(2) this connectivity is related to cognition, particularly memory performance
(3) mPFC-PCC connectivity is related to gray matter and white matter integrity in several brain areas outside the DMN
(4) cerebral blood flow measures are unrelated to DMN connectivity
So, mPFC – PCC connectivity in the DMN is likely a sensitive measure of brain aging.
AUTISM and DMN
The autism vs DMN study is “Functional abnormalities of the default network during self-and other-reflection in autism” by Daniel P. Kennedy and Eric Courchesne in Social Cognitive and Affective Neuroscience in 2008. (This is a good paper.)
Several studies of autism have identified functional
abnormalities of the DMN during a passive resting state. As we know, the DMN is heavily engaged in social, emotional and
introspective processing, so a dysfunction in it may be an important element of some of the difficulties individuals with autism experience.
In this research, Kennedy and Courchesne used tasks with “constrained social and introspective” elements. Thirteen autism and 12 control participants were scanned while making true/false judgments for various statements about themselves (SELF) or a close other person (OTHER), and pertaining to either psychological personality traits (INTERNAL) or observable characteristics and behaviors (EXTERNAL).
A MATH condition was the experimental baseline in which folk saw math equations like 45 + 8 = 53, and pressed a button as to whether the equation was true or false.
In the fMRI scanning, the medial prefrontal cortex/anterior cingulate cortex activity was reduced in the autism group across all judgment conditions indicating a “tasking dependent dysfunction of this region”.
In other DMN regions, levels of activity were not different between the autism and control groups. In some DMN regions (dMPFC and PCC), interactions were found only for INTERNAL/EXTERNAL judgments, and not SELF/OTHER judgments, which indicates a “task-specific dysfunction.”
These specific findings for social, emotional and introspective processes are important for understanding the structures/operation of autism.
So what’s the take-away? Whether it’s meditation, psilocybin, ayahuasca, autism, aging, or any of the others mentioned above, the DMN is a major, but not the only factor. There are other factors which make the manifestations unique, and determines whether they are psychedelic, meditative, hypnotic, or psychopathological. As w/all good science, further study is needed…and is occurring.