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Monkey Mind I: Subjectivity and the Brain's Default Mode Network

So, what do you think about when you’re not thinking about anything else? Where does your mind go when it isn’t busy with goal-directed tasks requiring your attention, or being drawn to the external world by its normal busy set of events, its normal information overload? What is that part of your mind which just won’t shut up when you are trying to get to sleep, or that gets in the way when you are trying to quiet and center yourself in meditation, or even just “sit quietly in a room alone,” the inability from which Blaise Pascal asserted all of humanity’s problems stem?

This is what Buddhist meditators call “monkey mind,” that chattering ego which may be the root of all human suffering. It turns out that there is network in the brain that is suspended when you lose yourself in a task, originally called the “task negative network,” deactivated during most externally focused goal-directed tasks, which becomes activated within less than a second of finishing a task. This “resting state connectivity,” showing synchronicity in functional magnetic resonance imaging (fMRI), is correlated with the alternate deactivation of the areas of the brain involved in perception, language, and attention tasks. Most of us, when not doing much of anything else, tend to be yammering away, talking to ourselves, mostly about ourselves and our close personal relationships, past and future.

Marcus Raichle, working at the Washington University Med School, called this the “Default Mode Network,” active when you are not focused on the outside world, when your mind is wandering or daydreaming, but it is also active when you are (1) thinking about others, (2) thinking about yourself, (3) remembering the past, and (4) planning for the future. So what else do you think about when you aren’t thinking about anything else, or aren’t focused on some external task? Actually, even goal-oriented tasks that are autobiographical or use social working memory are correlated with activation of the Default Mode Network. This is a large scale network of interacting brain regions with activity highly correlated with each other, and negatively correlated with other networks, such as those involved in attention.

The brain does not cease to operate when one is at rest. Indeed, Raichle and others have shown that a focused mental task increases the brain's consumption of energy by less than 5%. Indeed, blood flow in the frontal cortex is highest when a person is at rest, and there is “intrinsic oscillatory behavior” in vertebrate neurons generally in Purkinje cells in the cerebellum, in the inferior olivary nucleus and in the thalamus. Think of this ”intrinsic oscillatory behavior” as a coordinating pattern of firing, like an audience applauding. It may be one of the mechanisms behind “long-distance” interactions between relatively distant parts of the brain. We’ll return later to what happens when some of this goes out of sequence.

Marcus Raichle and his group originally published “A default mode of brain function” in the Proceedings of the National Academy of Sciences in 2001. I was aware of work showing that areas of the brain active when we aren’t focused on anything else involved language areas and our interior dialogues, mainly about our close personal relationships. Indeed, I included some of this work in an upper-level undergraduate colloquium I taught on “Brain, Mind, and Spirit,” from 2001-2004, and on “Neuromythology: Brains and Stories,” from 2005-2009. Nevertheless, because of robust findings on the “independent component analysis” showing the long-distance effects in the default network, that effortless resting scans could be easily done on a wide range of populations, including clinical, developmental, and even nonhuman primates, research that only produced a dozen articles prior to 2007, produced over a thousand across the next seven years.

As a working scholar, my focus was elsewhere, teaching and publishing my initial synthesis of “Neuromythology” in Zygon: Journal of Religion and Science in 2006, and focusing on “relationality” for a conference in Madrid in 2008, and for the Institute on Religion in an Age of Science in 2009 (published in Zygon in 2011), and then on narrative and meaning, embodied and extended cognition, emotional psychology, and finally “Knowing Ourselves by Telling Stories to Ourselves” (Zygon 2017).

One of the nice things about retiring from academia in 2017 is the ability to step back, have some more perspective, and see that some other important things are going on. Indeed, it was the recommendation by two young alums of Michael Pollan’s wonderful book How to Change Your Mind, that not only alerted me to the neuroscience of the default brain network, but to the renewal of several generations of long-lost research on psychedelic drugs, with extensive research projects going on at Johns-Hopkins, UCLA, and New York University. A major Swiss conference in 2006 included the nonagenarian Albert Hoffman, who first synthesized LSD in 1943, ten years before Aldous Huxley’s Doors of Perception

(published the year of my birth, in 1953). I was also surprised to learn that Huxley had his wife inject him with LSD on the day of his death, November 22, 1963, significant to my generation as the day President John F. Kennedy had his brains blown out in Dallas.

The Default Mode Network includes an anatomically defined set of brain regions. The functional hubs, for self-related information, include (1) the Posterior Cingulate Cortex which activates in all tasks involving the network, including those related to self, others, remembering the past and thinking about the future. The (2) Medial Prefrontal Cortex activates during decisions about personal information, autobiographical memories, future goals and events, and decisions about close personal relationships; the lower part being involved in positive emotion and internally values reward. Finally (3) the Angular Gyrus, a set of connective fibers linking perception, attention, spatial cognition, and action, helpsing with recall of episodic memories (of events in your life).

There are two subsystems of the Default Mode Network. (1) The Dorsal Medial subsystem, for thinking about others, including the functional hubs, as well as the dorso-medial prefrontal cortex, responsible foir determining or inferring other’s purposes, the temporal-parietal junction reflecting beliefs about others (“theory of mind”), and the lateral and anterior temporal cortex related to abstract conceptual information, particularly the social. (2) The Medial Temporal subsystem, for autobiographical memory and imagining the future, includes the hippocampus, involved in forming new memories, remembering and anticipating, several nearby structures related to scene recognition and spatial navigation, and the posterior inferior parietal lobe, which is the junction of auditory, visual, and somatosensory information. Overall, the Default Mode Network is involved in (1) autobiographical information, self-reference, and emotional self-reflection, (2) thinking about what others think and know (theory of mind), understanding and empathizing with others’ feelings, moral reasoning, and social categorization and evaluation, and (3) remembering one’s past and thinking about or imagining the future. Watching a movie, and listening to or reading a story produce highly correlated Default Mode Network activation.

The Default Mode Network certainly suggests that there is a lot going on, most of it focused on self and close others, when one is “at rest” and not doing much else, at least not much else toward goal-directed external tasks. “Monkey mind” indeed. But wait. Actual monkeys also show some of the same resting connectivity in similar regions to what is found in the default mode network in human beings, with he posterior cingulate being a central hub, although the connections to the medial prefrontal cortex are certainly smaller. But it is with the human developmental research that things get interesting. There is only limited evidence of a default mode network in infancy, and default network connectivity only becomes consistent by 9-12 years, before which it is only developing. It is disrupted in autism spectrum disorders, and in Alzheimer’s even before patients become symptomatic. People who have had long-term trauma, such as in childhood abuse or neglect, show lower connectivity in the default mode network, also associated with dysfunctions in attachment. PTSD shows lower connectivity. More interestingly, rumination in depression and in chronic pain are associated with hyperconnectivity. Psychotherapy, medication, and deep-brain stimulation can help normalize connectivity.

Functionally speaking the Default Mode Network looks a lot like the Freudian "ego," that fussy Victorian English Latinization of what was, in Freud’s German, just the Ich, so his book Das Ich und Das Es gets translated as The Ego and the Id, rather than a more telling “The I and the It.” But like the ego, we aren’t born with it (only with “the Id,” or “the It,” as in “that’s not me, but ‘it’ did it”), and since the default mode network doesn’t develop consistent connectivity until ages 9-12, it is largely undeveloped under age 5. Freud’s ego is, of course, largely formed from various defense mechanisms, ways of disowning experiences that otherwise produce overwhelming feelings of anxiety. You want to understand the boundaries of the ego? Look at what makes you anxious enough to avoid it. If you get good at avoiding thinking about something, you aren’t normally conscious of it. That’s what the “unconscious” is. When those ego defenses weaken in sleep, you can become aware of this material, even if disguised in the form of your dreams (the “royal road” to the unconscious).

During resting wakefulness, when you aren’t doing anything else, the functional connectivity in the default mode network is strong. With the onset of sleep, the connectivity between the default mode network and the “task positive” network decreases further than usual. In stage 2 sleep we show decreased connectivity between the functional hubs of the posterior cingulate and the medial prefrontal cortices, which decreases further in stage 3, but may increase during REM sleep (dreaming sleep). Long term practitioners of meditation show reduced activity and connectivity within the default mode network. Similar results are shown under the influence of psychedelic drugs: Under psilocybin, there is reduced blood flow to the posterior cingulate and medial prefrontal cortices. Under LSD, activity within the default mode network becomes desynchronized -- activity within different regions of the default network, the otherwise shared oscillatory patterns of distant regions, becomes less correlated. Not exactly the sound of “one hand clapping,” but certainly an applauding audience when the clapping desynchronizes. I can’t help but think of the slow clap that is meant to be ironic.

Shades of Aldous Huxley. Many terminal cancer volunteers, in contemporary research, reported that after a single guided psychedelic “journey,” they reconceived how they saw their cancer and the prospect of mortality, some reporting a complete loss of their fear of death. One researcher said, “Individuals transcend their primary identification with their bodies and experienced ego-free states.” Unlike children, adults normally don’t just take in the overwhelming buzzing and blooming confusion of the world, but make educated guesses about a sliver of information. This normally saves time and energy. It is filtered through what Thomas Metzinger called The Ego Tunnel. When LSD desynchronizes the default mode network, perhaps it disables this shorthand efficiency, returning a childlike immediacy and wonder. According to the Buddhists, our attachments, particularly to the self, are really the root of all suffering. Happily, the self is an illusion (or a construction), and surrendering our attachment to it is the path to enlightenment.

Clearly, there may be value to quieting the “monkey mind” of our chattering self. Meditation, and a range of other practices like floating in a sensory deprivation tank, or holotropic breathing, may provide one set of pathways. Do psychedelic drugs provide others, or just add other veils of illusion? Their similar effects on the connectivity of the default mode network may, if nothing else, provide us some valuable, and more readily accessible information on the neurochemistry of our sense of being, even when at rest from the busy task-oriented doing with which we are otherwise engaged.

The “classical psychedelics,” like mescaline (from the peyote cactus), psilocybin (magic mushrooms), or the artificially synthesized lysergic acid diethylamide, are all tryptamines, as is the neurotransmitter serotonin (abbreviated 5HT, for 5-hydroxytryptamine). Serotonin actually binds with a number of different receptor sites, not only throughout the brain, but with substantial representation in the digestive tract (remember the “enteric brain” discussion in “Your Guts,” the Neuromyth Blog of 9.15.2018). The classical psychedelics are strongly drawn to one of about a dozen serotonin receptors, the 5-HT2A , found in large numbers in the cerebral cortex.

My ancient understanding (which might have been drawn from reading John Lilly’s work) was that the psychedelics worked like a broken key in the locks of these receptors, effectively blocking the receptors and producing something like massive sensory deprivation, like one might get in an isolation tank (as illustrated in Ken Russell’s 1980 movie Altered States, based on the novel by Paddy Chayefsky, and also the actor William Hurt’s film debut), which can actually be found in most urban areas. I last tried one in Virginia Beach in 2015, only slowly realizing that the noise of the surf and the jungle beat I thought I was hearing were actually my own breathing and heartbeat. But the binding of psilocybin and LSD with the 5-HT2A receptors was actually not demonstrated until 1998, when Franz Vollenweider showed that a drug that actually blocked this receptor rendered psilocybin ineffective. It turns out that LSD may actually be “stickier” at these sites than even serotonin. The science linking LSD and serotonin has been around since the 1950s, and helped advance the field of neuropharmacology, including the use of the “selective serotonin reuptake inhibitors” (SSRIs like Prozac and Zoloft); the inhibition of serotonin reuptake by the presynaptic cell strengthens its effects.

I should caution readers here that the SSRIs are really only effective with “Typical,” “Melancholic,” or Type B depression, as an alternative to the MAO inhibitors that were previously used, but less effective with Type A “Atypical” depression, better treated with the tricyclic antidepressants. Type A may be more associated with deficiencies of dopamine and norepinephrine, Type B with serotonin deficiency. It may turn out that there are even more than two subtypes of depression, and they are likely related with a complicated set of balances between a variety of neurotransmitters. A major depressive episode I had in the spring of 2002, to which the events of 9/11/2001 may have contributed, may also have been due to a sudden drop in serotonin levels sometimes brought on by the introduction of anti-cholesterol medication, which I also began in the winter of 2001-2002. Nevertheless my particular depression was ultimately better treated with bupropion (Wellbutrin), which has an across-the-board effect on all three neurotransmitters, and also did not produce the notorious libidinal effects of the SSRIs.

It turns out that contemporary neuroscience, particularly that exploring the effects of psychedelic drugs, may have much to contribute to our understanding of the phenomenology of ego-dissolution and the collapse of the subject-object distinction found in mystical experience. This is a discussion that may also have something to contribute to a more unified understanding of the healthy functioning of human minds, down to the minds of children only beginning to construct a sense of themselves. I think much of it connects quite centrally to concepts of ego-integrity, and healthy resilience in its partial disintegration, what psychoanalysts refer to as “regression in service of the ego.” Unfortunately, such disintegration is exacerbated by the informational and social fragmentation of individuals into electronic information bubbles, and the formation of well bounded and informationally “siloed” communities of discourse.

Sigmund Freud famously said that our greatest certainty is the feeling of ourselves, our ego-consciousness. But the problem of this consciousness has become one of the central controversies in the cognitive sciences. What it feels like to be you, like “what it is like to be a bat,” as Thomas Nagle wrote in his seminal paper of that name in 1974, is the “hard problem.” How can the sciences of the mind account for that unique experience? My own perspective is that this is a category error: the very goal of science is to construct objective (or, more accurately, intersubjective) explanations. I don’t think it is some “non-material” aspect of brain function that must be invoked to account for subjectivity; I think the very project is flawed. Science may be able to tell us a great deal about what is generally true about brain function and its relationship to consciousness and individual subjectivity, which may always be not only informative but necessary to a full understanding. However (the big BUT), if the very phenomena in question are constituted by their subjectivity, by the particular perspective each unique individual has on their own functioning, an objective explanation will forever miss the mark. Each moment of our individual histories across a life-span may contribute to this “tip of the iceberg” of consciousness, as even identical twins start producing different experiences in the womb (part of the myth that your clone would be your doppelganger forgets this rather obvious fact). Not only will an intersubjective explanation, true across the board, simply miss most of what makes our particular subjective experience unique, but the very fact that it is a causal explanation will miss much of what makes it meaningful.

Causality does not exhaust meaning. As causality may be important to understand something in terms of its parts, and their efficient causal relationships with each other and with the world, it is not meant to address what this something “means” in terms of how it may itself be a part of larger and more inclusive systems, from the social to the universal, or even to the “ground of all being.” None of this, of course, remotely means that everything that really happens doesn’t have material causality, running back to the origins of the universe, or ever slips these material bonds. It is just that this causal and intersubjective account will never be the full story, and believing so is to commit the kind of category error that is behind many of the confusions in the cognitive sciences, to say nothing of the troubled relationship between the sciences and the humanities more generally. To brutally oversimplify, even if I can fully and materially account for the experience of tasting chocolate, it will still taste like chocolate in the unique way it tastes like chocolate to me. Even if I can explain “falling in love” I will still have my unique experience of doing so, conditioned by my lifetime of experiencing separation and reunion. And perhaps, by knowing more about their material and causal conditions, such experiences might be richer, rather than “explained away.”

Studying the “neural correlates of consciousness” is still an important endeavor, and may be providing even more profound insights when we begin to study the neural correlates of quite varied states of consciousness. Nobody in the cognitive sciences, or elsewhere, fails to understand that the study of the neural correlates of sleep and wakefulness has provided important contributions to the understanding of sentient life. So what might be contributed by the study of states of consciousness that are not only profound, but experienced as noetic, particularly in the experience of ego dissolution, losing the differentiation of subject and object?

We will continue this discussion in “Monkey Mind II: Mysticism, Childhood, and Mental Health.”