Neuronal Networks: The Central Executive Network... and some philosophy

In previous episodes I have tried to draw pictures in your mind (using those fat crayons that babies like to chew on) of some of the brain networks that are important in many mental illnesses.  We have talked specifically about the Default Mode Network (that is concerned with imaginal thoughts and self-referential thoughts and memories), the Dorsal and Ventral Attention Networks (that help us to identify and pick out details of both our environment and our thoughts and memories), and the Salience Network (that brings the most important details of our perceptions, thoughts, and memories to the forefront of our mind).  What we are missing is a network that takes those salient things, considers alternative options about what they mean and what to do about them, organizes a plan to execute, and motivates us to move.  Our Central Executive Network and its connections to the other networks are integral in these processes.

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References and readings (when available) are posted at the end of each episode transcript, located at psydactic.buzzsprout.com. All opinions expressed in this podcast are exclusively those of the person speaking and should not be confused with the opinions of anyone else. We reserve the right to be wrong. Nothing in this podcast should be treated as individual medical advice.

Transcript

Brain Networks: Central Executive Network… and some philosophy of science.

Welcome to PsyDactic…  I could say that no one in their right mind would claim that the content in this podcast speaks for them, but honestly, I don’t know whether they would or not, and that is the point.  I speak for myself.  My opinions are my own and should not be confused with those of anyone else.

I have another original poem for you.  Don’t worry.  It is not a limerick this time.  Also it is very short, so please don’t hit skip just yet.

I call it: A cinch

I turn this wrench to cinch this bolt up on the bench
and clench the wood just right.
I must mention it's not my intention to clench in one bolt too tight.

In previous episodes I have tried to draw pictures in your mind (using those fat crayons that babies like to chew on) of some of the brain networks that are important in many mental illnesses.  We have talked specifically about the Default Mode Network (that is concerned with imaginal thoughts and self-referential thoughts and memories), the Dorsal and Ventral Attention Networks (that help us to identify and pick out details of both our environment and our thoughts and memories), and the Salience Network (that brings the most important details of our perceptions, thoughts, and memories to the forefront of our mind).  What we are missing is a network that takes those salient things, considers alternative options about what they mean and what to do about them, organizes a plan to execute, and motivates us to move.  We need a network that can “cinch a bench.”  Our Central Executive Network and its connections to the other networks are integral in these processes.

According to most sources I have checked (for example, some of the papers and webpages cited at the end of the show transcript found at psydactic.buzzsprout.com) a the CEN is responsible for:
- Active tasks involving working memory
- Organized processing of new and remembered information 
- Integration of information from the other brain networks
- Rule-based problem solving
- Consideration of multiple things in a reasonable sequence
- Organizing our responses to these things and
- Reinforcement of visually perceived behaviors in ourselves and others

That's a lot of things, many of which sound a lot like the others.  To summarize, the CEN is able to take a lot of information, store it in our working memory, scan what we think about it and what we feel about it, and help us make decisions about what to do about it.  Some call it our “external mind” because it is primarily concerned with what’s going on around us, while our default mode network is our “internal mind” because it attends to our internal states.  But this dichotomy, I think, has limited utility.  Our working memory, which is controlled by our CEN, needs access to the details of our senses, how those things relate to us, and how the outcomes of our actions will relate to us.  It is likely that our networks are switching frequently.  Goals require more than accessible, organized lists of things.  They require the ability to place the outcomes we are planning into context and switch between possible outcomes when the context changes.

The CEN like the other networks I have discussed is not confined to one lobe of the brain or a single “functional area.”  That’s because to do brainy things requires multiple inputs, multiple processors, multiple outputs and an intricate balance of these things communicating with each other.  Having an area that can identify shapes is useless if it can’t be assigned some kind of importance and you don’t know how to do anything about it.

Some call the CEN the Frontoparietal Network, which from an anatomical perspective helps to orient us to its primary locations: the frontal lobes and the parietal lobes. But these are big areas, so let's get more granular.  The CEN has also been called the lateral frontoparietal network.  It is primarily composed of the dorsolateral prefrontal cortex and posterior parietal cortex. The lateral parts are the outside parts, the parts near the skull, not the more medial parts that are located on the surface of the brain where it folds into the center of your cranium.  That’s why TBIs can mess this system up so easily.  If the DLPFC smashes into bone, it doesn’t work so well after that.

The DLPFC is a target for treatment resistant depression.  If you remember way back to the TMS episodes, targeting the DLFPC with high frequency theta bursts has been shown to be effective in treatment resistant depression.  But that is not the only thing the DLPFC can affect.  Damage to this area can also result in the development of obsessive-like repetitive behaviors, loss of motivation, reduced speech, poor concentration, inability to complete complex tasks, and even in what one paper termed Machiavellian Tendencies (or an inability to trust other people).  That is a lot of claims.

But what does the parietal part do?  The lateral posterior parietal cortex seems to be involved in attending to sensory information both external and internal.  By attending, I mean helping to maintain attention on perceptual experiences, both from the world outside and within our bodies.  I wonder how or if this lateral posterior parietal cortex is involved in somatic symptoms disorders, when patients are preoccupied with their internal perceptual states?  This is very similar to how the patient lobe is reported to function in the salience network and other attention networks.

The CEN then, is distinguished from other networks in that it is very task or problem focussed.  If I want to do something, I need this network to function well.  If I want to ponder something, I need my DFM network functioning well.  If I want to understand what details are important, I need my Salience Network functioning well.  If I want to experience the world, I need my sensory networks working well. If I need to be able to pick out details from the environment, I need my attention networks functioning well.

In the last episode, I mentioned that neuroscientists have been very interested in the interplay of three networks, the CEN, SN, and DMN because these are frequently involved in many neuropsychiatric disorders.  They call this the Triple Network Model.

I should take a break here and consent the listener to the fact that I am not a neuroscientist.  I have a Masters Degree in Evolutionary Biology and a Medical Degree.  I am just an older than usual psychiatry resident.  When I read the papers that I report in these episodes, I constantly reach the limits of my knowledge and struggle to put the pieces together.  Science produces difficult technical language.

That being said.  In future episodes, I am going to try to put some of these pieces together the best that I can.  I believe that science is a slow, meticulous process that is infuriating at times.  Whether this triple network model is going to stand the test of time is less important to me than whether it is the next step to understanding how our brains work.  I expect it to fail, but it is adding important clues to our thinking.  Our behaviors are obviously outward manifestations of our individual expressions of our internalized biopsychosocial cultural context, but there is a reason that BIO is the first part of the biopsychosocial cultural formulations that we make.  The BIO drives the patient.  Honestly, we might as well discard the psycho from biopsycho, because it is redundant.  There is no psychological without the biological except for those who believe that our mind exists independently of our bodies.

I want to pause and lay down a layer of my own personal philosophical jelly on the toast that I just made.  Recently, I have encountered a lot of papers that argue against something often called biological psychiatry.  There is even a journal called Biological Psychiatry.  Psychiatry may well be the only field of medicine where there are biological practitioners and potentially “not biological” ones.  I am confused by this.

I have read that the quote “biological psychiatry” research has failed to provide any new or innovative treatments since its inception when we finally found some effective psychotropic medications and started making hypotheses about neurotransmitters. 

There was even a recent paper in Nature’s Molecular Psychiatry called “The serotonin theory of depression: a systematic umbrella review of the evidence.”  I would argue that there was never a serotonin theory of depression to begin with.  It was at best a model or a hypothesis.  The fact that it was ever referred to as a theory bothers me deeply.  It also reveals a larger misunderstanding among psychiatry about what a theory is.  We even refer to Sigmund Freud's speculations about the human mind as Freudian Theory.  I would suggest that he never even approached a theory.

I bring this up in this episode because I am talking about a hypothesized executive network that helps us to make decisions, to plan, to organize ourselves, and to accomplish goals.  It supposedly works primarily with two other brain networks to result in behaviors.  If someone were to call this the Triple Network Theory instead of the Triple Network Model at this point, that would be laughable.  Psychology and psychiatry and its innumerable “theories” are the frequent butt of jokes but more importantly of eye-rolling.

Probably the most relevant example of psychiatry’s highly imprecise use of language with respect to science is the biopsychosocial model, also expanded to biopsychosocial cultural spiritual model among others.  The strangest thing about this model to me is that it is called a model.  Models in science use some kind of quantitative measures to make predictions, but the biopsychosocial model has no mathematical basis by which to test its validity and is therefore not really a model, except to those of us with the hubris to think that we can model the world in our mind without a way to actually communicate this model reproducibly to others.  It is, I would propose, our desperate attempt to understand our patient, which has its own value.  That value, however, is not a model.  The Biopsychosocialcultural perspective is more aligned with ethics than science, and I’m not trying to say that ethics are bad.  I’m just saying, “It’s not a model.”

I am a scientific person and my main concern is that the bio or psycho or social or cultural or spiritual aspects of any treatment is founded firmly in scientific exploration, results are reproducible, and this treatment’s scope is limited to the evidence for it.  This is often not the case, especially in psychology which has a long track record of poor reproducibility.

Science is difficult, often thankless, and frequently criticized as impossibly slow to progress (although there is also a media centered view of science as something nearly effortless: like magic).  Science as slow and mundane is probably a more accurate depiction.

Psychology is complex and changing through time, even for an individual.  Our predictions now are poor at best, even at a population level.  Meteorologists are far better at predicting the weather, than any psychological model is at predicting how people will act, despite all the claims in the TED Talks you may have seen.

I talk about brain networks because these concepts appear to be a next step into understanding how we think and behave and give us insight into new possible treatments.  I have far more confidence in the future of brain networks than I do in Freudian Theory or any other highly speculative psychological hypothesis.  The most effective scientists are looking to answer very limited questions, not to build a model of everything.  Networking models are slowly piecing together minute details about how the brain functions.  The triple network model is a model because is has predictable behaviors.

But, I don’t want to give the impression that we are close to figuring everything out.  I’m not sure if we would even know if we were.  We are finding out more and more exactly what we don’t know, which is a great step in starting to know it.  But if anyone tells you that understanding our biology with respect to our thoughts and behaviors is a nearly pointless venture, tell them Dr. O respectfully disagrees.  If we are humble about it and attempt to prove ourselves wrong instead of proving ourselves right, and focus on one question at a time, we might have a fighting chance.

I am Dr. O, and this has been an episode of PsyDactic Residency Edition.

References
https://academy.o8t.com/brain-networks/central-executive-network

1. De Ridder D, Vanneste S, Song J-J, Adhia D. Tinnitus and the triple network model: A perspective. Clin Exp Otorhinolaryngol. 2022;15(3):205-212. doi:10.21053/ceo.2022.00815
2. Mandino F, Vrooman RM, Foo HE, et al. A triple-network organization for the mouse brain. Mol Psychiatry. 2022;27(2):865-872. doi:10.1038/s41380-021-01298-5
3. Cohen-Zimerman S, Chau A, Krueger F. Machiavellian Tendencies Increase Following Damage.
4. RICHMAN J, D. Ph. The Humor of Psychiatric Patients.
5. The Central Executive Network. Accessed September 28, 2022. https://academy.o8t.com/brain-networks/central-executive-network
6. Menon B. Towards a new model of understanding - The triple network, psychopathology and the structure of the mind. Med Hypotheses. 2019;133:109385. doi:10.1016/j.mehy.2019.109385
7. Menon V. Large-scale brain networks and psychopathology: a unifying triple network model. Trends Cogn Sci (Regul Ed). 2011;15(10):483-506. doi:10.1016/j.tics.2011.08.003
8. Supekar K, Cai W, Krishnadas R, Palaniyappan L, Menon V. Dysregulated Brain Dynamics in a Triple-Network Saliency Model of Schizophrenia and Its Relation to Psychosis. Biol Psychiatry. 2019;85(1):60-69. doi:10.1016/j.biopsych.2018.07.020