Key Points:

There’s a battle being waged inside our heads all the time. A battle between competing neural networks, vying for attention and access to information.

Networks don’t exist in an all or nothing, or “on/off” state. Rather, there’s an extraordinarily complex and dynamic balance of suppression and inhibition, the net summation of which determines the networks that win.

This hierarchical organization is of great use to neurologists, as when long silent networks are released by pathology in a suppressing network, the resultant release behavior is both indicative of the presence and general location of central nervous system dysfunction.

But beyond its clinical utility, this hierarchy has major implications for understanding the scope of human intelligence, and how it can be developed, as this hierarchical organization extends all the way to complex cognitive processes. And improving our cognitive and intellectual function may be as much or more about subtraction than addition.

Links

Classic MRI scan of Fronto-Temporal Dementia (FTD) with atrophy (areas of bright signal, indicative of fluid rather than brain tissue, which is darker):

Frontal Release Signs

Episode Transcript

Anne was devastated. Her husband Albert, a 53 year old marketing executive had been let go from his job six months prior for increasingly erratic and bizarre behavior.

“He’s just a different person.” She said at their first visit. “He won’t sit still. He’s always been pretty social, but now he talks to random strangers all the time. And he used to dress nice, but now he just grabs the first thing he sees. And I have to remind him to take a bath, or brush his teeth, or else he’ll never do it. And this is really embarrassing, but he’s even exposed himself in public.”

“Does he every start crying suddenly, for no reason?” “Yes.” She said, “He did that just this morning.” During this initial visit, Albert let from the examination table multiple times, wandering around the room, and ultimately towards the door, until Anne would grab his wrist and gently guide him back to the exam table.

In talking to him, he would often repeat back what I had said to him. “How are you today, Albert?” “How are you today, Albert?” He would reply. A phenomenon known as echolalia. I placed my index and middle finger in the palm of his hand, and he immediately gripped it tightly. “Let go, Albert, you’re going to hurt him.” Anne said. “It’s okay.” I replied, “He doesn’t mean to do it.”

The remainder of his examination was notable for a host of other signs of frontal lobe dysfunction. He failed all tests of impulse control. To no surprise, his MRI revealed atrophy in the temporal and parietal lobes, supporting a diagnosis of fronto-temporal dementia, a condition previously referred to as Pick’s disease, for reference to the microscopic pathology seen in the brain in this condition.

The cause is unknown, and it typically progresses relatively rapidly. This was the case with Albert. His impulsivity would worsen, and other strange behaviors would soon emerge.

At his next visit, Anne relayed that he was now hoarding household items. “I can’t find anything anymore. He takes everything he finds, tissues, pens, paper clips, the mail, and stuffs it into drawers. He paces around the house constantly, repeating the same phrase, ‘That’s the way it is.’ Over and over again. I just don’t understand how this is happening.” She said, in resigned despondence “This is just not the man I married.”

One of the more appealing things about being a neurologist is that because the nervous system is what produces our observable behavior, we can directly observe signs of breakdown. Aside from the skin, the output of the other organs, like the kidneys, liver, heart, spleen, stomach and so on, is largely hidden. So whereas assessing the function of those organs usually requires lab testing and imaging, technologies for seeing inside the body. Much of the workings of a nervous system are on full display, talking, walking, moving, sensing, these are things that we can directly observe and assess.

This is one feature that makes neurology unique in the field of medicine. And for many neurologists, myself included, central to its appeal. Every new patient is a puzzle, one that can usually be solved at the bedside, without fancy tools, through a thoughtful history and examination. Because when the nervous system breaks down, it does so in particular patterns, patterns that reflect its underlying organization. And learning to recognize those patterns is key to the practice of neurology.

Incidentally, this is why it’s also typically easy to spot when a sign or symptom is not rooted in pathology in the nervous system. And, when a neurologist encounters a patient with a particular symptom, or set of symptoms for the first time, the very first question to be answered is, “Is this the result of dysfunction of the nervous system or not?” If the answer to that question is a yes, then the next question is, “Where in the nervous system is that occurring?” In neurological circles, this is known as localizing a lesion, which is essentially a game of logic that attracts many people to the field of neurology, one only made possible by the fact the operation of the nervous system can be assessed directly through observation and bedside examination.

And when trying to answer these first two questions, “Is there a problem in the nervous system, and if so, where is it?” One of the most useful phenomenon that a neurologist looks for is the presence of release signs, as the presence of a release sign typically indicates, number one, that there is indeed pathology in the nervous system, and the particular release sign that we observe narrows the possible places where that pathology could be occurring.

The next question that follows is, “What’s the nature of this dysfunction, or disturbance, which brings in our understanding of the various kinds of disease processes. At birth every baby is born with a set of rudimentary reflexes and behaviors that are wired into the nervous system, along with other pre-programmed ones that will wire themselves up during early childhood.

While the human brain takes roughly two decades to reach full maturity, and develop all the networks that support the uniquely human cognitive abilities, a process that takes longer in humans than in any other animal. We aren’t born with nothing upstairs. In fact, assessing for these early reflexes and simple behaviors is one of the key elements of the neonatal neurological exam.

Some of those reflexes are necessary for the survival of an infant, some are holdovers from our evolutionary past, while others are perhaps an epiphenomenon of a nervous system that’s yet fully formed. A baby will reflexively suck on anything placed in its mouth, for example, a reflex that supports its ability to nurse. Press a finger in into the palm of a newborn’s hand and it will grip it tightly. Other primitive behaviors aren’t present at birth, but consistently wire themselves in during early childhood as part of the maturation process.

Parents observe their children going through phases, where certain behaviors will emerge and be repeated. For example, many kids will have a hoarding phase, a period of time where they may be especially preoccupied by gathering certain things in one place. In some cases, even hiding them from others. An instinct seen in many wild animals, as a means of protecting hard-won resources.

Watch closely, and you’ll also observe many children to go through a phase that looks like obsessive compulsive disorder, intrusive, and repetitive thoughts, disconnected from reality, various stereotype behaviors, including motor or vocal ticks, like a phrase that’s repeated endlessly, clearing of the throat, excessive blinking and so on. In fact, pay attention and you’ll find that most adults have a few of these too.

Over time, in most kids, these circuits and the behaviors they control will be reigned in, suppressed by parts of the brain that are brought online during the maturation process. So the behaviors they mediate will disappear unless they’re released by specific circumstances.

I feel compelled here to point out that sleep deprivation is one such circumstance. And sleep should be top priority for any parent with a child in whom these behaviors have become problematic. I’ve seen more than one tick disorder, and diagnosis of Tourette syndrome in a young boy, magically resolve once he’s getting adequate sleep.

So, over time, many of these reflexes, and rudimentary behaviors that are mediated by evolutionarily older parts of the brain disappear. But they don’t go away all together. Or more precisely, the Brian networks that mediate them don’t go away all together. This disappearance reflects a process that’s central to what’s happening as the brain matures.

One of the last parts of the brain to develop are the frontal lobes, which house some of our most uniquely human capacities. This includes our ability to think through ideas in the abstract, to imagine possible futures, and plan ahead. What’s often referred to as our executive function. The fact that this part of the brain is last to develop is not surprising, given its recent emergence in our evolutionary history.

This phenomenon isn’t unique to the nervous system. Evolution occurs through the modification of existing structure. One organism turns into another, a process that we can trace all the way back to the first single-celled creature. If an organism wants to build a new part, including brain circuits for a new behavior, we don’t destroy the old one and start over from scratch. So in many ways, our bodies, and our brains tell the story of our evolutionary past.

Life began in the sea, for example. We humans still show evidence of our aquatic past, and the way our arms and legs are attached to our bodies. This is also how we’ve ended up with vestigial structures in our bodies that have no function, like an appendix or goosebumps, parts of us that were useful when we were different animals adapted to different environments.

The same is true of our brain, with millions of years of modification on top of modification to get to where it is now. You’ve likely heard reference to our lizard or reptilian brain. Some of the oldest parts of our neural hardware that have been with us for hundreds of millions of years, and control some of our most basic, and vital functions.

Our brain has gone through massive evolutionary change since that time. So we have collections of circuits that got wired in at different parts in our evolutionary history, and they still get wired in during the developmental process in utero, and in early childhood.

Some of those circuits may mediate behaviors that once served our species well, but are not so appropriate in our modern world. Things like hoarding, for example. If we don’t want those networks influencing our behavior, then they must be actively suppressed.

The brain isn’t the series of on and off switches, but rather a dynamic balance of activation, and inhibition of all of its parts. Part of that suppression happens naturally as a scripted par of our brain’s development. The wiring in of the uniquely human parts of the brain during childhood and adolescence include the wiring that suppresses those unwanted circuits and behaviors. Continued engagement, and use of those networks strengthens and reinforces them, and enhances their ability to suppress the others.

In fact, in many ways the story of the maturation of the human brain is the story of impulse control, or the development of our brain’s ability to suppress the circuits for our behaviors that no longer serve our needs. But again, what’s important to remember is that they don’t turn off all together, but rather that their operation is held in check by other parts of the brain, which means that if that suppression is weakened, or removed, those reflexes and behaviors will reemerge.

There’s a never-ending battle going on inside your brain all the time, with countless warring factions vying for supremacy, and our ultimate behavior is a reflection of the ones that went out. It’s an elaborate hierarchy, a remarkably complicated dynamic balance of suppression and activation. So our behavior at any given moment is the ultimate summation, the net result of the faction that has the most influence at that particular moment in time.

This means that while one way to change our behavior is to create new circuits that control new behaviors to build new networks from scratch. Another way is to remove an existing network from suppression. One way this can happen is through pathology in the central nervous system.

If part a is always suppressing part b, damage or disease to part a will release b from that suppression, and the behavior or cognitive function that it controls will emerge. This hierarchy, this phenomenon of release is seen at every level of organization of the central nervous system, not just primitive behaviors and thoughts, but complex cognitive capacities as well.

Pathology in the spinal cord may release the bladder from suppression, such that it reflexively empties whenever it fills. Pathology in the motor system above the spinal cord releases spinal mediated reflexes from suppression, leading to hyperactive deep-tendon reflexes, and the well-known Babinski response, in which scratching the sole of the foot will cause the big toe to extend, instead of its usual flexion.

Pathology in higher order parts of the frontal lobe may release circuits in the basal ganglia, or limbic system, leading to ancient behaviors like hoarding, aggression, motor ticks, and hypersexuality. But because this hierarchy goes all the way up, it also applies to the most sophisticated of cognitive networks, and complex cognitive capacities. For anything to gain conscious access, to influence or produce a thought or behavior, it must suppress scores of others that are also vying for attention.

It’s a phenomenon that explains some astonishing, and seemingly impossible clinical observations that we’ll discuss in a future episode. And it’s a phenomenon that’s of crucial importance to an understanding of the scope and potential of human intelligence, and one that’s been vastly overlooked and underappreciated.

The tacit assumption, in the traditional view of aptitude is that we are able to assess and evaluate the full extent of an individual’s intelligence through observation and testing. An assumption that ignores the implications of the hierarchical organization of human cognition. The more accurate statement is that we can only assess and evaluate the parts of the brain that are winning the battle for attention, and information processing at any given moment.

Are you bad at drawing because you don’t possess that capacity, or because the part of the brain that’s good at drawing is being held hostage by a stronger network? A balance of power that may become increasingly one-sided the longer that stronger network is reinforced.

Do you struggle to be empathetic with your coworkers because you lack the capacity for empathy, or because something in the work environment tips the scales in the wrong direction? This balance of power amongst warring factions is influenced by many things, including the environments we’re in, the books we read, the things we learn, the things we do, the food we eat, the lives we lead, and so on.

So understanding that there is a hierarchy, and this idea of warring factions is critical to understanding how we release and develop intelligence, including the potential opportunity costs that come with our traditional approach to education. All of these behaviors that we see as a natural part of the course of frontotemporal dementia, behaviors that may have not been seen in decades, or ever, are not being added by the disease, rather, it’s the release from suppression of networks that haven’t seen action for a very long time, if ever.

So what this means is that many times a desired behavior, or capacity my already exist within you, and releasing it is a matter of creating the conditions that allow for its emergence.

Module #6: Hierarchy

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