Since the beginnings of neurology, the brain has been seen as a patchwork of specialized functional centers. Language, vision, motor skills, memory, etc., the neural lesions targeted in a center exclusively cause the alteration of its specific function. The clinical examples are innumerable. Broca’s and Wernicke’s aphasias, for example, gave their name to the areas of the same name. Great success of neurology, which by a fine clinical examination manages to precisely identify the cerebral site of a vascular accident.
Armed with this “geographical” concept of the brain, neurologists began to look for the centers of decision, consciousness, awakening, etc. And that’s where things went wrong. As much as it is easy to localize the processing of sensory impulses, which enter the brain through specific areas, the higher functions are difficult to identify. They rely on much larger networks. Arguments for the “centralization” of functions confront arguments to the contrary.
It is tempting to see the prefrontal cortex as the center of the personality, because its lesions trigger behavioral disorders, but these are far from being stereotyped as aphasias or paralysis. Let’s also examine a caricatural situation: callosotomy, section of the corpus callosum, enormous “cable” connecting the two hemispheres, an operation carried out in the last century in severe epilepsies. The hemispheres can no longer communicate, yet the person feels much the same as before. Major argument for the geographical location of higher functions? It would seem, since the section hardly disturbed them, less than a tiny infarction in a frontal area. But no, it shows above all that one hemisphere can manage without the other in most of its tasks. Mental functions are very lateralized.
Inspection by the hierarchy
We know that higher functions are essentially feedback controls. They dub or correct actions already fully initiated by the underlying functions. Almost all sensory information enters the brain not as data but as reflexes. Sequences recognized by the sensory areas and validated. The reflex is on the way at the same time as it reaches the higher functions. Not always recoverable, it can be counterbalanced quickly by a better judged action.
In other words, the coordination between neural networks takes place more between hierarchical levels than between cerebral hemispheres. The callosotomy does not involve the brainstem, where most of the exchanges between the two halves of the body take place. The feedbacks of the higher functions are separated by the section, but not the coordination of the motor stages. Body movements do not become disordered.
Impossible to know if we are upstanding
Callosotomy actually has major effects on higher functions. We can easily guess that the brain did not form 300 million nerve fibers in this thick cable for nothing. The integration of functions has broken down, but there is nothing in the brain to notice it. Nothing higher hierarchically than the conscious workspace could conceptualize it. You can explain to the person what they have lost; she can possibly believe us and represent that loss; but she does not feel it. We experience what we are at every moment, but to experience ourselves as different requires observing ourselves from a higher mental level, capable of making the comparison with a previous recording. When the highest working space is concerned, there is nothing even higher than it to memorize previous configurations1These configurations should not be confused with “alternate states of consciousness”, caused by drugs or sudden mood swings, which upset the entire functional hierarchy of the brain and not selectively the conscious workspace. In these alternate states, the consciousness perfectly experiences the changes in its contents and memorizes them without difficulty..
Completely unaware that they are reduced to a single hemisphere by the callosotomy, two conscious workspaces independently feed back their neural hierarchies. As these are networks pre-programmed by life prior to the section, these representations are always sought in the data. Even if it means inventing them, or finding approximations. The left hemisphere, linguistic and predictive, easily fabricates the reasons for the behavior of the right hemisphere to which it is no longer connected. Especially since the body, coordinated by the brainstem, functions normally. It only performs unexpected operations, which must be given meaning. The left is rushing to understand what could have motivated the right, just as a salesman tries to justify the slippages of the production plant. We are all on the same boat.
The new system boat
Here we have to introduce the fundamental principle of hierarchy in order to understand the mind. This principle, neurologists have been very wary of it, following the failure of the triune brain theory: Radical hierarchy and offering the beautiful role to the neocortex, dominator of the limbic brain, itself dominator of the reptilian. This theory proved untenable because the integration of functions is very advanced between the three regions. But if the integration is so strong, what meaning is left to the geographical classification of mental functions? How to explain the startling contrast between certain functions that disappear with the damage of a few connections, and others that persist unless the damage becomes very widespread?
A popular trend among neuroscientists is to view the brain as a single large neural system, with no delineation between functions or between conscious and unconscious. All our attempts at classification would be illusory, only there to satisfy our existing interpretations, while the assembly of neurons would not care about these territories. For these, consciousness would be as illusory as a working space as it is as a phenomenon.
A single look is blind
It is true that if we try to put ourselves in the place of neurons, we certainly cannot distinguish the borders of the cerebral areas. We just excite ourselves happily, not even for a yes or a no since these concepts have no meaning for a neuron. But then: what distinguishes, who interprets, who classifies? We are our neurons and nothing else, mentally. Flattening the hierarchy into a single neural space provides no explanatory power. It takes it away.
Rather than a model capable of merging this unique neural space, researchers continue to find new areas, which are in fact new hierarchical levels. This is the case of Gordon’s team in Saint-Louis, which has just published in Nature the discovery, between the classical areas, of regions hyperconnected to each other and to a cingulo-opercular network, essential for the action, the physiological control, wakefulness, error and pain processing. It is a movement control system activated as soon as it is planned, a hierarchy immediately superior to the motor centers.
The work to be done is precisely to show how a vast neural system can create an obvious hierarchy, with clear delimitations. Thought is quantified, sequence of independent ideas, some content accessible and some not. Our mind is impossible to explain without the conjunction of the continuous and the discontinuous. How do discontinuous excitations create continuous thought? How does a continuous neural network create discontinuous concepts?
Stratium, the neural pyramid
This is the work undertaken in Stratium, a theory abundantly detailed on this site. It combines the recognition of specific neural areas at the bottom of the mental hierarchy, processing sensory data, with an increasing extension of networks as they symbolize more complex concepts. Essential point: the meaning of a concept of high complexity takes shape only in the activated presence of the hierarchy which gives birth to it. Integrated information. The famous “Jennifer Aniston neuron” can only give rise to the image of the actress if all of its graphic hierarchy is present. Any amputation will also amputate the image, or even prevent its recognition.
The world and not its map
A neuron is nothing without its acolytes, but no acolyte has equal value. Neurons may be part of a single system, but like in human society, none have the same value. So, like us, they have their hierarchies, more important than their geographies. They have little power individually. Only their groups have them. The amount of power, for the most representative neurons, is the number of times it repeats “I am the symbol of a group of groups of groups of…”. Like any elected official, its power only exists through the presence of its electors.
The geographical conception of the brain is far exceeded by its hierarchical conception. This allows you to keep your consciousness at the very top, on a richly decorated balcony. The neural system is involved in its entirety, nevertheless we experience ourselves as haughty and sophisticated thought, not a meter of sensory impulses. Not system of elements but merging of contents. The world and not its map. Explanation does not replace experience.
A somato-cognitive action network alternates with effector regions in motor cortex, Gordon & al. Nature. 2023 Apr 19. doi: 10.1038/s41586-023-05964-2. PMID: 37076628.