THE BRAIN: A MODEL OF EXPANSION
If elastogenesis is a principle of enlargement, expansion and plasticity, as Richard Texier teaches us, we do not necessarily need to summon the cosmos in order to demonstrate its reality. It is enough to observe living things, and to recall that there are only twenty amino acids which, in their infinite combinations, build all the proteins of matter; that there are only four nucleic bases which suffice to create all the genes of living things; and that the seven notes of the musical range have enabled all the melodies in the world. Above all, we must evoke the brain, this “natural and mighty palimpsest” where “everlasting layers of ideas, images, feelings, have fallen […] softly as light,” as Baudelaire suggests in Artificial Paradises (1860). The brain is the elastogenic organ par excellence, an awestruck observer of its own existence and the object of the principle of expansion, both in terms of its structure and its functioning. As we will demonstrate below…
HUGE JELLYFISH
The brain can do anything. It is capable of anything. Hence how this gelatinous, formless, soft, flabby mass (which harks back to Richard Texier’s praise of slackness), weighing a little more than a kilo, composed of 80% water—a huge jellyfish, in short—can make us walk, dance, think, dream, feel pain, joy, pleasure… and send rockets into space. It enables us to imagine and create without limits and to manipulate a set of 26 symbols to create an infinity of words or phrases, a key elastogenic principle. Everything is in place at birth, but almost nothing works. The 100 billion neurons are there. They are just waiting to be stimulated, to connect with each other to form a network of main roads, secondary roads, bypasses, side paths, roundabouts, all in the service of functional modules (visual perception, selective attention, language, writing, motor skills, etc.) which will gradually become operative in the space of a few years. And within each module, we can discern subsets. Let’s take the network of visual perception. It will eventually encompass a system of analysis of the elementary components of the stimulus (colour, shape, movement, etc.), which can be an object or a face for example, leading to its identification and recognition (“system of what”), as well as a system for analysing its spatial position, enabling it to be located in space (the “system of where”). Similarly, the “language” module differentiates between a network for understanding verbal messages and a network to programme the vocal response.
Everything is organised and put in place by a gradual and exponential expansion. Each neuron can establish up to 10,000 connections with neighbouring neurons. If a researcher wanted to count the connections (synapses) of an adult brain, counting five per second, it has been calculated that it would take him not one year, not 10 years, not 100 years, but… three centuries! The incredible plasticity of the neural system is also made possible thanks to its permanent interaction with the environment. This dialogue creates the skills for which the brain is pre-programmed, in the manner of a computer that already contains the operating software and is waiting for the data in order to get under way. From this incandescent magma, agitated in every direction by a Brownian movement, coherent behaviours gradually emerge. The coherence is based on this organisation into networks, each being involved in a specific function.
NEURAL HURRICANE
The brain, which is the most elaborate organ in all creation, is the culmination of the elastogenic principle by its structural organisation, as we have just seen. But it is also elastogenic by its functioning… This principle of functional expansion is perpetually at work in our daily lives, without us being aware of it: in every effort of thought, reasoning, creation, idea association… but also in the most innocuous, insignificant or even limited brain events.
Proof of this is what happened in my brain, on a day of rest, on holiday in Charentes. I was lying still, my eyes half closed. About to doze off. The relaxation was absolute. My mind wandered a little, then let go. I was thinking of nothing. But is it possible to think of nothing? We are always thinking about something—we will come back to that later. For the moment, everything was still. Not a breath of air. Nothing but the crushing heat of a 15th of August. Nothing moved.
Really? There was just a leaf on the linden tree I was resting in the shade of, which trembled in a light gust of wind. It moved imperceptibly. Actually, I didn’t see it. I hadn’t seen it yet. Because I was not paying attention, engulfed as I was in this cloak of silence that isolated me from everything around me, and from myself. And yet this trembling leaf, this discrete movement of colour, an imperceptible event that was not consciously perceived, triggered a neural hurricane, involving millions of ion channels, generating action potentials that spread along the nerve fibres, releasing neurotransmitters, provoking extreme cellular changes, in short, causing turmoil in this apparently inert brain.
First, there was the meeting between the vibration of a certain wavelength frequency and the visual cones, structures of a few microns, located in large numbers (several million) on the periphery of my retina. But not just any cones: only those involved in the treatment of the colour green, thanks to their pigment which is sensitive to wavelengths of approximately 530 nanometres. The interaction with the light set the entire cellular mechanics in motion and released the photopsins. Under the action of the photon, the rhodopsin changed conformation. It then activated a protein, the transducin, which closed the sodium channels of the cell membrane, triggering the potential for electrical action that spread to the ganglion cells of the retina. The effect, and the goal, of this first, purely retinal step, was to transform the light energy into an electrical energy which then travelled along the various neurons that led it to the visual cortex of my brain. But here again, this journey could only occur thanks to a seismic protein storm which enabled it to cross the abyssal void of the synaptic cleft. Because if the depolarisation wave spreads quietly, step by step along the neuron, it is blocked and stops of its own accord at the nerve ending, because it cannot cross the space that separates it from the next neuron. How do we cross this void? How do we get the information across the river? It solved this challenge by triggering the release of glutamate molecules, called neurotransmitters, which are accumulated at the nerve ending. They wait for the signal that will free them from the pockets in which they are contained. Several hundred thousand molecules of glutamate therefore sacrificed themselves in the perilous leap to go and shelter in protein sacks, known as receptors, which are located on the opposite neuron. This contact then triggered the action potential that propagated along the next neuron. The sensory information thus progressed from the retina to the visual cortex of the brain. From adventure to adventure, it travelled through the optic chiasm, then through the lateral or external geniculate nuclei which are anchored to the brain stem. And there, there was another great leap to cross the synaptic void which separated them from the optical radiations which blossomed like a marvellous fan to make contact with all the millions of neurons of the extended visual cortex.
PLEASANT THOUGHT
The visual signal was reconstructed over several successive stages of treatment. Because what arrived was a broken up message, fragmented into different basic components that had to be reconstituted to form a coherent whole: one region processed the form, in this case the oval of the leaf, which it deduced from the analysis of its contours, another region processed the colour, here green, and a third was responsible for analysing the movement, certainly discreet (a regular swinging) but sufficient to create a living entity that the brain had to process.
Because the latter can leave nothing to chance. It must understand everything, explain everything, give meaning to any unknown or new event. That is its function. Even the discreet tremor of a leaf must be perceived, processed, recognised and identified. Nothing can be neglected because danger can come from anywhere. Especially since I had lowered my guard, on this 15th of August in the sultry summer heat. The watchman was standing guard. I could doze off and not think about anything. Alas… The image was reconstructed at the level of the visual associative areas. And through their own pathways, my olfactory neurons also perceived the very vague scent of linden. And the encounter, the fusion of these two parallel processes—that of the image and that of the scent—unknowingly triggered an emotional blaze, a cerebral conflagration that reactivated embers I had assumed had gone out.This metamorphosis of the states of matter, as announced by Richard Texier in his Manifeste de l’élastogenèse (2018, see pp. I-XXIV of this issue), albeit reduced here to nanoscale phenomena, activated lost mnesic traces, shreds clinging to some neurons of my hippocampus that awakened, became animated, and progressively stimulated the parahippocampal regions, the amygdala nuclei, thereby propagating a signal that gradually gained the neurons of the orbital frontal cortex and subsequently recomposed the totality of the scene that was imposed in spite of me, thanks to these multiple connections: that of gathering linden leaves from the family property, which were collected in large white canvas bags, and then the associated memory of suddenly escaping from the linden tree alley to race in the nearby fields of tall grass, higher than me. Then stopping, lying down in the grass that flattened out and created a secret islet, isolating me from the world in this space, surrounded by tall grasses that protected me, waiting for someone to call and then look for me. To create this fleeting moment (described 1000 times better by the great M.P.), several million of my brain cells had to coordinate in an elastogenic process of sensory and emotional expansion to revive this scene from a bygone past and bring it back to the realms of consciousness. A Brownian movement of ionic particles and molecules along interneuronal highways, secondary roads and local paths enabled the production of a memory and a coherent image thanks to specific treatments within prescribed regions. And this pleasant thought produced other hypnagogic images that accompanied me on my way to sleep, for a peaceful nap on this hot afternoon of August 15th.
Pr Bruno Dubois is Professor of Neurology at Sorbonne University in Paris and a member of the National Academy of Medicine.