José Antonio R. Piedrabuena —— Against the belief in neural networks

They should stop slandering real neurons, because the brain does not only work thanks to them, and change the name of neuronal networks. I believe that they cannot be considered to be the model of any ‘neural network’, beyond the pure appearance and opportunistic use of the name

We start from the fact that no artificial intelligence or neural network has the mission of coordinating, organising and maintaining all the organs of the body. By controlling all the variables of our metabolic and functional existence, while at the same time adapting to the circumstances of the environment, we maintain our personal identity, goals and complex mechanisms of survival of the species. And for that we have a brain.

There is no resemblance between a neuron of the so-called neural networks and those we have in the body. The functional unit in the brain is not the neuron, but the sum of its functions, the glia, the surrounding tissue and the perivascular feet, forming a set of metabolic, electrical and molecular processes that result in the governance of the body and the mind. The glial cells (smaller and more complex) exceed the number of neurons, which I don’t think is taken into account when we talk about neural networks, which give a total of around one hundred and eighty billion cells, each of which receives an average of ten thousand connections.

Neurons are all different, each region of the brain has several types of them and each one is adapted in its physiology to the specific functions of the region

A stimulus that reaches him can give rise to an infinite number of variable responses. And as if that were not enough, the input of information can impose a particular pattern of output discharge, because if a neuron receives 200,000 input connections, they all add up to signals in the cell body to become a single output signal, but no neuron behaves in the same way in terms of the output patterns of the information. Something to bear in mind is that the electrical and biochemical properties of the dentrites (branches through which information enters) vary from one cell to another, resulting in connections between them, synapses, that are different in size, identity of the transmitter and efficiency of transmission.

There are many that are activated rhythmically, others secrete hormones or neuromodulators in the form of bursts, as in the hypothalamus, some react at the beginning and ignore the successive stimuli, and others pause and then respond, something fundamental in the successive rhythmic processes such as breathing, heart rhythm, some endocrine glands, biorhythms.

The arrival signals have their entrance in their membranes, in entrance and exit channels, fast, electric, or slow for other substances that have to enter conducted by transporters. A whole set of activating or braking substances that are transformed into signals that have to go out through the only exit, the axon to some very precise targets or to thousands of neurons, generally in a diffuse way. All this to adapt to local requirements and demands and at different speeds.

Neurons and smaller glia cells have receptors with which they will pick up and recognise neurotransmitters, ions, hormones, nutrients, poisons, as well as the identification of other members of the species.

We already know that one neuron communicates with another through a synapse. These vary widely in shape, size, identity of the neurotransmitter, efficiency of transmission; because a transmitter, depending on the nature of the components with which it interacts can vary from one part of the brain to another and even in parts of the same neuron and produce different and even opposing actions. For example, dopamine has five different receptors or input pores with a different stimulating result. The nature of some other neurotransmitters are standard substances of life. For example, the amino acids glutamate, aspartate, GABA and glycine are nutrients for cells in the body because they function as an energy source for making proteins, and in the brain they exert widespread messaging functions.

We have one hundred different neurotransmitters and modulators manufacturing our thoughts and emotions, activating or blocking us, such as amino acids, simple amines or molecules such as adenosine and peptides, neurohormones that are waiting to be released, in the form of sachets, such as secretory granules, which may also contain endocrine hormones. The result is our metabolic, mental, social, reproductive, peaceful or fanatical life, which will also depend on something as small as sodium, potassium or chlorine ions that transform the neurons into a battery that charges or discharges and is activated when the calcium ion enters and the interior becomes positive. An ion can enter or leave a neuronal channel at up to one million units per second.

We repeat that the areas through which the neurons receive the signals are the spines, the equivalent of the branches of trees, the trunk and the roots would be the output axon.  Furthermore, somewhat more complex, the spines, the branches, which in addition to receiving information have other vital commands; they contain more than 30 proteins involved in energy generation and many other functions.

The responses to this flood can be from milliseconds to days

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We see that the brain for its sensory, motor and cognitive functions requires fast or slow but specific connections and operations to maintain all vital signs; sleep, waking up, attention, concentration, control of mood, levels of the contents of all body fluids and their contents, general excitability, metabolic state, command over the immune, endocrine and vascular systems, etc. And everything is intervened by different neurotransmitters, brought to their place of influence by the axons through connections that can be scattered, diffuse, winding or localised and structured and generally deployed from the most primitive part of the brain, the brainstem. Our personal and social life is commanded by regulation, the modulation of neuromodulators produced in the second most primitive area of our brain. This zone is being worked on by all the extremist and violent manifestations of behaviour outside the laws of conservation of life.

Sometimes, several thousand neurons form the centre of a system that can be diffuse like those in the aforementioned brain stem and do not connect one neuron with another, but pour their secretion into the liquid that bathes the whole brain and thus reaches millions of cells without synapses.

In the brain stem are the sites of production of substances known to all, such as dopamine, serotonin, noradrenaline, acetylcholine, which in this case only one of its neurons connects to another 250,000.

We cannot simplify this any further and we move on to the other component, the thirteen families of the neuroglia: astrocytes. These also synthesise neurotransmitters, as do the neurons, and up to 20 neuroactive compounds and modulate synaptic efficiency.

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