One of the effects of certain 'addictive' foods such as chocolate is a release of brain dopamine that increases the incentive value of pleasure-related stimuli.
Those who knew her say that my great-grandmother Rosa, who lived to be 103 years old, had lost the will to live and only wanted to die. But my great-aunt Felisa, who lived to almost 102, never lost that desire and always, until her last hours, found a reason to continue living, whether it was the wedding of a nephew, the christening of a new family member, the glass of brandy or the nougat from the town fair. I have always wondered what would be in the exhausted brain of each of my two elderly women to harbor such a different feeling.
One possible answer takes me back to the many years in which in our laboratory at the Autonomous University of Barcelona we have explored the behavior of the rats that press a small lever inside their cage to activate the device that sends small electrical shocks to their brain through an electrode implanted in it. We never doubted that these shocks were pleasant and that is why the rats press the lever continuously, hours and even days, until they fall exhausted from starvation. When they do this, neurons in one region of the brain stem (ventral tegmental area) release the neurotransmitter dopamine through their processes in another region of the base of the brain (the nucleus accumbens). That is why during the first years of research we believed, and this is how we explained it to our students, that dopamine was the brain substance that produces pleasure.
But things changed when the journal Nature published an article that showed that rats kept pressing the lever even when the dopamine had been depleted and was no longer being released in his brain, meaning that there was still pleasure without dopamine. What then does dopamine do, we wonder puzzled? Recent experimental findings have shown this. On the one hand, we now know that when dopamine is reduced in the brain of rats by injecting them with substances that disable it (6-hydroxy-dopamine), their ability to feel pleasure does not vanish, as their positive reactions to sweet taste remain intact. People with Parkinson's, who also have a shortage of dopamine in their brain, also do not lose their pleasure reactions to the sweet taste. On the other hand, it has also been proven that dopamine-deficient mice show a total loss of interest or motivation to perform behaviors, such as pressing a lever or going through a maze, aimed at achieving pleasures such as food, and only if they are restored Dopamine levels in the brain sites where it is normally released in animals regain motivation and behavior to achieve it.
It is very important to encourage the elderly to have a personal and social life that is as rich and active as possible so that their brain releases dopamine
For all that, what we now believe that dopamine does when released in the brain is to increase motivation and the incentive value of pleasant things, producing desire, although without causing pleasure or having a true hedonic impact. It is as if that substance motivates us to do what is necessary to achieve good, pleasure, wherever it may be. Interestingly too, there is data that indicates that Parkinson's patients treated with substances such as L-dopa, which increase brain dopamine, do not increase their positive reactions to pleasure, but they do exhibit some compulsive motivation, an increase in desire for activities such as games , hobbies , shopping, pornography, the Internet in general, etc., even when they do not see an increase in pleasure that could justify this behavior.
This motivating impact of dopamine is reflected in a very special way in the incontinence that we all feel in continuing to eat once we have opened our mouths with the first canape or a fried potato in a celebration. Rather than whet the appetite, which we already have, what seems to happen with the first and contained tasting is a release of brain dopamine that increases the incentive value of stimuli related to pleasure, with food in this case, but not pleasure. himself, making the ongoing behavior that seeks it more intense and frequent. This is why after the first fried potato we are no longer able to contain ourselves and stop eating. This incentive seems especially strong in the addict to a drug, or to any other type of addiction, before any stimulus related to its consumption. The mere sight of the "camel", of the place where the drug is obtained, can trigger brain dopamine and with it the desire and motivation to do whatever it takes to get it.
Now we also know that dopamine increases when we are stimulated by all kind of novelty, that is, when new and unexpected things happen in our environment, what neuroscience calls "prediction error". The novelty is almost always present in the rich life of the young, but much less in the often impoverished life of the elderly, who are sheltered by weakness, laziness or lack of family support in sedentary lifestyle and confinement. It is, therefore, very important to encourage by all means that the elderly have a personal and social life as rich and active as possible so that their brain releases dopamine and, with it, increases and maintains their motivation and their desire to continue living even in advanced ages.
Ignacio Morgado Bernal is Professor of Psychobiology at the Institute of Neurosciences and at the Faculty of Psychology of the Autonomous University of Barcelona. He is the author of 'Desire and pleasure: the science of motivations' (Ariel, 2019).
Gray matter it is a space that tries to explain, in an accessible way, how the brain creates the mind and controls behavior. The senses, motivations and feelings, sleep, learning and memory, language and consciousness, as well as their main disorders, will be analyzed in the conviction that knowing how they work is equivalent to knowing ourselves better and increasing our well-being and relationships with other people.
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