Prolonging one’s life only makes sense if you have something to live for. At least that’s what our brain is thinking. Let me explain why. With age, the life of a modern human is increasingly becoming a habit. And the reasons for it to continue, become trivial. To buy a new home, yacht, car, plane. Once again to lie down in the sun by the pool or on the white sand. To visit yet another country. To start another business. To make another billion. To lose another billion. To help another poor or miserable being. To see how another son, granddaughter, great-grandson, great-great-granddaughter will be born, go to school, marry, get married, give birth to someone. To see another sunrise, another sunset, another attraction. To climb another mountain.

It also happens that the reason to live is to live up to some event, leaving behind the question of what to do between now and this event. You can disconnect and wake up when the time comes. What’s after?

Most people live out of habit. And they want to live long too out of habit. Existential (abstract, not associated with a specific threat) fear of death is peculiar, it seems, only to humans. But why should people be afraid of dying, if they don’t know why they are living in the first place?

Kurt Vonnegut once wrote “If a person survives an ordinary span of sixty years or more, there is every chance that his or her life as a shapely story has ended and all that remains to be experienced is epilogue. Life is not over, but the story is.” Modern neuroscientists can observe this process in the dynamics of changes in the volume of gray matter in the hippocampus — the anatomical region of the human brain responsible for recording and recollecting the autobiographical (episodic) memory — the one that remembers or forgets what happens directly to us.

The hippocampus does not store this memory in itself. It stores only the addresses of the nodes (cells) of storage of individual elements, from which it reconstructs the memories every time we remember an events of our life.

The data of a node (storage cells) dedicated to a person, object, or phenomenon is updated each time that person, object, or event occurs in a new episode and behave in a different way than in previous episodes. The hippocampus registers this difference (prediction error) and updates the data in the relevant cell.

The hippocampus also keeps a diary of our life, writes its story, arranging episodes (segments with clear boundaries like in the movies) along the arrow of time. Each episode in the story (narrative, storyline) of life is a scheme where places, objects and participants are designated. The scheme is augmented with specific details in the process of reconstruction of the episode by the hippocampus, which loads data from the corresponding storage cells.

In the same way, the hippocampus builds episodes of future events. I foresees the future and registers the differences of the new sensory information from its prediction (prediction error). If there are no errors, the contents of the storage cells are no longer updated. For the hippocampus it is Groundhog Day. The story of life ends. Here we must bear in mind that the hippocampus is not interested in small stochastic oscillations of our life. Its predictions are crude and approximate, but sufficient to learn from them, and the natural background of uncertainty is always present and it is impossible to further reduce it by more learning. From underload, the hippocampus shrinks physically.

But even this is not important. Atrophy of the hippocampus with aging is typical for all primates. But in modern humans, the hippocampus begins to shrink much earlier than in all our closest relatives. Atrophy in humans is much faster and more significant than in chimpanzees, for example. The reason is our adaptation to a predictable environment, scientists believe. Neuroplasticity works both ways.

An article published last year in Nature crowns the long-term work of a team of scientists studying the effects on the hippocampus of various genres of computer games and strategies for the behavior of players in them. This is not a one-day study published under the catchy title. On the example of the players, the hippocampus shrinks under the influence of the response learning strategy responsible for habit formation. If the strategy of spatial learning dominates (associative thinking, fluid intelligence), the hippocampus grows.

A prediction error (it is also called unexpected uncertainty) feeds the brain with information, due to which it continues to comprehend the world. If the feeding stops the brain loses its purpose of existence. It ceases to struggle for existence. This is a spontaneous process over which we have no control.

It is impossible to deceive our brain. Therefore, all sorts of pills, young blood transfusions, rejuvenation procedures and healthy lifestyles are not able to prolong a person’s life if the brain refused to fight for it. Maximum they will extend the existence of the shell of a robot locked in the Groundhog Day.

But we can feed the brain with unexpected uncertainty. The environment is its natural source, including the social environment filled with people — the ideal sources of unexpected uncertainty. But people living by habit are machines, and machines become a source of unexpected uncertainty only when they break. Here love comes to our aid. But that’s another story.