SEED Magazine is a stylish, elegant science-and-culture magazine that I’ve discovered only today. Its February/March issue features an article by Jonah Lehrer called, “The Reinvention of the Self,” that deals with current research in neuroscience. The story’s protagonist is Elizabeth Gould (see photo), who discovered – or at least proved – eight years ago that the primate brain produces new cells: a feat called neurogenesis. Other researchers had previously uncovered anomalous evidence of this that had been dismissed because it conflicted with the prevailing assumption that the brain cells you are born with is are the only ones you’ll ever get.
Now the research in Gould’s lab is just one part of a whole burgeoning field of neurogenesis that explores the medical implications of this discovery. Evidently the scientists previously often failed to find no new brain cells because the animals that they studied were kept in plain, boring environments where they did not, in fact, generate new cells. This results from the circumstances of deprivation. A rat or monkey kept in a stimulating cage full of toys and novelties will produce new brain cells whereas it would not in a plain box.
The same goes for people. As it turns out, stress and deprivation of human beings, including during infancy or before birth, impairs the brain’s capacity for neurogenesis. Poverty or abuse leave lasting effects at the level of tissues. Post Traumatic Stress Disorder (PTSD) had been known to diminish the size of the hippocampus. Now the reason is known: the brain’s ability to renew itself has been ruined.
Depression is now considered another manifestation of impaired neurogenesis, and that theory accounts for another puzzling finding. The drug Prozac does help lift depression, but no one knew how. It had been believed that depression was caused by low levels of serotonin, but when doses of serotonin are administered, it takes a while for the depressed patient to start brightening up. This should not be the case theoretically, for the serotonin should start working immediately. Now the true explanation has come out: Prozac restores the brain’s neurogenesis. Depression lifts when the brain has replenished itself with new cells, as Prozac enables it to do.
Again, though stress actually impairs the brain, there are ways in which it can to some extent heal itself – especially through learning something new. An enriched and challenging environment can restore neurogenesis previously impaired by stress, though there may be other conditions that affect these outcomes. The search is on for other drugs that repair the capacity for neurogenesis.
All these findings highlight an important new general conclusion: that the structure of the brain is shaped by its functioning. Stress and depression prevent neurogenesis, whereas pleasurable stimulation restores the brain's capacity to make new cells.
All this fits with the theories that Steven Johnson famously proposed: that solving puzzles, playing video games, and following complex plots on television can make you smarter.
What neither Johnson nor Gould and her co-workers seem to have considered is the signal importance of the imagination. When they say that stress diminishes the brain's capacity, they mean the real stress of poverty and life’s hardships. But not all stress is based on one’s own predicaments. Sometimes it is based on empathizing with the stress of someone else. Saving Private Ryan is just light and sound on a screen, which you can watch in a comfortable chair while drinking beer and snacking on popcorn. Your own situation is not stressful at all, but you experience stress vicariously, and it has physiological consequences. Your peptides and T cells change. If Gould is right, your neurogenesis may be impaired too. Presumably even fantasizing will have a similar result, even if you are not watching a movie.
But fantasizing about love is good for you, and perhaps watching a tender scene of mutual affection, laughter, or joy will restore your brain’s ability to create new cells and repair the damage done by horror or action movies, or by watching the nightly newscast.
I am speculating, but I will bet $50 that when the research is done, we’ll find that the imagination is just as powerful as personal reality in creating or alleviating stress, and that the imagination will therefore be established as a major determinant of the structure of the human brain.