The myth

You can’t grow more brain cells. Every human starts with a finite number, some of which are destroyed – and never replaced – every time we figure out what two plus two makes, or try to remember where we’ve left our glasses.

The "truth"

This still-prevalent belief was expelled from the halls of orthodoxy some years ago, when scientists discovered that all vertebrate animals continue to produce new neurons (brain cells) throughout their lives, in at least some parts of the brain. More recently, it has been shown that the fresh cells are actively involved in the formation of memory. Other studies strongly suggest that some types of anti-depressants work by causing new neuron growth – and that depression itself can inhibit brain cell replacement. Readers will be unsurprised to learn that evidence for adult neuron growth was fi rst presented in the 1960s, and again in the 1980s, but was dismissed out of hand for no reason other than that it contradicted existing (untestable) theories.