• brain
• gene
• environment

Many have alluded to the importance of the environment on the developing brain. As a neuroscientist, I root and endorse that view in the bump and grind of brain cells. You are born with most of the brain cells you will ever have. It is the growth of the connections between the brain cells that accounts for the growth of the brain after birth. What is exciting is that the environment will influence the configuration of those connections. So even if you are a clone—that is, an identical twin—you will have a unique pattern of brain cell connections.

Genes play a part. I do not wish to denigrate genes; I merely wish to put them, despite all the hype, literally in their place. Genes make proteins, which are important biochemical baggage for brain cell circuits to work. But they are not a one-off; they are constantly being activated or switched off according to the caprices of the environment, whether it is the micro-milieu of the brain itself or the external environment in which you are moving.

Hence you will appreciate that it is impossible to make the old and hackneyed division between nature and nurture. Rather we should think of a dialogue, an interaction, where there is no genetic controller orchestrating events but a ceaseless interaction between the environment and the molecular landscape of the brain. What is important is that the environment can determine how that landscape looks.

Let me take, for example, what may seem to be a counter-example. The condition Huntingdon’s chorea—named after the Greek for “to dance”—is so-called because it is characterised by a wild involuntary flinging of the limbs in a grotesque form of dance. The reason for …