Dopamine plays an important part in movement, motivation, mood and memory. It also has a dark side. The neurotransmitter is implicated in addiction, schizophrenia, hallucinations and paranoia. Yet dopamine is best known for its role in pleasure.

In the popular press, dopamine is delight; the brain’s code word for bliss, the stuff that makes psychoactive drugs dope. The media describes dopamine as what makes life worth living, the chemical that permits every enjoyable moment to be savoured, the ‘hit’ everyone is chasing whether through social media, psychoactive substances, sports, food, sex or status.

But it may be time to rethink these ideas. Dopamine is not the pleasure molecule in the simple, direct way it is typically portrayed in the media; its function is much more nuanced.

PET scans of the basal ganglia to show dopaminergic innervation of the striatum in one healthy individual and three patients with PD of varying severity. Photos: J. A. Ritcher (University of Navarra).

Today the precise nature of dopamine is a matter of much controversy. Some researchers argue that dopamine, when acting within what has become known as the brain’s reward system, signals desire. Others claim that it helps the brain predict rewards and direct behaviour accordingly. A third group splits the difference, saying both explanations can be valid.

Ironically, if there is anything scientists now agree on about this neurotransmitter it is that dopamine does not neurologically define joy. Instead this little molecule may unlock the intricate mystery of what drives us. More recently, other researchers have focused on a different function for dopamine in the brain’s motivational systems. The brain uses dopamine in these regions not so much as a way to spur behaviour through wanting but as a signal that predicts which actions or objects will reliably provide a reward. It encodes the difference between what you’re getting and what you have expected.

Prof. Giuseppe Di Giovanni, coordinator of the Malta Neuroscience Network Programme at the University of Malta, is a world leader in studying dopamine's role in the brain.

Did you know?

• The typical brain is about two per cent of a body’s weight but uses 20 per cent of its total energy and oxygen intake.

• Your brain weighs about three pounds. Of that, the dry weight is 60 per cent fat, making your brain the fattiest organ.

• Only five minutes without oxygen can cause brain damage.

• As any parent can attest, teen brains are not fully formed. It isn’t until about the age of 25 that the human brain reaches full maturity.