Motivation is what drives us to act. Many diseases alter motivation.

Damage to some brain areas causes abnormal, misdirected motivation — sometimes leading to compulsive stereotyped behaviours, or unplanned impulsive acts. This can sometimes be dramatic, causing considerable embarassment for patients and their families.

A loss of motivation results in clinical apathy — a disabling disorder that can be difficult to pin down. It is often missed, and is hard to quantify. It carries a huge social and economic burden, and is often frustrating and distressing for carers.

We study what motivation is, in terms of computations. Is it the selection of an appropriate action, given a goal? Or is it the willingness to invest energy, at a cost, in a rewarding course of action? We found that: