Neuroskeptic readers will know that I'm a big fan of theories. Rather than just poking around (or scanning) the brain under different conditions and seeing what happens, it's always better to have a testable hypothesis.
I just found a 2007 paper by Israeli computational neuroscientists Niv et al that puts forward a very interesting theory about dopamine. Dopamine is a neurotransmitter, and dopamine cells are known to fire in phasic bursts - short volleys of spikes over millisecond timescales - in response to something which is either pleasurable in itself, or something that you've learned is associated with pleasure. Dopamine is therefore thought to be involved in learning what to do in order to get pleasurable rewards.
But baseline, tonic dopamine levels vary over longer periods as well. The function of this tonic dopamine firing, and its relationship, if any, to phasic dopamine signalling, is less clear. Niv et al's ...
