Dopamine neurons coding prediction errors in reward space, but not in aversive space: a matter of location?

Dopamine midbrain neurons are well known for prediction error coding in a reward context. A recent report by Christopher Fiorillo (Science 341: 546-549, 2013), however, suggests that these neurons behave markedly different when subjects get confronted with aversive, rather than appetitive, stimuli. Despite his findings being in line with indications of appetitive and aversive stimuli being processed by distinct neurotransmitter systems, they should still be interpreted with some caution due to a potential issue of recording location.