There are two basic modes of communication used between neurones in the nervous system: neurotransmission and neuromodulation. When representations of neural circuits are drawn, they tend to include only fast neurotransmission. This can lead us to believe that neurotransmission conveys information through the nervous system and that neuromodulation merely modifies the neurotransmission. Even the words that we use to describe these two forms of communication imply that meaning. However, the very act of modifying neurotransmission conveys information. Therefore, in order to better understand information flow in the nervous system, we need to determine how neuromodulation is integrated into neuronal circuits.