Neocortical neurons tend to be coactive in groups called ensembles. However, sometimes, individual neurons also spike alone, independent of the ensemble. What processes regulate the transition between individual and cooperative action? Inspired by classical work in biochemistry, we apply the concept of neuronal cooperativity to explore this question. With a focus on neocortical inhibitory interneurons, we offer a working definition of neuronal cooperativity, review its recorded incidences and proposed mechanisms, and describe experimental approaches that will demonstrate and further describe this action. We suggest that cooperativity of “neuron teams” is manifested in vivo through their coactivity, as well as via the action of individual “soloist neurons” in the low end of the sigmoidal cooperativity curve. Finally, we explore the evidence for and implications of individual and team action of neurons.