Neurofeedback has in fact undergone considerable metamorphosis over its 30-year life: from an initial focus on reinforcement of specific events (alpha and SMR spindle bursts) and amplitude training at the outset to the latest emergence of coherence, comodulation and phase-based training. There has also been a growing divergence of methodologies, with the growth of stimulation-based approaches to complement standard neurofeedback; with the maturation of EEG-driven stimulation; with the emergence of pulsed along with steady-state stimulation; and with the continuing maturation of both targeted and protocol-based training strategies. It is useful to ask what the commonalities are in these approaches that might constitute a "minimum set" of brain challenges that should be provided in neurofeedback for complete coverage of the clinical categories. Such a minimum set would be matched to the principal failure modes that have been identified thus far in the EEG. What remains are conditions which are responsive to neurofeedback, on the one hand, but unconnected with any observable EEG signature or deviation, on the other. To explain efficacy in such cases, a more inclusive network model is needed that accords primacy to the role of sub-cortical nuclei, for which disregulation involves no obvious cortical signature.