The neuronal correlates of consciousness (NCC) are the minimum neuronal mechanisms jointly sufficient for any one specific conscious experience. It is important to distinguish full NCC (the neural substrate supporting experience in general, irrespective of its specific content), content-specific NCC (the neural substrate supporting a particular content of experience — for example, faces, whether seen, dreamt or imagined) and background conditions (factors that enable consciousness, but do not contribute directly to the content of experience — for example, arousal systems that ensure adequate excitability of the NCC).
References
Koch, C., Massimini, M., Boly, M., & Tononi, G. (2016). Neural correlates of consciousness: progress and problems. Nature Reviews Neuroscience, 17(5), 307-321.