Decision making, planning, selective attention or perceptual identification shouldn't be studied, and models of the corresponding cerebral circuitry shouldn't be elaborated, without a reference to global plans relating cognition and the brain, seen as a whole and in relation to the body and the environment. Else, the risk is to just study mechanisms apart from the rationale for their existence and consequently to forget some of their fundamental characteristics and resources. In agreement with these considerations, we present here in a systemic view a general framework of brain modeling that has been elaborated in our team as a basis for several modeling studies of the brain, of learning mechanisms and of cognitive operations. It is also intended, for future specific studies of brain-inspired cognitive mechanisms, to serve as an outline in which each of these studies should be placed, for a better understanding of its contribution in general cognition and for consistency in this systemic view of cognition that we affirm here to be essential.