Neuroscience has made enormous progress in understanding the brain and its various neuro-sensory and neuro-cognitive functions. However, despite all progress, the model of the brain as well as its ontological characterization remain unclear. The aim in this first paper is the discussion of an empirically plausible model of the brain with the subsequent claim of a neuro-ecological model. Whitehead claimed that he inversed or reversed the Kantian notion of the subject by putting it back into the ecological context of the world, the so-called reformist subjectivist principle. Based on empirical evidence about the experience-dependence of the brain's spontaneous activity, I argue for an analogous inversion or reversion with regard to the model of brain: empirical evidence is well compatible with a neuro-ecological model which extends beyond and integrates both Humean neuro-sensory and Kantian neuro-cognitive models. I conclude that a neuro-ecological and process-based model of brain and its relationship to the world may offer a novel model of brain that carries major ontological implications as they shall be discussed in the second paper.