Wolfgang Köhler, answered from the texts and cited to the page.
The order we find in experience is not laid over a chaos in the brain; the brain processes that underlie a Gestalt are themselves organised, and organised in the same functional form.12 The seen figure and the cortical process are two aspects of one structured event — isomorphic, not identical, but sharing their form. Organisation in the mind mirrors organisation in the nervous system because both obey the dynamics of systems seeking equilibrium.3
And since Cartesius, neurologists have worked with the same concepts wherever they have dealt with orderly organic function in higher animals and in man. It is not the dynamics of nervous processes as such which they suppose tend toward coördinated function.Gestalt Psychology
The problem can be readily transformed, however, into a matter of brain physiology. At the very outset (Chap. II) it was proposed to use direct experience as an indicator of those physiological processes which, occurring between the realm of outer conditions and the overt behavior of the organism, are not directly observable at the present time.Gestalt Psychology
As in this case, organization comes nearer the objective facts in some essential points than the indifferent mosaic of stimuli does, so in our example, acoustical organization will correspond to something in the pianist which does not exist as such in the sound waves between him and his audience. Once more the mediating properties of the stimuli are their relationships.Gestalt Psychology
The general thesis — that organised experience answers to organised brain process — I hold; the SPECIFIC model, that steady cortical currents flow in fields answering to the perceived figure, was the vulnerable form of it, and the experiments against direct cortical currents told against that model. The principle of structural correspondence stands where my particular electrophysiology did not.