Common themes underlying three recent studies of mine on disparate topics are reviewed: the lamination of sensory cortex; the differentiation into subfields of the mammalian hippocampus; and the neuronal dynamics that might underlie the faculty for language in the human frontal lobes. These studies all discuss the evolution of cortical networks in terms of their computations, quantified by simulating simplified formal models. They all dwell on the interrelationship between qualitative and quantitative change. Finally, they all include, as a necessary ingredient of the relevant computational mechanism, a simple feature of pyramidal cell biophysics: firing rate adaptation.