Although a tremendous honour, it is with great sadness that this review is dedicated to Mircea's memory. Mircea has been, not only an inspiration throughout my career, but a generous and supportive friend whose kindly, incisive criticism has been a constant reminder that what we study in vitro must eventually be understood in the context of the whole system. Quoting from the Preface to his elegant monograph ‘The evolution of work on extremely simplified preparations has reached the point where some investigators are not shy to jump from single-cell properties to global brain functions, such as arousal and sleep, paroxysmal events of the epileptic type, and even conscious thinking.’ (Steriade, 2001). Bearing in mind that the properties both of single neurons and the connections between them might vary in different brain states and in different phases of cortical rhythms, in this review I summarize studies of the local circuitry of the thalamo-recipient layers 4 and 6 focussing on results obtained with dual intracellular recordings and biocytin-labelling in adult neocortical slices.