Cajal and Lorente de Nó on cortical interneurons: Coincidences and progress

This essay explores the contributions to the organization of neuronal microcircuits in the cerebral cortex by Rafael Lorente de Nó, a renowned disciple of Santiago Ramón y Cajal. Lorente de Nó was impressed by the advances in functional parcellation of the cerebral cortex, and wished to find an anatomical correlate, not in cytoarchitectonic charts but in the fine details of neurons and (soon) of neuronal circuits within a cortical locale. His early analysis culminated in two major papers in 1933 and 1934: he introduced a hypothetical frame in which to integrate circuit anatomical complexity with the ideas on the physiology of the neuron prevalent at the time. In an interlude (1934-1938), Lorente embarked in studies of neuron physiology that inclined him to a reductionist interpretation of the axon as the main functionally relevant entity of neurons. This essay describes my attempts at tracing the links between the master's tradition, the minutiae in the early Golgi studies by Lorente and his concepts of neurophysiology. These are the bases to approach his final synthesis: The cerebral cortex: architecture, intracortical connections and motor projections, published as an invited chapter in J.F. Fulton's Physiology of the Nervous System in 1938.