[Chronology of Justo Gonzalo's research on brain dynamics].

Introduction: The Spanish neuroscientist Justo Gonzalo y Rodriguez-Leal (1910-1986) investigated the functional organisation of the cerebral cortex over more than four decades. His findings led him to formulate a neurophysiological theory based on the laws of nervous excitability, which he called brain dynamics. This paper presents in chronological order how the main ideas on which it is based arose.

Development: In 1939, Gonzalo observed the phenomena of dynamic action: asynchrony or disaggregation, facilitation and cerebral repercussion. This was followed by two principles: the cerebral effect of lesions according to their magnitude and position (1941), and spiral development of the sensory field (1947). At the same time, he characterised what he called the central syndrome of the cerebral cortex. In the 1950s he developed the concepts of the cortical gradient, similarity and allometry. In contrast to modular conceptions of the cerebral cortex, in which one region is responsible for one function, Gonzalo argued that 'cortical gradients provide the location of systems, while similarity and allometry reveal their functional mechanism.'

Conclusions: The theory of brain dynamics was established in two stages. The first (between 1938 and 1950) had an important clinical foundation, involving the observation of new phenomena and the formulation of new concepts. The second (between 1950 and 1960) included the introduction of more far-reaching concepts, such as the functional cortical gradient, and allometry laws based on a change of scale. Today, various authors believe that the concept of the gradient is crucial for understanding how the brain is organised.