Brain Dynamics. The brain activity according to the dynamic conditions of nervous excitability. Volume 2
Dinámica Cerebral. La actividad cerebral en función de las condiciones dinámicas de la excitabilidad nerviosa. Tomo segundo

Abstract

This volume is the English translation of Volume 2 of the book "Dinámica Cerebral" written in Spanish by Justo Gonzalo Rodríguez-Leal (Barcelona 1910 – Madrid 1986), first published in 1950. The volume, devoted to tactile functions, is the continuation of Volume 1 (on general aspects and visual functions, English translation Open Access in https:/eprints.ucm.es/id/eprint/63730/) to which it refers continuously. A facsimile Spanish edition includindg Vol. 1, 2 and supplements was published by the Red Temática en Tecnologías de Computación Artificial/Natural (RTNAC) and the University of Santiago de Compostela in 2010, and whose on-line Open-Access version (http://dspace.usc.es/handle/10347/4341 ) maintains a significant rate of visits since its publication.

The author, after specialization in neurology and brain pathology in Austria and Germany (1933-35) developed a research on the human cerebral cortex.
The interest of the research described here lies, as in Volume 1, in the fact that it is surprisingly of current interest, apart from its undoubted historical interest. Some aspects were ahead of discoveries that were made later. It is remarkable that some of the phenomena exposed are still unknown and that the proposed functional dynamic unit of the cortex is closely related to current trends in the study of the brain.

This volume deals with tactile functions and further elaborates on concepts introduced in Volume 1. The tactile phenomenology in cases of central syndrome is described. This syndrome, already studied in Volume 1, is the result of a unilateral lesion in an association area in the left parieto-occipital cortex, equidistant from the visual, tactile and auditory primary areas. It consists of a multisensory alteration (visual, tactile, auditory) although the lesion does not involve specific areas, all functions being affected, from simple excitability to more complex functions, bilaterally and symmetrically. In particular, the striking phenomenon in which the visual image is tilted or nearly inverted (see Vol. 1), is now extended to the phenomenon of localization of stimuli in the tactile system. Inversion in tactile space is studied in detail in cases of central syndrome, being generalized to all sensory systems of a spatial nature, once confirmed in the auditory system.

Similarly to what happens in vision, the tactile phenomena in the mentioned syndrome have a dynamic character since the disorders vary with the intensity of the stimulus and with the facilitation by other stimulus. The phenomenon of facilitation by muscular effort is particularly noticeable. The greater the deficit in brain excitability (due to the lesion), the greater the effect of facilitation. In the process of tactile localization of a stimulus, up to five phases are distinguished, from simple sensation to specific localization (passing through inversion), as stimulation increases. This process is described as a spiral development of the organization of the sensory field (tactile and also visual).
As in vision, a continuity is found between the various functions that appear according to physiological requirements. Likewise, a continuity is established between sensory functions and gnosis, both being based on the same physiological laws. The schema function is studied in detail and considered in diverse degree according to the somatic model, postural model and praxis model.

In addition to the patients directly studied by the author, a reference case is also the famous Schneider patient of Goldstein and Gelb studied in 1918 and 1919, which deserves publications even at present, and which the author interpreted under the central syndrome. This syndrome is also related to Gerstmann's syndrome. In subsequent research, the author found 35 cases that also fit the central syndrome.

In a later publication (English translation, Open Access in https://eprints.ucm.es/id/eprint/30931/ ) the author exposed a model based on functional gradients through the cortex, according to which, its specificity is distributed in a continuous gradation, and in agreement with a continuous transition between the central syndrome and other cortical syndromes. The author continued to develop a functional brain model applying the principle of similarity of a dynamic system to the central syndrome, the latter being understood as a change of scale in nervous excitability with respect to a normal individual. This concept was already introduced in the preceding Vol. 1 and also in this Vol. 2.

A preface introduces some aspects of this research, its author and his subsequent research.