[On the anatomo-physiological basis of trance and dissociation]

This article presents information regarding the anatomic and physiological basis of hypnotic type trances and dissociation. Conjugated upward deviation of the eyes, as well as the so-called "rolling of the eyes" (explained in the text), which are present during trances, are suitable entry points for the study of the anatomic substrate underlying these experiences. The thalamus, posterior commissure, pretectal zone, and Cajal and Darschewitsch nuclei are the anatomic zones related with the upward gaze, "eye rolling" and trance type changes of consciousness. Independently of these facts, at least three different types of trance behavior can be differentiated: the form that we call passive is present in physiological sleep, and consists of the eyes turning upwards spontaneously. In the form called active, the trance is linked clearly to the upward stare and ocular rotation. Finally, a form that we call intermediate in this study accompanies personality changes in multiple personality disorder and some cases of psychogenic flight. This study attempts to demonstrate that the conjugated upward deviation of the eyes can be, in the absence of another disorder, a first-order indicator of disorder of consciousness of the type found in dissociative disorders.