The Location of Consciousness - A Historical View

In a distant past, it was accepted that, somewhere in the body, there was a substance responsible for the formation of consciousness. Such an idea used "to burn the neurons" of the ancient Greek philosophers, who believed that mind and consciousness dwelled in the lungs and the air was in charge of their production. Even when the concepts changed, around the sixth century B.C ., and the brain started being recognized as the centre of mental activities, it still persisted the idea that some substance gave rise to such activities. The responsibility was then transferred to the cerebrospinal fluid. At last, when that conception was abandoned, a new question arose : is there a center for consciousness ? In the XVII century , René Descartes, perhaps afraid of the powerful theological pressures of that era or because he really thought that way, stated that the mind was located at the pineal gland and, through it, the soul ( an immaterial kind of superior consciousness, later represented, metaphorically, by a homunculus* - a symbol created by medieval theology), communicated with the material soma.

Thus, soul and mind ( and by inference, consciousness ) became dissociated from brain and body. The birth of dualism! Three centuries later, Daniel Dennett, in his book "Consciousness Explained", would refer to Descartes´ theory as " The Cartesian Theater" and emphatically refute its scientific value.

* - This homunculus is different from the hominculi created by Penfield and Rasmussen, to represent the topographic organization of the sensorial and motor areas, located in the cortex. The homunculus of the "Cartesian Theater" sits in a virtual control room, in the center of the brain, monitoring a console of gauges and pulling strings, in order to command the person's mental and physical actions. Or, as it is shown in Fig. 1, he is a man, standing by a giant brain and watching, through this brain's eyes, the world around him.


The homunculus of Cartesian Theather, according to a conception presented by Stephen Jones in "Introduction to the Physiology of Ordinary Consciousness". Conference : "Towards a Science of Consciousness" ,
Tucson, Arizona, April,1996.

However, attempts to revive the theory of a localized center for consciousness have not ceased : When Derek Parfit found out that patients with the split-brain syndrome (in which each cerebral hemisphere functions separately), still identified themselves as a sole person, he concluded that this could only be explained by the existence of "an executive zone for consciousness", which would integrate all information generated in the brain.

Recently, Joseph Bogen indicated that the mechanism responsible for the formation of consciousness ( not consciousness itself ) is located in the intralaminar nuclei of the thalamus. Although these studies are quite relevant, it is now believed that consciousness is not restricted to any particular area. Actually, it spreads, diffusely, throughout the whole brain, according to one of its most important characteristics : to be, simultaneously, spatially multiple and temporally unified.

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