Van de Ville and chaotic brain patterns

Unlocking the mystery of consciousness is a major challenge of current neuroscience. In this context, a joint team from STI and Université de Genève has just shed some light on an important characteristic of conscious thinking. Thanks to cutting edge technologies in neuroimaging and also to mathematical analysis, this team has shown that conscious thought can be broken down into a succession of cerebral microstates, or “atoms of thought”. The temporal sequence of these microstates is neither random nor predetermined but chaotic; i.e., unpredictable but following a precise organizing principle. This chaotic orgainsation of cerebral activity seems to be the key method for allowing the brain to react rapidly to unexpected events. This study, which has been published in the periodical PNAS, constitutes a leap forward on the road to understanding consciousness, as well as certain mental illnesses. How consciousness actually functions is still a mystery to scientists. Many have tried to grasp the fundamental principles by elaborating theoretical models, but few have actually attempted to understand cerebral organisation by observing measurements of neuronal activity. Prof. Dimitri Van De Ville of the Insitute of Bioengineering in collaboration with Prof. Christoph Michel and Dr. Juliane Britz from UNIGE have created an experiment to grasp the concept of how spontaneous thought and conscious thought organize themselves.

In fact, these two scientists have measured the cerebral activity of volunteers by simultaneously using two methods of neuroimagery in the laboratory: electroencephalography (EEG), which makes possible measurements at intervals of around a millisecond, and functional Magnetic Imagery Resonance (fMRI), which allows them to follow cerebral activity at intervals of a second. During these examinations the volunteers were instructed to let their thoughts flow freely, without focussing on any particular idea. The signals recorded during these sessions were analyzed with mathematical tools.
Atoms of thought
As a result of these experiments the scientists deduced first of all that cerebral activity organizes itself in a succession of microstates. These microstates, considered to be “atoms of thought”, are the component parts of cognition, a little like “parts” of thought. Each microstate corresponds to a particular configuration of neuronal activity in the brain. The scientists have demonstrated four distinct microstates which correspond to visual, auditive, introspective and attentionate aspects of thought. One thought would therefore appear like a succession of visual, auditive, introspective and attentionate component parts.
Fractals on the brain
Moreover, by applying advanced mathematical analysis to the EEG and fMRI measurements, the researchers have made a surprising discovery: these atoms, or parts, of thought follow each other with a temporal structure similar to the two time scales of measurement. The same structure has been observed within a time scale of tenths of a second (with EEG) and within a time scale of tens of seconds (with fMRI). This property is the principal characteristic of fractals within chaos theory.

A fractal object presents the same pattern when examined with microsope, magnifying glass or even the naked eye. It would appear that the duration of microstates plays a predominant role in this fractal organisation of thought. “Take the analogy of a book in which the letters respresent the atoms of thought. These combine to form words, which themselves combine to form sentences; the sentences combine to form paragraphs, and so on until you have a whole book, all with the same syntactical rules,” explains Chrisoph Michel. “What we have put forward is a syntax of thought.”
In working order, thanks to chaos
It would therefore be thanks to this “chaotic” organization of thought that the brain can reorganize itself, and adapt very quickly according to its needs. Perturbations in these microstates could be at the origin of certain mental illnesses. For example, it has been observed among schizophrenics that microstates tend to have unusually short duration, suggesting the presence of incomplete thoughts. Following on from this discovery, the researchers are now going to be able to attempt to understand this neuronal syntax among neurological patients, as well as healthy subjects undergoing a change of conscious state, such as during sleep.