Information processing and knowledge generation in the nervous system

Abstract

In a classical psychological view data are gathered by the sensory systems and then processed sequentially in distinct neuronal structures. This bottom-up analysis is hierarchically organized, and somewhere on the way of this analysis data are turned into information (like in the sense organs), and information is turned into knowledge (like somewhere in cortical structures). Sometimes, information and knowledge are used, however, interchangeably. Although this is a classical view, it is still with us, often present as an implicit hypothesis. In a modern view, bottom-up and top-down analyses are intertwined. It might be useful to emphasize with the term information processing the bottom-up component and with the term knowledge generation the top-down component not forgetting of course their respective dependence. The distinction between the two aspects of analysis can for instance be demonstrated in the temporal analysis of information and organization of knowledge. Different transduction times in the visual and auditory modality or within the visual modality for surfaces with different flux, and the spatial distribution of neuronal activities which are basic to integrated mental activity result in a logistical problem: How does the brain structure the chaos of undefined (and undefinable) temporal availability of information that is basic to any percept or the programming of any precise movement? It is suggested that the brain creates endogenously atemporal system states within which incoming information is treated as co-temporal. According to the model a system state is implemented by relaxation-type neuronal oscillations, each period representing one such system state. Experimental evidence suggests that the duration of these system states or elementary processing units is approximately 30 to 40 msec. Support comes from studies on temporal order threshold, choice reaction time, latency of eye movements, stereopsis, midlatency response of the auditory evoked potential or the execution of simple movements. On a theoretical level, it is suggested that the integrated information within such system states is the neuronal basis of primordial events. The sequence of such events is temporally integrated up to approximately 2 to 3 seconds. This temporal integration process is pre-semantic and it defines a working platform for mental activity. Experimental evidence for such a universal integration process comes from studies on temporal reproduction, short term memory, spontaneous segmentation of speech, the duration of intentional acts, sensorimotor synchronization or the endogenous modulation of the mismatch negativity as studied with the MEG. Because of its omnipresence in different domains of the mental repertory, this integration process can be used to define each singular state of being conscious (STOBCON). Experimental evidence shows that the content within such STOBCONs is strongly modulated in a top-down way. What can be referred to as knowledge represented within such STOBCONs according to this model is up-dated in regular intervals by external information. The brain is asking autonomously in intervals of approximately 3 seconds what is new in the world? and by doing so re-generating its knowledge basis.