Abstract
Five assumptions, leading to and defining the hypothesis of the ‘informational underload syndrome’ of psychotic mental illness exhibiting hallucinosis, are described:
1. All clinically and experimentally occurring hallucinatory syndromes have, in spite of their differences, a common neurophysiological pattern;
2. Psychiatry has studied the neurophysiological aspects of ‘sensory deprivation’ or ‘sensory restriction’ inadequately; this study may hold important clues for our understanding of mental illness;
3. We assume, in spite of insufficient scientifically tenable evidence so far, that experimental conditions described under the label ‘sensory deprivation’ or ‘sensory restriction’ represent a unitary condition;
4. For its normal functioning the brain depends on both stored information as well as on continuously new extra-cerebral input; if the extracerebral inflow of new information falls below a certain threshold, then the brain must rely mainly on stored information and is assumed to develop a ‘state of informational underload’ which in due course may be characterized electrophysiologically. This pattern is thought to be at the basis of external behavioural manifestations of the sensory deprivation experiments;
5. Genetic, metabolic, degenerative, toxic, faulty learning and other pathogenetic processes may interfere with the sensory input regulating system, thus possibly leading to ‘informational underload’, which might be at the basis of some clinical psychiatric syndromes in which an analogy with sensory deprivation experiments cannot be recognized.
The described research attempts to answer whether different sensory deprivation experiments represent one common condition (‘informational underload’) and if so how this condition may be characterized neurophysiologically. Cats, living in colony fashion are used. The experimental set-up and the data acquisition system is then described, involving the study of auditory, visual, proprioceptive and other experimental parameters, singly or in combinations. Six electroencephalographic traces are obtained before and during the experimentation and stored on electromagnetic tape. Resting activity as well as reactivity to visual and auditory repetitive stimultations (evoked cortical responses) are under study, in which topographical interrelations are stressed rather than localized or generally occurring events.
The data-analysis system is discussed, involving analogue to digital conversion with the help of the IBM 1710 computer and eventually the mathematical procedures of autocorrelation, autospectral analysis, cross-correlation and cross-spectral analysis, concerning resting activity as executed by the IBM 7094 computer. For evoked responses a computer of analogue transients is presently in use.
Changes in evoked potentials are noticed under different experimental conditions. Concerning resting activity the preliminary impression is that there seems to occur a phenomenon characterized by fewer rhythms, the centre of which moves toward the lower frequency range. It is, however, far too early to allow for statistical analysis of groups of animals which have been subjected to the same experiment in order to establish statistical tendencies.