Die Bedeutung limbischer Funktionsstörungen für die Ätiologie kindlicher Schizophrenien*

Abstract

Discussing the aetiology of schizophrenia, preceding disposing factors previous to the manifestation of psychosis must be considered. In this connexion the high-risk-research is of great importance. Studying the precursors of adult schizophrenia on one side and examining the psychological and psychophysiological data derived from the investigation of children with high-risk-for-schizophrenia (children of schizophrenic parents) on the other side, there are indications of faulty processing of sensoric stimuli and of a cognitive deficit in those probands. Neuropsychological studies in schizophrenic, autistic and high-risk-children suggest an impairment of the information- processing system, affecting among other functions the selective perception, the attention range and the adequate interpretation of the importance of a distinct information. Neuropsychological experiments like association tests, sorting tasks, or auditory, visual and tactile sensory discrimination tests showed that relevant and irrelevant stimuli from the internal and external environment apparently are not sensibly integrated and can not be included in a rational scheme for thought and action. A breakdown of central filter mechanism can be hypothetisized. They are linked to the limbic system, especially to the functions of the hippocampus and the amygdala.

A further support for the hypothesis of an involvement of a limbic dysfunction in the aetiology of schizophrenia are the psycho-physiological findings in children with high-risk-for-schizophrenia on one side and of adult schizophrenics on the other side. High-risk-children, who later become schizophrenic themselves have a fast recovery of skin conductance response. This electrodermal orienting reaction is similar to that observed after experimental hippocampal lesions in animals leading to an enhanced orienting reaction with increased amplitude and shortened recovery time of the psychogalvanic skin conductance response. The reverse can be observed in animals with lesions of the amygdala, which cause diminution or extinction of electrodermal responsivity with reduced amplitude an delayed recovery time. This could be demonstrated in autistic children. The behaviour of autistic children and of autistic, withdrawn adult schizophrencis with reduced dynamic psychotic process activity is similar to that of monkeys with lesions of the amygdala who show a marked reduction of visual orientation towards unfamiliar stimuli and little or no reaction to environmental changes or familiar signals like gestures, facial expressions and mothers's face.

Further support of the eminent aetiological significance of limbic dysfunction in childhood psychoses comes from the high percentage of autistic and schizophrenic children and those with high risk for schizophrenia who show signs of mild hypoxic brain damage. It is known that the hippocampus and the amygdala are particulary sensitive to hypoxia. Furthermore neuropathological studies detected glial proliferations in the region of the hippocampus and other diencephalic structures, that could be attributed to virus infections. There is evidence from recent research that herpes simplex virus encephalitis plays an important role in patients who later develop a schizophrenic psychosis.

Neuropharmacologoical and neurochemical findings also suggest a participation of the limbic system in regard to the aetiology of schizophrenic psychosis. Discussing the possible importance of the limbic system for the development of childhood schizophrenia we consider the limbic system dysfunction solely as one link in the psychobiological complementary chain of mutually interacting factors obeying variable dynamics. But arguments derived from developmental psychology emphasize the importance of the limbic system for the manifestation of childhood psychoses. Limbic system structures with their close connections mainly to the hypothalamus, to the complex of the anterior nucleus of the thalamus and to mesencephalic structures are eminently impor-. tant for the emotivity, which in itself plays an important role in the development of delusions and hallucinations. During early life the anthropomorphic, syncretic, physiognomic and animistic experience of the external world by the child is very domineering. The magic-animistisch thinking of the child is fundamentally influenced by the emotivity. During early childhood the affective-dynamic nucleus of the child's personality participates extensiveley in the process of perception. The schizophrenic thinking is determined by an pathologically changed emotivity. The psychotic affect, especially the psychotic anxiety, plays an important role in regard to the origin of delusional and hallucinatory experience of the schizophrenic.

The supposed limbic dysfunction in schizophrenia is linked to a regression to primitive modes of behaviour which are characteristic of the phase of physiognomic-animistic perception of the world, during which emotivity occupies a central position. The psychopathological behaviour of schizophrenics as well as neuropsychological, psychophysiological, pharmacological, biochemical and electrophysiological research findings suggest a disturbance in the delicately tuned and harmonic interplay between neocortical and limbic functions in schizophrenia. However, the formulation of an unitary basic disturbance in schizophrenia is not possible with the present state of scientific knowledge.

Zusammenfassung

Das Theorem der multikonditionalen Bedingtheit endogener Psychosen gilt auch für die kindliche Schizophrenie. Auch bei Frühmanifestationen psychotisch-dynamischer Entgleisungen und Strukturverformüngen handelt es sich um heterogene Endstrecken psychopathologisch uneinheitlicher Erlebensund Verhaltensweisen des Betroffenen, resultierend aus einer Vielzahl verschiedener Teilursachen. Für die Erhellung ätiologisch bedeutsamer Komponenten schizophrener Psychosen des Kindes- und Erwachsenenalters erscheint die noch in den ersten Anfängen befindliche high-risk-Forschung besonders vielversprechend. Wie am Beispiel eines 9jährigen Mädchens dargestellt, können schon in der Kindheit bestehende neurale und entsprechende perzeptiv-kognitive Dysfunktionen und eine damit eng verknüpfte emotional-affektive Instabilität ätiologisch für die Schizophrenie-Genese eine sehr bedeutsame Rolle spielen. Neuropsychologische, psychophysiologische, pharmako-neurochemische und entwicklungspsychologische Befunde sowohl bei manifest Schizophrenen aller Altersstufen als auch bei Kindern mit einem erhöhten Schizophrenie-Risiko sprechen dafür, daß bei der Schizophrenie das feinabgestimmte dynamische Wechselspiel zwischen neocortikalen und limbischen Funktionen gestört ist. Bei schizophrenie-belasteten Kindern, die später manifest erkranken, bestehen schon vor Psychoseausbruch Störungen des informationsverarbeitenden Systems, insbesondere der selektiven Wahrnehmung und der Gesamterkrankungen Aufmerksamkeitszuwendung, der Bedeutungszumessung interner und externer sensorischer Reize und Wahrnehmungsqualitäten und damit letztlich eine Beeinträchtigung des Realitätsbezugs.

Die in der Arbeit beschriebenen neuropsychologischen Dysfunktionen bei einem 9jährigen high-risk-Kind können mit der Hypothese einer Funktionsstörung insbesondere des hippecampal-amygdaloidalen Neuronenkreises in Einklang gebracht werden, wofür u.a. die genialen neurophysiologischen Experimente von Vinogradova einen ebenso überzeugenden Beleg darstellen wie die psychophysiologisch-psychogalvanischen Untersuchungen von Mednick und Schulsinger, Gruzelier und Venables u.a., Die vermutete Beeinträchtigung von an limbische Kernstrukturen und Faserverbindungen gebundenen neural-kognitiven Leistungsfunktionen geht einher mit einem Rückfall in urtümlich-konkretistisches Denken und in magisch-animistisch-physiognomische Erlebnisweisen, wie sie für das Kleinkindesalter charakteristisch sind und die im wesentlichen durch das dynamische, affektiv-emotionale Zentrum der kindlichen Persönlichkeit beherrscht werden.