Duality of Symptomatology : Positive and Negative Symptoms

Abstract

  The idea that the symptoms of neurological disease are dual in nature, negative and positive, is scientifically valuable and practically useful. Hughlings Jackson claimed that the nervous system is an evolutionary hierarchy of three levels, from simple, organized, and most automatic state to complex, least organized and least automatic state. The higher level controlled and inhibited the function of lower levels so that neurological disease led to two sets of symptoms, negative and positive, which is called “duality of symptomatology”. Negative symptoms are related to loss of the controlling cortex while positive symptoms are associated with excitation or the release of lower levels from higher inhibitory control. Positive and negative symptoms are closely intertwined such that they both occur contemporaneously. The brain damage that gives the negative symptoms at the same time allows expression of the positive symptoms. For example, aphasic patients may show difficulties in recalling words (negative symptom) and echolalia (positive symptom) simultaneously. To comprehend complex neurological symptoms, it is important to consider duality of symptoms in relationship to the underlying neural mechanisms.