The Neurological Correlates of Pathological Consciousness in the Group of Schizophrenias

On the basis of clinical observation, we have previously suggested (Grant, 2002) that schizophrenia or at least some common types of it, can be accurately and usefully conceptualized as a form of pathological consciousness in which conscious experiences which belong to the subjective self are mistaken for conscious perceptions of or from external objects. In this paper we trace the neurological sensory pathways mediating both consciousness of objects and subjective self-consciousness to their meeting point in what we have called the common sensory pathway (the extended amygdala, the nucleus accumbens, the globus pallidus, and the dorsomedial thalamic nucleus). Having defined this common sensory pathway, it became possible for us to formulate a neurological hypothesis to complement our pathological consciousness hypothesis of some types of schizophrenia. Our neurological hypothesis is that in schizophrenia exhibiting the pathological consciousness (mistaking self for other) we have described (Grant, 2002), we should find pathological changes in the structures of the common sensory pathway. The paper is developed in several steps. (1) We examine the history of the idea of pathological consciousness in schizophrenia. (2) We trace the neurological pathways of consciousness of external objects and subjective self-consciousness to their meeting point in what we have called the common sensory pathway. (3) We examine neuroscience studies of the structures of this common sensory pathway in patients with schizophrenia, looking for evidence of pathological changes. (4) We discuss the implication for our pathological consciousness and common sensory pathway hypotheses of some studies that have found brain pathologies outside of the common sensory pathway in patients with schizophrenia. Our conclusion, which can only be tentative at the present stage of knowledge, is that there is sufficient consistency between our pathological consciousness and common sensory-pathway hypotheses and the neuroscience data in schizophrenia studies to warrant further research.