Aberrant Hippocampal Neuroregenerative Plasticity in Schizophrenia: Reactive Neuroblastosis as a Possible Pathocellular Mechanism of Hallucination.

Hallucination is a sensory perception that occurs in the absence of external stimuli during abnormal neurological disturbances and various mental diseases. Hallucination is recognized as a core psychotic symptom and is particularly more prevalent in individuals with schizophrenia. Strikingly, a significant number of subjects with Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and other neurological diseases like cerebral stroke and epileptic seizure also experience hallucination. While aberrant neurotransmission has been linked to the neuropathogenic events of schizophrenia, the precise cellular mechanism accounting for hallucinations remains obscure. Neurogenesis is a cellular process of producing new neurons from the neural stem cells (NSC)-derived neuroblasts in the brain that contribute to the regulation of pattern separation, mood, olfaction, learning, and memory in adulthood. Impaired neurogenesis in the hippocampus of the adult brain has been linked to stress, anxiety, depression, and dementia. Notably, many neurodegenerative disorders are characterized by the mitotic and functional activation of neuroblasts and cell cycle re-entry of mature neurons leading to a drastic alteration in neurogenic process, known as reactive neuroblastosis. Considering their neurophysiological properties, the abnormal integration of neuroblasts into the existing neural network or withdrawal of their connections can lead to abnormal synaptogenesis, and neurotransmission. Eventually, this would be expected to result in altered perception accounting for hallucination. Thus, this article emphasizes a hypothesis that aberrant neurogenic processes at the level of reactive neuroblastosis could be an underlying mechanism of hallucination in schizophrenia and other neurological diseases.