Electrical activity of neurons in the mammalian brain responds to oscillatory rhythms detected by electroencephalography. The coordinated activation of these various waves, which administers, for instance, the processing of sensory inputs or the consolidation of memories, enables the brain to function correctly.
Yet, dysfunctions in these communication pathways could be strongly correlated with the onset of schizophrenia. For the first time, scientists from the University of Geneva (UNIGE), Switzerland, within the framework of the Synapsy National Centre of Competence in Research, have successfully demonstrated this phenomenon in human beings.
Scientists analyzed the brain activity of children, adolescents, and young adults with a genetic risk of the disease. They demonstrated that a reduction in the activation of gamma waves was correlated with the emergence of psychotic symptoms even before full-blown disorders appeared.
Stephan Eliez, professor in the Department of Psychiatry, and Christoph Michel, professor in the Department of Basic Neuroscience, said, “We suspected that gamma waves, the highest frequency of the brain rhythms, play a decisive role in developing of schizophrenia symptoms. However, we still had to confirm that this impaired synchronization of neural communication pathways observed in mice does indeed exist in humans.”
Valentina Mancini, a doctoral student in Stephan Eliez’s laboratory and the first author of this study, said, “People with a chromosomal microdeletion 22q11 have a 25 to 30% risk of developing schizophrenia in adulthood. Therefore, they are a particularly relevant at-risk population for studying the cerebral development of this disease.”
“People with schizophrenia often suffer from a reduced capacity to process auditory information; to detect any disturbance in brain communication, the scientists, therefore, measured gamma wave activation following an auditory stimulus in 22q11 patients of all ages, compared with people without this microdeletion.”
Vincent Rochas, a scientific collaborator in Christoph Michel’s laboratory, said, “Children and adolescents at genetic risk of schizophrenic disorders but without visible symptoms showed the same patterns of gamma wave disruption as patients suffering from the disease. In addition, linear growth of the gamma-band oscillations was observed in people with no genetic predisposition to schizophrenia, showing a progressive maturation of communication between the cerebral areas during development.”
“However, this maturation is absent in 22q11 patients, whatever their age, suggesting an abnormal development of circuits underlying neural oscillations in adolescence.”
Scientists also identified a strong correlation between the gamma-band activation deficit and the severity of psychotic symptoms, such as auditory hallucinations, thus confirming the existence of a neurobiological progression of the disease.
Scientists noted, “Our results confirm that this dysfunction appears very early. We now want to identify the best time during the child’s development to intervene in relation to this pathological shift.”
- Valentina Mancini et al. Aberrant Developmental Patterns of Gamma-Band Response and Long-Range Communication Disruption in Youths With 22q11.2 Deletion Syndrome. DOI: 10.1176/appi.ajp.2021.21020190