[Roles of brain science in psychiatry]

At the opportunity of celebrating the 100th Anniversary of the Japanese Society of Psychiatry and Neurology, I am filled with deep emotion when I recall the time only a few decades ago, when mental disorders were believed to be an illness of the mind without any disorder in the brain. It has now become apparent that a mental disease emerges from the malfunction of the brain's unique biological mechanisms, so that any mental disease can be cured or prevented if the cause of the malfunction is clarified. Analyses of intercellular as well as intracellular signal transduction and the mechanisms underlying gene regulation in brain cells have recently advanced markedly and have brought a marked improvement in the methods and technology for investigating pathogenesis of neurological and psychiatric diseases. These impressive results have been derived in the search for the cause of Parkinson's disease, Alzheimer's disease and spinocerebellar degeneration. Certain minor changes in the molecular structure of sodium channels have been found to cause epilepsy. It has also been revealed that ten particular sites in chromosomes harbor the remote cause of schizophrenia and depression. These sites are probably responsible for production of certain synaptic transmitters and modulators. Another major challenge in the field of psychiatry is to understand the unique symptoms exhibited by patients with psychiatric disorders, which requires research to head in a direction different from molecular and cellular brain science. It is a challenge similar to the very fundamental challenge of determining how our brain, which is composed of numerous brain cells, yields our mind (or, should I say, supports our mind). To understand the brain as a complex system is more difficult than researching its molecular and cellular machinery, and accordingly, the progress of research in this field has been slow. However, it is gradually gaining speed thanks to the improvement in non-invasive methods for measuring activities in conscious human brains as well as that to the establishment of computational models. For example, it is a major mystery why a schizophrenic patient experiences auditory hallucinations, but an interesting hypothesis is derived by considering activities of the thinking brain as a neural system. Under this hypothesis, we gather information from the outside world by using our sensory systems and establish its internal model in our brain. Thus, manipulation of the internal model to run a simulation is an important part of our thinking activities. When an internal model behaves abnormally, abnormal information is generated, which makes the patient mistake it for sound from the outside, thus causing auditory hallucinations. It is highly expected that substantial progress will be made in psychiatry through proposals of new hypothetical models such as this one as well as verification of them through non-invasive measurement of brain activities. In the near future, patients with mental disorders will most likely benefit from the results of this two-directional research in psychiatry. The expectation is high for the strong leadership of the Japanese Society of Psychiatry and Neurology to promote research in Japan. Effective research effort requires efficient collection of human materials and systematic survey of patients, which will inevitably increase the involvement of patients in basic research. Improvement of research environments such as by developing a method for assessing research ethics and upgrading brain banks is urgently needed.