For some time now it has been known that certain hereditary factors enhance the risk of schizophrenia or a manic-depressive disorder.

However, just how this occurs had remained obscure. German researchers are now able to answer this question, at least for one common genetic variant: the genetic variant impairs the interoperation of certain regions of the brain.

The study is to appear in the May issue of the scientific journal Science.

Researches believe the study is salient and will provide fresh stimuli for the search for cures.

The scientists examined test persons with whom a certain genetic trait had undergone a characteristic mutation. A year ago, a research team had demonstrated that this mutation was, amongst other things, associated with an enhanced risk of schizophrenia.

In addition to this, people carrying this variant were more susceptible to a bipolar malady, also known as a manic-depressive disorder. In the present case, however, results were based on examinations of 115 healthy subjects.

“At this point, no-one had the slightest idea of what effect the genetic variant we had observed might have on the brain”, declares Professor Dr. Andreas Meyer-Lindenberg, the initiator of the study.

“We examined our test subjects in magnetic resonance tomographs, which reveal how the various areas of the brain interoperate”.

The findings were revealing as persons suffering from this high-risk genetic variant exhibited a change in the communication between their dorsolateral prefrontal cortex (DLPFC) and other regions of their brains.

The DLPFC plays an active role in the working memory and diverse “higher” cerebral functions. It comprises a right-hand and a left-hand fraction, and it was the communication between these two halves which had become impaired.

In contrast to this, the link between the DLPFC and the hippocampus, a further region of the brain of importance for the memory, was improved. Both these noteworthy phenomena had already been shown to exist in patients suffering from schizophrenia.

Moreover, carriers of this high-risk gene also displayed an enhanced linkage between the amygdala and a number of other cerebral regions. The amygdala, also known as the “almond”, plays an active role in the manner in which we cope with our emotions.

“Which is why we have related this phenomenon to the bipolar impairment, which is, as we know, characterised by erratic mood swings”, Professor Dr. Henrik Walter of Bonn University explains.

Over 100 years ago, the German psychiatrist Carl Wernicke had already suspected that schizophrenia might be attributable to impaired interoperation between different regions of the brain. The new study, employing an innovative combination of modern genetics and cerebral imaging, has confirmed this suspicion.

The mutated gene contains the building plan for a protein whose precise function is still not clear. Diverse study groups worldwide are currently engaged in finding answer to this question – amongst other reasons, because this could provide approaches to novel treatments.

“It is impressive that using modern methods we are able to trace such subtle genetic effects in the living brain”, says Professor Dr. Peter Kirsch, head of the Study Group for Cerebral Imaging in Mannheim. Carriers of this variant, incidentally, must not be worried that they are destined to suffer from schizophrenia or bipolar impairment.

“This genetic variant plays only a minor role in these disorders”, says Dr. Christine Esslinger from the Zentralinstitut für Seelische Gesundheit. Other factors must at all events become involved before a disorder such as this breaks out.

Source: University of Bonn