The mental problems experienced by schizophrenia patients stem in large part from a disruption in the way events are processed within the hippocampus and parahippocampal region of their brains. This discovery was made recently by neuroscientist Lucia Talamini of the University of Amsterdam (UvA) and a team of researchers from the UvA Academic Medical Center (AMC-UvA) and VU University Amsterdam. Their findings will be published shortly in PloS One.
In healthy individuals, the various components of any given event (such as people, objects, smells and places) are linked together and stored in areas deep within the temporal lobe of the brain: the hippocampus and parahippocampal region. These areas of the brain ensure that we store an event as an integral whole and derive meaning from the sum of its parts. For example, if we see a man lying in the street and someone else running off with a club, then we are more likely to suspect that the man has been clubbed to the ground than that he is taking a nap. Thus, we take the context into account whenever we interpret a situation.
Reduced use of contextual informationThe new study demonstrated that schizophrenia patients made less use of contextual information than healthy study subjects. These findings are important because they supply a new basis for developing methods to treat the mental disorders associated with schizophrenia.
This reduced use of contextual information in schizophrenia is probably caused by a small aberration in the structure of the hippocampal and parahippocampal regions. The researchers found that in schizophrenia patients brain cells in precisely this area make fewer connections than in healthy individuals, and that this can cause information about events to be stored in a fragmented way. The result is that while different components of an event do get stored, the links between them are weak. Accordingly, patients' thought processes are directed more by individual objects, people or concepts than by the relationships between various pieces of information.
New perspective on schizophrenia researchSchizophrenia is a disease with far-reaching consequences for patients, many of whom need lifelong psychiatric care. Treatment costs in the Netherlands come to more than half a billion euros annually, making schizophrenia the most expensive disease after depression.
However, this study is helping to shift the perspective on schizophrenia. Since the 1950s, our understanding of schizophrenia has emphasised neurochemical dysfunction. Specifically, it was blamed on elevated levels of dopamine - a signalling molecule - in the brains of patients. This so-called ‘dopamine hypothesis' was inspired mainly by the chance discovery of the first antipsychotic drugs, which proved to block the effects of dopamine. The study conducted at the UvA makes it plausible that, in fact, an aberrant structure in a certain part of the brain is responsible for the disruption in how people with schizophrenia process information. Such structural aberrations, which appear to form before birth, are gaining a steadily more prominent place in theories about the origins and symptoms of this disease.