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In this PET study we compared cerebral blood flow in people with
schizophrenia and healthy volunteers when they looked at pictures that evoke unpleasant emotions. The people with schizophrenia
were unable to activate the "emotion circuits" in their brains. These areas of decreased flow are shown in blue. Note that
the regions are distributed throughout the brain, reflecting a "misconnection syndrome" that involves multiple brain regions.
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Schizophrenia
is one of the most important public health problems in the modern world. It affects 1% of the population worldwide. According
to the World Health Organization, it ranks 9th among all medical illnesses in terms of the global burden of disease--above
cancer, AIDS, heart disease, diabetes, and other important illnesses. Perhaps the most striking thing about schizophrenia
is its sweepingly broad injury to a large array of cognitive and emotional systems in the human brain. The signs and symptoms
of schizophrenia are diverse; they include disorders of perception (i.e., hallucinations), inferential thinking (delusions),
goal directed behavior (avolition), and emotional expression (affective blunting), to mention only a few. No single one of
its many signs and symptoms can be considered to be pathognomonic or defining. Each is present in some patients, but none
is present in all. In this respect, schizophrenia differs from most other mental illnesses, which typically affect a single
mind/brain system, such as Alzheimer's disease (memory) or manic-depressive illness (mood).
Because the signs
and symptoms of schizophrenia are so complex and diverse, an effort has been made to simplify thinking about the illness by
subdividing them into natural categories. The modern reconceptualization developed by Dr. Andreasen divides symptoms into
“positive” and “negative” and defines positive symptoms as an exaggeration of normal functions (the presence of something
that should be absent), and negative symptoms as a loss of normal functions (the absence of something that should be present).
Positive symptoms include delusions, hallucinations, disorganized speech, and disorganized behavior. Negative symptoms include
alogia, avolition, anhedonia, and affective blunting.
Schizophrenia is caused by a mixture of genetic influences and
non-genetic influences such as birth injuries, exposure to toxins and drugs of abuse, hormonal changes, and other factors.
These influence the development of the brain during the prolonged period of brain maturation that occurs in human beings
and that is not completed until the early twenties. it damages the way regions are connected to one another, so that a breakdown
in signal transfer occurs, and the messages sent back and forth between various brain regions are garbled or confused. In
the language of neuroscience, schizophrenia is a disease that affects distributed neural circuits rather than single cells
or single regions. Such disorders are sometimes referred to as “misconnection syndromes.” Most people with schizophrenia
have a subjective sense that their ability to think and feel has somehow become disorganized, disconnected, or misconnected.
The tools of neuroimaging have allowed us to study how the brains of people with schizophrenia function differently from
healthy individuals when they are performing similar mental tasks. These studies have shown us that the subjective experience
of “misconnection” or “disorganization” reflects an underlying problem in the ability of distributed brain regions to send
messages back and forth efficiently and accurately. The name of the illness is therefore appropriate. It literally means
"fragmented" or "misconnected" (schizo) "mind" (phenia).
Dr. Andreasen is currently conducting many studies that are
contributing to our knowledge of schizophrenia. These include structural and functional neuroimaging studies, studies of
longitudinal course and outcome, and studies that examine genetic and genomic factors and integrate them with neuroimaging
studies.
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