Link between brain chemical, cognitive decline in schizophrenia demonstrated

Washington, Mar 11 : UC Davis researchers have demonstrated a link between brain chemical, cognitive decline in schizophrenia.

In one of the first such studies involving human patients with schizophrenia, researchers provided evidence that deficits in a brain chemical may be responsible for some of the debilitating cognitive deficits — poor attention, memory and problem-solving abilities — that accompany the delusions and hallucinations that are the hallmarks of the disorder.

Published in the Journal of Neuroscience, the study suggests an important avenue of inquiry for improving cognitive function in people who suffer from schizophrenia, according to Jong H. Yoon, an assistant professor of psychiatry and behavioral sciences at UC Davis Health System and the study''s lead author.

"We still know very little about the neurobiology of schizophrenia, particularly at the level of specific circuits and molecules and how their impairments affect behavior and cognition in the disease," said Yoon, a researcher at the UC Davis Imaging Research Center. "We need this level of specificity to guide targeted treatment development. This is one of the first studies to show that there is a strong association between cognitive deficits and a decrease in a particular neurotransmitter."

Schizophrenia is characterized by psychosis — abnormalities in the perception or expression of reality. Sufferers may experience visual or auditory hallucinations and have paranoia, delusions and disorganized speech and thinking. But they also experience profound cognitive difficulties that interfere with daily functioning.

Psychosis is treated with a variety of antipsychotic medications that dampen overactivity of the neurotransmitter dopamine, an acknowledged cause of psychotic behavior.

But no medications are available to address cognitive deficits in schizophrenia because the source of the deficits has not been determined. Deficits in one brain chemical, the neurotransmitter gamma-aminobutyric acid, or GABA, have been implicated as playing a causal role in cognitive difficulties in people with schizophrenia in research involving animal models and post-mortem analyses of GABA concentrations in human schizophrenic brains.

"People think of schizophrenia as being related to psychosis. But patients'' cognitive limitations can be even more debilitating for them," said Cameron Carter, professor of psychiatry and behavioral sciences, director of the Imaging Research Center and the study''s senior author. "This study actually looked at brain chemistry in live patients in relation to cognitive performance to determine the underlying neurobiology of the cognitive deficits. Our ultimate goal is discovering ways to help patients lead more productive lives."