TUESDAY, May 6 (HealthDay News) -- Recently developed types of imaging techniques enable researchers to map brain circuits and chemical systems believed to play a role in depression, bipolar disorder and other mood disorders, and may help lead to improved treatments.

Information about these techniques was expected to be presented Tuesday during a news conference by researchers taking part in U.S. National Institute of Mental Health symposiums at the American Psychiatric Association annual meeting, in Washington, D.C.

"These studies contribute new information about how the brain malfunctions in depression and bipolar disorder, what goes wrong with brain chemicals, and where in the brain the problems arise," Dr. Ellen Leibenluft, of the NIMH, said in a prepared statement. "We find that the brain systems involved and the exact nature of the difficulties differs among patients, even when those patients have similar symptoms. Eventually, data like these will allow us to develop more individualized and targeted treatments for depression."

In one study, University of Michigan researchers using molecular imaging with positron emission tomography (PET) found that patients with untreated major depression had an overall reduction in the concentration of serotonin 1A receptors in the hippocampus, a brain region that helps regulate stress.

"The reductions in these receptors were correlated with the functional impairment of the patients in work and with their families, with greater impairment being associated with lower receptor concentrations in this region," study author Dr. Jon-Kar Zubieta said in a prepared statement.

The patients responded to treatment with citalopram.

In another study, Zubieta and colleagues found that people with untreated major depression had reduced concentrations of "mu" opioid receptors in the thalamus, an area of the brain involved in the regulation of emotions. The mu receptors play a key role in regulating mood and triggering brain reward systems. A reduction in the receptors was associated with greater concentrations of stress hormones.

The researchers also found that depressed patients who didn't respond to the antidepressant fluoxetine (Prozac) had lower concentrations of mu receptors in the anterior cingulate, an area of the brain involved in the processing of emotional states.

In other studies, NIMH researchers used PET and functional MRI to identify abnormal patterns of neural activity and chemical function in the brain's reward pathway that underlie depressed patients' inability to experience pleasure.

"The identification of brain systems and circuits whose activity can be correlated with specific symptoms is a first step toward the development of more targeted and effective treatments for depression and other disorders of the brain," Dr. Wayne Drevets, of the NIMH, said in a prepared statement.

In another study, Yale School of Medicine researchers using specialized applications of MRI found that people with bipolar disorder have reduced volume of the brain's prefrontal cortex and its subcortical connections sites, including the amygdala.

Previous research found that patients with bipolar disorder have abnormal functioning of these brain structures, especially during the processing of emotional stimuli and during tasks that require inhibition of impulsive responses.

In other studies, scientists found that fMRI can help determine whether children have biploar disorder or severe irritability with attention-deficit hyperactivity disorder (ADHD). This suggests that brain imaging may prove useful in making a correct diagnosis.

"We're finding that these very irritable children with ADHD share some characteristics with children with bipolar disorder but also have significant differences," said Leibenluft.

Children with these conditions are easily frustrated, have difficulty reading facial emotional cues, and have social cognition deficits.

"Yet what's happening in the brain during frustration differed between the two groups. So these data indicate that, even when two groups of patients exhibit the same symptoms, the brain mechanisms underlying that symptom can differ. Data like these indicate how, eventually, psychiatric diagnosis will be based on brain mechanisms, in addition to symptoms," Leibenluft said.

More information

The U.S. Center for Mental Health Services has more about mood disorders.

-- Robert Preidt

SOURCE: U.S. National Institute of Mental Health, news release, May 6, 2008

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