Brain specimens were provided by the Stanley Foundation Brain Bank, which collects donated postmortem brains for research on mental illness, and the subjects were matched according to age, gender, brain weight and other variables.
Researchers from UT Southwestern, working with a team from Texas A&M University System Health Science Center, used special computer-imaging systems to meticulously count the number of nerve cells in the thalamus.
Results showed an increase of 37 percent and 26 percent, respectively, in the number of nerve cells in the mediodorsal and anteroventral/anteromedial areas of the thalamus in subjects with MDD when compared with similar cells in those with no psychiatric problems. The number of nerve cells in subjects with bipolar disorder and schizophrenia was normal.
Researchers also found that the size of the affected areas of the thalamus in subjects with MDD was 16 percent larger than those in the other groups.
"The thalamus is often referred to as the secretary of the cerebral cortex the part of the brain that controls all kinds of important functions such as seeing, talking, moving, thinking and memory," Dr. German said. "Most everything that goes into the cortex has to go through the thalamus first.
"The thalamus also contains cells that are not involved with emotion. Our studies found these portions of the thalamus to be perfectly normal. But the ones that are involved in emotion are the ones that were abnormal."
Researchers also looked at the effect of antidepressant medications on the number of nerve cells and found no significant difference among any of the subject groups whether they had taken antidepressants or not reinforcing the belief that abnormalities in brain development are responsible for depression.
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Contact: Donna Steph Hansard
donna.hansard@utsouthwestern.edu
214-648-3404
UT Southwestern Medical Center
1-Jul-2004