Depression coincides with a smaller hippocampus, a brain center crucial for memory and learning, says Washington University psychiatry professor Yvette Sheline. Sheline and colleagues scanned the brains of 48 women with a history of clinical depression. They found that the size of the hippocampus was inversely related to the number of bouts of depression. Other scientists have found a correlation between depression and decreased activity in brain areas associated with excitability, reaction time, reward and memory.
Lack of Excitability
The brains of people with depression respond less to muscle movement, reports University of Edinburgh medical researcher Klaus Ebmeier, M.D. Ebmeier and colleagues used transcranial magnetic stimulation applied over areas of the brain that control motion to induce targeted muscle movement. They found that the artificially excited muscles twitched less in depressed people than in people who had never been depressed or had recovered from depression. The study indicates that depression can have damping effects on areas of the brain that control movement, says Ebmeier.
Slower Reaction Times
Ebmeier's research team also measured study participants' reaction times and motor speed by exposing them to computer-generated tasks and keyboard tapping tests. They found that depressed people had longer reaction times and tapped slower on the keyboard than healthy individuals. People who had recovered from depression did significantly better than individuals with depression but still not quite as good as people who had never been depressed, reports Ebmeier.
Lack of Reward
Depression correlates with less activity in the brain's reward center, reported a research team in the August 2009 issue of "NeuroReport." The scientists asked five healthy and 16 recently depressed subjects to provide a list of music they really liked and a list of music they neither liked nor disliked. The subjects then listened to the music while the researchers scanned their brains. Even though the participants rated music they liked equally high, the recently depressed individuals demonstrated significantly less activity in areas of the brain associated with reward processing.
Brain Plaques
A history of clinical depression is significantly correlated with increased plaques and tangles in the brains of Alzheimer's patients, says Mount Sinai School of Medicine researcher Michael Rapp, M.D. Rapp and colleagues looked at the brains of 44 Alzheimer's patients with a history of depression and 51 without a history. They found that the hippocampi of patients with a history of depression had a greater build-up of the protein plaques that cause Alzheimer's. The detrimental effects were even worse in patients who suffered from depression at the time they were diagnosed with Alzheimer's, report the scientists.
New Brain Cells with Anti-Depressants
Common anti-depressant treatments can reverse the detrimental effects of depression on the brain, says Rockefeller neuroscientist Jennifer Warner-Schmidt. Warner-Schmidt and Ronald Duman of Yale University found that the anti-depressant medications Prozac and Norpramin as well as electroconvulsive shock increased the production of vascular endothelial growth factor, or VEGF, in the hippocampus of rodents. The scientists found that the increased VEGF levels led to the birth of new neurons. Conversely, blocking expression of this growth factor led to an atrophy of cells in the hippocampus.
References
- Science Daily: Depression May Shrink Key Brain Structure
- Science Daily: Brain Less Responsive During Depression, But Can Recover
- Science Daily: Clinical Depression Causes Early Malfunctions In The Brain’s Pleasure Center, Study Shows
- Science Daily: History Of Depression Linked To More Brain Plaques And Tangles
- Science Daily: How Anti-Depressants Create New Brain Cells
