Depressed patients have a well-known tendency to process and remember negative emotional information. The researchers propose that this bias stems from dysregulated acetylcholine systems in some patients. They reasoned that such patients would show aberrant visual cortex activity in response to negative emotional features of a working memory task. They also expected to find that patients with more dysfunctional acetylcholine systems would respond better to scopolamine treatment.
Before receiving scopolamine, participants performed a working memory task while their brain activity was monitored via fMRI. For some trials, it required that they pay attention to, and remember, the emotional expression (sad, happy, etc.) of faces flashing on a computer monitor. For other trials, they had to pay attention to only the identity, or non-emotional feature, of the faces. After scanning, and over the following several weeks, 15 patients with depression and 21 healthy participants randomly received infusions of a placebo (salt solution) and/or scopolamine. Mood changes were monitored with depression rating scales.
Overall, scopolamine treatment reduced depression symptoms by 63 percent, with 11 of the patients showing a significant clinical response. The strength of this response correlated significantly with visual cortex activity during key phases of the working memory task while participants were paying attention to the emotional content of the faces. There was no such correlation for trials when they attended to the identity of the faces.
The findings suggest that acetylcholine system activity drives visual cortex activity that predicts treatment response and that differences seen between depressed patients and controls may be traceable to acetylcholine dysfunction. Overall, patients showed lower visual cortex activity than controls during the emotion phase of the task. P
|Contact: Jules Asher|
NIH/National Institute of Mental Health