Daily life requires that people cope with distracting emotions--from the basketball player who must make a crucial shot amidst a screaming crowd, to a salesman under pressure delivering an important pitch to a client.
Researchers have now discovered that the brain is able to prevent emotions from interfering with mental functioning by having a specific "executive processing" area of the cortex inhibit activity of the emotion-processing region.
The findings also offer insight into how sufferers of post-traumatic stress disorder (PTSD) or depression are unable to control emotional intrusion into their thoughts, said the researchers, Amit Etkin, Joy Hirsch, and colleagues, who reported the discovery. They published their findings in the September 21, 2006, issue of the journal Neuron, published by Cell Press.
Their studies were based on previous findings that specific parts of an area of the brain called the anterior cingulate cortex (ACC)--a center for so-called "executive" control of neural processing--are connected to the amygdala. The amygdala is the brain's major center for processing emotional events.
The experimental challenge for Etkin, Hirsch, and colleagues was to determine whether this region of the ACC was responsible merely for "monitoring" conflict between cognitive and emotional processing or for actively "resolving" that conflict.
To distinguish the two processes, Etkin and colleagues designed experiments in which volunteer subjects were asked to indicate by pressing a button whether a face image was happy or fearful. The subjects were instructed to ignore labels of "fear" or "happy" written across each face.
These labels might be either "congruent" (e.g., happy face, "happy" word) or "incongruent" (e.g., happy face, "fear" word) with the image. Incongruent face-word combinations constituted a response conflict between emotional and cognitive stimuli. The researchers found that subjects could "resolve" this conflict more readily if an incongruent image was preceded by another incongruent image. This resolution represented an anticipation by the subjects' brains from the first image that they could resolve the conflict depicted in the second image
As the researchers scanned the subjects' brains with functional magnetic resonance imaging (fMRI), they presented the subjects with a series of such images designed to reveal what parts of the brain were active during such conflict resolution. The technique of fMRI involves using harmless magnetic fields and radio waves to measure blood flow in brain regions, which reflects brain activity.