For the first time, researchers have seen in action how the "hot" emotional centers of the brain can interfere with "cool" cognitive processes such as those involved in memory tasks. Their functional magnetic resonance imaging (fMRI) images of human volunteers exposed to emotional distraction revealed a "see-saw" effect, in which activation of emotional centers damped activity in the "executive" centers responsible for such processing.
The findings of the Duke University Medical Center researchers provide insight into the basic brain mechanisms responsible for the distraction caused by emotional stimuli that are irrelevant to a task. Moreover, they said, the findings offer a new approach to understanding how people with depression and post-traumatic stress disorder cope with traumatic events and memories. It is known that people with such problems are far more affected by emotional distraction.
The researchers compared the effects of three different kinds of distracters on the ability to memorize faces.
In their experiments, the researchers asked volunteer subjects to memorize sets of images of three human faces. Next, they exposed the subjects to one of three types of distracters -- emotional images such as injured people or aggressive behavior; neutral images such as people shopping or working; and scrambled images that meant nothing. The subjects were then showed a face image and asked to determine whether it was one of the original "to-be-memorized" faces or a new face.
Throughout the tests, the subjects' brains were scanned using fMRI. This widely used technique involves using harmless magnetic fields and radio waves to scan the brain to detect levels of blood flow, which indicates increased or decreased brain activity.
Stimuli that evoke an emotional reaction not only activate the ventral system of the brain but also reduce activity in the dorsal regions involved in rational thinking.
In earlier studies, the researchers had found that emotional images activated a "ventral affective system" in the brain that encompasses regions involved in emotional processing. In contrast, they found, cognitive tasks involving memory processes activated a "dorsal executive system." To their surprise, the researchers also found that the emotional distracters not only activated the ventral system, but also deactivated the dorsal regions.
In the new study, the researchers observed the same patterns of activation and deactivation of the regions. The emotional images produced greater activation of the ventral system and deactivation of the dorsal system than did the neutral or scrambled images, they found.
But most importantly, they found graded behavioral effects of the images. The emotional distracters produced the most detrimental effect on memory performance, the neutral distracters impaired performance to a lesser extent; and the scrambled images impaired performance very little. "Along with the fMRI results, these findings provide the first direct evidence concerning the neural mechanisms mediating cognitive interference by emotional distraction," said Dolcos.
Emotional distracter: That sounds like a technical term for "girlfriend".
People who could inhibit their emotional response were less distracted.
The researchers also found individual differences among the subjects in their response to the images. Those people who showed greater activity in a brain region associated with the inhibition of response to emotional stimuli rated the emotional distracters as less distracting. Said Dolcos, "One interpretation of this finding is that, because this region is associated with inhibitory process, people who engage that region more could cope better with distracting emotions."
I bet that genetic variations are partially responsible for people differing in their abilities to inhibit their emotional responses. For some inhibition of their emotions comes easy and surely the ability exists on a sliding scale. Also, there's probably not a single ability to inhibit all emotions. Some probably can more easily inhibit sadness and others anger and so on. If you have a particular form of emotion you have a hard time inhibiting then when you need to think clearly you are best off avoiding situations that will present stimuli that'll trigger that emotion.
This report of how emotional stimuli shut down areas of the brain involved in rational thought reminds me of another recent post of mine: "Political Partisans Addicted To Irrational Defense Of Their Tribes". This latest report throws more light on that previous report. People who are emotionally worked up about politics have a hobbled ability to think rationally.
|Share |||Randall Parker, 2006 February 15 10:47 PM Brain Emotions|