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.
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.
"The design of these experiments gave us an excellent chance to fill in a missing link in our earlier studies," said Dolcos. "It enabled us to determine whether there was, indeed, a behavioral connection between deactivation of the dorsal system and impaired performance.
"The experimental design mimicked the kind of distraction people experience in everyday life," Dolcos added. "For example someone driving on a highway, attempting to pay atte
Contact: Dennis Meredith
Duke University Medical Center