Brain Activation and Defensive Response Mobilization During Sustained Exposure to Phobia-related and Other Affective Pictures in Spider Phobia

Wendt, J., Lotze, M., Weike, A. I., Hosten, N., & Hamm, A. O. (2008).  Brain activation and defensive response mobilization during sustained exposure to phobia-related and other affective pictures in spider phobia.  Psychophysiology, 45(2), 205-215.  Retrieved from EBSCOhost.  doi:10.1111/j.1469-8986.2007.00620.x

In Chapter 16 of our textbook, there is a section on anxiety disorders.  The textbook notes that some of the most common psychiatric conditions are due to anxiety disorders.  There are many types of anxiety disorders, but the one that I chose my article on was about specific phobias.  When an individual has a specific phobia, he or she experiences fear or arousal when exposed to certain things in specific situations (i.e. animals, blood, heights).  The amygdala is the brain region that is known to be involved in fear learning and activation of fear and phobia.  According to this study, individuals with specific phobias have overreactive defense systems.  They also have “phobia-specific startle potentiation” of the startle reflex when they view images of the objects that they fear.  In this study, the researchers aimed to discover three things: if a sustained exposure to phobia-relevant stimuli would provoke a continuous defensive response mobilization in those individuals with specific phobias, if there would be an increase in the activation of the amygdala when shown a phobia-relevant stimuli rather than a neutral stimuli, and if there would be an increase in the activation of the insula during the processing of phobia-relevant stimuli.  Thirty-two women participated in this study.  They were asked to complete the German version of the Spider Phobia Questionnaire (SPQ).  After the participants took the questionnaire, researchers discovered that 16 participants had a spider phobia (experimental group) and 16 participants did not have a spider phobia (control group).  The participants viewed 150 different pictures from the International Affective Picture System.  These pictures were from five different categories, which included spiders (phobia relevant), mushrooms (neutral), pleasant contents (i.e. babies), unpleasant contents (i.e. animal attack), and complex neutral pictures (i.e. buildings).  There was a time lapse of three seconds between each picture that was shown.  The participants were measured while viewing the images on the eyeblink component of the startle response (electromyographic or EMG activity) and on their brain activation using fMRI technology.  The researchers found that the participants in the spider phobia group had increased activation of the amygdala when viewing the spider pictures as well as larger eyeblink magnitudes.  These results, however, are not necessarily fear specific because other pleasant pictures caused the same activation level in the amygdala as did the spider images.  Another finding was that the activation of the insula was increased during sustained phobic exposure.  The results of this study suggest that the activation of the amygdala is due to “motivationally relevant” stimuli with the activation of the insula associated with an actual or anticipated defensive response mobilization.  This study enables other psychologists and scientists to understand that there are other brain regions besides the amygdala that are responsible for fear and specific phobias.