Time course of the subjective emotional response to aversive pictures: relevance to fMRI studies.

Using functional magnetic resonance imaging (fMRI) to study brain activity related to the experience of emotion presents unique challenges to neuroscientists. One important consideration arises when an experimentally induced subjective emotional response persists after the end of the emotional stimulation epoch. In this case, brain activity related to the emotional response may continue during the subsequent control or comparison epoch. The comparison epoch of the experiment may then contain a lingering emotional response. This study was conducted to better understand the time course of the subjective emotional response to intensely aversive pictures, with the goal of applying this knowledge to the design and analysis of fMRI studies of emotion. A total of 18 women in two separate experiments were shown a series of aversive, neutral and scrambled pictures presented in alternating block designs. Subjects rated the intensity of their negative feelings every 4 s while viewing the pictures. Results indicate that the subjective emotional response persists well after the end of the emotional stimulation epoch. Following a 16-s block of aversive pictures, an average of an additional 16 s elapsed before self-reported negative feelings showed a 74-80% decline. These data suggest that fMRI studies of emotion should consider the time course of the subjective response to emotionally laden stimuli.