Affective Expectations Influence Neural Responses to Stressful Images in Soldiers

In the present study, we examined how expectations about the affective valence of an event influence immediate neurocognitive responses to the event. Both neutral images and negative images displaying war photos were shown to active duty military personnel undergoing predeployment training. Expectations regarding the affective content of upcoming images were manipulated by means of abstract visual cues that were valid only 75% of the time. Besides providing greater ecological validity, inclusion of invalid cues enabled us to examine separately, effects of the expected and actual valence of the images. Neurocognitive responses within the first second after image presentation were examined using the late positive potential (LPP), a noninvasive measure of brain electrical activity known to index affective processes. Negative images evoked an enhanced LPP relative to neutral images over central-parietal and right anterior electrode sites. Both the central-parietal and anterior LPP were found, likewise, to be modulated by expected valence. Expectation of negative versus neutral images led to an enhanced central-parietal LPP and an attenuated anterior LPP over both hemispheres independent of image valence. These findings are interpreted in terms of the allocation of attention to motivationally salient events, affective interpretation of those events, and induced affective/motivational states. By helping to characterize affective responses to acute stress and the regulation of those responses by psychological context, our study contributes to a basic understanding of how such regulation may become disordered and may aid in the development of targets for therapeutic interventions.