We investigated how viewing task-irrelevant emotional pictures affects the performance of a subsequent non-emotional visual detection task. Subjects performed target-detection trials following the offset of individual unpleasant, pleasant and neutral pictures. Sustained interference occurred when subjects viewed blocked unpleasant pictures (mutilated bodies). Such slowing down of reaction time appeared to "build up" with time, consistent with the instatement of a defensive emotional state. With a randomized picture presentation, only a transient interference effect was observed, consistent with increased attentional demands during the processing of unpleasant pictures. During blocked presentation of affiliative pleasant pictures, reaction times were faster, suggesting the activation of appetitive motivational systems. Ultimately, both attentional and motivational systems are intricately tied in the brain and, together, determine behavior.The processing of emotional stimuli can have both advantageous and detrimental effects on behavioral performance in general, and response time (RT) in particular. For instance, subjects were faster at detecting fearful or threatening target faces relative to neutral ones

Tonic immobility, characterized by profound motor inhibition, is elicited under inescapable threat in many species. To fully support the existence of tonic immobility in humans, our aim was to elicit this reaction in a laboratory setting and measure it objectively. To mimic exposure to life-threatening events in the lab, trauma-exposed participants with PTSD (n=18) and without PTSD (n=15) listened to the script of their autobiographical trauma. Posturography and electrocardiography were employed. Reports of script-induced immobility were associated with restricted area of body sway and were correlated with accelerated heart rate and diminished heart rate variability, implying that tonic immobility is preserved in humans as an involuntary defensive strategy. Immobility reports seemed more evident in PTSD, suggesting that, in some patients, tonic immobility may be elicited during re-experiencing episodes in daily life. This study provided a measure of tonic immobility, a peritraumatic reaction for which cumulative clinical evidence had linked to the severity of PTSD.

Previous studies showed that heart period decreases during and recovers after an acute stress. We investigated if individual predispositions and emotional priming influence heart period recovery after a speech stress task. Psychometric scales and resting cardiac vagal tone were used to measure individual traits. The presentation of a sequence of either pleasant or unpleasant pictures, as emotional primers, preceded the speech stress. Heart period was measured throughout the experiment. Stress induced tachycardia irrespective of emotional priming or traits. In the recovery period, participants with higher resting cardiac vagal tone or presenting higher resilience significantly reduced the heart acceleration. Furthermore, these traits interacted synergistically in the promotion of the recovery of heart period. Pleasant priming also improved recovery for participants with lower negative affect. In conclusion, the stress recovery measured through heart period seemed dependent upon individual predispositions and emotional priming. These findings further strengthen previous observations on the association between greater cardiac vagal tone and the ability to regulate emotion.

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