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Abstract. The study presents self-report and psychophysiological data obtained in response to short film clips representing scenes related to different emotions. This was done in order to obtain evidence on the structure of positive and negative affective states following a combined dimensional/categorical approach to emotion and based on responses to stimuli that are more realistic than the static pictures usually employed in the study of emotion. Affective ratings and self-report measures showed a differential structure of the response to positive and negative films (Experiment 1). While all negative films were rated as low in valence and high in arousal, positive films were differentiated into arousing (happy and pleasure contents) and de-arousing (relax contents) categories. A more complex pattern emerged in Experiment 2, using two psychophysiological measures that are differentially sensitive to the main affective dimensions of valence and arousal, skin conductance response (SCR) and facial electromyography (fEMG). First, high arousal positive and negative films produced larger skin conductance responses. Second, fEMG measures showed differentiated response patterns within the positive and negative film categories. Within the positive category, happy and relaxing films had opposed effects, with happy films increasing and relax films decreasing activity over the zygomaticus muscle region. In the case of negative films, only those eliciting disgust produced a differentiated pattern of fEMG activity characterized by large corrugator responses and a modest increase of zygomatic responses. These results are discussed in relation to the adequacy of the dimensional and categorical approaches to emotion, the usefulness of combining subjective and psychophysiological measures, and the advantages of using realistic, dynamic stimuli for the study of emotion.

Over the course of evolution, the human brain has been shaped to prioritize cues that signal potential danger. Thereby, the brain does not only favor species-specific prepared stimulus sets such as snakes or spiders but can learn associations between new cues and aversive outcomes. One important mechanism to achieve this is associated with learning induced plasticity changes in sensory cortex that optimizes the representation of motivationally relevant sensory stimuli. Animal studies have shown that the modulation of gamma band oscillations predicts plasticity changes in sensory cortices by shifting neurons’ responses to fear relevant features as acquired by Pavlovian fear conditioning. Here, we report conditioned gamma band modulations in humans during fear conditioning of orthogonally oriented sine gratings representing fear relevant and irrelevant conditioned cues. Thereby, pairing of a sine grating with an aversive loud noise not only increased short latency (during the first 180 ms) evoked visual gamma band responses, but was also accompanied by strong gamma power reductions for the fear irrelevant control grating. The current findings will be discussed in the light of recent neurobiological models of plasticity changes in sensory cortices and classic learning models such as the Rescorla–Wagner framework.