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Facing emotions. Towards a better understanding of automatic facial expression processing mechanisms in typical and atypical populations.

Boek - Dissertatie

As social beings, we often linger in a social environment in which we interact with others. However, these social interactions are not automatically successful and they require social sensitivity and social cognition. One of the key components of social cognition is facial emotion processing. Facial emotion processing expands beyond merely attending to and perceiving facial expression information; it also involves assessing the nature and the importance of the emotional cues to accurately interpret the information and to respond appropriately. In the current doctoral project, we applied different implicit and explicit techniques to enhance our understanding of the underlying mechanisms of automatic facial expression processing and to explore whether these mechanisms are universal.In a more fundamental study, we investigated the role of specific spatial frequencies in conveying facial fear. More specifically, we examined which spatial frequency information is minimally required to rapidly and automatically detect fearful faces. Although this has been investigated in many previous studies before, a straightforward conclusion on the relative contribution of low versus high spatial frequencies to facial fear is hampered by, for example, the high variability in demarcations of the spatial frequency spectrum and the high variability in task demands. To move the field forward, we investigated automatic and implicit facial fear processing by systematically sweeping through an entire spatial frequency range using fast periodic visual stimulation (FPVS) in combination with frequency-tagging electroencephalography (EEG). Progressively varying the spatial frequency content of the faces allowed us to pinpoint the threshold of optimal spatial frequency information for the rapid detection of fearful faces, without constraints of predefined cut-offs for low or high spatial frequencies.In a series of applied studies, we investigated the implicit and explicit facial expression processing of school-aged boys with and without autism spectrum disorder (ASD). Individuals with ASD are characterized by difficulties in social communication and interaction, which are thought to be strongly related to difficulties in emotional face processing. The plethora of behavioural studies on facial expression processing in individuals with and without ASD yields mixed and inconsistent results. These highly variable findings may result from the large variability and limited sensitivity of (certain) behavioural measures. Moreover, the interpretation of explicit emotion processing results can be impeded due to mechanisms beyond facial expression processing per se, such as compensatory mechanisms. Therefore, we focussed on a series of implicit measures to gain more insight in the underlying automatic emotion processing mechanisms that might account for difficulties in facial expression processing in ASD. First, we applied FPVS combined with frequency-tagging EEG to investigate possible neural differences in facial emotion discrimination between boys with and without ASD, and whether the neural sensitivity for expressive faces is influenced by the orientation of the faces and by attentional focus to the eyes versus mouth. Difficulties in emotion processing may also occur when one fails to inspect the most relevant facial cues. In addition, also spontaneous facial mimicry is found to be related to emotion processing. Spontaneous facial mimicry refers to the automatic movements of face muscles as an implicit response to observed facial emotions. This natural tendency often lacks in individuals with ASD, possibly contributing to emotion processing deficits. Therefore, we simultaneously recorded eye gaze patterns and spontaneous facial mimicry of boys with and without ASD during an explicit expression recognition task.In a clinical intervention study, we investigated the modulatory effects of a single dose of oxytocin on the behavioural and neural sensitivity for facial expression processing in healthy adults. Oxytocin is a neuropeptide that functions as a hormone and neurotransmitter, and has been identified as a key player in social cognition. To date, therapeutic interventions for ASD are mainly based on behavioural social skills trainings, since biomedical therapies or pharmacological interventions targeting social dysfunctions are largely unproven. However, in recent years, intranasal administration of oxytocin has been found to induce behavioural improvements in the social domain in individuals with ASD. To explore its effects on the neural level, we designed a double-blind, within-subjects, cross-over, placebo-controlled oxytocin clinical trial in healthy adult men.