۱- Introduction

۲- Method

۳- Results

۴- Eye tracking

۵- EEG evoked potentials

۶- General discussion

۷- Future directions and challenges

۸- Conclusion

References

Abstract

While behavioural difficulties in facial emotion recognition (FER) have been observed in individuals with Autism Spectrum Disorder (ASD), behavioural studies alone are not suited to elucidate the specific nature of FER challenges in ASD. Eye tracking (ET) and electroencephalography (EEG) provide insights in to the attentional and neurological correlates of performance, and may therefore provide insight in to the mechanisms underpinning FER in ASD. Given that these processes develop over the course of the developmental trajectory, there is a need to synthesise findings in regard to the developmental stages to determine how the maturation of these systems may impact FER in ASD. We conducted a systematic review of fifty-four studies investigating ET or EEG meeting inclusion criteria. Findings indicate divergence of visual processing pathways in individuals with ASD. Altered function of the social brain in ASD impacts the processing of facial emotion across the developmental trajectory, resulting in observable differences in ET and EEG outcomes.

Introduction

A considerable degree of human communication occurs through nonverbal means, with actions, gestures and postures conveying signals to others about an individuals’ thoughts, feelings and intentions (Darwin, 1872; Meeran et al., 2005). Facially expressed emotions contribute significantly to this communication with movements presented on the face relaying information about internal emotional and mental states (Ekman and Friesen, 1978; Ekman and Oster, 1979). In typical development, the ability to recognise emotions begins in early infancy, developing and improving throughout adolescence and adulthood (Herba and Phillips, 2004; Somerville et al., 2011). Emotion recognition abilities typically begin with the six basic emotions (happy, sad, fear, anger, disgust, surprise) with discrimination of these emotions reported to be present in children aged five to seven months (Barrera and Maurer, 1981). By 10 years of age, children are postulated to perform at a level similar to adults when asked to match neutral, surprised, happy and disgusted expressions (Mondloch et al., 2003). Complex emotions (such as jealousy or guilt) are distinct from basic emotions in that they are typically more nuanced, rely more heavily on context, and usually involve greater theory of mind and belief-based decision making (Johnson and Oatley, 1989). Given the increased complexity of these emotions, their processing reaches maturity considerably later (Tonks et al., 2006), improving throughout adolescence and adulthood (Rodger et al., 2015; Thomas et al., 2007). Impairments in FER are consistently associated with Autism Spectrum Disorder (ASD); an early onset neurodevelopmental condition characterised by deficits in social communication and social interaction alongside stereotypic, repetitive, restricted behaviours and interests causing adaptive impairments (American Psychiatric Association, 2013). In previous research these behavioural difficulties have, in part, been attributed to challenges in recognising the emotions of others (Baron-Cohen et al., 1985; B & lte and Poustka, 2003; Harms et al., 2010; Kuuskikko et al., 2009; Lozier et al., 2014; Uljarevic and Hamilton, 2013). A meta-analysis concluded that these impairments are apparent across the developmental trajectory and the six basic emotions, and cannot be accounted for by the intellectual capabilities of the individual with ASD (Uljarevic and Hamilton, 2013). Recent research conducted with children suggests that ASD linked difficulties in FER appear cross-culturally, indicating a universal nature of FER challenges in the ASD population (Fridenson-Hayo et al., 2016).