Congenital facial palsy and emotion processing: The case of Moebius syndrome

Abstract

According to the Darwinian perspective, facial expressions of emotions evolved to quickly communicate emotional states and would serve adaptive functions that promote social interactions. Embodied cognition theories suggest that we understand others' emotions by reproducing the perceived expression in our own facial musculature (facial mimicry) and the mere observation of a facial expression can evoke the corresponding emotion in the perceivers. Consequently, the inability to form facial expressions would affect the experience of emotional understanding. In this review, we aimed at providing account on the link between the lack of emotion production and the mechanisms of emotion processing. We address this issue by taking into account Moebius syndrome, a rare neurological disorder that primarily affects the muscles controlling facial expressions. Individuals with Moebius syndrome are born with facial paralysis and inability to form facial expressions. This makes them the ideal population to study whether facial mimicry is necessary for emotion understanding. Here, we discuss behavioral ambiguous/mixed results on emotion recognition deficits in Moebius syndrome suggesting the need to investigate further aspects of emotional processing such as the physiological responses associated with the emotional experience during developmental age.

Deficits of visual working memory representations of emotional facial expressions in patients with congenital facial palsy

“…However, this interpretation seems unlikely given the absence of group differences in reaction times. Also another study employing a labeling task showed that Moebius children and controls show similar latency response (De Stefani et al 2019) thus supporting the idea that general visuocognitive impairments are not present in these patients. We cannot currently rule out this potential alternative explanation of our results.…”

“…Other studies, using labeling paradigms, have reported that Moebius children show deficits not only in autonomic responses to emotional stimuli but also in categorizing facial expressions (Nicolini et al 2019;De Stefani et al 2019), as predicted by sensorimotor simulation models. The conclusions of our and other studies seem to contrast with two previous studies in which either a deficit of recognition/discrimination of facial expressions of emotions was not observed in Moebius participants (Bogart and Matsumoto, 2010) or, using a single-VWM deficits in Moebius subjects -Gambarota et al…”

“…A correct diagnosis is challenging due to unclear criteria (Picciolini et al, 2016) and the prevalence is estimated to be 1 in 50.000 to 1 in 500.000 live births (Lindsay et al, 2010;Rasmussen et al, 2015;Picciolini et al, 2016;De Stefani et al, 2019). Within this complex syndromic framework, the main clinical aspect is the partial or total facial palsy caused by a congenital malformation of the VI (abducent) and VII (facial) cranial nerves (Kumar, 1990;De Stefani et al, 2019). Despite the inability to produce facial expressions, these patients seem to have a normal cognitive development (De Stefani et al, 2019).…”

“…Within this complex syndromic framework, the main clinical aspect is the partial or total facial palsy caused by a congenital malformation of the VI (abducent) and VII (facial) cranial nerves (Kumar, 1990;De Stefani et al, 2019). Despite the inability to produce facial expressions, these patients seem to have a normal cognitive development (De Stefani et al, 2019).…”

Blocking facial mimicry affects recognition of facial and body expressions

“…In line with this proposal, neuroimaging techniques have shown that (pre)motor and somatosensory regions representing the face are active during the perception of emotional face [32][33][34][35], and neural activity in these regions correlates with the degree of facial mimicry [36][37][38]. Moreover, damage to, or transcranial magnetic stimulation (TMS) interference with, the face representations in motor and somatosensory areas disrupts facial mimicry and impairs the recognition and interpretation of emotional expressions [39][40][41][42][43][44] (see also [45]). Furthermore, sensorimotor simulation would in turn affect theory of mind and emotion-related regions including the amygdala and the insula [31], especially for dynamic emotional stimuli [46,47].…”