Recognition of emotion from subtle and non-stereotypical dynamic facial expressions in Huntington's disease.

Emotion recognition deficits in Huntington's disease (HD) are well-established. However, most previous studies have measured emotion recognition using stereotypical and intense facial expressions, which are easily recognized and artificial in their appearance. By contrast, everyday expressions are often more challenging to recognize, as they are subtle and non-stereotypical. Therefore, previous studies may have inflated the performance of HD patients and it is difficult to generalize their results to facial expressions encountered in everyday social interactions. In the present study, we tested 21 symptomatic HD patients and 28 healthy controls with a traditional facial expression set, as well as a novel stimulus set which exhibits subtle and non-stereotypical facial expressions. While HD patients demonstrated poor emotion recognition in both sets, when tested with the novel, ecologically looking facial expressions, patients' performance declined to chance level. Intriguingly, patients' emotion recognition deficit was predicted only by the severity of their motor symptoms, not by their cognitive status. This suggests a possible mechanism for emotion recognition impairments in HD, in line with embodiment theories. From this point of view, poor motor control may affect patients' ability to subtly produce and simulate a perceived facial expression, which in turn may contribute to their impaired recognition.