Attentional emotional bias in Huntington's disease: The "Hyper-Positive" effect

In addition to motor symptoms, Huntington's disease (HD) is associated with cognitive deficits, including the ability to recognize emotions (fear, disgust, and anger) from faces and voices, while happiness and neutral expressions are relatively preserved. Yet the underlying mechanisms remain unclear. We investigated both explicit emotion recognition and implicit attentional biases in manifest HD patients to assess whether altered attentional orienting may explain the selective deficit in negative emotions. To our knowledge, this represents the first study of its kind in HD. Twenty patients with manifest HD and 25 controls completed an explicit facial emotion recognition task (neutral, disgust, fear, and happiness) and two dot-probe tasks (100 ms and 500 ms SOAs) to dissociate automatic and controlled attentional processes. Attentional Facilitation Index (AFI) and Disengagement Index (DI) were calculated. Huntington's disease patients showed reduced accuracy and slower reaction times in recognizing negative emotions (fear and disgust). At the 100-ms SOA in the dot-probe task, they exhibited reduced attentional facilitation for fearful faces and greater facilitation for happy faces compared with controls, with a similar pattern observed for attentional disengagement. No significant differences emerged at 500 ms SOA. These findings reveal a "hyperpositivity effect" in HD: an early automatic prioritization of positive stimuli alongside reduced attentional capture by negative ones. This pattern, which parallels the positivity bias in normal aging, may contribute to the selective impairment in negative emotion recognition. A plausible underlying mechanism involves striatal dopaminergic dysregulation. Longitudinal studies in premanifest gene carriers are needed to clarify this bias's development.