Abstract
Huntington’s disease (HD) is a neurodegenerative movement disorder associated with deficits in the processing of emotional stimuli, including alterations in the self-reported subjective experience of emotion when presented with pictures of emotional scenes. The aim of this study was to determine whether individuals with HD, compared to unaffected controls, display abnormal visual scanning of emotionally evocative natural scenes. Using eye-tracking, we recorded eye-movements of 25 HD participants (advanced pre-symptomatic and early symptomatic) and 25 age-matched unaffected control participants during a picture viewing task. Participants viewed pictures of natural scenes associated with different emotions: anger, fear, disgust, happiness, or neutral, and evaluated those pictures on a valence rating scale. Individuals with HD displayed abnormal visual scanning patterns, but did not differ from controls with respect to their valence ratings. Specifically, compared to controls, HD participants spent less time fixating on the pictures and made longer scan paths. This finding highlights the importance of taking visual scanning behavior into account when investigating emotion processing in HD. The visual scanning patterns displayed by HD participants could reflect a heightened, but possibly unfocussed, search for information, and might be linked to attentional deficits or to altered subjective emotional experiences in HD. Another possibility is that HD participants may have found it more difficult than controls to evaluate the emotional valence of the scenes, and the heightened search for information was employed as a compensatory strategy.
Highlights
Huntington’s disease (HD) is an autosomal dominant neurodegenerative movement disorder
To answer the question of whether HD and control participants differ in the portion of viewing time spent fixating on the scene stimuli, and to test whether possible group differences would differ between the emotional conditions, we analyzed the total fixation ratio using 2 × 5 repeated-measures ANOVAs with the factors Group (HD vs. control) and Emotion
Fear pictures were rated as slightly less negative, possibly due to the choice of scenes, often involving dangerous animals that are likely to be seen as a part of Consistent with our hypothesis of abnormal fixation and saccade behavior during emotion processing in HD, we found that individuals with HD, compared to controls, spent a lower portion of picture viewing time fixating and made longer scan paths
Summary
Huntington’s disease (HD) is an autosomal dominant neurodegenerative movement disorder. Neural loss originates in the basal ganglia, and spreads progressively to a wide range of subcortical and cortical regions (Vonsattel et al, 1985, 2008; Aylward et al, 2004). HD is characterized by motor impairments, cognitive decline, and psychiatric symptoms (Craufurd et al, 2001; Paulsen and Conybeare, 2005; Van Duijn et al, 2007). The gene mutation that causes HD was identified in 1993, and a person’s genetic status can be determined before the diagnosis of HD (The Huntington’s Disease Collaborative Research Group, 1993). The symptoms of disease most typically do not manifest until middle adulthood (Folstein, 1989)
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