Abstract
Huntington's disease (HD) is a genetic neurodegenerative disorder affecting the basal ganglia. These subcortical structures are particularly important for motor functions, response selection and implicit learning. In the current study, we have assessed prodromal and symptomatic HD participants with an implicit contextual learning task that is not based on motor learning, but on a purely visual implicit learning mechanism. We used an implicit contextual learning task in which subjects need to locate a target among several distractors. In half of the trials, the positions of the distractors and target stimuli were repeated. By memorizing this contextual information, attention can be guided faster to the target stimulus. Nine symptomatic HD participants, 16 prodromal HD participants and 22 control subjects were included. We found that the responses of the control subjects were faster for the repeated trials than for the new trials, indicating that their visual search was facilitated when repeated contextual information was present. In contrast, no difference in response times between the repeated and new trials was found for the symptomatic and prodromal HD participants. The results of the current study indicate that both prodromal and symptomatic HD participants are impaired on an implicit contextual learning task.
Highlights
Huntington’s disease (HD) is a neurodegenerative disease, caused by a CAG repeat expansion leading to an abnormal huntingtin protein
Separate one-way analysis of variance (ANOVA) were used to analyze the results of the different neuropsychological tests, comparing the symptomatic and prodromal HD group with the control subjects
In our study, such a contextual cueing effect was found for the healthy control subjects, but not for the symptomatic or prodromal HD participants
Summary
Huntington’s disease (HD) is a neurodegenerative disease, caused by a CAG repeat expansion leading to an abnormal huntingtin protein. The most characteristic symptoms of HD are motor deficits, including chorea, rigidity, and abnormal posturing. In addition to motor symptoms, cognitive and behavioral changes are generally found, such as memory and executive dysfunctions, depression, apathy and other psychiatric manifestations. Since HD is a disorder with a known genetic etiology, (Huntington’s Disease Collaborative Research Group, 1993), people that are at risk of having the disease can be identified before onset of the first symptoms, allowing for directed search of preclinical deficits. This has indicated that subtle cognitive impairments can be found in prodromal
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