All participants underwent comprehensive baseline evaluations including blood draw, neurological/motor examination, cognitive assessment, psychiatric and psychological questionnaires, and brain MRI. Table 1 Characteristics of study participants Table 1 shows that age, years of education, and gender were well balanced between the control and the prHD groups. As expected, the prHD group exhibited more symptoms on the UHDRS motor scale than the control group. In the prHD group, the ranges for age (20.1–74.9 years) and CAG-repeat length (38–50) indicate a wide variation in baseline progression levels Inhibitors,research,lifescience,medical (Zhang et al. 2011). Cognitive tests PREDICT-HD participants completed

a battery of neuropsychological tests and computerized cognitive tasks once a year. From this battery five tests were selected that represent different cognitive domains including attention and information speed, verbal working memory, verbal learning and memory, negative emotion processing, Inhibitors,research,lifescience,medical and temporal processing. These domains of cognitive functioning are known to decline in prHD (Rowe et al. 2010; Stout et al. 2011; Harrington et al. 2012). Attention and processing speed was measured by the SDMT

(total correct in 90 sec) (Smith 1982). Verbal working memory was measured by the Wechsler Adult Intelligence Scale-III Inhibitors,research,lifescience,medical Letter-Number Sequencing (total correct) (Wechsler 1997). Verbal learning and memory was measured by the Hopkins Verbal Learning Test-Revised (HVLT-R) (immediate recall, total number correct) (Brandt and Inhibitors,research,lifescience,medical GDC-0449 molecular weight Benedict 2001). Negative Emotion processing was measured using a computerized emotion recognition task where the participant viewed photographs of faces expressing one of six emotions (fear, disgust, happiness, sadness, surprise, anger) or a neural expression, and then matched the facial expression with a verbal description

(Johnson et al. 2007). The number correct for the negative emotions was the dependent measure as it best discriminates prHD from control participants (Stout et al. 2011). Temporal Inhibitors,research,lifescience,medical processing was assessed Rolziracetam by the paced timing task (Rowe et al. 2010), wherein the participant starts out by tapping in synchrony with a 550 msec isochronous tone and then continues tapping without the tone at the same pace (continuation phase). The measure of timing precision is the reciprocal of the within-subject intertap interval standard deviation during the continuation phase. This study reports cross-sectional data from a sample of participants whose cognitive testing coincided with their first PREDICT-HD brain MRI, which was conducted at either the first visit or the third visit. Due to the potential effects of practice on task performance for individuals at their third visit, we tested for the effects of the number of visits and group (control vs.