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Eye movements and electrodermal responsivity as possible genetic markers of Huntington’s chorea Lacoste, Diane


This study examined two possible genetic markers of Huntington's chorea: eye movements and electrodermal responsivity. Seven subjects in the early stages of Huntington's disease were compared to twenty-nine subjects in each of two other groups, a group of subjects at-risk for Huntington's chorea and a group of controls. Subjects completed a series of smooth pursuit and saccadic eye tracking tasks as well as listened to soft tones, loud tones, and sounds while electrodermal activity was recorded. Visual inspection of the eye movement data revealed that the Huntington's chorea group performed the poorest, across all the eye tracking tasks. Data analyses showed that the at-risk subjects, when compared with control subjects, tracked with a greater lag when the target moved at the greatest speed. There were no differences between the two groups on similar eye tracking tasks at the target's slower speeds. The at-risk and the control groups performed the vertical smooth pursuit, horizontal saccadic, and vertical saccadic tracking tasks equally well, at all target speeds. No differences between the at-risk and the control group emerged when direction of eye movement (right, left, up or down) was analyzed. Subjects in both groups tracked more poorly when they moved their eyes to the right in the horizontal tasks. The electrodermal data yielded uniformly negative results indicating that there were no differences between the three groups in their responsiveness to soft tones, to loud tones or to the sounds of a barking dog and a newsroom teletype. The positioning of the three groups on the dependent measures were as described in previous research in that the Huntington group was the least responsive and the control group the most responsive. However, mean responsivity, as measured by amplitude, latency to response, the number of spontaneous skin conductance responses emitted, and the number of subjects who failed to respond did not significantly differentiate the groups. An examination of habituation did not support the hypothesis that the Huntington subjects would be fast habituators or that they would not habituate at all. This study supports previous research which found differences in the smooth pursuit eye tracking of at-risk and Huntington subjects when compared with normal controls. The overlap among the three groups suggests, however, that individual differences are too large to use smooth pursuit eye tracking as a genetic marker of Huntington's chorea. In contrast with previous research, there is no support for the contention that electrodermal indices of responsiveness can be used as markers.

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