Evidence from a line bisection task for visuospatial neglect in Left Hemiparkinson's disease

The perception of extrapersonal space in Parkinson's disease was examined w ith two line bisection tasks. One was a conventional pencil and paper test, the line bisection section of the Behavioural Inattention Test. In the oth er, the stimuli were displayed on a large (2 x 2.4 m) screen and varied in length (48-480 mm) and also in location on the screen (left, centre and rig ht). They were presented at two viewing distances (0.6 and 1.5 m). Subjects remotely adjusted the position of a cursor until it appeared to bisect the stimulus line, using two push-buttons, one in each hand. The PD participan ts (n = 18) had a marked asymmetry of motor symptoms. They were divided int o two groups. those with predominantly left-sided motor symptoms (LPD, n = 9), and those with predominantly right-sided motor symptoms (RPD, n = 9). T he control group (n = 9) were all right-handed. No significant differences between the groups were found on the BIT bisection task. In contrast. when the stimuli were presented on the screen, LPD subjects showed a significant rightward bias in their settings of the cursor, particularly for lines on the left and centre of the screen, which was greater, the longer the stimul us line. The RPD group bisected lines slightly to the left, in common with the control group (pseudo-neglect). In a second experiment, Parkinsonian su bjects repeated this task, but with the buttons reversed between the hands, so that the cursor was moved to the left by the right hand, and vice versa , but the pattern of results was the same as in the first experiment. The d ata suggest a small but reliable neglect in left hemiparkinson's disease, w hich is contralateral to the non-dominant (and probably worse affected) hem isphere. The dissociation between the response and the bisection error sugg ests a visuospatial impairment in LPD. (C) 2001 Elsevier Science Ltd. All r ights reserved.