FIGURE 4.

Line extension task. Mean (SEM) LIs of the seven right brain patients and six control participants for rightward (R) and leftward (L) extended lines (length: 4, 6, and 8 cm). The subject had to reproduce the length of a horizontal line in two rightward and leftward movement conditions. In each condition, the end of the line was aligned with the mid-sagittal plane of the body, and the patient reproduced the perceived length of the segment with a rightward or leftward extension. The stimuli were horizontal twenty-four black lines, 1 mm in width, with eight lines for three lengths (4, 6, and 8 cm). The length of the segment drawn by each subject on each trial was measured to the nearest mm. For the leftward extension of each line drawing, a following laterality index score (LI) was computed: Leftward extended length minus length of the right-sided line/leftward extended length plus length of the right-sided line × 100. For the rightward extension of each line drawing, the LI was: Rightward extended length minus length of the left-sided line/rightward extended length plus length of the left-sided line × 100. Positive/negative values of the LI indicate over/under-extension. Mean LIs were computed for the two directions of extension (rightward, leftward), and for three line lengths (4, 6, and 8 cm). All seven patients and six controls were tested. The Figure showed that 7 patients make a leftward overextension for three line lengths (4, 6, and 8 cm) while laterality scores for rightward extension do not differ from those of controls.