Effects of hand and spatial conditions on visual line bisection.

Abstract

This study examined the effects of hand and spatial conditions on a visual line bisection task with normal right-handers and proposed a normal range of deviation for this task in middle and advanced age. Twentyfour normal dextrals in their fifties and sixties performed a visual line bisection task using either the left or right hand under three spatial conditions : at the midline and in the left and right hemispaces. Our results revealed that performance was significantly affected by the hand used but not spatial conditions : Left hand performance was significantly further leftward than right hand performance. There was no significant interaction between the hand and spatial conditions. The mean deviation of the right hand was 2.2% of the half line length to the right of the true center. The possibility of left unilateral spatial neglect should be considered if a patient bisects a line with a deviation greater than 10% of the half line length to the right, line bisection ; normal range ; effect of used hand ; effect of hemispace The visual line bisection task is a common test for detecting unilateral spatial neglect (USN). When required to bisect a horizontal line, patients with left USN are expected to mark the midpoint to the right of the true center, because they neglect the left side of the line.There have only been a few studies on the performance of a visual line bisection task in normal subjects. Schenkenberg et al. (1980) had 20 hospitalized, non-neurological, right-handed control patients bisect lines and reported that they had a tendency to bisect lines o the left of center when using their left hand, and on or slightly to the right of center when using their right hand. Bradshaw et al. (1985) found that normal students using their right hand demonstrated a significant tendency to bisect to the left of the true center on both a visual line and a tactile rod bisection task. Ferro et al. (1987) studied 14 normal controls and concluded that the subjective midpoint were slightly deviated to the left of the

Pseudoneglect: a review and meta-analysis of performance factors in line bisection tasks

“…Most studies have used mixed sex subject groups [31,48,50,60,79,95,113,120] or failed to report the sex of subjects [4,6,9,11,40,57,95,103,111]. The majority of studies examining the in¯uence of sex report non-signi®cant eects [16,19,30,42,73,86,92,110,115]. However, Roig and Cicero [105] found that males erred more to the 2 While various response criteria have been used to measure bisection performance, this review uses mean signed deviation from veridical center as a response measure since it captures both the direction and amplitude of bisection errors.…”

“…Most studies have limited testing to dextral subjects [19,23,30,31,38,41,42,48,50,60,61,62,79,84,87,91,94,97,111,115,120,126]. Many, however, fail to disclose subject handedness [4,6,11,22,40,57,98,103,113,118].…”

“…Most authors report that subjects err to the left of veridical line center with either hand, although when the left hand is used subjects err farther left than when the right hand is used [13,19,42,80,97,101,105,110]. However, two studies found that when the right hand was used, subjects erred to the right of veridical, whereas when the left hand was used, subjects erred to the left of veridical [44,111].…”

Asymmetries of Visuospatial Attention in Schizophrenia

“…Line bisection is a task that may be affected by different factors [13][14][15][16][17][18][19][20][21][22][23][24][66][67][68][69][70][71][72][73]. However, the factors related to the stimulus were comparable between the studies that found a leftward and those that found a rightward bisection bias.…”

“…Further, when normal subjects are asked to bisect radial or vertical lines, they usually deviate away from, or above the true midpoint, respectively [11,12]. The magnitude and the direction of bisection errors may be influenced by stimulus or task factors, such as line length [13,14] and location [15][16][17], the hand used [18,19], the presence of contextual stimuli [20][21][22][23], the directional scanning [24].…”