Reading direction and spatial neglect

Many American and European investigators have reported that hemispatial neglect is more frequent and more severe after right than left hemisphere lesions. This hemispheric asymmetry may be due to biological asymmetries, learned behavior, or both. Readers of European languages, unlike readers of Semitic languages, scan from left to right. Learned rightward scanning may increase the unilateral neglect associated with right hemisphere lesions and reduce the severity of neglect associated with left hemisphere lesions. To learn if hemispheric asymmetries of neglect are influenced by learned scanning behavior, we used line bisection and cancellation tasks to study patients with unilateral stroke who read only a Semitic or European language before the age of fifteen. We found that independent of reading direction, unilateral neglect was more commonly associated with right than left hemisphere lesions. After right hemisphere damage right to left readers bisected lines closer to center than left to right readers, but on the cancellation test readers of European languages did not perform differently than readers of Semitic languages. These findings suggest that whereas learned scan direction may influence the severity of neglect when measured by line bisection, these learned directional scans cannot fully account for the observed hemisphere asymmetries of neglect. They also suggest that the line bisection test is more influenced by the direction of scanning than is the cancellation test.     

Cultural influence on directional tendencies in children’s drawing

The present study was aimed at investigating how print experience as a cultural factor influences directional tendencies in children’s drawing in the interplay with biomechanical (hand), syntactic (shape orientation) and semantic (shape meaning) factors. Eighty-eight right-handed children from three literacy/age groups (preliterate, first graders and third graders) had to copy a geometrical shape adapted from the Rey–Osterrieth complex figure. The shape was presented alternatively leftward and rightward, while using both dominant (right) and non-dominant (left) hands. Directional tendencies were assessed regarding directionality of drawing movements at global, intermediate and local levels and deviation error in centre line bisection. Results show a global improvement of drawing quality and strategies across groups and an advantage for the dominant right hand from 6 years onward. Regarding directional tendencies, a reinforcement of a congruency effect between conditions and writing direction was found from preliterates to third graders. These results are discussed as a cultural embodiment process and have implications for psychological testing.     

Cultural influences on the development of lateral preferences: A comparison between French and Tunisian children

We compared the development of laterality in two cultures that differ in pressure against left‐handedness. Tunisian children, who are discouraged by their parents from using their left hand for all food‐related activities, were compared to French children, who are allowed to use either the left or right hand. The subjects were 5, 7, and 9 years of age. To check the development of laterality, we tested hand preference (for writing and for performing 14 other manual activities), right–left performance difference, eye preference, and foot preference. The results showed that the frequency of left‐handedness and left‐eyedness was lower among Tunisian than among French children; this was particularly clear at age 5. Group difference almost disappeared in primary school children. Footedness did not differ between the two groups. Tunisian right‐hand writers, although they probably included some children who might not have been right‐handed without the cultural pressure, were not less consistent than French right‐hand writers on the 14‐item scale; they even showed a greater performance difference in favour of the right hand than the French on the pegboard task. These results may indicate that cultural pressure influences handedness at an early age, perhaps by leading towards right‐handedness in children whose genetic background might otherwise have induced a chance‐determined pattern of handedness.     

Cultural influences on the development of lateral preferences: a comparison between French and Tunisian children

We compared the development of laterality in two cultures that differ in pressure against left-handedness. Tunisian children, who are discouraged by their parents from using their left hand for all food-related activities, were compared to French children, who are allowed to use either the left or right hand. The subjects were 5, 7, and 9 years of age. To check the development of laterality, we tested hand preference (for writing and for performing 14 other manual activities), right-left performance difference, eye preference, and foot preference. The results showed that the frequency of left-handedness and left-eyedness was lower among Tunisian than among French children; this was particularly clear at age 5. Group difference almost disappeared in primary school children. Footedness did not differ between the two groups. Tunisian right-hand writers, although they probably included some children who might not have been right-handed without the cultural pressure, were not less consistent than French right-hand writers on the 14-item scale; they even showed a greater performance difference in favour of the right hand than the French on the pegboard task. These results may indicate that cultural pressure influences handedness at an early age, perhaps by leading towards right-handedness in children whose genetic background might otherwise have induced a chance-determined pattern of handedness.     

Choosing sides: lateralization in line trisection and quadrisection as a function of reading direction and handedness

It might be intuited that a person's reading direction will impact linguistic and/or oculomotor tasks. Whether it also influences nonlanguage tasks, and by what means, is less clear. A novel technique to probe this effect is introduced in this paper, and the affirmative results are presented. The line bisection task has been a standard bedside diagnostic technique for assessing hemifield spatial neglect for many years. In recent years, numerous studies have also examined how normal subjects perform on this task. A recent line of study has focused on the reading habits of the subjects and the effect it has on line bisection. Most European languages are read from left to right, and it is thus postulated that readers of those languages will scan a line from left to right. On the other hand, Hebrew is read from right to left. These previous studies have yielded intriguing results about the role that reading direction plays in nonlanguage tasks. The present study utilized two other line partition tasks, line trisection and line quadrisection, and subjects whose principal reading language was either right-to-left or left-to-right. These tasks are ambiguous when used without instructing the subject on which side to perform the line transection. It was found that principal language was correlated with the side on which the subject chose to trisect or quadrisect the line. However, there was no correlation between preferred side and writing hand and there was no significant difference in accuracy between the preferred side and the secondary side. Thus, the preferred side in this nonlanguage task does not seem to be influenced by writing hand or accuracy but rather would seem to depend exclusively upon the earliest legitimate point, as determined by reading direction.     

Influence of reading habits on line bisection

The effect of scanning direction on perception of space is studied with a visuo-motor bisection task, among 120 normal dextrals with opposite reading habits (60 French subjects, 60 Israeli subjects). Bisection is found to depend upon subject's reading habits. Israeli bisected the line to the right of the objective centre, while French subjects placed their subjective middle to the left of the objective one. Results are discussed with respect to hemispheric activation theories, directional hypotheses and the neglect syndrome.     

Vertical scanning biases and their possible influence on reading direction: celtic wisdom or folly?

The reason people read from top to bottom is unknown, but could be related to brain-mediated directional biases or environmental factors. To learn if there is a brain-mediated directional bias responsible for top-down reading direction, we evaluated the directional scanning in the vertical dimension by using directional letter and face cancellation tasks. Twenty participants were instructed to cancel either target letters or faces using either an up-down or down-up direction, with the stimuli located in left, right, and center hemispace. The results indicated significant differences in completion time between the search direction (up vs. down) and spatial position for the letter cancellation task, with a faster completion time for the bottom-up scan in right space and top-down in left space. Because the left hemisphere primarily attends to contralateral right hemispace our results suggest that, when attending to letter stimuli, the left hemisphere is biased to scan in a proximal to distal (upward) direction. Although the reasons why this is reversed in left hemispace and why we did not see directional biases in the face condition remains unclear, these results do suggest that the direction in which we learn to read is inconsistent with the brain's intrinsic directional bias.     

The relation of hand preference to hand performance in left-handers: importance of the left brain.

The associations among hand preference, hand skill (peg moving time, PMT) and hand performance (dot filling/20 s) were analyzed in left-handed subjects. In the total sample, the degree of left-hand preference linearly decreased from -100 to zero (Geschwind scores, GSs) as the number of dots placed by the right hand increased (direct correlation); the left hand did not show any significant relation to GSs. The right-hand PMT linearly decreased as the GSs decreased (negative linear correlation); the left hand skill did not exhibit any significant correlation with GSs. There was a negative linear correlation between right-hand PMT and dot-filling with right hand; the left-hand PMT was not related to dot-filling with left hand. In males, the right-hand PMT showed a negative linear correlation with GSs; no significant correlation between PMT and GSs was found for the left hand. There was a negative linear correlation between right minus left (R - L) PMT and GSs. Dot-filling with right hand was found to be positively linearly correlated with GSs (no correlation for the left hand). The L - R dot-filling showed a negative linear correlation with GSs. PMT for the right hand exhibited a significant negative linear relation to dot-filling only with right hand. Sex and familial sinistrality caused minor changes in these relationships. It was concluded that the left brain would constitute the main factor determining the degree of left-handedness.     

Right fronto-parietal dysfunction underlying spatial attention in bipolar disorder

Although the neural underpinning of bipolar disorder (BD) is still unknown, recent research suggests that the right fronto-parietal cortex is particularly affected in BD patients. If this were true, we would expect atypical functional cerebral asymmetries in allocation of visuospatial attention. To test this hypothesis, euthymic BD patients and age- and gender-matched healthy controls were compared on the visual line-bisection task, a reliable measure of visuospatial attention, associated with right parietal function. Line bisection performance (i.e. absolute and directional bias) was compared between groups as a function of response hand and line position. The results showed a typical hand-use effect in healthy controls involving a larger leftward bias (i.e. pseudoneglect) with the left hand than with the right hand. Although euthymic BD patients did not differ from healthy controls in the overall accuracy (i.e. absolute bias), they differed significantly in the directional line bisection bias. In contrast to healthy controls, BD patients did not significantly deviate from the veridical center, regardless of which hand was used to bisect horizontal lines. This finding indicates an atypical functional cerebral asymmetry in visuospatial attention in euthymic BD patients, supporting the idea of a dysfunction especially in the right fronto-parietal cortex.     

Corpus Callosum Maturation and Line Bisection Performance in Healthy Children

Line bisection performance in children has been hypothesized to be a measure of corpus callosum maturation. Several previous studies have shown that normal prepubescent children bisect lines to the right of true center with their right hand and to the left with their left hand (symmetrical neglect). In contrast, children entering puberty reportedly bisect lines to the left with both the right and left hands (pseudoneglect). The shift from symmetrical to pseudoneglect has been hypothesized to reflect corpus callosum maturation and its involvement in the transfer of attention-based visuospatial processes. In the current study, line bisection performance and MR quantitative corpus callosum volumes were examined in 46 healthy children ages 8–18 years. A linear relationship between corpus callosum volume and age was found. However, the expected age-contingent line bisection performance pattern was not observed. In addition to the expected two patterns of line bisection bias, pseudoneglect and symmetric neglect, two additional distinct patterns of line bisection were identified. These findings, and other findings in the literature, raise important questions about the reliability and validity of the line bisection test. No relationship was found between corpus callosum volume and amount or direction of line bisection deviation. Our findings do not support previous hypotheses regarding line bisection-corpus callosum relationship.     

Lateral preferences among indian school children

In the first study, 718 children from India, aged 4 to 11 years, were observed for their hand preference for ten common unimanual activities. The prevalence of left-handedness was found to be only 3.2 percent, i.e. one-third of that (9.6%) observed in a French study using a similar procedure. The degree (weak to strong) but not the direction of hand preference was found to be related to the children's age, with stronger preference among older children. The factor structure of handedness items was similar in France and India. In the second study, 400 schoolchildren from India, aged 6 to 18 years, were examined for handedness, footedness, eyedness, use of hand in space, and absolute and relative hand skill assessed by a peg-moving task and a dot-filling task. Prevalence of left-handedness was 4.2%. A sex difference was observed for handedness, footedness, use of hand in space. and relative hand skill, with higher proportions of right preferences and higher degree of lateralization (i.e., relative between hands asymmetry) in females. The degree of hand skill asymmetry increased with age. These results are discussed in relation to findings from previous studies in other countries using similar procedures.     

Components of neglect from right-hemisphere damage: an analysis of line bisection

Two versions of a line bisection task were given to patients with posterior right-hemisphere damage and normal control subjects. One, which we refer to as the directed-manual task, was the traditional bisection task in which lines were transected with a pen held in the right hand. In the other task, referred to as the directed-visual task, subjects observed the experimenter move a pen along a line from right-to-left (the left-scan task) or from left-to-right (the right-scan task) and they verbally indicated the subjective midpoint. Patients showed significant left neglect in the manual and the left-scan tasks only. Controls showed no consistent biases and no influence of scanning direction. Right and left cues biased bisection for both groups. The results indicate that when the directed manual response is eliminated, scan direction determined the presence or absence of neglect on bisection. The findings are discussed in terms of the efficiency of visual orienting.     

Grade-related changes in event-related potentials (ERPs) in primary school children: differences between two reading tasks.

Event-related potentials (ERPs) were recorded from the left and right temporal and parietal sites during word reading in a group of children who were followed over three consecutive years, starting at Grade 1. The first task required the child to read repeatedly presented words; the second task consisted of a series of different words, with each word being presented only once. All ERP components showed changes in amplitude as a function of grade: P240, N530, the parietal N150, and SW all decreased, whereas the temporal N360 and SW both increased. In addition, SW changed from no asymmetry to larger positivity over the right site, whereas N360 changed from symmetric amplitudes to larger amplitudes over the left hemisphere with grade. Single word presentations were associated with smaller SW activity and larger N530 and N360 amplitudes than were repeated word presentations. It was also found that proficient readers showed larger SW and N360 asymmetries and shorter vocal response times than did less proficient readers. In addition, a positive relationship was found between reading performance and ERP amplitudes over the left temporal hemisphere at Grades 2 and 3, particularly in the single word reading task. The results are discussed in terms of age-related changes in right and left hemisphere functions involved in learning to read.     

Left minineglect or inverse pseudoneglect in children with dyslexia?

This study compared the visuospatial asymmetries in children with dyslexia and healthy children by using the manual line bisection task, and investigated the processing of spatial context with a 'local' cueing paradigm consisting of geometric symbols placed on the extremities of the lines. The performance between healthy children (leftward bias) and children with dyslexia (rightward bias) was significantly different. Furthermore, the bisection mark was shifted in the direction of the unilaterally cued extremities in all children. As children with dyslexia showed a rightward bias in their spatial representation, which did not interfere with local context processing, we proposed the term 'inverse pseudoneglect' to depict their behaviour in line bisection.     

Right fronto-parietal dysfunction in children with ADHD and developmental dyslexia as determined by line bisection judgements

Visual line bisection is a reliable and valid laterality task that is typically used with patients with acquired brain damage to assess right hemisphere functioning. Neurologically normal individuals tend to bisect lines to the left of the objective midline whereas those with right parietal damage bisect lines to the right. In this study children with ADHD were matched with children with developmental dyslexia on IQ and gender to test the hypothesis that right hemisphere neurological abnormalities underlie the behavioural deficits observed in these two disorders. Line bisection performance was compared between groups as a function of response hand, scanning direction and line position. In contrast to results typically found with neurologically normal children, a rightward bias was found for both clinical groups, but to different degrees depending on which hand was used to bisect lines. These findings suggest pathology of the corpus callosum and/or the right fronto-parietal cortex.     

Grade-related changes in event-related potentials (ERPs) in primary school children: Differences between two reading tasks

Abstract

Event-related potentials (ERPs) were recorded from the left and right temporal and parietal sites during word reading in a group of children who were followed over three consecutive years, starting at Grade 1. The first task required the child to read repeatedly presented words; the second task consisted of a series of different words, with each word being presented only once. All ERP components showed changes in amplitude as a function of grade: P240, N530, the parietal N150, and SW all decreased, whereas the temporal N360 and SW both increased. In addition, SW changed from no asymmetry to larger positivity over the right site, whereas N360 changed from symmetric amplitudes to larger amplitudes over the left hemisphere with grade. Single word presentations were associated with smaller SW activity and larger N530 and N360 amplitudes than were repeated word presentations. It was also found that proficient readers showed larger SW and N360 asymmetries and shorter vocal response times than did less proficient readers. In addition, a positive relationship was found between reading performance and ERP amplitudes over the left temporal hemisphere at Grades 2 and 3, particularly in the single word reading task. The results are discussed in terms of age-related changes in right and left hemisphere functions involved in learning to read.     

Modulation of hemispatial neglect by directional and numerical cues in the line bisection task

We investigated the effects of arrows, eye gaze, and digits presented as irrelevant flankers in a line bisection task that was administered to 17 right brain damaged patients with or without left neglect. The rightward bias of neglect patients was selectively modulated by the direction of eye gaze and by the magnitude of two identical digits. The bisection error was shifted contralesionally by leftward-gazing eyes and "small" digits, whereas it was shifted ipsilesionally by rightward-gazing eyes and "large" digits. Therefore, the performance of neglect patients was influenced by task-irrelevant cues whose directional meaning was either explicitly represented (eye gaze) or related to the activation of a spatially oriented mental representation (digits). Regression analyses of the overall performance revealed that size of the rightward bias and error variability were predicted by neglect assessment scores across the entire sample of right brain damaged patients. The increased variability in line bisection performance is consistent with the "indifference zone" theory and it appears to be a subtle but stable marker of neglect.     

Perceptual asymmetries in a time estimation task with emotional sounds

Four experiments investigated potential interactions between emotional content and perceptual asymmetries in the estimation of short time intervals. In all experiments, the word “bower” was presented monaurally to the left or right ear in an emotional tone and participants performed a temporal bisection task. In Experiment 1, angry and neutral stimuli ranged in duration from 260 to 440 ms (in steps of 20 ms) whereas in Experiments 2–4, durations ranged from 260 to 480 ms (in steps of 20 ms). In Experiment 3, the emotional tone of happiness replaced anger. In Experiment 4, anger and happiness were used as stimuli. In all experiments, results showed a larger bisection point for the right compared to the left ear. In addition, in all experiments, the constant error was farther away from zero for the right than for the left ear. The bisection point was also longer for the angry (Experiments 1 and 2) or happy (Experiment 3) than for the neutral emotional tone. Finally, happiness produced a shorter bisection point than anger in Experiment 4. Results are discussed in terms of their implications for time perception mechanisms and their potential cerebral representation.     

The relationship between line bisection performance and emotion processing: Where do you draw the line?

ABSTRACT

A recent study demonstrated that higher accuracy on a line bisection task related to greater ratings of evocative impact from paintings. The authors suggested that line bisection accuracy may act as a “barometer” for both visuospatial and emotion processing, likely as a function of overlapping neural correlates in the right temporoparietal region. We suggest and test an alternative explanation: that visuospatial bias interacted with asymmetries in the paintings and the rating scales to produce the apparent relationship between emotion and visuospatial functions. In the present study, using both visual-analogue and numeric rating scales, the relationship between line bisection performance and ratings of paintings (evocative impact, aesthetics, novelty, technique, and closure) was examined in a young adult sample. We demonstrate that left-hand line bisection bias direction, not line bisection accuracy, is related to most ratings, and that line bisection bias interacts with stimulus orientation (non-mirrored/mirrored) and rating scale direction (ascending/descending) in such a way that can explain the results of the previous study. We conclude that the line bisection task appears to be a sensitive measure of visuospatial attentional biases, which can influence ratings of asymmetrical paintings, and may affect how individuals perceive stimuli in their environment.     

Space representation in children with dyslexia and children without dyslexia: Contribution of line bisection and circle centering tasks

Line bisection tasks (different space locations and different line lengths) and circle centering tasks (visuo-proprioceptive and proprioceptive explorations, with left or right starting positions) were used to investigate space representation in children with dyslexia and children without dyslexia. In line bisection, children with dyslexia showed a significant rightward bias for central and right-sided locations and a leftward bias for left-sided location. Furthermore, the spatial context processing was asymmetrically more efficient in the left space. In children without dyslexia, no significant bias was observed in central lines but the spatial context processing was symmetrical in both spaces. When the line length varied, no main effect was shown. These results strengthen the ‘inverse pseudoneglect’ hypothesis in dyslexia. In the lateral dimension of the circle centering tasks, children showed a response bias in the direction of the starting hand location for proprioceptive condition. For radial dimension, the children showed a forward bias in visuo-proprioceptive condition and more backward error in proprioceptive condition. Children with dyslexia showed a forward bias in clockwise exploration and more accurate performance in counterclockwise exploration for left starting position which may be in accordance with leftward asymmetrical spatial context processing in line bisection. These results underline the necessity to use the line bisection task with different locations as an appropriate experimental paradigm to study lateral representational bias in dyslexia. The contribution of the present results in the understanding of space representation in children with dyslexia and children without dyslexia is discussed in terms of attentional processes and neuroanatomical substrate.