Spatial field advantages for tactile line bisection as a function of hemispheric specialisation inferred from dichotic listening

The Effect of Aerobic Exercise on Visuospatial Attention in Young Adults

Our objective in this study was to investigate the effect of moderate-intensity aerobic exercise on visuospatial attention bias. We examined line bisection performance at rest before exercise and then immediately after exercise in 20 young adults. Pre-exercise, there was a larger leftward bias in subjective midpoint judgment of all participants than post-exercise (p < .001). Thus, leftward error magnitude decreased according to aerobic exercise, as there were rightward shifts after the exercise. The participants' performancse were modulated by the hand used to perform manual bisection tasks (p < .02). Participants erred to the left of the true midpoint with the non-dominant hand and to the right of the true midpoint with the dominant hand. The use of the non-dominant hand led to greater leftward error than the errors obtained using the dominant hand, though there was no interaction effect between hand use and effort. These findings suggest that moderate aerobic exercise can benefit visuospatial attention in adults.

Development of spatial biases in school-aged children

In the adult brain, biases in the allocation of spatial attention can be measured using a line bisection task and are directly relatable to neural attention signals in the fronto-parietal attention network. Behavioral studies on the development of spatial biases have yielded a host of inconsistent results, likely due to variance in sample size, definition of experimental groups, and motor confounds introduced by using a paper-and-pencil version of a line bisection task. Here, we used a perceptual, computerized version of this task and examined the development of spatial biases in 459 children from grades 1-8 and 61 college freshmen. We found that children in early elementary grades exerted a significant leftward bias that gradually diminished with advancing grade level. We further show that among children in early elementary school grades, the degree of leftward spatial bias predicted better performance on a rapid automatized naming test, a predictor of reading ability. Significant leftward biases in early elementary school grades may be due to reading experience, thereby reflecting an interaction of the attention network with the evolving reading network.

Related but different: Examining pseudoneglect in audition, touch and vision

Although researchers have consistently demonstrated a leftward attentional bias in visual and representational (e.g. tactile/mental number line) line bisection tasks, the results from audition have been mixed. Differences in methodology between auditory and visual bisection tasks, especially with regards to the location of stimuli of peripersonal versus extrapersonal space, have also meant that researchers have not been able to compare performance in visual, tactile and auditory line bisection directly. In this research, 39 neurologically typical individuals participated in standard visual and tactile line bisection tasks, together with a newly developed auditory line bisection task. Results demonstrated significant leftward bisection biases across all three modalities. Hence, we demonstrate auditory pseudoneglect in peripersonal space for the first time. Tactile and auditory line bisections showed a relatively small but statistically reliable correlation, but neither task correlated with visual line bisection. This suggests that the processes underlying auditory line bisection are not synonymous to those involved in visual perceptual bisection, and further we argue that this bias may be related to representational pseudoneglect.

Touching base: The effect of participant and stimulus modulation factors on a haptic line bisection task

Acquiring information about our environment through touch is vital in everyday life. Yet very little literature exists about factors that may influence haptic or tactile processing. Recent neuroimaging studies have reported haptic laterality effects that parallel those reported in the visual literature. With the use of a haptic variant of the classical line bisection task, the present study aimed to determine the presence of laterality effects on a behavioural level. Specifically, three handedness groups including strong dextrals, strong sinistrals, and-the to-date largely neglected group of-mixed-handers were examined in their ability to accurately bisect stimuli constructed from corrugated board strips of various lengths. Stimulus factors known to play a role in visuospatial perception including stimulus location, the hand used for bisection, and direction of exploration were systematically varied through pseudo-randomisation. Similar to the visual domain, stimulus location and length as well as participants' handedness and the hand used for bisection exerted a significant influence on participants' estimate of the centre of haptically explored stimuli. However, these effects differed qualitatively from those described for the visual domain, and the factor direction of exploration did not exert any significant effect. This indicates that laterality effects reported on a neural level are sufficiently pronounced to result in measurable behavioural effects. The results, first, add to laterality effects reported for the visual and auditory domain, second, are in line with supramodal spatial processing and third, provide additional evidence to a conceptualisation of pseudoneglect and neglect as signs of hemispheric attentional asymmetries.

Grasping at sticks: pseudoneglect for perception but not action

A current question in theories of visual cognition is whether distinct cognitive processes subserve perceptual judgments and perception for action. This paper examines bisection tasks which have previously been used to demonstrate a dissociation between perception and action in brain injured patients. Forty neurologically intact participants completed a standard line bisection task and a variant of this task--rod bisection. A typical leftwards bias was observed for line bisection but when asked to locate the centre of wooden rods using perceptual judgments, a distinct rightwards bias was shown. By contrast, when participants were asked to pick the rods up by the centre, their judgments showed no bias. The results are in line with theories suggesting that perception and action are independent; however, alternative explanations are also considered.

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

An exhaustive qualitative (vote-counting) review is conducted of the literature concerning visual and non-visual line bisection in neurologically normal subject populations. Although most of these studies report a leftward bisection error (i.e., pseudoneglect), considerable between-study variability and inconsistency characterize this literature. A meta-analysis of this same literature is performed in which the total quantitative data set, comprising 73 studies (or sub-studies) and 2191 subjects, is analyzed with respect to 26 performance factors. The meta-analytic results indicate a significant leftward bisection error in neurologically normal subjects, with an overall effect size of between -0.37 and -0.44 (depending on integration method), which is significantly modulated to varying degrees by a number of additional task or subject variables. For example, visual bisection tasks, midsagittal-pointing tasks and tactile bisection tasks all lead to leftward errors, while kinesthetic tasks result in rightward errors. Tachistoscopic forced-choice testing methods reveal much greater estimates of bisection error (effect size = -1.32) than do manual method-of-adjustment procedures (effect size= -0.40). Subject age significantly modulates line bisection performance such that older subjects err significantly rightward compared to younger subjects, and to veridical line midpoint. Male subjects make slightly larger leftward errors than do female subjects. Handedness has a small effect on bisection errors, with dextrals erring slightly further to the left than sinistral subjects. The hand used to perform manual bisection tasks modulated performance, where use of the left hand lead to greater leftward errors than those obtained using the right hand. One of the most significant factors modulating bisection error is the direction in which subjects initiate motor scanning (with either eye or hand), where a left-to-right scan pattern leads to large leftward errors while a right-to-left scan pattern leads to rightward errors.

Length representation in normal and neglect subjects with opposite reading habits studied through a line extension task

In the first part of this paper, 45 French (left-to-right readers) and 30 Israeli (right-to-left readers) normal dextrals were given half a line and requested to construct the missing other with the same length (either the left one or the right one). Using this line extension task, a significant effect of reading habits on the performance was found, with no significant bias for Israeli subjects, and a significant underconstruction when building the left half from the right one for French subjects. In the second part, two patients with opposite reading habits (one French, one Israeli) suffering from left unilateral neglect were submitted to the same protocol. Both patients were found to under-construct the right half of the line from the left given half, and to over-construct the left half from the right given one, hence reproducing the well-known line bisection bias. Results are discussed with regard to enhancement and activation hypotheses, and current theories of the neglect syndrome.

Is left always right? Directional deviations in visual line bisection as a function of hand and initial scanning direction

Directional deviations in visual line bisection were investigated using normal subjects. Significant main effects were found for hand and initial scan direction resulting from significantly greater deviations to the left by the left hand compared with the right hand and by a scan from the left compared with a scan from the right. These results suggest that the amelioration of neglect can only be inferred from the left hand deviations of neglect patients if they are significantly leftwards of the objective middle and that the degree of leftward deviation in normal subjects results from an interaction between right hemispheric activation and unilateral allocation of attention.