Vertical Line Bisection Research Articles

39 Does Pseudoneglect Modifies The Visuospatial After-Effects Of Vertical Prism Adaptation?

Objective:The prism adaptation (PA) with rightward shifting lenses is a promising rehabilitation technique for left hemispatial neglect. The PA has also been applied in healthy individuals to investigate cognitive mechanism(s) underlining such adaptation. Importantly, studies have suggested that PA may primarily impact the functions of the dorsal or the ventral attentional stream, and we have previously reported that PA to the upward and downward shifting lenses leads to a significant aftereffect in vertical line bisection task. However, this post-adaptation effect, similarly to that seen in the horizontal plane, might have been modified by the presence of the vertical pseudoneglect healthy participants often experience prior to PA. Thus, the aim of this study was to test this hypothesis.Participants and Methods:30 right-handed healthy adults (age M=22,4) performed a computerized line bisection (LB) in vertical and horizontal condition. The bisections were performed twice: before and after PA procedure. Participants took experimental procedure three times, each in at least 24 h of break, each time in one of three conditions of shifting lenses; down, up, control. Both LB tasks (vertical and horizontal) consisted of 24 lines, each centered on 23" touch screen. The participants were asked to find the middle of the line. Throughout the experiment, participants were comfortably seated with their head positioned on a chinrest. Participants were fitted with prismatic goggles that deviated their visual field by 10 degrees. For the adaptation we used the Peg-the-mole procedure consisting of 120 pointing movements.Results:To assess the effect of the vertical PA on landmark judgments we performed a repeated measures ANOVA with direction of PA (upward/downward), the condition of LB (vertical/ horizontal) and pre- vs post adaptation as a between-subjects factor. This analysis revealed a main effect of the direction of PA (p< 0.001) and a main effect of condition (p< 0.001). Overall, however, only adaptation in up-shifting lenses led to significant aftereffects (p<0.05). Further, when we excluded participants who did not exhibited horizontal pseudoneglect in preadaptation LB, the effect of PA in downshifting PA emerged in vertical LB (p<0.05). Further, this group also exhibited the aftereffect of PA in up-shifting lenses for the horizontal (p<0.01) and the vertical LB (p<0.05). Additionally, these participants exhibited a congruent tendency after upward and downward PA, and tended to allocate their attention more upward and rightward.Conclusions:The results of this study confirm that the vertical PA evokes a visuo-spatial bias. Moreover, the PA aftereffect seems to be modified by the presence of the pre-adaptation pseudoneglect. Whereas the mechanism inducing this bias is not fully known, it might be explained in light of the interhemispheric activation-inhibition balance. Both the upward and downward PA may primarily lead to activation of the posterior regions of the right hemisphere, and this activation may result with the upward and rightward bias in the LB task. However, future research with neuroimaging techniques is needed to test this hypothesis.

Altered Allocation of Vertical Attention in Individuals With Autism Spectrum Disorder.

Typical adults most frequently orient their attention to other people's eyes, whereas individuals with autism spectrum disorder (ASD) orient their attention to other people's mouths. Typical adults also reveal visuospatial biases on tasks such as vertical and horizontal line bisections. Therefore, the difference in face viewing might be related to a more general group difference in the allocation of vertical attention. To use vertical line bisection and quadrisection tasks to evaluate whether individuals with ASD have a more downward-oriented vertical attentional bias than do typical individuals. We recruited 20 individuals with ASD and 20 control participants matched for age (6-23 years), IQ, and sex. We asked the individuals to bisect and quadrisect lines on the top and bottom when the vertical lines were placed at the intersection of their right, left, and center egocentric sagittal planes and their coronal plane. The distances from the true midpoint and quadripoint were measured, and between-group performances were compared. No significant difference was found between the ASD and control groups for vertical line bisections or lower line quadrisections. However, when the ASD group was compared with the control group for higher line quadrisections, the ASD group exhibited a greater upward deviation. There is no downward vertical attentional spatial bias associated with ASD that could help to explain these individuals' attentional bias toward the mouth. However, additional studies are required to learn if this atypical upward vertical attentional bias might account for some of the symptoms and signs associated with ASD.

Degenerative dementia with proximal radial and lower vertical spatial neglect

ABSTRACT A 75 year-old man had a two-year history of progressive memory loss, trouble with finances and getting lost. On examination, he scored 16/30 in MoCA test, noticeably impaired on the attentional tasks. His screening bloodtests werenormal. Brain imaging revealed hippocampal atrophy and bilaterallarge areas of leukoaraiosis below posterior parietal lobes. On vertical line bisection he revealed a large upward bias and on radial bisection, a distal bias. Degeneration of his posterior parietal cortex may have caused both the leukoaraiosis and vertical-radial neglect. Unawareness of portions of space can be a source of disability and cause injury. Therefore, patients with degenerative dementia, especially those with similar patterns of leukoaraiosis or parietal degeneration should be tested for vertical and radial forms of spatial neglect.

A case of posterior cortical atrophy with vertical neglect

ABSTRACTPosterior cortical atrophy (PCA) is a syndrome caused by a neurodegenerative disease that often presents with visuospatial deficits, and can be debilitating. PCA is often characterized by elements of Balint’s syndrome and dyslexia. The most common underlying pathology has been found to be Alzheimer’s disease. Signs of horizontal neglect are frequently associated with PCA, but the presence of vertical (or altitudinal) neglect has not yet been reported in a patient with PCA or other forms of neurodegenerative dementia. In this paper, we present a patient with PCA who on vertical line bisection and cancellation tests revealed upper altitudinal spatial neglect. Detection of this abnormality may have important implications for diagnosis, therapeutic interventions, and patient safety.

Does gravity influence the visual line bisection task?

The visual line bisection task (LBT) is sensitive to perceptual biases of visuospatial attention, showing slight leftward (for horizontal lines) and upward (for vertical lines) errors in healthy subjects. It may be solved in an egocentric or allocentric reference frame, and there is no obvious need for graviceptive input. However, for other visual line adjustments, such as the subjective visual vertical, otolith input is integrated. We hypothesized that graviceptive input is incorporated when performing the LBT and predicted reduced accuracy and precision when roll-tilted. Twenty healthy right-handed subjects repetitively bisected Earth-horizontal and body-horizontal lines in darkness. Recordings were obtained before, during, and after roll-tilt (±45°, ±90°) for 5 min each. Additionally, bisections of Earth-vertical and oblique lines were obtained in 17 subjects. When roll-tilted ±90° ear-down, bisections of Earth-horizontal (i.e., body-vertical) lines were shifted toward the direction of the head (P < 0.001). However, after correction for vertical line-bisection errors when upright, shifts disappeared. Bisecting body-horizontal lines while roll-tilted did not cause any shifts. The precision of Earth-horizontal line bisections decreased (P ≤ 0.006) when roll-tilted, while no such changes were observed for body-horizontal lines. Regardless of the trial condition and paradigm, the scanning direction of the bisecting cursor (leftward vs. rightward) significantly (P ≤ 0.021) affected line bisections. Our findings reject our hypothesis and suggest that gravity does not modulate the LBT. Roll-tilt-dependent shifts are instead explained by the headward bias when bisecting lines oriented along a body-vertical axis. Increased variability when roll-tilted likely reflects larger variability when bisecting body-vertical than body-horizontal lines.

Vertical line quadrisection: “What” it represents and who gets the upper hand

BackgroundNormal adults demonstrate a slight upward bias (vertical pseudoneglect) when attempting vertical line bisection. The mechanism for this bias is unknown. Activation of the allocentric (object-centered) ventral visual system during attempted bisection may induce this bias. This object-centered ventral stream may also mediate focal attention. As compared to bisection, when normal participants perform a vertical line quadrisection task that requires more focal attention, they may have a greater upward bias. MethodsSixteen participants bisected and quadrisected vertical lines. ResultsThe mean upward bias (deviation error) for the quadrisection tasks was significantly higher than the mean error for the line bisections. ConclusionsThese results are consistent with the hypothesis that activation of the ventral stream by a task that requires focal allocentric attention can induce an upward vertical bias that is greater than the upward bias observed with allocentric line bisection, a task that requires more global attention.

Famous faces but not remembered spaces influence vertical line bisections

Whereas the ventral visual processing stream mediates facial and object recognition, the dorsal stream mediates recognition of spatial relationships. In addition, ventral lesions have been reported to induce visual inattention to the upper visual field and dorsal lesions inattention to the lower field. The purpose of this study is to test the hypothesis that activation of the ventral stream will induce an upward attentional bias and activation of the dorsal stream, a downward bias, as assessed by vertical line bisection tests. Twelve healthy right-handed individuals performed vertical line bisections. During these trials, either pictures of famous faces or dots in different spatial locations were presented above and below the line. The participants were asked to recognize and remember the faces or locations of dots while they performed the bisections. In control trials, they were no faces or dots. An upward bias was observed in all conditions. This upward bias was significantly increased in the face recognition and recall condition, but not altered in the dot location condition. Although the face task appeared to activate the ventral stream and increase the upward vertical bias, the failure of the dot localization task to alter the bias may be related task selection. Dorsolateral lesions cause optic ataxia, a disorder of the egocentric “where” system, and the dot location task in this study was allocentric. Thus, further research will be needed to learn whether an egocentric spatial localization task, with a memory component, will alter the vertical attentional bias.

Right up there: Hemispatial and hand asymmetries of altitudinal pseudoneglect

BackgroundPseudoneglect is a normal left sided spatial bias observed with attempted bisections of horizontal lines and a normal upward bias observed with attempted bisections of vertical lines. Horizontal pseudoneglect has been attributed to right hemispheric dominance for the allocation of attention. The goal of this study was to test the hypothesis that the upward bias in vertical line bisection may also relate to right hemispheric dominance for the allocation of attention and/or action-intention. MethodsTwenty right handed healthy adults were asked to bisect vertical lines presented in the midsagittal plane (center space) and in sagittal planes to the left and right of the midsagittal plane (left and right hemispace) when using a pen held in either the right or left hand. ResultsVertical line bisections were biased upward in all three sagittal planes and higher in left than right hemispace. However, bisections made with the left hand were lower than those made with the right hand. DiscussionWhereas these results suggest a left hemispace-right hemispheric visuospatial attentional upward bias and a relative left hemispheric-right hand upward action-intentional bias, further studies are needed to document this intentional versus attentional bias and to understand the brain mechanisms that produce these biases.

Effects of auditory pitch on vertical line bisection: bottom-up or top-down processing?

Effects of auditory pitch on vertical line bisection: bottom-up or top-down processing?

On the origin of vertical line bisection errors

Four experiments examined the biases of individual subjects when attempting to bisect vertical lines, and tested various hypotheses concerning the origin of vertical bisection errors (VBEs). In each experiment, individual differences on the vertical line bisection task were compared to individual differences on another task to evaluate whether the tasks were systematically related. In the first experiment, VBEs were found not to correlate with horizontal line bisection errors (HBEs). In the second experiment, VBEs were found not to correlate with the size of the horizontal-vertical illusion (HVI). In the third experiment, VBEs were found not to correlate with differences in perceived length of vertical lines presented in the upper and lower visual fields that were displaced horizontally. In the fourth experiment, VBEs were found to correlate with bisection errors of an open vertical interval. The results of the first three studies are counter to various hypotheses of the origins of vertical bisection errors. The last experiment suggests that lines, per se, are unnecessary for VBEs. Rather, it is important that the upper and lower segments of the stimulus that are judged to be equal on vertical bisection tasks are co-extensive.

Peripersonal spatial attention in children with spina bifida: Associations between horizontal and vertical line bisection and congenital malformations of the corpus callosum, midbrain, and posterior cortex

Horizontal and vertical line bisection was studied in 129 children and adolescents between 8 and 19 years of age, one group ( n = 32) of typically developing controls and one group ( n = 97) with spina bifida (SBM), a neurodevelopmental disorder associated with dysmorphology of the corpus callosum, posterior cortex, and midbrain. For each participant, structural brain MRIs were analyzed qualitatively to identify beaking of the midbrain tectum and corpus callosum agenesis and hypoplasia and quantitatively by segmentation and volumetric analyses of regional cortical white and gray matter. Each group showed the line length effect, whereby greater estimation errors are made with longer lines. The group with SBM differed from controls in terms of both accuracy and variability of line bisection. Children with SBM showed pseudoneglect, attending more than controls to left hemispace. The extent of rightward bisection bias was unrelated to right posterior brain volumes, although an intact corpus callosum during development moderated and normalized the exaggerated leftward line bisection bias. More children with SBM than controls attended to inferior hemispace. A normal midbrain and greater posterior cortex volume during development moderated and normalized the downward bias. Children with SBM showed more intra-subject variability than controls. Line bisection in children with SBM reflects three deficits: an exaggerated attentional bias to left hemispace, an abnormal attentional bias to inferior hemispace; and a larger zone of subjective uncertainty in bisection judgments.

Representational bias does not affect bisection of lines with a pictorially or semantically defined top by patients with left hemispatial neglect

Normal subjects may have both representational and visual-based components determining bias in bisection of horizontal, vertical, and radial lines. The influence of these components is less clear in patients with neglect. We asked 25 patients with right hemisphere stroke and clinical features of neglect to bisect lines oriented horizontally, vertically, and radially above and below eye level. Objects including human silhouette figures, arrowheads, and the words ‘TOP’ and ‘BOTTOM’ were placed at either end of each line. These figures were presented either upright or upside down in some orientations, and presented rightward and leftward in other orientations, to pictorially or semantically define a “top” to each line independent of the actual top of the visual field. Patients demonstrated a rightward bias on all horizontal line bisections, with similar bias and greater magnitude than normal subjects. Patients also demonstrated visual-based biases on some of the vertical, radial down, and radial up lines presented. However, patients did not demonstrate a significant representational bias with any of the visual cues presented on any of the line orientations. Patients with acute right hemisphere stroke demonstrate a rightward bias when asked to perform line bisection in the horizontal line orientation, as well as an upward bias in vertical line bisection. The lack of representational bias in patients with neglect may be due to a greater degree of visual-based neglect as compared to representational neglect, or it may be due to an absence of representational bias in patients with right hemisphere stroke.

Dopamine and the representation of the upper visual field: evidence from vertical bisection errors in unilateral Parkinson’s disease

It has been suggested that dopamine is an important neurotransmitter in the brain mechanisms which represent the upper visual field. This idea was tested with a vertical line bisection task in unilateral Parkinson’s disease. Stimuli of a range of lengths were presented on a large screen in three positions (left, centre and right) and at two viewing distances (0.6 and 1.5 m). The patients, who were compared with a group of normal age-matched controls, comprised 16 sufferers from predominantly unilateral disease, 8 with more severe left-sided symptoms (LPD) and 8 with more severe right-sided symptoms (RPD). The LPD group consistently set the bisecting cursor below the midpoint of the stimulus lines, and their bisection error became larger as the length of the line increased. In contrast, the controls set the cursor above the midpoint of the line, an error which also increased with line length. The settings of the RPD group were similar to those of the controls. The results suggest altitudinal neglect in left unilateral PD, and support the hypothesis of dopaminergic involvement in the coding of upper visual space, with the proviso that the perceptual component of this involves the right hemisphere in humans.

The Neural Basis of Vertical and Horizontal Line Bisection Judgments: An fMRI Study of Normal Volunteers

Bisection of horizontal lines is used as a clinical test of spatial cognition in patients with left visuospatial neglect after right hemisphere lesions. Bisection of vertical lines has also been employed, albeit less frequently. Interestingly, normal subjects often bisect horizontal lines too far left and vertical lines too high. We used fMRI to investigate whether vertical/horizontal stimulus orientation interacts with the neural mechanisms associated with line bisection judgments (the Landmark task). For control of orientation per se, subjects performed a visual detection task with the same stimuli. Statistical analysis of evoked BOLD responses employed SPM99. The Landmark task increased neural activity (P < 0.05, corrected) in the superior and inferior parietal lobes bilaterally, though predominantly on the right; early visual processing areas bilaterally; and cerebellar vermis, left cerebellar hemisphere, anterior cingulate, and prefrontal cortex bilaterally. Vertical lines (relative to horizontal lines and vice versa) increased neural activity in early visual processing areas, consistent with differential retinotopic stimulation. In addition, vertical lines activated right parietooccipital and superior posterior parietal cortex bilaterally. No significant interactions between the neural mechanisms associated with task and stimuli were observed. Increased neural activation in parietal and parietooccipital cortex associated with vertical lines may reflect increased attentional demands associated with this stimulus orientation. The right hemispheric dominance observed in posterior parietal during the Landmark task irrespective of stimulus orientation is consistent with lesion studies. Our results suggest that the behavioral patterns observed in normal subjects and neurological patients result from different stimulus effects rather than differential task demands.

Line bisection performances of 650 normal children

When bisecting lines, an important number of brain damaged patients tend to place their bisection marks in the hemispace ipsilateral to their lesion. Biases have also been reported in normal adults. In vertical bisection both patients and normal subjects present with upward shifts, although a downward displacement may occur eventually. Surprisingly, little is known on line bisection (LB) in normal or brain damaged children. A total of 650 subjects, aged 7–12 years, performed a horizontal and vertical LB task with their preferred hand. Asymmetry indices (AIs) were used to measure directional bias. Unsigned AIs served to evaluate accuracy and mastery of the LB skill. In vertical bisection a general and significant upward bias was found, whereas in horizontal bisection subject (gender, handedness, utilized hand, age) and stimulus variables (orientation, length, position) yielded significantly different AIs. Although with increasing age significantly increasing accuracy was observed, none of the participating children mastered LB to mathematical precision. Differences in IQ-level and attention test score did not yield significantly different AIs. Impact from reading proficiency could not be demonstrated. It is suggested that stimulus length effect results are compatible with the Halligan and Marshall [Halligan, P., and Marshall, J. Toward a principled explanation of unilateral neglect. Cognitive Neuropsychology, 1994, 11, 167–206] model of hemispatial neglect. Moreover, data may support the hypothesis of greater hemispheric specialization of visuo-spatial skills in boys than in girls.

Standardised Analysis of Visual-spatial Perception after Brain Damage

Disorders of visual space perception and cognition are frequent in patients with brain damage. In this paper we describe further developments of a new PC-based system (termed VS) that allows the quantitative assessment of a variety of visual-spatial abilities (Subjective Visual Axes, Visual Orientation Discrimination, Length, Distance, Form and Position Discrimination, and Line and Distance Bisection). Besides other features, VS offers various useful properties, i.e. the automatic computation of psychophysical parameters (method of limits), the experimental manipulation of task parameters, the definition of macro files, and the configuration of high quality graphic laser printouts. The basic features of this system have already been described in a preceding paper (Kerkhoff & Marquardt, 1995). In the present paper we describe five useful clinical standard examinations together with preliminary normative data and present graphic printouts of the results developed with this system. These standard examinations include a short (5 subtests) and a long screening examination (11 tests), a test of the Subjective Axes and of Form Discrimination (“Efron Shapes”). Furthermore, an investigation of cueing effects in horizontal and vertical Line Bisection is described. Finally, special options such as bedside tests and repeated testing to evaluate changes in performance over time are illustrated. We show in a sample of 20 brain-damaged patients that there are no significant retest effects within a period of 1-3 weeks when twice tested with the same investigation in VS. These standard examinations are easy to implement in clinical practice and can be performed within 10-40 minutes depending on the type of investigation. In summary, the clinical and experimental features of VS may be of clinical utility and may progress the knowledge about visuospatial functions in brain-damaged patients.

Focal and global attention modulate the expression of visuo-spatial neglect: A case study

We report a case of severe left visuo-spatial neglect consequent upon right-hemisphere stroke. In Experiment 1, we show that while the patient bisects horizontal lines significantly to the right of true centre, he is extremely accurate in placing a mark at the centre of an equivalent outlined square, Experiment 2 confirms that the lateral and radial accuracy obtained in the latter (square) task cannot be predicted from the lateral and radial displacements found in horizontal and vertical (radial) line bisection; the experiment also shows that the individual horizontal lines of a square can be bisected significantly more accurately than the same lines presented individually. Experiment 3 shows that the crucial figural component requisite for the accurate estimation of lateral extent is a large vertical (radial) line in right space. The obtained figural modulation of neglect is consistent with a model in which a large, unitary stimulus in right space engages and enhances the lesioned right hemisphere's intrinsic capacity to deploy global attention.

Figural modulation of visuo-spatial neglect: A case study

We report a case of severe left visuo-spatial neglect consequent upon right-hemisphere stroke. In Experiment 1, horizontal and vertical (radial) line bisection is performed; the patient displays left neglect and “altitudinal” (radial) neglect, placing his transections too far to the right and to the top, respectively. In Experiment 2, the patient is required to place a dot at the centre of squares and circles, the horizontal and vertical extents of which are identical to the length of the lines employed in Experiment 1. Performance is now extremely accurate. In Experiment 3, the height of the rectangular or elliptical figure whose midpoint is to be estimated is held constant whilst length varies. In Experiment 4, the length of the figure is held constant whilst height is varied. Both manipulations exert a profound, lawful influence on the patient's estimate of each figure's midpoint. We provide some preliminary hypotheses concerning how configurational constraints may affect perceptual and attentional processes in visual neglect.