Objective: The objective of this study was to evaluate the impact of directed and sustained attention on the allocation of visuospatial attention. Healthy people often have left lateral and upward vertical spatial attentional biases. However, it is not known whether there will be an increase in bias toward the attended portion of the stimulus when volitional spatial attention is allocated to a portion of a stimulus, whether there are asymmetrical spatial alterations of these biases, and how sustained attention influences these biases. Methods: We assessed spatial bias in 36 healthy, right-handed participants using a variant of horizontal and vertical line bisections. Participants were asked to focus on one or the other end of vertical or horizontal lines or entire vertical or horizontal lines, and then to bisect the line either immediately or after a 20 second delay. Results: We found a significant main effect of attentional focus and an interaction between attentional focus and prolonged viewing with delayed bisection. Focusing on a certain portion of the line resulting in a significant deviation toward the attended portion and prolonged viewing of the line prior to bisection significantly enhanced the degree of deviation toward the attended portion. Conclusions: The enhanced bias with directed and sustained attention may be useful modifications of the line bisection test, particularly in clinical populations. Thus, future studies should determine whether prolonged viewing with delayed bisection and spatially focused attention reveals attentional biases in patients with hemispheric lesions who perform normally on the traditional line bisection test. (JINS, 2019, 25, 65–71)

Objectives: There is increasing evidence of non-motor, sensory symptoms, mainly involving the spatial domain, in cervical dystonia (CD). These manifestations are likely driven by dysfunctional overactivity of the parietal cortex during the execution of a sensory task. Few studies also suggest the possibility that visuospatial attention might be specifically affected in patients with CD. Therefore, we asked whether non-motor manifestations in CD might also comprise impairment of higher level visuospatial processing. Methods: To this end, we investigated visuospatial attention in 23 CD patients and 12 matched healthy controls (for age, gender, education, and ocular dominance). The patients were identified according to the dystonia pattern type (laterocollis vs. torticollis). Overall, participants were right-handers, and the majority of them was right-eye dominant. Visuospatial attention was assessed using a line bisection task. Participants were asked to bisect horizontal lines, using their right or left hand. Results: Participants bisected more to the left of true center when using their left hand to perform the task than when using their right hand. However, overall, torticollis patients produced a significantly greater leftward deviation than controls. Conclusions: These data are consistent with preliminary findings suggesting the presence of biased spatial attention in patients with idiopathic cervical dystonia. The presence of an attentional bias in patients with torticollis seem to indicate that alterations of attentional circuits might be implicated in the pathophysiology of this type of CD. (JINS, 2018, 24, 23–32)

Neurologically normal individuals show a bias toward the left side of space, referred to as pseudoneglect due to its similarity to clinical hemispatial neglect. The left bias appears to be stronger in the lower visual field during free-viewing, which could result from preferential dorsal stream processing. The current experiments used modified greyscales tasks, incorporating motion and isoluminant color, to explore whether targeting dorsal or ventral stream processing influenced the strength of the left bias. It was expected that the left bias would be stronger on the motion task than on a task incorporating isoluminant color. In Study 1, similar left biases were observed during prolonged viewing for luminance, motion and red, but not green color. The unexpected finding of a leftward bias for red under prolonged viewing was replicated in Study 2. A leftward bias for motion was also evident during 150 ms viewing in Study 2. In Study 3, the left bias was not apparent when using a blue/yellow condition, suggesting the left bias for red under prolonged viewing was likely unique to red. Furthermore, the leftward bias for red disappeared under brief viewing conditions. It is suggested that dorsal stream processing likely underlies visual field differences in pseudoneglect. (JINS, 2012, 18, 251–259)

Patterns of cerebral asymmetry related to visuospatial functions may change with age. The typical leftward bias on a line bisection task may reflect cerebral asymmetry. With age, such leftward bias decreases. This study demonstrated that the age-related decrease of leftward bias may actually be sex-specific. In addition, previous research suggests that young adults’ deviation in line bisection may reflect asymmetric hemispheric activation of perceptual–attentional “where” spatial systems, rather than motor-intentional “aiming” spatial systems; thus, we specifically fractionated “where” and “aiming” bias of men and women ranging in age from 22 to 93 years old. We observed that older men produced greater rightward line bisection errors, of primarily “where” spatial character. However, women's errors remained leftward biased, and did not significantly change with age. “Where” spatial systems may be linked to cortico-cortical processing networks involving the posterior part of the dorsal visuospatial processing stream. Thus, the current results are consistent with the conclusion that reduced right dorsal spatial activity in aging may occur in the male, but not female, adult spatial system development. (JINS, 2011, 17, 455–462)

A space-based dissociation has been observed in clinical hemineglect, wherein neglect can be specific to either peripersonal or extrapersonal space. This same dissociation might occur in pseudoneglect, where both space-based and visual field differences have been observed. Upper and bottom visual field differences were examined within-subjects (N = 39), by presenting the greyscales task in both peripersonal and extrapersonal space. The leftward bias was strongest in the bottom visual field; however, no space-based differences were observed. It appears that perceptual biases differ between the upper and bottom visual fields, but this is not related to space-based perceptual biases. (JINS, 2010, 16, 210–214.)

Neurologically normal people tend to collide with objects on the right side more frequently than with objects located on the left side of space. This phenomenon could be attributable to pseudoneglect wherein individuals selectively attend to the left field. The current study investigated this effect using a virtual route-following task that was presented centrally, in the lower field, and in the upper field. Handedness was also examined. Fifty-two participants (four left handed) completed this task, and when presented in the lower field, more left-side collisions emerged. In the upper condition, this bias reversed direction to the expected rightward bias. In the central condition, there was no significant directional bias in collision behavior. An interaction between handedness and presentation condition indicated that left-handed participants experienced more right-side collisions in the central condition. Collectively, these results suggest that directional biases (i.e., left vs. right) in collision behavior are modulated by both location in the visual field (central, upper, or lower) and handedness. (JINS, 2009, 15, 225–230.)

The spatial allocation of attention influences estimates of stimulus magnitude, including line length and the line bisection task has been used to assess the asymmetrical allocation of spatial attention. The purpose of this study is to learn if normal subjects' allocation of attention changes as a function of the trunk–head centered spatial position of the line stimuli. Normal subjects were asked to bisect lines placed in five different head–trunk centered special positions (central, right up–distal, left up–distal, right down–proximal, left down–proximal). When compared with the central condition, deviations in the right or left lateral conditions were only significant in the down–proximal conditions, such that the bisection bias significantly shifted direction to the left of the objective midline in left hemispace and to the right of the objective midline in right hemispace, suggesting that stimuli presented in lateral hemispace primarily activate the contralateral hemisphere's attentional systems. The finding that the lines presented in down–proximal lateral hemispace induce a greater spatial bias than lines in up–distal lateral space suggests that the portion of the brain's dorsal visual system, which processes stimuli in down–proximal space, influences the horizontal (right–left) spatial allocation of attention more than does the brain's ventral visual system. (JINS, 2006, 12, 532–537.)

Psychophysical functions are used to characterize both normal perception and altered perception among patients with neglect, yet the reliability of these functions is rarely examined. The present study examined two-week, test-retest reliability for power functions derived from line bisection data among 58 normal, young and old, male and female subjects. Power function exponents and constants were, at best, moderately reliable over time. The size of the exponent tended to decrease at retesting. Reliability coefficients varied by age and gender; they were highly significant for young men, marginally significant for older men, and non-significant for women. Race influenced reliability as coefficients were significant for Caucasian subjects but not for African American subjects. Age and gender effects in this study parallel those in the literature on pseudoneglect, and they may reflect hemispheric differences in visuo-spatial processing, magnitude estimation, or both. (JINS, 2003, 9, 72–78.)

Various factors influence the degree of leftward error (pseudoneglect) that typifies the performance of normal individuals in line bisection tasks. This experiment reveals that the eye through which stimuli are viewed also exerts a modulating influence on spatial attention, as indexed by significant alterations in the magnitude of pseudoneglect. Using a forced-choice tachistoscopic line bisection protocol, 24 participants (12 male; 12 female) bisected horizontally oriented lines (22.6° w × 0.39° h) presented to central vision in 3 conditions: left uniocular viewing (L), right uniocular viewing (R), and binocular viewing (B). Perceived line midpoint, a measure of bisection accuracy, deviated significantly leftward of veridical ( p < .05) in all viewing conditions, confirming a tonic asymmetry of visuospatial attention in normal young observers. In addition, a significant influence of viewing condition was found (p < .05) where pseudoneglect was greatest in the L condition, followed by the B and R conditions, respectively. Analysis of the slopes of the psychometric functions revealed significantly greater bisection precision in the binocular versus uniocular viewing conditions (p < .05). The results are interpreted to suggest that phasic effects on spatial attention can be produced by uniocular viewing via asymmetric retinotectal projections. The results are consistent with activation–orientation theories of attentional asymmetry. (JINS, 2001, 7, 391–395.)