Landmark Task Research Articles

The influence of baseline directional differences in pseudoneglect on distractibility

Neurologically normal individuals demonstrate a reliable bias to the left side of space, known as pseudoneglect. The magnitude of this attentional asymmetry varies, depending on factors such as location within the visual field. Prior research has shown that the presence of distractors in the upper visual field increase leftward biases. The current study investigated whether brief distractors in the periphery, which recruit exogenous attention influence the strength of pseudoneglect. In addition, to further investigate the interaction of vertical and horizontal attentional asymmetries, a vertical landmark task with horizontally presented distractors was also performed. Experiment 1 findings illustrated that single visual field distractors led to stronger leftward biases, when compared to dual visual field distractors. Results also indicated that upward biases for vertical lines were unchanged by horizontal distractors. A baseline landmark task was included in Experiment 2 to allow for participants to be separated into left- and right-responder groups. Results showed that upper space distractors increased the magnitude of asymmetries scores depending on the baseline direction. Left-responders showed increased leftward biases and right-responders showed increased rightward biases when distractors were presented in upper space. As in Experiment 1, horizontal distractors did not influence upward biases. Furthermore, horizontal and vertical asymmetries were not correlated in either experiment. The current results demonstrate a novel influence of distractors on individual differences in pseudoneglect, which is consistent with the suggestion that a subset of individuals show reliable rightward biases. This highlights the importance of accounting for baseline attentional asymmetries.

Evoking visual neglect-like deficits in healthy volunteers - an investigation by repetitive navigated transcranial magnetic stimulation.

In clinical practice, repetitive navigated transcranial magnetic stimulation (rTMS) is of particular interest for non-invasive mapping of cortical language areas. Yet, rTMS studies try to detect further cortical functions. Damage to the underlying network of visuospatial attention function can result in visual neglect-a severe neurological deficit and influencing factor for a significantly reduced functional outcome. This investigation aims to evaluate the use of rTMS for evoking visual neglect in healthy volunteers and the potential of specifically locating cortical areas that can be assigned for the function of visuospatial attention. Ten healthy, right-handed subjects underwent rTMS visual neglect mapping. Repetitive trains of 5Hz and 10 pulses were applied to 52 pre-defined cortical spots on each hemisphere; each cortical spot was stimulated 10 times. Visuospatial attention was tested time-locked to rTMS pulses by a landmark task. Task pictures were displayed tachistoscopically for 50ms. The subjects' performance was analyzed by video, and errors were referenced to cortical spots. We observed visual neglect-like deficits during the stimulation of both hemispheres. Errors were categorized into leftward, rightward, and no response errors. Rightward errors occurred significantly more often during stimulation of the right hemisphere than during stimulation of the left hemisphere (mean rightward error rate (ER) 1.6±1.3% vs. 1.0±1.0%, p=0.0141). Within the left hemisphere, we observed predominantly leftward errors rather than rightward errors (mean leftward ER 2.0±1.3% vs. rightward ER 1.0±1.0%; p=0.0005). Visual neglect can be elicited non-invasively by rTMS, and cortical areas eloquent for visuospatial attention can be detected. Yet, the correlation of this approach with clinical findings has to be shown in upcoming steps.

Morningness/eveningness and the synchrony effect for spatial attention

There is evidence that a decrease in alertness is associated with a rightward shift of attention. Alertness fluctuates throughout the day and peak times differ between individuals. Some individuals feel most alert in the morning; others in the evening. Our aim was to investigate the influence of morningness/eveningness and time of testing on spatial attention. It was predicted that attention would shift rightwards when individuals were tested at their non-optimal time as compared to tests at peak times. A crowdsourcing internet marketplace, Amazon Mechanical Turk (AMT) was used to collect data. Given questions surrounding the quality of data drawn from such virtual environments, this study also investigated the sensitivity of data to demonstrate known effects from the literature. Five-hundred and thirty right-handed participants took part between 6 am and 11 pm. Participants answered demographic questions, completed a question from the Horne and Östberg Morningness/Eveningness Scale, and performed a spatial attentional task (landmark task). For the landmark task, participants indicated whether the left or right segment of each of 72 pre-bisected lines was longer (longer side counterbalanced). Response bias was calculated by subtracting the ‘number of left responses’ from the ‘number of right responses’, and dividing by the number of trials. Negative values indicate a leftward attentional bias, and positive values a rightward bias. Well-supported relationships between variables were reflected in the dataset. Controlling for age, there was a significant interaction between morningness/eveningness and time of testing (morning=6 am–2.30 pm, evening=2.30 pm–11 pm) (p<0.05) such that there was a relative rightward shift of attention from peak to off-peak times of testing for those identifying as morning types, but not evening types. Findings support the utility of crowdsourcing internet marketplaces as data collection vehicles for research. Results also suggest that the deployment of spatial attention is modulated by an individual's peak time (morningness/eveningness) and time of testing.

The head direction cell system and behavior: The effects of lesions to the lateral mammillary bodies on spatial memory in a novel landmark task and in the water maze.

The head direction system is composed of neurons found in a number of connected brain areas that fire in a sharply tuned, directional way. The function of this system, however, has not been fully established. To assess this, we devised a novel spatial landmark task, comparable to the paradigms in which stimulus control has been assessed for spatially tuned neurons. The task took place in a large cylinder and required rats to dig in a specific sand cup, from among 16 alternatives, to obtain a food reward. The reinforced cup was in a fixed location relative to a salient landmark, and probe sessions confirmed that the landmark exerted stimulus control over the rats’ cup choices. To assess the contribution of the head direction cell system to this memory task, half of the animals received ibotenic acid infusions into the lateral mammillary nuclei (LMN), an essential node in the head direction network, while the other received sham lesions. No differences were observed in performance of this task between the 2 groups. Animals with LMN lesions were impaired, however, in reversal learning on a water maze task. These results suggest that the LMN, and potentially the head direction cell system, are not essential for the use of visual landmarks to guide spatial behavior.

End of the line: Line bisection, an unreliable measure of approach and avoidance motivation

Approach motivation leads to greater left hemisphere activation, whereas an avoidant motivational state activates the right hemisphere. Recent research, which served as the basis for the current experiment, suggests line bisection provides a simple measure of approach/avoidance lateralisation. Findings from Experiment 1 indicated that the landmark task was sensitive enough to identify lateral asymmetries evoked by happy and angry faces; however, follow-up experiments failed to replicate this finding. When task instructions were slightly modified or when a mixed design was used, motivation did not influence landmark task performance. The use of images in lieu of faces also failed to produce a significant effect. Importantly, a straight replication of Experiment 1 produced a null result. Line bisection does not appear to be a suitable measure of lateralised approach/avoidance biases, possibly due to the high individual variability inherent in visuospatial biases. Implications for null hypothesis significance testing are also discussed.

Right hemisphere control of visuospatial attention in near space

Traditionally, the right cerebral hemisphere has been considered to be specialized for spatial attention and orienting. A large body of research has demonstrated dissociable representations of the near space immediately surrounding the body and the more distance far space. In this study, we investigated whether right hemisphere activations commonly reported for tasks involving spatial attention (such as the line bisection and landmark tasks) are specific to stimuli presented in near space. In separate blocks of trials, participants judged either whether a vertical transector was to the left or right of the centre of a line (landmark task) or whether the line was red or blue (colour task). Stimuli were seen from four distances (30, 60, 90, 120cm). We used EEG to measure an ERP component (the ‘line-bisection effect’) specific to the direction of spatial attention (i.e., landmark minus colour). Consistent with previous results, spatial attention produced a right-lateralized negativity over occipito-parietal channels. The magnitude of this negativity was inversely related to viewing distance, being largest in near space and reduced in far space. These results suggest that the right occipito-temporal cortex may be specialized not just for the orientation of spatial attention generally, but specifically for orienting attention in the near space immediately surrounding the body.

Hunting for right and left parietal hot spots using single-pulse TMS: modulation of visuospatial perception during line bisection judgment in the healthy brain.

A series of studies have consistently reproduced left neglect-like bias on line length estimation tasks in healthy participants by applying transcranial magnetic stimulation (TMS) over the right posterior parietal cortex (PPC), while no significant changes have been reported when stimulating the left PPC. However, a notable inter-individual variability in the right parietal site where TMS modulates visuospatial perception can be observed, and no general agreement exists on how to identify the optimal parietal site of stimulation. In the present study, we propose a new site-finding TMS protocol to easily identify the optimum parietal location, or “hot spot,” where TMS may modulate visuospatial perception on a line length estimation task (the Landmark task). Single-pulse TMS at 115% of motor threshold was applied 150 ms after the visual stimulus onset over nine different sites of a 3 cm × 3 cm grid, centred over right or left PPC (P4 and P3 according to the 10–20 EEG system, respectively) in eight healthy participants. Stimulation of right PPC induced a significant left neglect-like bias, when the coil was applied over the most posterior and dorso-posterior sites. Unexpectedly, TMS over left PPC also produced left neglect-like bias. However, in this case significant effects were found when targeting the most anterior and dorso-anterior portions of the grid. These results are discussed in relation to recent findings on neural networks underlying spatial cognition. The hunting protocol we propose might offer an economical and easy-to-use tool to functionally identify the optimal parietal site where TMS can modulate visuospatial perception, in healthy subjects and possibly in post-stroke patients undergoing repetitive transcranial magnetic stimulation treatment.

A rightward shift in the visuospatial attention vector with healthy aging.

The study of lateralized visuospatial attention bias in non-clinical samples has revealed a systematic group-level leftward bias (pseudoneglect), possibly as a consequence of right hemisphere (RH) dominance for visuospatial attention. Pseudoneglect appears to be modulated by age, with a reduced or even reversed bias typically present in elderly participants. It has been suggested that this shift in bias may arise due to disproportionate aging of the RH and/or an increase in complementary functional recruitment of the left hemisphere (LH) for visuospatial processing. In this study, we report rightward shifts in subjective midpoint judgment relative to healthy young participants whilst elderly participants performed a computerized version of the landmark task (in which they had to judge whether a transection mark appeared closer to the right or left end of a line) on three different line lengths. This manipulation of stimulus properties led to a similar behavioral pattern in both the young and the elderly: a rightward shift in subjective midpoint with decreasing line length, which even resulted in a systematic rightward bias in elderly participants for the shortest line length (1.98° of visual angle, VA). Overall performance precision for the task was lower in the elderly participants regardless of line length, suggesting reduced landmark task discrimination sensitivity with healthy aging. This rightward shift in the attentional vector with healthy aging is likely to result from a reduction in RH resources/dominance for attentional processing in elderly participants. The significant rightward bias in the elderly for short lines may even suggest a reversal of hemisphere dominance in favor of the LH/right visual field under specific conditions.

Landmarks in Hybrid Planning

Although planning techniques achieved a significant progress during recent years, solving many planning problem still difficult even for modern planners. In this paper, we will adopt landmark concept to hybrid planning setting - a method that combines reasoning about procedural knowledge and causalities. Landmarks are a well-known concept in the realm of classical planning. Recently, they have been adapted to hierarchical approaches. Such landmarks can be extracted in a pre-processing step from a declarative hierarchical planning domain and problem description. It was shown how this technique allows for a considerable reduction of the search space by eliminating futile plan development options before the actual planning. Therefore, we will present a new approach to integrate landmark pre-processing technique in the context of hierarchical planning with landmark technique in the classical planning. This integration allows to incorporate the ability of using extracted landmark tasks from hierarchical domain knowledge in the form of HTN and using landmark literals from classical planning. To this end, we will construct a transformation technique to transform the hybrid planning domain into a classical domain model. The methodologies in this paper have been implemented successfully, and we will present some experimental results that give evidence for the consid- erable performance increase gained through planning system.

Spatial attention: Differential shifts in pseudoneglect direction with time-on-task and initial bias support the idea of observer subtypes

Asymmetry in human spatial attention has long been documented. In the general population the majority of individuals tend to misbisect horizontal lines to the left of veridical centre. Nonetheless in virtually all previously reported studies on healthy participants, there have been subsets of people displaying rightward biases.In this study, we report differential time-on task effects depending on participants' initial pseudoneglect bias: participants with an initial left bias in a landmark task (in which they had to judge whether a transection mark appeared closer to the right or left end of a line) showed a significant rightward shift over the course of the experimental session, whereas participants with an initial right bias shifted leftwards.We argue that these differences in initial biases as well as the differential shifts with time-on task reflect genuine observer subtypes displaying diverging behavioural patterns. These observer subtypes could be driven by differences in brain organisation and/or lateralisation such as varying anatomical pathway asymmetries (Thiebaut de Schotten et al., 2011).

Use of a non-navigational, non-verbal landmark task in children

Two hundred and twenty two children (104 females), 1–8 years of age and young adults, were tested for up to 25 days on five versions of a non-verbal, non-navigational landmark task that had previously been used for monkeys. In monkeys, performance on this task is severely impaired following damage to the parietal cortex. For the basic task, the positive of two identical stimuli concealed a food reward and was designated by spatial proximity of a salient landmark. None of the 1- and 2-year-old children learned the task, i.e., they failed to consistently reach for and displace the positive stimulus in 25 test days. Of the 3-, 4-, and 5- year-old groups, 56%, 70%, and 77% of the children, respectively, mastered the task within 25 days. Children older than 5 and adults rapidly mastered the task. In Experiment #2, all subjects, 1–6 years of age, rapidly mastered a non-relational task when the choice stimulus was attached to the landmark, but the youngest children failed to transfer performance when the landmark was subsequently detached. Children under the age of 5 did not tolerate relational ambiguity as well as adults did. Replications of the first two experiments produced virtually identical results and indicated that the tests have a high degree of reliability. In Experiment #5, there were two distinct proximal landmarks, one of which always designated the positive stimulus. This manipulation did not improve performance of younger children. As compared to results from navigational landmark tasks, results obtained in the Wisconsin General Testing Apparatus (WGTA) indicate a very narrow focus of attention on the response site. Thus, small separations between discriminative cue and response site significantly affect performance, especially in younger children. By comparing the present results with those from monkeys, we speculate that components of the parietal pathways involved with attention and reaching mature between 1 and 5 years of age in children.

The Predictive Nature of Pseudoneglect for Visual Neglect: Evidence from Parietal Theta Burst Stimulation

Following parietal damage most patients with visual neglect bisect horizontal lines significantly away from the true centre. Neurologically intact individuals also misbisect lines; a phenomenon referred to as ‘pseudoneglect’. In this study we examined the relationship between neglect and pseudoneglect by testing how patterns of pre-existing visuospatial asymmetry predict asymmetry caused by parietal interference. Twenty-four participants completed line bisection and Landmark tasks before receiving continuous theta burst stimulation to the left or right angular gyrus. Results showed that a pre-existing pattern of left pseudoneglect (i.e. right bias), but not right pseudoneglect, predicts left neglect-like behaviour during line bisection following right parietal cTBS. This correlation is consistent with the view that neglect and pseudoneglect arise via a common or linked neural mechanism.

A test-retest fMRI dataset for motor, language and spatial attention functions

BackgroundSince its inception over twenty years ago, functional magnetic resonance imaging (fMRI) has been used in numerous studies probing neural underpinnings of human cognition. However, the between session variance of many tasks used in fMRI remains understudied. Such information is especially important in context of clinical applications. A test-retest dataset was acquired to validate fMRI tasks used in pre-surgical planning. In particular, five task-related fMRI time series (finger, foot and lip movement, overt verb generation, covert verb generation, overt word repetition, and landmark tasks) were used to investigate which protocols gave reliable single-subject results. Ten healthy participants in their fifties were scanned twice using an identical protocol 2–3 days apart. In addition to the fMRI sessions, high-angular resolution diffusion tensor MRI (DTI), and high-resolution 3D T1-weighted volume scans were acquired.FindingsReliability analyses of fMRI data showed that the motor and language tasks were reliable at the subject level while the landmark task was not, despite all paradigms showing expected activations at the group level. In addition, differences in reliability were found to be mostly related to the tasks themselves while task-by-motion interaction was the major confounding factor.ConclusionsTogether, this dataset provides a unique opportunity to investigate the reliability of different fMRI tasks, as well as methods and algorithms used to analyze, de-noise and combine fMRI, DTI and structural T1-weighted volume data.

Shifting Attentional Priorities: Control of Spatial Attention through Hemispheric Competition

Regions of frontal and posterior parietal cortex are known to control the allocation of spatial attention across the visual field. However, the neural mechanisms underlying attentional control in the intact human brain remain unclear, with some studies supporting a hemispatial theory emphasizing a dominant function of the right hemisphere and others supporting an interhemispheric competition theory. We previously found neural evidence to support the latter account, in which topographically organized frontoparietal areas each generate a spatial bias, or "attentional weight," toward the contralateral hemifield, with the sum of the weights constituting the overall bias that can be exerted across visual space. Here, we used a multimodal approach consisting of functional magnetic resonance imaging (fMRI) of spatial attention signals, behavioral measures of spatial bias, and fMRI-guided single-pulse transcranial magnetic stimulation (TMS) to causally test this interhemispheric competition account. Across the group of fMRI subjects, we found substantial individual differences in the strengths of the frontoparietal attentional weights in each hemisphere, which predicted subjects' respective behavioral preferences when allocating spatial attention, as measured by a landmark task. Using TMS to interfere with attentional processing within specific topographic frontoparietal areas, we then demonstrated that the attentional weights of individual subjects, and thus their spatial attention behavior, could be predictably shifted toward one visual field or the other, depending on the site of interference. The results of our multimodal approach, combined with an emphasis on neural and behavioral individual differences, provide compelling evidence that spatial attention is controlled through competitive interactions between hemispheres rather than a dominant right hemisphere in the intact human brain.

Prism adaptation theory in unilateral neglect: motor and perceptual components

Prism adaptation theory in unilateral neglect: motor and perceptual components

The Influence of Prism Adaptation on Perceptual and Motor Components of Neglect: A Reply to Saevarsson and Kristjansson

The Influence of Prism Adaptation on Perceptual and Motor Components of Neglect: A Reply to Saevarsson and Kristjansson

Enhanced lateralization in expert musicians: an fMRI investigation of visuospatial processing

Event Abstract Back to Event Enhanced lateralization in expert musicians: an fMRI investigation of visuospatial processing Laura Ewens1*, Lynette J. Tippett1 and Donna R. Addis1 1 The University of Auckland, New Zealand Background: Expert musicians are regarded as an excellent model of neuroplasticity due to their early and intensive musical training. Cross-sectional research consistently identifies behavioural and neural differences between musicians and non-musicians, across a range of cognitive domains and brain regions. Previous behavioural and electrophysiological research has indicated musicians have an enhanced ability to direct visual attention to both sides of space, however to date this has not been explored with functional magnetic resonance imaging (fMRI). This study sought to identify differences in the lateralization of activation during two visuospatial attention tasks, with musicians expected to have more bilateral, and non-musicians more right-sided activation. Method: Visuospatial processing and its neural correlates were assessed in 14 adult musicians and 13 non-musicians using fMRI. Two tests of visuospatial processing were employed: the Landmark task (a variant of a line bisection task) and a visual search task. Laterality index (LI) scores were calculated to assess lateralization in parietal and occipital ROIs. Results: Preliminary behavioural data suggests that musicians were more accurate in the two tasks. The LI scores indicate that, contrary to predictions, musicians appeared to be more strongly right-lateralised than non-musicians on the Landmark task. On the Visual Search task, LI scores in both groups indicated bilateral activation with no significant group difference. Discussion: Musicians were more accurate than non-musicians with comparable reaction times. This is in line with previous research indicating enhanced visuospatial processing in musically trained individuals. Against predictions, musicians were more right-lateralised on the Landmark task. This suggests that previous behavioural research finding more symmetric visual attention in musicians is a result of enhanced processing in right-hemispheric visuospatial regions. Keywords: visuospatial processing, visuospatial attention, musicians, fMRI, plasticity Conference: ACNS-2013 Australasian Cognitive Neuroscience Society Conference, Clayton, Melbourne, Australia, 28 Nov - 1 Dec, 2013. Presentation Type: Poster Topic: Sensation and Perception Citation: Ewens L, Tippett LJ and Addis DR (2013). Enhanced lateralization in expert musicians: an fMRI investigation of visuospatial processing. Conference Abstract: ACNS-2013 Australasian Cognitive Neuroscience Society Conference. doi: 10.3389/conf.fnhum.2013.212.00140 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 17 Sep 2013; Published Online: 25 Nov 2013. * Correspondence: Miss. Laura Ewens, The University of Auckland, Auckland, New Zealand, lauraewens@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Laura Ewens Lynette J Tippett Donna R Addis Google Laura Ewens Lynette J Tippett Donna R Addis Google Scholar Laura Ewens Lynette J Tippett Donna R Addis PubMed Laura Ewens Lynette J Tippett Donna R Addis Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Spatial and non-spatial aspects of neglect

Spatial and non-spatial aspects of neglect

Task- and response related dissociations between neglect in near and far space: a morphometric case study.

Introduction: Patients with unilateral neglect may show line bisection errors selectively in either near (within hand reaching) or far (beyond hand reaching) space which suggests that these two spatial areas are coded differently by the brain. This exploratory study investigated, whether any difference in performance between these spatial domains might be task-independent or modulated by the requirement for a motor response.Methods: A 31-year-old right brain damaged patient (MF) and a group of age matched healthy controls were assessed with two serial visual search tasks and a Landmark paradigm. Both types of task required either a directional (pointing) or non-directional (button press) motor response. Participants were assessed with both task types and response modes in near (57 cm) and far space (114 cm).Results: MF showed left neglect during visual search only in far space for the perceptual condition and in near space for the motor condition. MF showed no neglect in both versions of the Landmark task irrespective of spatial distance. A voxel-based morphometric assessment of MF's brain lesion showed marked damage in the right ventro-temporal cortex, superior temporal gyrus, insula, inferior frontal gyrus, angular gyrus and bilaterally in the posterior cingulate cortex.Conclusions: Our preliminary findings suggest that processing of far space during visual search is associated with ventral stream damage but only when space is coded through visual information. Neglect involving directional motor activity in near space seems to be associated with damage of structures sharing close connections with the dorsal stream.

Task- and Response Related Dissociations between Neglect in Near and Far Space: A Morphometric Case Study

Introduction: Patients with unilateral neglect may show line bisection errors selectively in either near (within hand reaching) or far (beyond hand reaching) space which suggests that these two spatial areas are coded differently by the brain. This exploratory study investigated, whether any difference in performance between these spatial domains might be task-independent or modulated by the requirement for a motor response.Methods: A 31-year-old right brain damaged patient (MF) and a group of age matched healthy controls were assessed with two serial visual search tasks and a Landmark paradigm. Both types of task required either a directional (pointing) or non-directional (button press) motor response. Participants were assessed with both task types and response modes in near (57 cm) and far space (114 cm).Results: MF showed left neglect during visual search only in far space for the perceptual condition and in near space for the motor condition. MF showed no neglect in both versions of the Landmark task irrespective of spatial distance. A voxel-based morphometric assessment of MF's brain lesion showed marked damage in the right ventro-temporal cortex, superior temporal gyrus, insula, inferior frontal gyrus, angular gyrus and bilaterally in the posterior cingulate cortex.Conclusions: Our preliminary findings suggest that processing of far space during visual search is associated with ventral stream damage but only when space is coded through visual information. Neglect involving directional motor activity in near space seems to be associated with damage of structures sharing close connections with the dorsal stream.