Modulation of the Directional Attention Deficit in Visual Neglect by Hemispatial Factors

Using a visuo-spatial cuing paradigm, Posner and collaborators (Posner, Cohen, & Rafal, 1982; Posner, Walker, Friedrich, & Rafal, 1984) reported that subjects with a parietal lobe lesion have difficulty in disengaging their visual attention from an invalidly precued location in the ipsilesional hemifield when the target they have to respond to is presented in the contralesional field. Later, these authors (Posner, Walker, Friedrich, & Rafal, 1987) proposed that this disengagement deficit is one involving spatial shifts of attention in a contralesional direction, irrespective of the visual hemifield in which the target is presented. This proposal of a directional disengagement deficit along the horizontal axis, present in either hemifield, contrasts with a report by Baynes, Holtzman, & Volpe (1986) showing, in right parietal subjects, a disengagement deficit for shifts of attention along the vertical axis that is only manifest in the contralesional hemifield. In the present report, we assessed the disengagement deficit of a neglect subject along the horizontal and vertical axes. Results show a disengagement deficit restricted to shifts of attention in the contralesional direction (horizontal axis), which is significant only in the contralesional visual hemifield. However, there is a clear trend for a directional disengagement deficit in the ipsilateral field. These observations indicate that the attention deficit present in neglect is directional and is modulated either by hemispatial factors or by the lateral target location in the visual field. On the basis of the present results, it is proposed that the deficit of parietal subjects may best be conceptualized as one of attentional capture for stimuli located on the contralesional side of the current focus of attention rather than one of disengagement.     

Response Channel Activation and the Temporoparietal Junction

When we learn to make one motor response to one visual stimulus and a different motor response to another, representations of these stimulus–response associations must be maintained to efficiently transduce perception into action. When an irrelevant distractor is presented adjacent to a target stimulus, interference is observed when the two stimuli are associated with conflicting responses, presumably due to response channel activation by the incompatible information. We have explored the neural bases of these interference effects. In a previous study, patients with hemispatial neglect showed normal interference from contralesional flankers. In another study, patients with lesions of the lateral prefrontal cortex were found not to show interference from distractors presented in the contralesional hemifield. The current study provided a more anatomically detailed investigation of the effects of posterior association cortex lesions on flanker interference. Patients with chronic, unilateral lesions involving the temporoparietal junction (TPJ), two of whom had hemispatial neglect, were compared with patients with lesions of the posterior association cortex not involving the TPJ. All patients performed a color discrimination task at fixation while a congruent or incongruent colored flanker was briefly presented (16.7 ms) in the adjacent contralesional or ipsilesional hemifield. Patients with TPJ lesions showed no interference effects from the contralesional flankers. These results suggest that the TPJ, in combination with the dorsolateral prefrontal cortex, is involved in transducing perception into action.     

The imbalance of oculomotor capture in unilateral visual neglect

Visual neglect has been associated with an imbalance in the level of activity in the saccadic system: activity in the contralesional field is suppressed, which makes target selection unlikely. We recorded eye movements of a patient with hemispatial neglect and a group of healthy participants during an oculomotor distractor paradigm. Results showed that the interfering effects of a distractor were very strong when presented in her ipsilesional visual field. However, when the distractor was presented in her contralesional field, there were no interfering effects when the target was presented in her ipsilesional field. These findings could not be explained by the presence of a visual field defect as revealed by the results of two hemianopic patients. Our results are in line with an imbalance in the level of activity in the saccadic system in visual neglect because visual elements presented in the contralesional field did not compete for saccadic selection.     

Asynchronous stimulus presentation in visual extinction: A psychophysical study

Patients showing visual extinction as a consequence of a unilateral brain lesion can correctly detect a single stimulus in either hemifield but fail to detect the contralesional stimulus (or at least process the stimulus less efficiently) when it is presented simultaneously with an ipsilesional stimulus. In an attempt to uncover the nature of the underlying deficit, some studies have manipulated the temporal characteristics of stimulus presentation. Contra- and ipsilesional stimuli with different stimulus onset asynchronies are typically used. In the present study, visual extinction was investigated in a group of left neglect patients (N=10) using a psychophysical paradigm with different stimulus onset asynchronies of target and distractor stimuli presented in different hemifields. Contrast thresholds for a target grating were determined with the target either in isolation or in the presence of an irrelevant distractor grating. When target and distractor gratings were presented simultaneously, neglect patients showed a significant extinction effect, i.e., a significant interference from the right hemifield distractor with left hemifield contrast sensitivity. When the right hemifield distractor preceded the left hemifield target stimulus by 250 ms, two different patterns of results were observed in the neglect patients. Five patients showed a significant improvement compared to the simultaneous presentation condition, five other patients showed a significant increase of the extinction effect. The results suggest that different underlying mechanisms, maybe due to different lesion locations, can cause extinction in neglect patients.     

Probability cuing of target location facilitates visual search implicitly in normal participants and patients with hemispatial neglect

We explored how variability in the probability of target locations affects visual search in normal individuals and in patients with hemispatial neglect, a deficit in attending to the contralesional side of space. Young and elderly normal participants responded faster when targets appeared in the more probable region than when targets appeared in the less probable region. Similarly, patients were sensitive to the distribution of targets, even in the neglected field. Although the attentional gradient that characterizes neglect was not eliminated, the response facilitation due to the probability distribution was proportionate to that of control participants and equal in magnitude across the neglected field. All participants exploited the uneven distribution of targets to enhance task performance without explicit instructions to do so or awareness of biases in their behavior. These results suggest that attentional orientation and sensitivity to external probabilities are possibly dissociable. An early sensory and a late motor mechanism are postulated as possibly being involved in the observed probability–matching behavior of participants.     

Neurocognitive,physiological, and biophysical effects of transcranial alternating current stimulation

Transcranial alternating current stimulation (tACS) can modulate human neural activity and behavior. Accordingly, tACS has vast potential for cognitive research and brain disorder therapies. The stimulation generates oscillating electric fields in the brain that can bias neural spike timing, causing changes in local neural oscillatory power and cross-frequency and cross-area coherence. tACS affects cognitive performance by modulating underlying single or nested brain rhythms, local or distal synchronization, and metabolic activity. Clinically, stimulation tailored to abnormal neural oscillations shows promising results in alleviating psychiatric and neurological symptoms. We summarize the findings of tACS mechanisms, its use for cognitive applications, and novel developments for personalized stimulation.     

Right visual field advantage for perceived contrast: Correlation with an auditory bias and handedness

Studies have suggested that supramodal attentional resources are biased rightward due to asymmetric spatial fields of the two hemispheres. This bias has been observed especially in right-handed subjects. We presented left and right-handed subjects with brief uniform grey visual stimuli in either the left or right visual hemifield. Consistent with the proposed asymmetry in attentional resources, right-handed subjects estimated right hemifield targets as having a higher contrast than physically identical stimuli presented in the left hemifield. Left-handed participants did not show a systematic rightward or leftward bias. However, the group of left-handed participants also took part in a dichotic listening experiment whose results showed that visual bias score correlated positively with ear-advantage in dichotic listening. Our results are consistent with the view that supramodal processing resources are biased towards the right hemispace, and that this bias is influenced by handedness.     

Right visual field advantage for perceived contrast: correlation with an auditory bias and handedness

Studies have suggested that supramodal attentional resources are biased rightward due to asymmetric spatial fields of the two hemispheres. This bias has been observed especially in right-handed subjects. We presented left and right-handed subjects with brief uniform grey visual stimuli in either the left or right visual hemifield. Consistent with the proposed asymmetry in attentional resources, right-handed subjects estimated right hemifield targets as having a higher contrast than physically identical stimuli presented in the left hemifield. Left-handed participants did not show a systematic rightward or leftward bias. However, the group of left-handed participants also took part in a dichotic listening experiment whose results showed that visual bias score correlated positively with ear-advantage in dichotic listening. Our results are consistent with the view that supramodal processing resources are biased towards the right hemispace, and that this bias is influenced by handedness.     

Biases of spatial attention in vision and audition

Neurologically normal observers misperceive the midpoint of horizontal lines as systematically leftward of veridical center, a phenomenon known as pseudoneglect. Pseudoneglect is attributed to a tonic asymmetry of visuospatial attention favoring left hemispace. Whereas visuospatial attention is biased toward left hemispace, some evidence suggests that audiospatial attention may possess a right hemispatial bias. If spatial attention is supramodal, then the leftward bias observed in visual line bisection should also be expressed in auditory bisection tasks. If spatial attention is modality specific then bisection errors in visual and auditory spatial judgments are potentially dissociable. Subjects performed a bisection task for spatial intervals defined by auditory stimuli, as well as a tachistoscopic visual line bisection task. Subjects showed a significant leftward bias in the visual line bisection task and a significant rightward bias in the auditory interval bisection task. Performance across both tasks was, however, significantly positively correlated. These results imply the existence of both modality specific and supramodal attentional mechanisms where visuospatial attention has a prepotent leftward vector and audiospatial attention has a prepotent rightward vector of attention. In addition, the biases of both visuospatial and audiospatial attention are correlated.     

Psychological,endocrine, and neural correlates of attentional bias in subclinical depression

Background: Our knowledge with respect to psychological, endocrine, and neural correlates of attentional bias in individuals with high vulnerability to developing depression – the subclinically depressed, still remains limited. Design: The study used a 2?×?2 mixed design. Methods: Attentional bias toward happy and sad faces in healthy (N?=?26) and subclinically depressed individuals (N?=?22) was assessed via a neuroimaging dot-probe attention task. Participants also completed trait and state psychological measures and provided saliva samples for cortisol analysis. Results: The subclinical group showed attentional bias toward happy faces; past use of problem-focused coping strategies when dealing with a personally relevant stressor as well as state levels of anxiety, together, contributed to this bias. In the control group, the happy attentional bias was positively correlated with activity in the right caudate. In the subclinical group, the bias was negatively associated with the left fusiform gyrus and positively with the left inferior parietal lobule and bilateral putamen. We observed group differences in association between cortisol levels during the task and neural activity during happy attentional bias processing within the key regions involved in attention. Conclusions: The attentional bias toward happy faces may reflect an active coping attempt by the subclinical participants.     

Auditory and multisensory aspects of visuospatial neglect

Spatial neglect is a common neurological syndrome in which awareness of contralesional space is disrupted after unilateral (typically right) stroke. Although most research has focused on visual aspects of neglect, there is increasing evidence that neglect can often be multisensory. Here we focus on auditory disturbances that can co-occur with visual neglect. Patients selected for showing visual neglect often also show deficits in localization of single sounds; and also in the detection or identification of contralesional sounds, particularly in the presence of an ipsilesional competitor. Moreover, auditory and visual aspects of neglect often correlate in their severity across patients. These results are considered in relation to recent neuroimaging findings in the normal brain, showing that the brain regions typically damaged in neglect patients might contain multimodal representations of space.     

Effects of chronic exercise on attentional bias among individuals with methamphetamine use disorder

BackgroundIndividuals with substance use disorder show attentional bias toward drug-related cues, which may be associated with attentional control deficits. Although exercise improves attention in healthy people, whether individuals with substance use disorder also benefit is unknown. We explored the effects of chronic exercise on behavioral and neural correlates of attentional bias in men with methamphetamine use disorder.MethodsSixty-one such men were randomized to high- or moderate-intensity exercise or to a control group with little exercise for 12 weeks. The dot-probe task assessed attentional bias before and after exercise intervention, with event-related potentials recorded during the task to determine underlying neural mechanisms.ResultsAttentional bias scores and event-related potential amplitudes significantly decreased after high- or moderate-intensity chronic exercise, but not in controls.ConclusionsChronic exercise reduces attentional bias in individuals with methamphetamine use disorder by enhancing early identification of drug-related stimuli and diverting attention to reduce conflict processing.     

Malleability of attentional bias for positive emotional information and anxiety vulnerability

Recent research supports a causal link between attentional bias for negative emotional information and anxiety vulnerability. However, little is known about the role of positive emotional processing in modulating anxiety reactivity to stress. In the current study, we used an attentional training paradigm designed to experimentally manipulate the processing of positive emotional cues. Participants were randomly assigned to complete a computerized probe detection task designed to induce selective processing of positive stimuli or to a sham condition. Following training, participants were exposed to a laboratory stressor (i.e., videotaped speech), and state anxiety and positive affect in response to the stressor were assessed. Results revealed that individual variability in the capacity to develop an attentional bias for positive information following training predicted subsequent emotional responses to the stressor. Moreover, individual differences in social anxiety, but not depression, moderated the effects of the attentional manipulation, such that, higher levels of social anxiety were associated with diminished attentional allocation toward positive cues. The current findings point to the potential value of considering the role of positive emotional processing in anxiety vulnerability.     

Temporal order judgements as a sensitive measure of the spatial bias in patients with visuospatial neglect

Visuospatial neglect is not a unitary phenomenon, but can be better considered a syndrome, consisting of a multitude of different spatial and non‐spatial components. In this study, we used a temporal order judgement (TOJ) test in a large sample of stroke patients (n = 73) to scrutinize the contribution of a spatial bias to the performance on shape cancellation and line bisection tests. In the TOJ test, patients were presented with two elements, one in each visual field, after which the one needed to indicate which of the two elements was presented earlier. For each visual field, the presentation of the stimuli was determined by a staircase procedure where the interval between the two stimuli was determined by the performance of the patient. Results indicated that the strength of the spatial bias was strongly correlated with an object cancellation test, but not with a line bisection test. We argue that these findings are explained by differences in the extent to which a spatial bias determines performance on both tasks: In contrast to shape cancellation tests, successful performance on line bisection tests depends primarily on an object‐based, allocentric representation of space, unrelated to any spatial bias in the detection of elements in the contralesional visual field.     

Cortisol,stress, and attentional bias toward threat

Abstract

Attentional bias toward threatening stimuli is a central characteristic of anxiety and acute stress. Recent small-scale studies have provided divergent perspectives on the association between the stress hormone cortisol and attentional bias toward threat cues. In a larger sample size than previous studies, we examined this association by investigating the impact of cortisol on attentional bias in two studies using a psychological stressor (N=35) and a physical stressor (N=65), respectively. Attentional bias and salivary cortisol were measured prior to and following the administration of a stressful task designed to increase cortisol levels. Results across these studies were equivocal relative to the association between baseline cortisol and baseline attentional bias. In addition, the association between acute change in cortisol and change in attentional bias appeared to differ as a function of the presence or absence of psychological stress. There was a trend toward a stronger negative association between acute cortisol change and attentional bias change among women relative to men. These results imply that the association between cortisol and attentional bias may be moderated by additional factors, such as gender or presence of stress.     

Engagement Attentional Bias toward Value-Associated Stimuli

Recent evidence has shown that learning to associate the value of behavioral outcomes with specific stimuli (i.e., value learning/association) can induce attentional capture in a subsequent visual search task. Here we investigated the component of attentional bias toward value-associated stimuli in the dot-probe paradigm. In the training phase, participants learned to associate nonsense shape outlines with monetary wins or losses. The shapes were then used as cues in an explicit no feedback dot-probe task. Probe appeared at either the salient (congruent trial) or nonsalient location (incongruent trial). Results indicate attentional bias toward value-associated stimuli, futher more this attentional bias is driven by an engagement bias.     

Visuospatial Neglect: The Ultimate Deconstruction?

Unilateral visuospatial neglect is now widely acknowledged to be a highly heterogeneous condition: The overt manifestations of visual neglect can vary as a function of task, spatial domain, and mode of response (at least). Double dissociations (sometimes of the strong form) have already been reported between most of the components of what was originally thought to be a relatively stable construct within the visual modality. Nonetheless, throughout successive fractionations of neglect, reported cases of bidirectional task-specific neglect after unilateral brain damage are rare. We now report two such cases. After right hemisphere stroke, the first patient reliably showed severe left neglect on cancellation but right neglect on line bisection. After left hemisphere stroke, the second case showed right neglect on cancellation but left neglect on line bisection. Extensive investigation of case 1 confirmed our previous conjecture that the crucial distinction between these tasks lies in the presence or the absence of an overt target. In contrast to cancellation, line bisection demands the internal computation of the location of the “target” (the midpoint), followed by executing a motor response toward the precise location of that “imaginary” midpoint. The relative attentional and premotor contributions of the intact and damaged hemispheres to these forms of bidirectional neglect are also assessed.     

Higher attention bias for fear at 8 months of age is associated with better socioemotional competencies during toddlerhood

BackgroundIn previous studies, an attention bias for signals of fear and threat has been related to socioemotional problems, such as anxiety symptoms, and socioemotional competencies, such as altruistic behaviors in children, adolescents and adults. However, previous studies lack evidence about these relations among infants and toddlers.AimsOur aim was to study the association between the individual variance in attention bias for faces and, specifically, fearful faces during infancy and socioemotional problems and competencies during toddlerhood.Study design and subjectsThe study sample was comprised of 245 children (112 girls). We explored attentional face and fear biases at the age of 8 months using eye tracking and the face-distractor paradigm with neutral, happy and fearful faces and a scrambled-face control stimulus. Socioemotional problems and competencies were reported by parents with the Brief Infant and Toddler Social Emotional Assessment (BITSEA) when children were 24 months old.Outcome measures and resultsA higher attentional fear bias at 8 months of age was related to higher levels of socioemotional competence at 24 months of age (β = .18, p = .008), when infants’ sex and temperamental affectivity, maternal age, education and depressive symptoms were controlled. We found no significant association between attentional face or fear bias and socioemotional problems.ConclusionsWe found that the heightened attention bias for fearful faces was related to positive outcomes in early socioemotional development. Longitudinal study designs are needed to explore the changes in the relation between the attention bias for fear or threat and socioemotional development during early childhood.     

The influence of theta transcranial alternating current stimulation (tACS) on working memory storage and processing functions

The study aimed to explore the role of the fronto-parietal brain network in working memory function—in temporary storage and manipulation of information. In a single blind sham controlled experiment 36 respondents solved different working memory tasks after theta transcranial alternating current stimulation (tACS) was applied to left frontal, left parietal and right parietal areas. Both verum tACS protocols stimulating parietal brain areas (target electrodes positioned at location P3, or P4) had a positive effect on WM storage capacity as compared with sham tACS, whereas no such influence was observed for the stimulation of the left frontal area (target electrode positioned at location F3). A second finding was that left parietal theta tACS had a more pronounced influence on backward recall than on forward recall, which was not related to task content (spatial or verbal). The influence of theta tACS on WM executive processes was most pronounced for right parietal stimulation. The results are discussed in the broad theoretical framework of the multicomponent model of working memory.     

低自尊个体对拒绝性信息的注意偏向

自尊是个体对自我的情感性评价, 影响着个体对周围环境的应对方式。低自尊个体由于容易知觉到外部的拒绝性信息, 也更倾向于将别人的行为知觉为拒绝, 因而存在对拒绝性信息的注意偏向。本文首先综述了低自尊个体的认知与行为特点, 其次简单介绍了低自尊个体注意偏向的常用研究范式(Stroop范式、点探测任务、空间线索任务、惊吓探测范式、注意监测任务、注意转移任务), 随后列举了解释低自尊个体注意偏向的理论(社会计量理论、关系图式理论、注意成分说、注意控制说), 最后总结了低自尊个体注意偏向的脑机制研究。未来的研究应更多关注自尊结构的复杂性, 注意偏向的信息加工阶段性及其脑机制, 注意训练的作用机制及低自尊个体注意偏向的本土研究等问题。