Neurodisruption of selective attention: insights and implications

Mechanisms of selective attention are vital for coherent perception and action. Recent advances in cognitive neuroscience have yielded key insights into the relationship between neural mechanisms of attention and eye movements, and the role of frontal and parietal brain regions as sources of attentional control. Here we explore the growing contribution of reversible neurodisruption techniques, including transcranial magnetic stimulation and microelectrode stimulation, to the cognitive neuroscience of spatial attention. These approaches permit unique causal inferences concerning the relationship between neural processes and behaviour, and have revealed fundamental mechanisms of attention in the human and animal brain. We conclude by suggesting that further advances in the neuroscience of attention will be facilitated by the combination of neurodisruption techniques with established neuroimaging methods.     

Consciousness: converging insights from connectionist modeling and neuroscience

Over the past decade, many findings in cognitive neuroscience have resulted in the view that selective attention, working memory and cognitive control involve competition between widely distributed representations. This competition is biased by top-down projections (notably from prefrontal cortex), which can selectively enhance some representations over others. This view has now been implemented in several connectionist models. In this review, we emphasize the relevance of these models to understanding consciousness. Interestingly, the models we review have striking similarities to others directly aimed at implementing 'global workspace theory'. All of these models embody a fundamental principle that has been used in many connectionist models over the past twenty years: global constraint satisfaction.     

The development of perceived structure and attention: evidence from divided and selective attention tasks

Three experiments provide converging evidence for the view that both perceived structure and attention change during the elementary school years. Kindergarteners, second graders, and adults performed three speeded tasks: divided attention to conjunctions of features, selective attention to orthogonal dimensions and selective attention to correlated dimensions. The tasks were performed with sizes and shapes that were either spatially integrated or spatially separated. In the divided attention task, conjunctions were identified as quickly as single features with integrated stimuli at all ages, but conjunctions were identified more slowly than single features with separated stimuli by all age group. In the orthogonal dimensions task, interference was observed with integrated stimuli across ages, but the interference in adult performance was asymmetric. With separated stimuli, interference was gradually eliminated with increasing age. In correlated dimensions tasks, younger children showed a redundancy gain with integrated stimuli, but no gain was observed in the performances of the older subjects. With separated stimuli there was no redundancy gain at any age. These results were interpreted to mean that integrated stimuli are initially perceived as wholes by all subjects, but that features become more accessible with increasing age. Even so, attention remains constrained by stimulus structure. In contrast, separated stimuli are initially perceived as features at all ages, and the improvement in performance with increasing age is attributable to the increasing command of attentional resources that accompanies development. Our discussion of these findings focuses on three issues: multiple trends in perceptual development, the characteristics of an adequate theory of perceptual representation and processing, and a comparison of the separability hypothesis and other developmental accounts of perceptual development.     

Abrupt visual onsets and selective attention: evidence from visual search

The effect of temporal discontinuity on visual search was assessed by presenting a display in which one item had an abrupt onset, while other items were introduced by gradually removing line segments that camouflaged them. We hypothesized that an abrupt onset in a visual display would capture visual attention, giving this item a processing advantage over items lacking an abrupt leading edge. This prediction was confirmed in Experiment 1. We designed a second experiment to ensure that this finding was due to attentional factors rather than to sensory or perceptual ones. Experiment 3 replicated Experiment 1 and demonstrated that the procedure used to avoid abrupt onset--camouflage removal--did not require a gradual waveform. Implications of these findings for theories of attention are discussed.     

Traffic-entry behavior and crash risk for older drivers with impairment of selective attention

Current research suggests that older drivers with declines in selective attention would make more unsafe traffic-entry judgments than would older drivers with normal attention. This hypothesis was tested using an instrumented vehicle and a LIDAR speed and range detector. Participants were 20 older drivers: 10 (M=72.0 yr.) had impairments of selective attention, measured with the Visual Attention Analyzer, Model 3000, and 10 were nonimpaired (M=71.2 yr.). Drivers pressed a button to indicate the last possible moment they could safely cross a road in front of an oncoming vehicle. The speed and distance of the oncoming vehicles were measured and time-to-contact was calculated. Each driver's time-to-cross the roadway was independently measured. Attention-impaired drivers showed shorter time-to-contact values (5.60 sec. versus 6.86 sec.), took longer to cross the roadway (5.41 sec. versus 4.84 sec.), and had shorter safety cushions (the difference between time-to-contact and time-to-cross the roadway). Monte Carlo simulation showed that these performance differences increased the crash risk of the impaired group by up to 17.9 times that of the nonimpaired group.     

Role of Gestalt grouping in selective attention: evidence from the Stroop task

Selective attention has been intensively studied using the Stroop task. Evidence suggests that Stroop interference in a color-naming task arises partly because of visual attention sharing between color and word: Removing the target color after 150 msec reduces interference (Neumann, 1986). Moreover, removing both the color and the word simultaneously reduces interference less than does removing the color only (La Heij, van der Heijden, & Plooij, 2001). These findings could also be attributed to Gestalt grouping principles, such as common fate. We report three experiments in which the role of Gestalt grouping was further investigated. Experiment I replicated the reduced interference, using words and color patches. In Experiment 2, the color patch was not removed but only repositioned (<2 degrees) after 100 msec, which also reduced interference. In Experiment 3, the distractor was repositioned while the target remained stationary, again reducing interference. These results indicate a role for Gestalt grouping in selective attention.     

Selecting from dynamic environments: attention distinguishes between blinking and moving

Pinto, Olivers, and Theeuwes (2006) showed that a static target can be efficiently found among different types of dynamically changing distractors. They hypothesized that attention employs a broad division between static and dynamic information, a hypothesis that conforms with earlier research. In the present study, we investigated whether attention can only make use of this crude division or can exploit more subtle discriminations within the dynamic domain. In Experiment 1, participants were able to efficiently find a blinking target among moving distractors and moving targets among blinking distractors, although all items changed at the same rate and produced the same change in local luminance. In Experiment 2, search for a dynamic target among dynamic distractors was aided when we gave the distractors additional dynamic cues. Experiment 3 showed that making the displays equiluminant affected search efficiency for a static target among moving distractors, but not among blinking distractors. The findings refute the broad division hypothesis and suggest that object continuity plays an important role in selection.     

Number-knower levels in young children: insights from Bayesian modeling

Lee and Sarnecka (2010) developed a Bayesian model of young children’s behavior on the Give-N test of number knowledge. This paper presents two new extensions of the model, and applies the model to new data. In the first extension, the model is used to evaluate competing theories about the conceptual knowledge underlying children’s behavior. One, the knower-levels theory, is basically a “stage” theory involving real conceptual change. The other, the approximate-meanings theory, assumes that the child’s conceptual knowledge is relatively constant, although performance improves over time. In the second extension, the model is used to ask whether the same latent psychological variable (a child’s number-knower level) can simultaneously account for behavior on two tasks (the Give-N task and the Fast-Cards task) with different performance demands. Together, these two demonstrations show the potential of the Bayesian modeling approach to improve our understanding of the development of human cognition.     

To see dynamic change: continuous focused attention facilitates change detection,but the effect persists briefly

What is the role of continuously focused attention on an object in change detection? To ensure focused attention on one object, we conducted a single object change detection task, manipulating an object’s location between pre-change and post-change displays (same or different location), and also manipulating a blank duration (the FOD task) and a pre-change object presentation duration (the FBD task). If attention is continuously focused at the spatial location of the pre-change object, a location shift of the post-change object should interrupt change detection due to a cognitive cost of attentional shift. Results suggest attention is focused continuously for a brief blank duration, and attention can facilitate the detection of change occurring at the location of attentional focus. Additionally, although attention is focused continuously for a long time if a target is visible, the effect of attention declines with time. The results clarify the new temporal characteristics of focused attention.     

Biased attention and dysphoria: Manipulating selective attention reduces subsequent depressive symptoms

Selective attention for dysphoric stimuli has been observed in individuals with depression and those at risk for depression. To date, no studies have investigated the effects of directly manipulating selective attention for dysphoric stimuli on depressive symptoms. Mild to moderately depressed college students (N=34) were randomly assigned to complete 4 sessions of either attention training (AT) or no training (NT) during a two-week period. Participants completed self-reported assessments of depressive symptoms at baseline, post-training, and follow-up. Participants in the AT condition had a significantly greater decrease in depressive symptoms from baseline to follow-up than participants in the NT condition. This group difference was mediated by change in attention bias. Our findings suggest that biased attention may have a causal role in the maintenance of depressive symptoms.     

Distinguishing blocking from attenuation in visual selective attention

Sensory information must be processed selectively in order to represent the world and guide behavior. How does such selection occur? Here we consider two alternative classes of selection mechanisms: In blocking, unattended stimuli are blocked entirely from access to downstream processes, and in attenuation, unattended stimuli are reduced in strength but if strong enough can still access downstream processes. Existing evidence as to whether blocking or attenuation is a more accurate model of human performance is mixed. Capitalizing on a general distinction between blocking and attenuation-blocking cannot be overcome by strong stimuli, whereas attenuation can-we measured how attention interacted with the strength of stimuli in two spatial selection paradigms, spatial filtering and spatial monitoring. The evidence was consistent with blocking for the filtering paradigm and with attenuation for the monitoring paradigm. This approach provides a general measure of the fate of unattended stimuli.     

Confronting complexity: insights from the details of behavior over multiple timescales

Young children tend to generalize novel names for novel solid objects by similarity in shape, a phenomenon dubbed 'the shape bias'. We believe that the critical insights needed to explain the shape bias in particular, and cognitive development more generally, come from Dynamic Systems Theory. We present two examples of recent work focusing on the real-time decision processes that underlie performance in the tasks used to measure the shape bias. We show how this work, and the dynamic systems perspective, sheds light on the controversy over the origins and development of the shape bias. In addition, we suggest that this dynamic systems perspective provides the right level for explanations of development because it requires a focus on the details of behavior over multiple timescales.     

高、低趋近积极情绪对不同注意加工阶段的影响

本研究采用事件相关电位(ERP)技术和Flanker任务, 探讨由甜点和风景图片分别诱发的高、低趋近积极情绪对注意的早期和晚期加工的影响。同时, 为更精细考察情绪对视觉注意范围早期加工阶段的影响, 在75%的Flanker试次中加入了一个白色方块探测刺激, 该刺激位于中央Flanker字母的左侧或右侧。研究结果表明, 在注意加工的早期感知阶段, 高趋近积极情绪下, 带有白色探测刺激的Flanker字母比低趋近积极情绪条件下诱发了更小的P1, 表明高趋近积极情绪窄化了早期注意加工范围; 在注意加工的晚期选择阶段, 高趋近积极情绪下的Flanker字母诱发了更大的N2b成分, 低趋近积极情绪下诱发了更大的P3成分, 表明高趋近积极情绪增强了对干扰的抑制能力, 而低趋近积极情绪下个体调用了更多的注意资源用以加工周边刺激。     

When motor attention improves selective attention: The dissociating role of saliency

There is evidence that preparing and maintaining a motor plan (“motor attention”) can bias visual selective attention. For example, a motor attended grasp biases visual attention to select appropriately graspable object features (Symes, Tucker, Ellis, Vainio, & Ottoboni, 2008). According to the biased competition model of selective attention, the relative weightings of stimulus-driven and goal-directed factors determine selection. The current study investigated how the goal-directed bias of motor attention might operate when the stimulus-driven salience of the target was varied. Using a change detection task, two almost identical photographed scenes of simplistic graspable objects were presented flickering back and forth. The target object changed visually, and this change was either high or low salience. Target salience determined whether or not the motor attended grasp significantly biased visual selective attention. Specifically, motor attention only had a reliable influence on target detection times when the visual salience of the target was low.     

Cross-modal selective attention: on the difficulty of ignoring sounds at the locus of visual attention

In three experiments, we investigated whether the ease with which distracting sounds can be ignored depends on their distance from fixation and from attended visual events. In the first experiment, participants shadowed an auditory stream of words presented behind their heads, while simultaneously fixating visual lip-read information consistent with the relevant auditory stream, or meaningless "chewing" lip movements. An irrelevant auditory stream of words, which participants had to ignore, was presented either from the same side as the fixated visual stream or from the opposite side. Selective shadowing was less accurate in the former condition, implying that distracting sounds are harder to ignore when fixated. Furthermore, the impairment when fixating toward distractor sounds was greater when speaking lips were fixated than when chewing lips were fixated, suggesting that people find it particularly difficult to ignore sounds at locations that are actively attended for visual lipreading rather than merely passively fixated. Experiments 2 and 3 tested whether these results are specific to cross-modal links in speech perception by replacing the visual lip movements with a rapidly changing stream of meaningless visual shapes. The auditory task was again shadowing, but the active visual task was now monitoring for a specific visual shape at one location. A decrement in shadowing was again observed when participants passively fixated toward the irrelevant auditory stream. This decrement was larger when participants performed a difficult active visual task there versus fixating, but not for a less demanding visual task versus fixation. The implications for cross-modal links in spatial attention are discussed.     

Learning disability and hyperactivity: Deficits in selective attention

Differences in performance on a variety of cognitive measures and differences in patterns of ability between learning disabled (LD) and nonlearning disabled (non-LD) children were examined. Younger and older LD and non-LD children were administered tests of central and incidental learning and selective attention. Teacher ratings of classroom hyperactivity were also examined. LD children, particularly the younger ones, performed significantly more poorly than non-LD children on both attention/memory tasks. Performance on the two tasks was consistently interrelated for the non-LD children and less consistently so for the LD subjects. Hyperactivity was also related to poorer performance on the cognitive measures. Results are discussed in terms of components of selective attention.     

Working memory load can both improve and impair selective attention: Evidence from the Navon paradigm

Selective attention to relevant targets has been shown to depend on the availability of working memory (WM). Under conditions of high WM load, processing of irrelevant distractors is enhanced. Here we showed that this detrimental effect of WM load on selective attention efficiency is reversed when the task requires global- rather than local-level processing. Participants were asked to attend to either the local or the global level of a hierarchical Navon stimulus while keeping either a low or a high load in WM. In line with previous findings, during attention to the local level, distractors at the global level produced more interference under high than under low WM load. By contrast, loading WM had the opposite effect of improving selective attention during attention to the global level. The findings demonstrate that the impact of WM load on selective attention is not invariant, but rather is dependent on the level of the to-be-attended information.     

Top-down modulation: bridging selective attention and working memory

Selective attention, the ability to focus our cognitive resources on information relevant to our goals, influences working memory (WM) performance. Indeed, attention and working memory are increasingly viewed as overlapping constructs. Here, we review recent evidence from human neurophysiological studies demonstrating that top-down modulation serves as a common neural mechanism underlying these two cognitive operations. The core features include activity modulation in stimulus-selective sensory cortices with concurrent engagement of prefrontal and parietal control regions that function as sources of top-down signals. Notably, top-down modulation is engaged during both stimulus-present and stimulus-absent stages of WM tasks; that is, expectation of an ensuing stimulus to be remembered, selection and encoding of stimuli, maintenance of relevant information in mind and memory retrieval.