The attentional effects of peripheral cueing as revealed by two event-related potential studies

Attention allocation in foreign language reading anxiety during lexical processing - An ERP study with cue-target paradigm

Extensive behavioral and pedagogical studies emphasize the negative impact of foreign language reading anxiety on foreign language reading. This study investigated whether foreign language reading anxiety is correlated with dysregulation of attentional allocation while foreign language reading. We used event-related potential (ERP) indices as biomarkers to examine attention allocation between groups with high foreign language reading anxiety (HFLRA) and low foreign language reading anxiety (LFLRA) using a cue-target paradigm under conditions that posed high (valid condition) or low (invalid condition) expectations on target location. Behavioral results indicated that HFLRA individuals exhibited significantly lower accuracy compared to LFLRA individuals in both valid and invalid conditions. ERP analyses demonstrated that HFLRA individuals showed significant differences in attentional allocation compared to LFLRA individuals, as reflected by later N2 latency and stronger LPC amplitude, particularly in the invalid condition. Additionally, LFLRA individuals demonstrated a significant difference in N2 latency between valid and invalid conditions, which was not observed in HFLRA individuals. These findings suggest that HFLRA individuals experience inefficient attentional allocation during foreign language reading.

Valence versus motivation: The different impact of emotion on space- and object-based attention

Numerous studies have indicated that both the broaden-and-build model and the motivational dimensional model emphasize the impact of emotion on spatial attention by altering the attentional scope. However, no prior research has investigated the impact of emotional valence and motivational intensity on spatial attention within the same paradigm. Furthermore, object-based attention, characterized by distinct neural mechanisms from space-based attention and also susceptible to attentional scope, represents a major pattern of selective attention. Nevertheless, it is still unclear whether and how emotional valence and motivation play a role in object-based attentional selection. Therefore, the present study aimed to explore these areas. Using a two-rectangle paradigm, Experiment 1 found that motivational intensity modulated space-based effects, whereas emotional valence modulated object-based effects. Experiment 2 used a traditional spatial cueing paradigm to further study the stability of modulating effect of motivation intensity on space-based attention, yielding results consistent with those of Experiment 1. The present study indicated that the broaden-and-build model and motivational dimensional model were not either one or the other, but both played a role in object- and space-based attention. This study provides crucial empirical evidence for theoretical complementation and integration of emotional attention.

Altered resting-state network connectivity patterns for predicting attentional function in deaf individuals: An EEG study

Multiple aspects of brain development are influenced by early sensory loss such as deafness. Despite growing evidence of changes in attentional functions for prelingual profoundly deaf, the brain mechanisms underlying these attentional changes remain unclear. This study investigated the relationships between differential attention and the resting-state brain network difference in deaf individuals from the perspective of brain network connectivity. We recruited 36 deaf individuals and 34 healthy controls (HC). We recorded each participant's resting-state electroencephalogram (EEG) and the event-related potential (ERP) data from the Attention Network Test (ANT). The coherence (COH) method and graph theory were used to build brain networks and analyze network connectivity. First, the ERPs of analysis in task states were investigated. Then, we correlated the topological properties of the network functional connectivity with the ERPs. The results revealed a significant correlation between frontal-occipital connection in the resting state and the amplitude of alert N1 amplitude in the alpha band. Specifically, clustering coefficients and global and local efficiency correlate negatively with alert N1 amplitude, whereas the characteristic path length positively correlates with alert N1 amplitude. In addition, deaf individuals exhibited weaker frontal-occipital connections compared to the HC group. In executive control, the deaf group had longer reaction times and larger P3 amplitudes. However, the orienting function did not significantly differ from the HC group. Finally, the alert N1 amplitude in the ANT task for deaf individuals was predicted using a multiple linear regression model based on resting-state EEG network properties. Our results suggest that deafness affects the performance of alerting and executive control while orienting functions develop similarly to hearing individuals. Furthermore, weakened frontal-occipital connections in the deaf brain are a fundamental cause of altered alerting functions in the deaf. These results reveal important effects of brain networks on attentional function from the perspective of brain connections and provide potential physiological biomarkers to predicting attention.

Neural bases of unconscious orienting of attention in hemianopic patients: Hemispheric differences

The aim of this research was to study the behavioral and neurophysiological correlates of visual attention orientation to unseen stimuli presented to the blind hemifield of hemianopic patients, and the existence of hemispheric differences for this kind of unconscious attention. Behaviorally, by using a Posner paradigm, we found a significant attention effect in speed of response to unseen stimuli similar to that observed in the sighted hemifield and in healthy participants for visible stimuli. Moreover, event-related potential (ERP) and oscillatory attention-related activity were present following stimulus presentation to the blind hemifield. Importantly, in patients this pattern of activity was different as a function of the side of the brain lesion: Left damaged patients showed attention-related ERP and oscillatory activity broadly similar to that found in healthy participants. In contrast, right damaged patients showed a radically different pattern. These data confirm and extend to neurophysiological mechanisms the existence of unconscious visual orienting and are in keeping with a right hemisphere dominance for both unconscious and conscious attention.

Investigating behavior inhibition in obsessive-compulsive disorder: Evidence from eye movements

We investigated the role of inhibition failure in Obsessive Compulsive Disorder (OCD) through an eye tracking experiment. Twenty-five subjects with OCD were recruited, as well as 25 with Generalized Anxiety Disorder (GAD) and 25 healthy controls. A 3 (group: OCD group, GAD group and control group) × 2 (target eccentricity: far and near) × 2 (saccade task: prosaccade and antisaccade) mixed design was used, with all participants completing two sets of tasks involving both prosaccade (eye movement towards a target) and antisaccade (eye movement away from a target). The main outcome was the eye movement index, including the saccade latency (the time interval from the onset of the target screen to the first saccade) and the error rate of saccade direction. The antisaccade latency and antisaccade error rates for OCDs were much higher than those for GADs and healthy controls. OCDs had longer latency and error rates for antisaccades than for prosaccades, and for far-eccentricity rather than near-eccentricity stimuli. These results suggest that OCDs experience difficulty with behavior inhibition, and that they have higher visual sensitivity to peripheral stimuli. In particular, they show greatest difficulty in inhibiting behavior directed towards peripheral stimuli.

ERP-study on the time course of disgust-motivated spatial avoidance

Recently, we showed that disgusting sound cues direct spatial attention away from the location of their origin to the opposite location indicating spatial disgust avoidance (Zimmer et al., 2015, Psychophysiology; 2016, Neuroimage). However, in these studies, we had solely used an inter-stimulus interval (ISI) of 200-300 ms, leaving unclear how disgust avoidance develops over time. Studies have shown that spatial attraction due to anger persists longer when induced by auditory rather than visual stimuli. In the present ERP-study, one of two laterally presented sounds (neutral/disgust) cued a laterally presented visual target. ISIs varied from short (50-150 ms) over middle (350-450 ms) to long (650-750 ms). For disgust stimuli, response times were longer for invalidly cued targets compared to validly cued targets, reflecting disgust avoidance. There was an increased P3 amplitude for validly versus invalidly cued targets consistent with disgust avoidance. In contrast, in the neutral condition, we found evidence of inhibition of return (IOR), as we observed a reversal of the usual validity effect from short to long ISI in the behavioral data and on the P1-component. These results indicate that spatial avoidance motivated by auditory disgust persists over time, presumably enforced by emotional rather than general attentional processes.

Perceptual learning induces changes in early and late visual evoked potentials

Studies of visual cortical responses following visual perceptual learning (VPL) have produced diverse results, revealing neural changes in early and/or higher-level visual cortex as well as changes in regions responsible for higher cognitive processes such as attentional control. In this study, we investigated substrates of VPL in the human brain by recording visual evoked potentials with high-density electroencephalography (hdEEG) before (Session 1) and after (Session 2) training on a texture discrimination task (TDT), with two full nights of sleep between sessions. We studied the following event-related potential (ERP) components: C1 (early sensory processing), P1 and N1 (later sensory processing, modulated by top-down spatial attention), and P3 (cognitive processing). Our results showed a significant decrease in C1 amplitude at Session 2 relative to Session 1 that was positively correlated with the magnitude of improvement in behavioral performance. Although we observed no significant changes in P1 amplitude with VPL, both N1 amplitude and latency were significantly decreased in Session 2. Moreover, the difference in N1 latency between Session 1 and Session 2 was negatively correlated with behavioral improvement. We also found a significant increase in P3 amplitude following training. Our results suggest that VPL of the TDT task may be due to plasticity in early visual cortical areas as well as changes in top-down attentional control and cognitive processing.

Several studies with significant C1 attention effects survive critical analysis

In a discussion paper (Slotnick, this issue), I conducted a selective review of spatial attention studies to compare experimental parameters and determine whether particular stimulus, task, or analysis conditions were more likely to produce significant attentional modulation of the event-related potential (ERP) C1 component. It was concluded that to maximize C1 attention effects, stimuli should be in the upper visual field, there should be distractors, conditions should be high perceptual or attentional load, there should be exogenous cuing, and effects should be measured at midline parietal-occipital electrodes POz, Pz, and CPz. Commentaries were received by Fu (this issue), Qu and Ding (this issue), Zani and Proverbio (this issue), Pitts and Hillyard (this issue), Di Russo (this issue), and Mohr and Kelly (this issue). Comments included additional ideas to amplify C1 attention effects, support for some conclusions, and challenges to some conclusions. The challenges led to a more in depth analysis of many issues pertaining to C1 attention effects including optimal electrode and stimulus locations, null V1 source localization attention effects, whether all significant C1 attention effects can be discounted, and the number of studies with null versus significant C1 attention effects. Analysis of the studies that survived critical analysis, which included several that observed significant C1 attention effects, led to the same conclusions as Slotnick (this issue). Lines of future research include replicating studies that have observed C1 attention effects using identical experimental parameters and systematically manipulating parameters to determine the impact of each parameter on C1 spatial attention effects.

Independent effects of motivation and spatial attention in the human visual cortex

Motivation and attention constitute major determinants of human perception and action. Nonetheless, it remains a matter of debate whether motivation effects on the visual cortex depend on the spatial attention system, or rely on independent pathways. This study investigated the impact of motivation and spatial attention on the activity of the human primary and extrastriate visual cortex by employing a factorial manipulation of the two factors in a cued pattern discrimination task. During stimulus presentation, we recorded event-related potentials and pupillary responses. Motivational relevance increased the amplitudes of the C1 component at ∼70 ms after stimulus onset. This modulation occurred independently of spatial attention effects, which were evident at the P1 level. Furthermore, motivation and spatial attention had independent effects on preparatory activation as measured by the contingent negative variation; and pupil data showed increased activation in response to incentive targets. Taken together, these findings suggest independent pathways for the influence of motivation and spatial attention on the activity of the human visual cortex.

The spatiotemporal characteristics of the C1 component and its modulation by attention

Slotnick (this issue) provided a selective review of studies on the attentional modulation of the C1 component of the visual evoked potential, and offers a number of guidelines to maximize the likelihood of observing such modulation in terms of electrode choice, stimulus placement, and types of attentional cue and target stimulus. However, the broader literature pertaining to attentional modulation of the C1 does not support many of these guidelines, and the question of why exactly C1 modulations are so rare remains very much open. Here, we provide clarifications that are critical to an accurate appraisal of the current state of this literature.

Open and cautious towards the "minority view"

According to the 'minority view', the initial afferent processing on C1 can be modulated by attention under certain experimental conditions. However, evidence supporting this 'minority view' is relatively rare and needs more replication, and the optimal conditions for eliciting attentional modulations on C1 have not yet been clearly defined. V1-tuned stimuli with distractors, peripheral cuing paradigms, and high perceptual loads seem to be important factors in favor of the 'minority view'. The signal-noise issue for C1, especially between attended and unattended conditions, needs to be considered.

Expectations regarding action sequences modulate electrophysiological correlates of the gaze-cueing effect

Predictive mechanisms of the brain are important for social cognition, as they enable inferences about others' goals and intentions, thereby allowing for generation of expectations regarding what will happen next in the social environment. Therefore, attentional selection is modulated by expectations regarding behavior of others (Perez-Osorio, Müller, Wiese, & Wykowska, 2015). In this article, we examined-using the ERPs of the EEG signal-which stages of processing are influenced by expectations about others' action steps. We used a paradigm in which a gaze-cueing procedure was embedded in successively presented naturalistic photographs composing an action sequence. Our results showed (a) behavioral gaze-cueing effects modulated by whether the observed agent gazed at an object that was expected to be gazed at, according to the action sequence; (b) the N1 component locked to the onset of a target was modulated both by spatial gaze validity and participants' expectations about where the agent would gaze to perform an action; (c) a more positive amplitude, locked to the shift of gaze direction for action-congruent gaze, relative to incongruent and neutral conditions-over parieto-occipital areas in the time window between 280 and 380 ms. Taken together, these findings revealed that confirmation or violation of expectations concerning others' goal-oriented actions modulate attentional selection processes, as indexed by early ERP components.

Biased towards food: Electrophysiological evidence for biased attention to food stimuli

We investigated the neural mechanisms involved in bias for food stimuli in our visual environment using event related lateralized (ERL) responses. The participants were presented with a cue (food or non-food item) to either identify or hold in working memory. Subsequently, they had to search for a target in a 2-item display where target and distractor stimuli were each flanked by a picture of a food or a non-food item. The behavioural data showed that performance was strongly affected by food cues, especially when food was held in WM compared to when the cues were merely identified. The temporal dynamics of electrophysiological measures of attention (the N1pc and N2pc) showed that the orienting of attention towards food stimuli was associated with two different mechanisms; an early stage of attentional suppression followed by a later stage of attentional orienting towards food stimuli. In contrast, non-food cues were associated only with the guidance of attention to or away from cued stimuli on valid and invalid trials. The results demonstrate that food items, perhaps due to their motivational significance modulate the early orienting of attention, including an initial suppressive response to food items.

Ad-hoc and context-dependent adjustments of selective attention in conflict control: an ERP study with visual probes

Cognitive conflict control in flanker tasks has often been described using the zoom-lens metaphor of selective attention. However, whether and how selective attention - in terms of suppression and enhancement - operates in this context has remained unclear. To examine the dynamic interplay of selective attention and cognitive control we used electrophysiological measures and presented task-irrelevant visual probe stimuli at foveal, parafoveal, and peripheral display positions. Target-flanker congruency varied either randomly from trial to trial (mixed-block) or block-wise (fixed-block) in order to induce reactive versus proactive control modes, respectively. Three EEG measures were used to capture ad-hoc adjustments within trials as well as effects of context-based predictions: the N1 component of the visual evoked potential (VEP) to probes, the VEP to targets, and the conflict-related midfrontal N2 component. Results from probe-VEPs indicate that enhanced processing of the foveal target rather than suppression of the peripheral flankers supports interference control. In incongruent mixed-block trials VEPs were larger to probes near the targets. In the fixed-blocks probe-VEPs were not modulated, but contrary to the mixed-block the preceding target-related VEP was affected by congruency. Results of the control-related N2 reveal largest amplitudes in the unpredictable context, which did not differentiate for stimulus and response incongruency. In contrast, in the predictable context, N2 amplitudes were reduced overall and differentiated between stimulus and response incongruency. Taken together these results imply that predictability alters interference control by a reconfiguration of stimulus processing. During unpredictable sequences participants adjust their attentional focus dynamically on a trial-by-trial basis as reflected in congruency-dependent probe-VEP-modulation. This reactive control mode also elicits larger N2 amplitudes. In contrast, when task demands are predictable, participants focus selective attention earlier as reflected in the target-related VEPs. This proactive control mode leads to smaller N2 amplitudes and absent probe effects.

Attentional orienting and response inhibition: insights from spatial-temporal neuroimaging

Attentional orienting and response inhibition have largely been studied separately. Each has yielded important findings, but controversy remains concerning whether they share any neurocognitive processes. These conflicting findings may originate from two issues: (1) at the cognitive level, attentional orienting and response inhibition are typically studied in isolation; and (2) at the technological level, a single neuroimaging method is typically used to study these processes. This article reviews recent achievements in both spatial and temporal neuroimaging, emphasizing the relationship between attentional orienting and response inhibition. We suggest that coordinated engagement, both top-down and bottom-up, serves as a common neural mechanism underlying these two cognitive processes. In addition, the right ventrolateral prefrontal cortex may play a major role in their harmonious operation.

Extinguishing Extinction: Hemispheric Differences in the Modulation of TMS-induced Visual Extinction by Directing Covert Spatial Attention

The topic of spatial attention is of great relevance for researchers in various fields, including neuropsychology, cognitive neuroscience, and cognitive psychology, as well as for clinical practice. Deficits of spatial attentional arising from parietal brain damage remain largely confined to the left visual field. The mechanisms underlying this hemispheric asymmetry are still elusive. We mimicked the neuropsychological syndrome of contralesional extinction by temporarily inducing a spatial attentional bias in healthy volunteers with TMS. We investigated whether directing covert spatial attention could enhance or, more importantly, counteract the resulting behavioral deficits. Although both the left and right parietal TMS induced contralateral extinction, only left hemifield extinction following right parietal TMS was severely aggravated by a competing stimulus in the ipsilesional (right) hemifield. We put forward the hypothesis that an asymmetry with respect to the ability of detaching attention from a distractor is contributing to the right hemispheric lateralization with regard to extinction. On a broader level, we suggest that “virtual patients” might be used for evaluating neuropsychological treatment in an early stage of development, reducing the burden on actual patients.

Perceptual load, voluntary attention, and aging: an event-related potential study

The locus of attentional selection is known to vary with perceptual load (Lavie et al., 2004). Under voluntary attention, perceptual load modulates selective visual processing at an early cortical stage, as reflected in the posterior P1 and N1 components of the event-related potentials (ERPs). Adult aging also affects both behavioral and ERP signs of attentional selection. However, it is not known whether perceptual load modulates this relationship. Accordingly, in the present study ERPs were recorded in a voluntary attention task. Young and old participants were asked to discriminate the direction of a target line embedded within a display of four lines that appeared in the left or right visual field. Participants responded faster and more accurately to valid relative to invalid trials and to low-load relative to high-load condition. Older participants responded more slowly and with lower accuracy than young participants in all conditions. The amplitudes of the posterior contralateral P1 and N1 components in valid trials were larger than that in invalid trials in all conditions. N1 amplitude was larger under the high load condition than that in the low load condition. Moreover, in the high perceptual load condition, the old group had a larger N1 than the young group at contralateral sites. The findings suggest that under voluntary attention, perceptual load and aging modulates attentional selection at an early but not the earliest stage, during the N1 (120-200ms) time range. Increased N1 amplitude in older adults may reflect increased demands on target discrimination in high perceptual load.

Magnocellular and parvocellular influences on reflexive attention

Previous studies have provided conflicting evidence regarding whether the magnocellular (M) or parvocellular (P) visual pathway is primarily responsible for triggering involuntary orienting. Here, we used event-related potentials (ERPs) to provide new evidence that both the M and P pathways can trigger attentional capture and bias visual processing at multiple levels. Specifically, cued-location targets elicited enhanced activity, relative to uncued-location targets, at both early sensory processing levels (indexed by the P1 component) and later higher-order processing stages (as indexed by the P300 component). Furthermore, the present results show these effects of attentional capture were not contingent on the feature congruency between the cue and expected target, providing evidence that this biasing of visual processing was not dependant on top-down expectations or within-pathway priming.

Do the early attentional components of ERPs reflect attentional bias in depression? It depends on the stimulus presentation time

OBJECTIVE

The study aimed to utilize behavioral and electrophysiological data to investigate whether depressed patients show an attentional bias in a task that allows for explicit insight into the time course of selective attention processes.

METHODS

Event-related potentials (ERPs) were collected from 24 patients with major depressive disorder (MDD) and 25 never-depressed individuals (ND) during a dot-probe task, using pairs of affectively valenced pictures as cues. Cue presentation time was either 100 ms or 500 ms.

RESULTS

When the cue presentation time was 500 ms, bias scores for positive-neutral picture pairs (POS-NEU) were negative for the MDD group and positive for the ND group which means ND individuals were able to successfully select positive information. These behavioral effects were supported by ERP results. In the ND group, at the right parietal-occipital region, P1 amplitude during valid POS-NEU pairs was significantly larger than that during invalid POS-NEU pairs; this pattern did not appear in the MDD group.

CONCLUSIONS

These results suggest that MDD patients are characterized by a deficit in protection bias, meaning that these participants cannot avoid attending to negative information in their environment, but only when negative stimuli are presented for a sufficient period of time.

SIGNIFICANCE

Attentional bias is modulated by duration of emotional pictures presentation in depression.

Dissociation of visual C1 and P1 components as a function of attentional load: an event-related potential study

The earliest cortical location at which attention influences visual processing is controversial. To address this issue, the C1 and P1 components of cue-elicited ERPs were examined in a spatially-cued task under high and low levels of attentional load (active vs. passive viewing). Cues were presented either to the left or to the right visual field in separate trials (unilateral presentation), or to both visual fields simultaneously (bilateral presentation). For the unilateral presentation, C1 (peak latency approximately 80 ms) was not modulated by attentional load, whereas P1 (peak latency approximately 120-140 ms) was larger for high-relative to low-load condition. Bilateral presentation of the stimuli enhanced the amplitude of the C1 component relative to unilateral presentation; however, the increase of signal/noise ratio of C1 revealed no attentional load effect on C1. Results show that attentional load modulates visual processing in the P1, but not in the C1 time range, regardless of the increased signal/noise ratio by bilateral presentation. While it remains unclear about the conditions under which a C1 attentional effect is reliably elicited, the present results suggest that the direct manipulation of attentional load under a voluntary attention task seems not crucial for eliciting C1 attentional effect.

Neuroelectric source imaging using 3SCO: a space coding algorithm based on particle swarm optimization and l0 norm constraint

The electroencephalogram (EEG) neuroelectric sources inverse problem is usually underdetermined and lacks a unique solution, which is due to both the electromagnetism Helmholtz theorem and the fact that there are fewer observations than the unknown variables. One potential choice to tackle this issue is to solve the underdetermined system for a sparse solution. Aiming to the sparse solution, a novel algorithm termed 3SCO (Solution Space Sparse Coding Optimization) is presented in this paper. In 3SCO, after the solution space is coded with some particles, the particle-coded space is compressed by the evolution of particle swarm optimization algorithm, where an l0 constrained fitness function is introduced to guarantee the selection of a suitable sparse solution for the underdetermined system. 3SCO was first tested by localizing simulated EEG sources with different configurations on a realistic head model, and the comparisons with minimum norm (MN), LORETA (low resolution electromagnetic tomography), l1 norm solution and FOCUSS (focal underdetermined system solver) confirmed that a good sparse solution for EEG source imaging could be achieved with 3SCO. Finally, 3SCO was applied to localize the neuroelectric sources in a visual stimuli related experiment and the localized areas were basically consistent with those reported in previous studies.

Orienting and Focusing in Voluntary and Involuntary Visuospatial Attention Conditions

In the present study, we used event-related potentials (ERPs) and behavioral measurements in a peripherally cued line-orientation discrimination task to investigate the underlying mechanisms of orienting and focusing in voluntary and involuntary attention conditions. Informative peripheral cue (75% valid) with long stimulus onset asynchrony (SOA) was used in the voluntary attention condition; uninformative peripheral cue (50% valid) with short SOA was used in the involuntary attention condition. Both orienting and focusing were affected by attention type. Results for attention orienting in the voluntary attention condition confirmed the “sensory gain control theory,” as attention enhanced the amplitude of the early ERP components, P1 and N1, without latency changes. In the involuntary attention condition, compared with invalid trials, targets in the valid trials elicited larger and later contralateral P1 components, and smaller and later contralateral N1 components. Furthermore, but only in the voluntary attention condition, targets in the valid trials elicited larger N2 and P3 components than in the invalid trials. Attention focusing in the involuntary attention condition resulted in larger P1 components elicited by targets in small-cue trials compared to large-cue trials, whereas in the voluntary attention condition, larger P1 components were elicited by targets in large-cue trials than in small-cue trials. There was no interaction between orienting and focusing. These results suggest that orienting and focusing of visual-spatial attention are deployed independently regardless of attention type. In addition, the present results provide evidence of dissociation between voluntary and involuntary attention during the same task.

Perceptual load interacts with involuntary attention at early processing stages: event-related potential studies

Perceptual load is known to influence the locus of attentional selection in the brain but through an unknown underlying mechanism. We used event-related potentials (ERPs) to investigate how perceptual load interacts with cue-driven involuntary attention. Perceptual load was manipulated in a line orientation discrimination task in which target location was cued involuntarily by means of peripheral cues. Attentional modulation was observed for P1m (the posterior midline P1 component with peak latency between 108 and 140 ms) with invalid trials eliciting larger P1m than valid trials. This attentional effect on P1m increased as a function of perceptual load, suggesting an early temporal locus for the interaction of perceptual load and involuntary attention. Attentional modulation for the C1 component (peak latency at approximately 80 ms) was also observed, but only for high-load stimuli that were presented intermixed with low-load stimuli. Results suggest that (a) perceptual load affects attentional selection at early processing stages; (b) perceptual load interacts with involuntary attention earlier and with different brain mechanisms relative to voluntary attention; and (c) attentional modulation in the C1 time range is possible under optimal experimental conditions.

An ERP investigation of the modulation of subliminal priming by exogenous cues

Marzouki, Grainger, and Theeuwes [Marzouki, Y., Grainger, J., and Theeuwes, J. 2007. Exogenous spatial cueing modulates subliminal priming. Acta Psychol. 126, 34-45.] demonstrated that masked repetition priming of letter identification is affected by the allocation of spatial attention to the prime location by an exogenous cue. Behavioral priming effects were obtained only when the exogenous cue was valid (prime at the same location as the cue). The present ERP study provides a further investigation of such exogenous influences on masked priming. Results showed a significant modulation of the amplitude of the P3 ERP component generated by centrally located target letters as a function of repetition priming and cue validity. The amplitude difference between repetition and unrelated primes was found to be enhanced in the presence of a valid exogenous cue. The electrophysiological data therefore confirm the influence of exogenous cues on the processing of subliminally presented prime stimuli, and show that such effects can be obtained in the absence of eye movements. The results further point to a relatively late influence of prime stimuli on target processing when these stimuli occupy distinct locations.

Electrophysiological correlates of spatial orienting towards angry faces: a source localization study

The goal of this study was to examine behavioral and electrophysiological correlates of involuntary orienting toward rapidly presented angry faces in non-anxious, healthy adults using a dot-probe task in conjunction with high-density event-related potentials and a distributed source localization technique. Consistent with previous studies, participants showed hypervigilance toward angry faces, as indexed by facilitated response time for validly cued probes following angry faces and an enhanced P1 component. An opposite pattern was found for happy faces suggesting that attention was directed toward the relatively more threatening stimuli within the visual field (neutral faces). Source localization of the P1 effect for angry faces indicated increased activity within the anterior cingulate cortex, possibly reflecting conflict experienced during invalidly cued trials. No modulation of the early C1 component was found for affect or spatial attention. Furthermore, the face-sensitive N170 was not modulated by emotional expression. Results suggest that the earliest modulation of spatial attention by face stimuli is manifested in the P1 component, and provide insights about mechanisms underlying attentional orienting toward cues of threat and social disapproval.

When and where perceptual load interacts with voluntary visuospatial attention: an event-related potential and dipole modeling study

Perceptual load is recognized to affect visual selective attention, but at an unknown spatiotemporal locus in the brain. To examine this issue, event-related potentials (ERPs) were recorded while participants performed an orientation discrimination task, under conditions of low or high perceptual load. Participants were required to respond to targets (10% of trials) presented in the attended visual field while ignoring all stimuli in the unattended visual field. The interaction between voluntary attention and perceptual load was significant for the posterior N1 component (190 ms) but not for the earlier C1 (84 ms) or P1 (100 ms) components. This load by attention interaction for N1 was localized to the temporoparietal-occipital (TPO) gyrus by dipole modeling analysis. Dipole modeling also showed that a reversed attentional effect in the C1 time range was due to ERP overlap from the subsequent attention-sensitive P1 component. Results suggest that perceptual load affects voluntary visuospatial attention at an early (but not the earliest) processing stage and that the TPO gyrus mediates target selection at the discrimination stage.

Attention shortage resistance of negative stimuli in an implicit emotional task

Considerable evidence from behavioral studies has indicated that people tend to pay attention to negative stimuli preferentially. The attentional bias can occur rapidly and automatically. In the current study, a 'cue-target' paradigm was utilized to manipulate the attention allocation. Seventeen healthy undergraduates participated in the experiment. The stimuli were emotional pictures (positive, neutral and negative), which were upper and lower adjacent patchworks of a normal scene and its inverted copy. The subjects should judge whether the normal scene (compared with the inverted scene) was located in the upper or lower part of the whole patchwork. We used this implicit emotional task to avoid the task relevance effect. It was found that the amplitude of P2 waves was enlarged by the negative pictures and there was a significant interaction between the cue effect and the emotional valence. We can conclude that the negative information exerts an attentional bias effect in the emotional perception, and that the negative contents suffer less in the insufficient attention condition compared with the positive and the neutral conditions.

The Mechanism of Involuntary Visual Spatial Attention Revealed by a New Linear Computation Model

EEG reveals brain electrical activities with high temporal resolution. Yet, multiple implicit variables may be involved in limited event related potential (ERP) measures. Special computation techniques are needed to recover these parameters. In the study of involuntary visual spatial attention, we may obtain the ERP in valid cued (V), invalid cued (I) and neutral cued (N) conditions. Usually, the effect of involuntary attention is computed by the subtraction model with the assumption that V/I and N are independent. Yet, they should be related. Treating V/I as a function of N, a linear model V(I) = W + GN is assumed, where W and G are implicit in the ERP measures. G is the gain control on the neutral function. Provided G and W are constant over a local brain region, we may use the Total Least Square (TLS) algorithm to compute their values. The values of W and G computed from an involuntary attention experiment data show that multiple implicit variables are involved in obtained ERPs. Here G acts as a "top-down" sensory modulator on the neutral ERPs and W is related to possible newly involved neural activities. The parameters derived from the new linear model also suggest that there are different mechanisms involved in involuntary attention and voluntary allocation of attention.

Interactions between endogenous and exogenous attention on cortical visual processing

Sensory processing is affected by both endogenous and exogenous mechanisms of attention, although how these mechanisms interact in the brain has remained unclear. In the present study, we recorded event-related potentials (ERPs) to investigate how multiple stages of information processing in the brain are affected when endogenous and exogenous mechanisms are concurrently engaged. We found that the earliest stage of cortical visual processing, the striate-cortex-generated C1, was immune to attentional modulation, even when endogenous and exogenous attention converged on a common location. The earliest stage of processing to be affected in this experiment was the late phase of the extrastriate-cortex-generated P1 component, which was dominated by exogenous attention. Processing at this stage was enhanced by exogenous attention, regardless of where endogenous attention had been oriented. Endogenous attention, however, dominated a later, higher-order stage of processing indexed by an enhancement of the P300 that was unaffected by exogenous attention. Critically, between these early and late stages, an interaction was found wherein endogenous and exogenous attention produced distinct, and overlapping, effects on information processing. At the same time that exogenous attention was producing an extended enhancement of the late-P1, endogenous attention was enhancing the occipital-parietal N1 component. These results provide neurophysiological support for theories suggesting that endogenous and exogenous mechanisms represent two attention systems that can affect information processing in the brain in distinct ways. Furthermore, these data provide new evidence regarding the precise stages of neural processing that are, and are not, affected when endogenous and exogenous attentions interact.

Effects of nicotine on visuo-spatial selective attention as indexed by event-related potentials

Nicotine has been shown to specifically reduce reaction times to invalidly cued targets in spatial cueing paradigms. In two experiments, we used event-related potentials to test whether the facilitative effect of nicotine upon the detection of invalidly cued targets is due to a modulation of perceptual processing, as indexed by early attention-related event-related potential components. Furthermore, we assessed whether the effect of nicotine on such unattended stimuli depends upon the use of exogenous or endogenous cues. In both experiments, the electroencephalogram was recorded while non-smokers completed discrimination tasks in Posner-type paradigms after chewing a nicotine polacrilex gum (Nicorette 2 mg) in one session and a placebo gum in another session. Nicotine reduced reaction times to invalidly cued targets when cueing was endogenous. In contrast, no differential effect of nicotine on reaction times was observed when exogenous cues were used. Electrophysiologically, we found a similar attentional modulation of the P1 and N1 components under placebo and nicotine but a differential modulation of later event-related potential components at a frontocentral site. The lack of a drug-dependent modulation of P1 and N1 in the presence of a behavioral effect suggests that the effect of nicotine in endogenous visuo-spatial cueing tasks is not due to an alteration of perceptual processes. Rather, the differential modulation of frontocentral event-related potentials suggests that nicotine acts at later stages of target processing.

Task-dependent exogenous cuing effects depend on cue modality

Task-dependent exogenous cuing effects on reaction time in detection and discrimination tasks have been ascribed to delayed withdrawal of attention in discrimination tasks. Alternatively, these differences may be due to cue-induced response inhibition in detection tasks. Unimodal and crossmodal versions of the Posner paradigm were examined with short cue-target intervals. Targets above or below fixation required either detection or discrimination responses. Cuing effects were determined for the target-elicited P1 component and for the lateralized readiness potential (LRP). Task-dependent cuing effects on reaction time were found in the unimodal but not in the crossmodal version, but not for the P1 component. The LRP data indicated that inhibition of return in the unimodal detection task had a premotoric locus. These findings suggest that inhibition in the unimodal detection task resulted from speeded motor inhibition triggered by the visual cue.

Exogenous attentional selection of transparent superimposed surfaces modulates early event-related potentials

Using a transparent motion paradigm, [Valdes-Sosa, M., Bobes, M. A., Rodriguez, V., & Pinilla, T. (1998). Switching attention without shifting the spotlight object-based attentional modulation of brain potentials, Journal of Cognitive Neuroscience, 10, 137-151; Valdes-Sosa, M., Cobo, A., & Pinilla, T. (2000). Attention to object files defined by transparent motion, Journal of Experimental Psychological: Human Perception and Performance, 26, 488-505] found that when attention is endogenously directed to one surface, observers can more reliably report the direction of a brief translation of the cued than the uncued surface. Using a similar design [Reynolds, J. H., Alborzian, S., & Stoner, G. R. (2003). Exogenously cued attention triggers competitive selection of surfaces, Vision Research, 43, 59-66] found that even in the absence of an endogenous cue, the first translation acted as a potent exogenous cue that impaired the observer's ability to discriminate a subsequent translation of the other surface. We investigated the neural basis of this exogenous cueing effect by recording visual event-related potentials (ERPs) elicited by translations of the cued and uncued surfaces. Subjects were given the task of judging whether or not the first and second translations were identical in direction, and their performance was impaired when the second translation occurred on the uncued, as compared to the cued surface. The posterior C1 (75-110 ms) and N1 (160-210 ms) components of the ERP elicited by the second translation of the cued surface were larger than those elicited by translation of the uncued surface. These behavioral and ERP cueing effects were present even when the two surfaces were identical in color and thus could not be attributed to attention-related modulations of the gain of color channels. These findings provide evidence that exogenous cueing results in preferential selection of the cued surface at both early and intermediate stages of visual-cortical processing.

Appearing and disappearing stimuli trigger a reflexive modulation of visual cortical activity

From the vast array of stimuli continually inundating our senses, only a very small portion is selected for higher-order processing. This selection is influenced by voluntary and reflexive mechanisms that may act at multiple stages of analysis. Extensive research has revealed that top-down voluntary mechanisms modulate information processing at both "early" (e.g., perceptual) and "late" (e.g., semantic) stages. Bottom-up sensory-driven mechanisms, however, are less well understood. Previous investigations of bottom-up mechanisms may have been influenced by top-down mechanisms because the stimuli were task-relevant and required overt responses. Here, we directly measured bottom-up influences on visual information processing by recording event-related brain potentials (ERP) to sequences of task-irrelevant visual stimuli. We found that abrupt visual events triggered an automatic enhancement of extrastriate visual activity (the P1 ERP component) to subsequent visual stimuli occurring at the same location. In contrast to theories suggesting that the abrupt appearance of a new object is unique in being able to trigger bottom-up effects, we found that disappearing objects triggered the same enhancement of subsequent stimulus processing as did appearing objects. The present data, however, also provide new electrophysiological evidence for a level of analysis in the brain that may be specific to the appearance of new objects. These data thus provide evidence that abruptly appearing objects may evoke specialized processing at certain stages of analysis in the brain but that, despite this difference, appearing and disappearing objects both trigger reflexive mechanisms that bias neural activity in human extrastriate visual cortex.

Effects of attention and arousal on early responses in striate cortex

Humans employ attention to facilitate perception of relevant stimuli. Visual attention can bias the selection of a location in the visual field, a whole visual object or any visual feature of an object. Attention draws on both current behavioral goals and/or the saliency of physical attributes of a stimulus, and it influences activity of different brain regions at different latencies. Attentional effect in the striate and extrastriate cortices has been the subject of intense research interest in many recent studies. The consensus emerging from them places the first attentional effects in extrastriate areas, which in turn modulate activity of V1 at later latencies. In this view attention influences activity in striate cortex some 150 ms after stimulus onset. Here we use magnetoencephalography to compare brain responses to foveally presented identical stimuli under the conditions of passive viewing, when the stimuli are irrelevant to the subject and under an active GO/NOGO task, when the stimuli are cues instructing the subject to make or inhibit movement of his/her left or right index finger. The earliest striate activity was identified 40-45 ms after stimulus onset, and it was identical in passive and active conditions. Later striate response starting at about 70 ms and reaching a peak at about 100 ms showed a strong attentional modulation. Even before the striate cortex, activity of the right inferior parietal lobule was modulated by attention, suggesting this region as a candidate for mediating attentional signals to the striate cortex.

Brain mechanisms of involuntary visuospatial attention: an event-related potential study

The brain mechanisms mediating visuospatial attention were investigated by recording event-related potentials (ERPs) during a line-orientation discrimination task. Nonpredictive peripheral cues were used to direct participant's attention involuntarily to a spatial location. The earliest attentional modulation was observed in the P1 component (peak latency about 130 ms), with the valid trials eliciting larger P1 than invalid trials. Moreover, the attentional modulations on both the amplitude and latency of the P1 and N1 components had a different pattern as compared to previous studies with voluntary attention tasks. In contrast, the earliest visual ERP component, C1 (peak latency about 80 ms), was not modulated by attention. Low-resolution brain electromagnetic tomography (LORETA) showed that the earliest attentional modulation occurred in extrastriate cortex (middle occipital gyrus, BA 19) but not in the primary visual cortex. Later attention-related reactivations in the primary visual cortex were found at about 110 ms after stimulus onset. The results suggest that involuntary as well as voluntary attention modulates visual processing at the level of extrastriate cortex; however, at least some different processes are involved by involuntary attention compared to voluntary attention. In addition, the possible feedback from higher visual cortex to the primary visual cortex is faster and occurs earlier in involuntary relative to voluntary attention task.

Modulation of the C1 visual event-related component by conditioned stimuli: evidence for sensory plasticity in early affective perception

Previous research has demonstrated optimized processing of motivationally significant stimuli early in perception. In the present study, the time course and underlying mechanisms for such fast differentiation are of interest. We investigated the involvement of the primary visual cortex in affective evaluation of conditioned stimuli (CSs). In order to elicit learning within the visual system we chose affective pictures as unconditioned stimuli and used laterally presented gratings as CSs. Using high-density electroencephalography, we demonstrated modulation of the C1 visual event-related component for threat-related stimuli versus neutral stimuli, which increased with continuing acquisition of affective meaning. The differentiation between aversive and neutral visual stimuli occurred as early as 65-90 ms after stimulus onset and suggested involvement of the primary visual areas in affective evaluation. As an underlying mechanism, we discuss short-term reorganization in visual cortex, enabling sensory amplification of specific visual features that are related to motivationally relevant information.

Event-related potentials reveal dissociable mechanisms for orienting and focusing visuospatial attention

The neural mechanisms supporting visuospatial orienting and focusing were investigated by recording event-related potentials (ERPs) in a cued, line-orientation discrimination task. Search arrays flashed randomly in the left or right visual field and were preceded by peripheral cues that varied in validity (valid or invalid, with 50% each) and size (large or small, with 50% each). Facilitation of response time was observed for valid trials, regardless of cue size. In contrast to previous cued search studies, however, small (i.e., more precise) cues were associated with delayed responses. Both the timing and the amplitudes of the early ERP components, P1 and N1, were modulated by attentional orienting, with valid trials eliciting a larger and later contralateral vP1 (ventral P1) and a smaller and later contralateral N1 compared to invalid trials. Attentional focusing modulated only the amplitudes of the P1 component, with precisely cued trials eliciting a larger dP1 (dorsal P1) than less precisely cued trials at both contralateral and ipsilateral sites. Thus, both attentional orienting and focusing modulate early stimulus processing stages that overlap in time, but with dissociable effects on the scalp distribution of these components, indicating possibly different underlying mechanisms. In addition, the results support the notion that voluntary and involuntary allocations of visuospatial attention are mediated by different underlying neural processes.

Modulations of the visual N1 component of event-related potentials by central and peripheral cueing

OBJECTIVE

The aim of this study is to investigate the effects of the central and peripheral cueing on N1 component of the event-related potentials (ERPs) and the time course of these effects.

METHODS

ERPs were recorded while participants performed a discrimination task on the height of target bars, which were presented after informative-central, informative-peripheral or uninformative-peripheral cues with stimulus onset asynchronies (SOAs) of 100, 300, 500 or 700 ms.

RESULTS

Peripheral cues (informative and uninformative) elicited stronger effects of cue validity on N1 300 ms after cue onset, whereas central cues led to a more sustained validity effect on N1, with later stronger effects, at 500 ms SOA.

CONCLUSIONS

The present data showed that central and peripheral cues affected to the level of processing reflected by the N1 component, but there were differences in the time course of these effects. Attentional orienting in response to central cueing resulted in a sustained validity effect on N1, relative to the more transitory activation of the process reflected by the N1 validity effect in this peripheral cueing task.

SIGNIFICANCE

This study provides a detailed within-subject analysis of the time course of the effects of central and peripheral cueing on N1.

Kanizsa subjective figures capture visual spatial attention: evidence from electrophysiological and behavioral data

Figural binding and attention are two important processes that help to perceive the outside world. Binding is necessary to link together the different features of single objects which are represented in a distributed fashion in the brain. Attention serves to focus onto a small subset of incoming information. It is still not clear how exactly these two mechanisms operate and interact. We performed two experiments employing illusory Kanizsa figures (KFs) to investigate the temporal order of figural binding and spatial attention. In a visual search task, subjects had to detect the presence of a KF among distractor stimuli. We found only a slight increase of reaction times when increasing the number of distractors, indicating that KFs popped out and drew the perceiver's attention. In a further event-related potential (ERP) study, we used displays of the search task as non-informative cue for a subsequent target choice-reaction task. Enhanced contralateral negative amplitudes (starting at about 230 ms) over ventral occipital areas were found for cue displays which included a KF. For target stimuli, faster reaction times and enhanced ipsilateral N1 amplitudes over occipito-parietal areas were observed for validly (target presentation inside a KF) as compared to invalidly cued targets (target presentation outside a KF). Furthermore, enhanced contralateral N1 amplitudes were found for invalidly cued targets. It might be that interactions between perceptual closure processing of the ventral pathway and spatial target processing of the dorsal pathway contributed to the present result. We conclude that KFs automatically capture spatial attention when used as visual cues.

The time course of the effects of central and peripheral cues on visual processing: an event-related potentials study

OBJECTIVE

The varying results of visual event-related potential (ERP) studies of central and peripheral cueing suggest that these types of cue may modulate stimuli processing with different time courses. The aim of this study was to investigate differences in the time course of facilitatory effects on the visual processing induced by peripheral and central cues.

METHODS

ERPs were recorded for visual target stimuli that were preceded by informative-central, informative-peripheral or uninformative-peripheral cues with stimulus onset asynchronies (SOAs) of 100, 300, 500 or 700 ms.

RESULTS

Validly cued stimuli elicited an enhanced P1 component with peripheral cueing at 100 ms SOA. P1 amplitude in valid trials was reduced at 300, 500 and 700 ms SOAs with uninformative-peripheral cueing, but only at 500 ms SOA with informative-peripheral cueing. With informative-central cueing, there was no validity effect on P1.

CONCLUSIONS

These results suggest that the automatic attraction of attention by a peripheral cue results in improved sensory processing at the cued location. This facilitation is replaced by an inhibitory effect when SOA increases, although cue informativeness may modulate this effect. Central cueing does not affect sensory processing at the P1 level.