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1.  Neural processing stages during object-substitution masking and their relationship to perceptual awareness 
Neuropsychologia  2013;51(10):1907-1917.
The extent of visual perceptual processing that occurs in the absence of awareness is as yet unclear. Here we examined event-related-potential (ERP) indices of visual and cognitive processes as awareness was manipulated through object-substitution masking (OSM), an awareness-disrupting effect that has been hypothesized to result from the disruption of reentrant signaling to low-level visual cortical areas. In OSM, a visual stimulus array is briefly presented that includes a parafoveal visual target denoted by a cue, typically consisting of several surrounding dots. When the offset of the target-surrounding cue dots are delayed relative to the rest of the array, a striking reduction in the perception of the target image surrounded by the dots is observed. Using faces and houses as the target stimuli, we found that successful OSM reduced or eliminated all the measured electrophysiological indices of visual processing stages after 130 ms post-stimulus. More specifically, when targets were missed within the masked condition (i.e., on trials with effective OSM that disrupted awareness), we observed fully intact early feed-forward processing up through the visual extrastriate P1 ERP component peaking at 100 ms, followed by reduced low-level activity over the occipital pole 130–170 ms post-stimulus, reduced ERP indices of lateralized shifts of attention toward the parafoveal target, reduced object-generic visual processing, abolished object-category-specific (face-specific) processing, and reduced late visual short-term-memory processing activity. The results provide a comprehensive electrophysiological account of the neurocognitive underpinnings of effective OSM of visual-object images, including evidence for central roles of early reentrant signal disruption and inadequate visual attentional deployment.
doi:10.1016/j.neuropsychologia.2013.05.023
PMCID: PMC3919456  PMID: 23751171
Vision; awareness; perception; attention; substitution masking; electrophysiology
2.  Task preparation processes related to reward prediction precede those related to task-difficulty expectation 
NeuroImage  2013;84:10.1016/j.neuroimage.2013.09.039.
Recently, attempts have been made to disentangle the neural underpinnings of preparatory processes related to reward and attention. Functional magnetic resonance imaging (fMRI) research showed that neural activity related to the anticipation of reward and to attentional demands invokes neural activity patterns featuring large-scale overlap, along with some differences and interactions. Due to the limited temporal resolution of fMRI, however, the temporal dynamics of these processes remain unclear. Here, we report an event-related potentials (ERP) study in which cued attentional demands and reward prospect were combined in a factorial design. Results showed that reward prediction dominated early cue processing, as well as the early and later parts of the contingent negative variation (CNV) slow-wave ERP component that has been associated with task-preparation processes. Moreover these reward-related electrophysiological effects correlated across participants with response-time speeding on reward-prospect trials. In contrast, cued attentional demands affected only the later part of the CNV, with the highest amplitudes following cues predicting high-difficulty potential-reward targets, thus suggesting maximal task preparation when the task requires it and entails reward prospect. Consequently, we suggest that task-preparation processes triggered by reward can arise earlier, and potentially more directly, than strategic top-down aspects of preparation based on attentional demands.
doi:10.1016/j.neuroimage.2013.09.039
PMCID: PMC3863725  PMID: 24064071
Reward; attention; event-related potentials; contingent negative variation; visual attention
3.  Experience-Dependent Hemispheric Specialization of Letters and Numbers is Revealed in Early Visual Processing 
Journal of cognitive neuroscience  2014;26(10):2239-2249.
Recent functional magnetic resonance imaging research has demonstrated that letters and numbers are preferentially processed in distinct regions and hemispheres in the visual cortex. In particular, the left visual cortex preferentially processes letters compared to numbers, while the right visual cortex preferentially processes numbers compared to letters. Because letters and numbers are cultural inventions and are otherwise physically arbitrary, such a double dissociation is strong evidence for experiential effects on neural architecture. Here, we use the high temporal resolution of event-related potentials (ERPs) to investigate the temporal dynamics of the neural dissociation between letters and numbers. We show that the divergence between ERP traces to letters and numbers emerges very early in processing. Letters evoked greater N1 waves (latencies 140–170 ms) than did numbers over left occipital channels, while numbers evoked greater N1s than letters over the right, suggesting letters and numbers are preferentially processed in opposite hemispheres early in visual encoding. Moreover, strings of letters, but not single letters, elicited greater P2 ERP waves, (starting around 250 ms) than numbers did over the left hemisphere, suggesting that the visual cortex is tuned to selectively process combinations of letters, but not numbers, further along in the visual processing stream. Additionally, the processing of both of these culturally defined stimulus types differentiated from similar but unfamiliar visual stimulus forms (false fonts) even earlier in the processing stream (the P1 at 100 ms). These findings imply major cortical specialization processes within the visual system driven by experience with reading and mathematics.
doi:10.1162/jocn_a_00621
PMCID: PMC4261939  PMID: 24669789
Letter processing; number processing; ERP; hemispheric specialization
4.  Differential Functional Roles of Slow-Wave and Oscillatory-Alpha Activity in Visual Sensory Cortex during Anticipatory Visual–Spatial Attention 
Cerebral Cortex (New York, NY)  2011;21(10):2204-2216.
Markers of preparatory visual–spatial attention in sensory cortex have been described both as lateralized, slow-wave event-related potential (ERP) components and as lateralized changes in oscillatory-electroencephalography alpha power, but the roles of these markers and their functional relationship are still unclear. Here, 3 versions of a visual–spatial cueing paradigm, differing in perceptual task difficulty and/or response instructions, were used to investigate the functional relationships between posterior oscillatory-alpha changes and our previously reported posterior, slow-wave biasing-related negativity (swBRN) ERP activity. The results indicate that the swBRN reflects spatially specific, pretarget preparatory activity sensitive to the expected perceptual difficulty of the target detection task, correlating in both location and strength with the early sensory-processing N1 ERP to the target, consistent with reflecting a preparatory baseline-shift mechanism. In contrast, contralateral event-related decreases in alpha-band power were relatively insensitive to perceptual difficulty and differed topographically from both the swBRN and target N1. Moreover, when response instructions emphasized making immediate responses to targets, compared with prescribing delayed responses, contralateral alpha-event-related desynchronization activity was particularly strong and correlated with the longer latency target-P3b activity. Thus, in contrast to the apparent perceptual-biasing role of swBRN activity, contralateral posterior alpha activity may represent an attentionally maintained task set linking stimulus-specific information and task-specific response requirements.
doi:10.1093/cercor/bhq279
PMCID: PMC3169654  PMID: 21372123
attention; biasing; control; EEG; ERP
5.  The Temporal Dynamics of Object Processing in Visual Cortex During the Transition from Distributed to Focused Spatial Attention 
Journal of cognitive neuroscience  2011;23(12):4094-4105.
Several major cognitive neuroscience models have posited that focal spatial attention is required to integrate different features of an object to form a coherent perception of it within a complex visual scene. Although many behavioral studies have supported this view, some have suggested that complex perceptual discrimination can be performed even with substantially reduced focal spatial attention, calling into question the complexity of object representation that can be achieved without focused spatial attention. In the present study, we took a cognitive neuroscience approach to this problem by recording cognition-related brain activity both to help resolve the questions about the role of focal spatial attention in object-categorization processes and to investigate the underlying neural mechanisms, focusing particularly on the temporal cascade of these attentional and perceptual processes in visual cortex. More specifically, we recorded electrical brain activity in humans engaged in a specially designed cued-visual-search paradigm to probe the object-related visual processing before and during the transition from distributed to focal spatial attention. The onset times of the color-popout cueing information, indicating where within an object array the subject was to shift attention, was parametrically varied relative to the presentation of the array (i.e., either occurring simultaneously or being delayed by 50 or 100 ms). The electrophysiological results demonstrate that some level of object-specific representation can be formed in parallel for multiple items across the visual field under spatially distributed attention, before focal spatial attention is allocated to any of them. The object-discrimination process appears to be subsequently amplified as soon as focal spatial attention is directed to a specific location and object. This set of novel neurophysiological findings thus provides important new insights on fundamental issues that have been long-debated in cognitive neuroscience concerning both object-related processing and the role of attention.
doi:10.1162/jocn_a_00045
PMCID: PMC3422653  PMID: 21563884
6.  Electrophysiological Evidence for the Involvement of the Approximate Number System in Preschoolers’ Processing of Spoken Number Words 
Journal of cognitive neuroscience  2014;26(9):1891-1904.
Little is known about the neural underpinnings of number-word comprehension in young children. Here we investigated the neural processing of these words during the crucial developmental window in which children learn their meanings and whether such processing relies on the Approximate Number System (ANS). Event-related potentials (ERPs) were recorded as 3- to 5-year-old children heard the words one, two, three or six while looking at pictures of 1, 2, 3 or 6 objects. The number word was incongruent with the number of visual objects on half the trials, and congruent on the other half. Children’s number-word comprehension predicted their ERP incongruency effects. Specifically, children with the least number-word knowledge did not show any ERP incongruency effects, whereas those with intermediate and high number-word knowledge showed an enhanced, negative-polarity ERP incongruency response (Ninc) over centro-parietal sites from 200–500 ms after the number-word onset. This negativity was followed by an enhanced, positive- polarity incongruency effect (Pinc) that emerged bilaterally over parietal sites at about 700 ms. Moreover, children with the most number-word knowledge showed ratio dependence in the Pinc (larger for greater compared to smaller numerical mismatches), a hallmark of the ANS. A similar modulation of the Pinc from 700–800 ms for number words “one”, “two” and “three” was found in children with intermediate number-word knowledge. These results provide the first neural correlates of spoken number-word comprehension in preschoolers and are consistent with the view that children map number words onto approximate-number representations before they master the verbal count list.
doi:10.1162/jocn_a_00631
PMCID: PMC4228473  PMID: 24702455
7.  The cross-modal spread of attention reveals differential constraints for the temporal and spatial linking of visual and auditory stimulus events 
The integration of multisensory information has been shown to be guided by spatial and temporal proximity, as well as to be influenced by attention. Here we used neural measures of the multisensory spread of attention to investigate the spatial and temporal linking of synchronous versus near-synchronous auditory and visual events. Human participants attended selectively to one of two lateralized visual-stimulus streams while task-irrelevant tones were presented centrally. Electrophysiological measures of brain activity showed that tones occurring simultaneously or delayed by 100ms were temporally linked to an attended visual stimulus, as reflected by robust cross-modal spreading-of-attention activity, but not when delayed by 300ms. The neural data also indicated a ventriloquist-like spatial linking of the auditory to the attended visual stimuli, but only when occurring simultaneously. These neurophysiological results thus provide unique insight into the temporal and spatial principles of multisensory feature integration and the fundamental role attention plays in such integration.
doi:10.1523/JNEUROSCI.5298-10.2011
PMCID: PMC3224815  PMID: 21632920
Multisensory; Attention; Temporal; Spatial; ERP; Ventriloquism
8.  Face Processing is Gated by Visual Spatial Attention 
Human perception of faces is widely believed to rely on automatic processing by a domain-specific, modular component of the visual system. Scalp-recorded event-related potential (ERP) recordings indicate that faces receive special stimulus processing at around 170 ms poststimulus onset, in that faces evoke an enhanced occipital negative wave, known as the N170, relative to the activity elicited by other visual objects. As predicted by modular accounts of face processing, this early face-specific N170 enhancement has been reported to be largely immune to the influence of endogenous processes such as task strategy or attention. However, most studies examining the influence of attention on face processing have focused on non-spatial attention, such as object-based attention, which tend to have longer-latency effects. In contrast, numerous studies have demonstrated that visual spatial attention can modulate the processing of visual stimuli as early as 80 ms poststimulus – substantially earlier than the N170. These temporal characteristics raise the question of whether this initial face-specific processing is immune to the influence of spatial attention. This question was addressed in a dual-visual-stream ERP study in which the influence of spatial attention on the face-specific N170 could be directly examined. As expected, early visual sensory responses to all stimuli presented in an attended location were larger than responses evoked by those same stimuli when presented in an unattended location. More importantly, a significant face-specific N170 effect was elicited by faces that appeared in an attended location, but not in an unattended one. In summary, early face-specific processing is not automatic, but rather, like other objects, strongly depends on endogenous factors such as the allocation of spatial attention. Moreover, these findings underscore the extensive influence that top-down attention exercises over the processing of visual stimuli, including those of high natural salience.
doi:10.3389/neuro.09.010.2007
PMCID: PMC2525978  PMID: 18958224
N170; ERPs; FFA; STS; event-related potentials; visual attention
9.  Resolving conflicting views: Gaze and arrow cues do not trigger rapid reflexive shifts of attention 
Visual cognition  2013;21(1):61-71.
It has become widely accepted that the direction of another individual’s eye gaze induces rapid, automatic, attentional orienting, due to it being such a vital cue as to where in our environment we should attend. This automatic orienting has also been associated with the directional-arrow cues used in studies of spatial attention. Here, we present evidence that the response-time cueing effects reported for spatially non-predictive gaze and arrow cues are not the result of rapid, automatic shifts of attention. For both cue types, response-time effects were observed only for long-duration cue and target stimuli that overlapped temporally, were largest when the cues were presented simultaneously with the response-relevant target, and were driven by a slowing of responses for invalidly cued targets rather than speeding for validly cued ones. These results argue against automatic attention-orienting accounts and support a novel spatial-incongruency explanation for a whole class of rapid behavioral cueing effects.
doi:10.1080/13506285.2013.775209
PMCID: PMC3634615  PMID: 23626482
Attention; conflict; gaze cues; arrow cues; automatic orienting
10.  Is one enough? The case for non-additive influences of visual features on crossmodal Stroop interference 
When different perceptual signals arising from the same physical entity are integrated, they form a more reliable sensory estimate. When such repetitive sensory signals are pitted against other competing stimuli, such as in a Stroop Task, this redundancy may lead to stronger processing that biases behavior toward reporting the redundant stimuli. This bias would therefore, be expected to evoke greater incongruency effects than if these stimuli did not contain redundant sensory features. In the present paper we report that this is not the case for a set of three crossmodal, auditory-visual Stroop tasks. In these tasks participants attended to, and reported, either the visual or the auditory stimulus (in separate blocks) while ignoring the other, unattended modality. The visual component of these stimuli could be purely semantic (words), purely perceptual (colors), or the combination of both. Based on previous work showing enhanced crossmodal integration and visual search gains for redundantly coded stimuli, we had expected that relative to the single features, redundant visual features would have induced both greater visual distracter incongruency effects for attended auditory targets, and been less influenced by auditory distracters for attended visual targets. Overall, reaction times were faster for visual targets and were dominated by behavioral facilitation for the cross-modal interactions (relative to interference), but showed surprisingly little influence of visual feature redundancy. Post-hoc analyses revealed modest and trending evidence for possible increases in behavioral interference for redundant visual distracters on auditory targets, however, these effects were substantially smaller than anticipated and were not accompanied by a redundancy effect for behavioral facilitation or for attended visual targets.
doi:10.3389/fpsyg.2013.00799
PMCID: PMC3813948  PMID: 24198800
multisensory conflict; stroop task; redundancy gains; stimulus onset asynchrony (SOA)
11.  Rapid brain responses independently predict gain-maximization and loss-minimization during economic decision-making 
Success in many decision-making scenarios depends on the ability to maximize gains and minimize losses. Even if an agent knows which cues lead to gains and which lead to losses, that agent could still make choices yielding suboptimal rewards. Here, by analyzing event-related potentials (ERPs) recorded in humans during a probabilistic gambling task, we show that individuals’ behavioral tendencies to maximize gains and to minimize losses are associated with their ERP responses to the receipt of those gains and losses, respectively. We focused our analyses on ERP signals that predict behavioral adjustment: the fronto-central feedback-related negativity (FRN) and two P300 (P3) subcomponents: the fronto-central P3a and the parietal P3b. We found that, across participants, gain-maximization was predicted by differences in amplitude of the P3b for suboptimal versus optimal gains (i.e., P3b amplitude difference between the least good and the best possible gains). Conversely, loss-minimization was predicted by differences in the P3b amplitude to suboptimal versus optimal losses (i.e., difference between the worst and the least bad losses). Finally, we observed that the P3a and P3b, but not the FRN, predicted behavioral adjustment on subsequent trials, suggesting a specific adaptive mechanism by which prior experience may alter ensuing behavior. These findings indicate that individual differences in gain-maximization and loss-minimization are linked to individual differences in rapid neural responses to monetary outcomes.
doi:10.1523/JNEUROSCI.4242-12.2013
PMCID: PMC3683537  PMID: 23595758
12.  The rapid distraction of attentional resources toward the source of incongruent stimulus input during multisensory conflict 
Journal of cognitive neuroscience  2012;25(4):623-635.
Neuroimaging work on multisensory conflict suggests that the relevant modality receives enhanced processing in the face of incongruency. However, the degree of stimulus processing in the irrelevant modality and the temporal cascade of the attentional modulations in either the relevant or irrelevant modalities are unknown. Here, we employed an audiovisual conflict paradigm with a sensory probe in the task-irrelevant modality (vision) to gauge the attentional allocation to that modality. Event-related potentials (ERPs) were recorded as subjects attended to and discriminated spoken auditory letters while ignoring simultaneous bilateral visual letter stimuli that were either fully congruent, fully incongruent, or partially incongruent (one side incongruent, one congruent) with the auditory stimulation. Half of the audiovisual letter stimuli were followed 500-700 ms later by a bilateral visual probe stimulus. As expected, ERPs to the audiovisual stimuli showed an incongruency ERP effect (fully incongruent versus fully congruent) of an enhanced, centrally distributed, negative-polarity wave starting ~250 ms. More critically here, the sensory ERP components to the visual probes were larger when they followed fully incongruent versus fully congruent multisensory stimuli, with these enhancements greatest on fully incongruent trials with the slowest response times. In addition, on the slowest-response partially incongruent trials, the P2 sensory component to the visual probes was larger contralateral to the preceding incongruent visual stimulus. These data suggest that, in response to conflicting multisensory stimulus input, the initial cognitive effect is a capture of attention by the incongruent irrelevant-modality input, pulling neural processing resources toward that modality, resulting in rapid enhancement, rather than rapid suppression, of that input.
doi:10.1162/jocn_a_00336
PMCID: PMC3662056  PMID: 23249355
13.  Strategic allocation of attention reduces temporally predictable stimulus conflict 
Journal of cognitive neuroscience  2012;24(9):1834-1848.
Humans are able to continuously monitor environmental situations and adjust their behavioral strategies to optimize performance. Here we investigate the behavioral and brain adjustments that occur when conflicting stimulus elements are, or are not, temporally predictable. Event-related potentials (ERPs) were collected while manual-response variants of the Stroop task were performed in which the stimulus onset asynchronies (SOAs) between the relevant-color and irrelevant-word stimulus components were either randomly intermixed, or held constant, within each experimental run. Results indicated that the size of both the neural and behavioral effects of stimulus incongruency varied with the temporal arrangement of the stimulus components, such that the random-SOA arrangements produced the greatest incongruency effects at the earliest irrelevant-first SOA (−200 ms) and the constant-SOA arrangements produced the greatest effects with simultaneous presentation. These differences in conflict processing were accompanied by rapid (~150 ms) modulations of the sensory ERPs to the irrelevant distracter components when they occurred consistently first. These effects suggest that individuals are able to strategically allocate attention in time to mitigate the influence of a temporally predictable distracter. As these adjustments are instantiated by the subjects without instruction, they reveal a form of rapid strategic learning for dealing with temporally predictable stimulus incongruency.
doi:10.1162/jocn_a_00209
PMCID: PMC3632454  PMID: 22360623
Stroop task; conflict processing; event-related potentials (ERPs); incongruency; Stimulus Onset Asynchrony (SOA)
14.  Cochlear implants: matching the prosthesis to the brain and facilitating desired plastic changes in brain function 
Progress in brain research  2011;194:117-129.
The cochlear implant (CI) is one of the great success stories of modern medicine. A high level of function is provided for most patients. However, some patients still do not achieve excellent or even good results using the present-day devices. Accumulating evidence is pointing to differences in the processing abilities of the “auditory brain” among patients as a principal contributor to this remaining and still large variability in outcomes. In this chapter, we describe a new approach to the design of CIs that takes these differences into account and thereby may improve outcomes for patients with compromised auditory brains.
doi:10.1016/B978-0-444-53815-4.00012-1
PMCID: PMC3697475  PMID: 21867799
cochlear implant; cochlear prosthesis; auditory prosthesis; brain–machine interface; brain plasticity; neural prostheses; hearing; deafness; central auditory processing; auditory cortex
15.  The influence of different Stop-signal response time estimation procedures on behavior-behavior and brain-behavior correlations 
Behavioural Brain Research  2012;229(1):123-130.
The fundamental cognitive-control function of inhibitory control over motor behavior has been extensively investigated using the Stop-signal task. The critical behavioral parameter describing stopping efficacy is the Stop-signal response time (SSRT), and correlations with estimates of this parameter are commonly used to establish that other variables (e.g., other behavioral measures or brain activity measures) are closely related to inhibitory motor control. Recently, however, it has been argued that SSRT estimates can be strongly distorted if participants strategically slow down their responses over the course of the experiment, resulting in the SSRT no longer reliably representing response-inhibition efficacy. Here, we performed new analyses on behavioral and functional data from an fMRI version of the Stop-signal task to gauge the consequences of using different SSRT estimation approaches that are differentially prone to the influence of strategic response slowing. The results indicate that the SSRT estimation approach can dramatically change behavior-behavior correlations. Specifically, a correlation between the SSRT and Go-trial accuracy that was highly significant with one estimation approach, virtually disappeared for the other. Additional analyses indeed supported that this effect was related to strategic response slowing. Concerning brain-behavior correlations, only the left anterior insula was found to be significantly correlated with the SSRT within the set of areas tested here. Interestingly, this brain-behavior correlation differed little for the different SSRT-estimation procedures. In sum, the current results highlight that different SSRT-estimation procedures can strongly influence the distribution of SSRT values across subjects, which in turn can ramify into correlational analyses with other parameters.
doi:10.1016/j.bbr.2012.01.003
PMCID: PMC3306010  PMID: 22245527
inhibitory motor control; Stop-signal task; Stop-signal response time; brain-behavior correlations; human
16.  Rapid Electrophysiological Brain Responses are Influenced by both Valence and Magnitude of Monetary Rewards 
Journal of cognitive neuroscience  2008;20(11):2058-2069.
Negative outcomes, whether self-identified or resulting from feedback, cause a short-latency negative deflection in the event-related-potential (ERP) waveform over medial frontal electrode sites. This brain response is considered a type of “error related negativity” representing a coarse evaluation of performance; within monetary gambling tasks, it has been postulated to signal the valence of the chosen outcome. Yet, under such feedback circumstances, other information besides experienced valence may be critical for the adaptive control of behavior. Here, we used a gambling task in which subjects chose between two options that could vary in both outcome valence (gain or loss) and outcome magnitude (larger or smaller). We measured changes in brain ERP responses associated with the presentation of the outcomes. We found, as shown in prior studies, that valence of the chosen outcome has an early effect upon frontal ERPs, peaking at ~250 ms. However, our results demonstrated that the early ERP responses to outcome feedback were driven not just by valence, but by the combination of valence and magnitude for both chosen and unchosen options. Beginning even earlier, at around 150 ms, responses to high-consequence outcomes showed a greater, more centrally distributed, positive potential than those involving low-consequence outcomes, independent of valence. Furthermore, the amplitude of these early effects was significantly modulated by the sequence of outcomes in previous trials. These results indicate that early evaluation of feedback goes beyond simple identification of valence – it involves the consideration of multiple factors, including outcome magnitude, context of unchosen options, and prior history.
doi:10.1162/jocn.2008.20134
PMCID: PMC3612129  PMID: 18416673
17.  Electrophysiological Measures of Time Processing in Infant and Adult Brains: Weber’s Law Holds 
Journal of cognitive neuroscience  2008;20(2):193-203.
Behavioral studies have demonstrated that time perception in adults, children, and nonhuman animals is subject to Weber’s Law. More specifically, as with discriminations of other features, it has been found that it is the ratio between two durations rather than their absolute difference that controls the ability of an animal to discriminate them. Here, we show that scalp-recorded event-related electrical brain potentials (ERPs) in both adults and 10-month-old human infants, in response to changes in interstimulus interval (ISI), appear to obey the scalar property found in time perception in adults, children, and nonhuman animals. Using a timing-interval oddball paradigm, we tested adults and infants in conditions where the ratio between the standard and deviant interval in a train of homogeneous auditory stimuli varied such that there was a 1:4 (only for the infants), 1:3, 1:2, and 2:3 ratio between the standard and deviant intervals. We found that the amplitude of the deviant-triggered mismatch negativity ERP component (deviant-ISI ERP minus standard-ISI ERP) varied as a function of the ratio of the standard to deviant interval. Moreover, when absolute values were varied and ratio was held constant, the mismatch negativity did not vary.
doi:10.1162/jocn.2008.20016
PMCID: PMC3607948  PMID: 18275328
18.  The Involvement of the Dopaminergic Midbrain and Cortico-Striatal-Thalamic Circuits in the Integration of Reward Prospect and Attentional Task Demands 
Cerebral Cortex (New York, NY)  2011;22(3):607-615.
Reward has been shown to promote human performance in multiple task domains. However, an important debate has developed about the uniqueness of reward-related neural signatures associated with such facilitation, as similar neural patterns can be triggered by increased attentional focus independent of reward. Here, we used functional magnetic resonance imaging to directly investigate the neural commonalities and interactions between the anticipation of both reward and task difficulty, by independently manipulating these factors in a cued-attention paradigm. In preparation for the target stimulus, both factors increased activity within the midbrain, dorsal striatum, and fronto-parietal areas, while inducing deactivations in default-mode regions. Additionally, reward engaged the ventral striatum, posterior cingulate, and occipital cortex, while difficulty engaged medial and dorsolateral frontal regions. Importantly, a network comprising the midbrain, caudate nucleus, thalamus, and anterior midcingulate cortex exhibited an interaction between reward and difficulty, presumably reflecting additional resource recruitment for demanding tasks with profitable outcome. This notion was consistent with a negative correlation between cue-related midbrain activity and difficulty-induced performance detriments in reward-predictive trials. Together, the data demonstrate that expected value and attentional demands are integrated in cortico-striatal-thalamic circuits in coordination with the dopaminergic midbrain to flexibly modulate resource allocation for an effective pursuit of behavioral goals.
doi:10.1093/cercor/bhr134
PMCID: PMC3278318  PMID: 21680848
attention; fMRI; midbrain; reward; task demands
19.  Is conflict monitoring supramodal? Spatiotemporal dynamics of cognitive control processes in an auditory Stroop task 
The electrophysiological correlates of conflict processing and cognitive control have been well characterized for the visual modality in paradigms such as the Stroop task. Much less is known about corresponding processes in the auditory modality. Here, electroencephalographic recordings of brain activity were measured during an auditory Stroop task, using three different forms of behavioral response (Overt verbal, Covert verbal, and Manual), that closely paralleled our previous visual-Stroop study. As expected, behavioral responses were slower and less accurate for incongruent compared to congruent trials. Neurally, incongruent trials showed an enhanced fronto-central negative-polarity wave (Ninc), similar to the N450 in visual-Stroop tasks, with similar variations as a function of behavioral response mode, but peaking ~150 ms earlier, followed by an enhanced positive posterior wave. In addition, sequential behavioral and neural effects were observed that supported the conflict-monitoring and cognitive-adjustment hypothesis. Thus, while some aspects of the conflict detection processes, such as timing, may be modality-dependent, the general mechanisms would appear to be supramodal.
doi:10.3758/s13415-011-0060-z
PMCID: PMC3422637  PMID: 21964643
Auditory; Stroop; Conflict; EEG; Incongruency
20.  Reward Associations Reduce Behavioral Interference by Changing the Temporal Dynamics of Conflict Processing 
PLoS ONE  2013;8(1):e53894.
Associating stimuli with the prospect of reward typically facilitates responses to those stimuli due to an enhancement of attentional and cognitive-control processes. Such reward-induced facilitation might be especially helpful when cognitive-control mechanisms are challenged, as when one must overcome interference from irrelevant inputs. Here, we investigated the neural dynamics of reward effects in a color-naming Stroop task by employing event-related potentials (ERPs). We found that behavioral facilitation in potential-reward trials, as compared to no-reward trials, was paralleled by early ERP modulations likely indexing increased attention to the reward-predictive stimulus. Moreover, reward changed the temporal dynamics of conflict-related ERP components, which may be a consequence of an early access to the various stimulus features and their relationships. Finally, although word meanings referring to potential-reward colors were always task-irrelevant, they caused greater interference compared to words referring to no-reward colors, an effect that was accompanied by a relatively early fronto-central ERP modulation. This latter observation suggests that task-irrelevant reward information can undermine goal-directed behavior at an early processing stage, presumably reflecting priming of a goal-incompatible response. Yet, these detrimental effects of incongruent reward-related words were absent in potential-reward trials, apparently due to the prioritized processing of task-relevant reward information. Taken together, the present data demonstrate that reward associations can influence conflict processing by changing the temporal dynamics of stimulus processing and subsequent cognitive-control mechanisms.
doi:10.1371/journal.pone.0053894
PMCID: PMC3542315  PMID: 23326530
21.  Arrow-elicited cueing effects at short intervals: Rapid attentional orienting or cue-target stimulus conflict? 
Cognition  2011;122(1):96-101.
The observation of cueing effects (faster responses for cued than uncued targets) rapidly following centrally-presented arrows has led to the suggestion that arrows trigger rapid, automatic, shifts of spatial attention. However, these effects have primarily been observed during easy target-detection tasks when both cue and target remain on the screen until the behavioral response. We manipulated stimulus duration and task difficulty in an attention-cueing experiment to explore non-attentional explanations for rapid cueing effects. Contrary to attention-based predictions, short-interval cueing effects were observed only for long-duration cue and target stimuli, occurred even when the cue and target were presented simultaneously, and were driven by slowing of the uncued-target responses, rather than any facilitation for cued targets. We propose that, under these long-duration, short-interval conditions, the processing of the cue and target interact more extensively in the brain, and that when the cue and target convey incongruent spatial information (i.e., on invalidly cued trials) it leads to conflict-related slowing of responses
doi:10.1016/j.cognition.2011.08.018
PMCID: PMC3215838  PMID: 21975079
Spatial cueing; Arrow cues; Attention; Automatic orienting; Conflict
22.  Overlapping Parietal Activity in Memory and Perception: Evidence for the Attention to Memory Model 
Journal of cognitive neuroscience  2011;23(11):3209-3217.
The specific role of different parietal regions to episodic retrieval is a topic of intense debate. According to the Attention to Memory (AtoM) model, dorsal parietal cortex (DPC) mediates top–down attention processes guided by retrieval goals, whereas ventral parietal cortex (VPC) mediates bottom–up attention processes captured by the retrieval output or the retrieval cue. This model also hypothesizes that the attentional functions of DPC and VPC are similar for memory and perception. To investigate this last hypothesis, we scanned participants with event-related fMRI whereas they performed memory and perception tasks, each comprising an orienting phase (top–down attention) and a detection phase (bottom–up attention). The study yielded two main findings. First, consistent with the AtoM model, orienting-related activity for memory and perception overlapped in DPC, whereas detection-related activity for memory and perception overlapped in VPC. The DPC overlap was greater in the left intraparietal sulcus, and the VPC overlap in the left TPJ. Around overlapping areas, there were differences in the spatial distribution of memory and perception activations, which were consistent with trends reported in the literature. Second, both DPC and VPC showed stronger connectivity with medial-temporal lobe during the memory task and with visual cortex during the perception task. These findings suggest that, during memory tasks, some parietal regions mediate similar attentional control processes to those involved in perception tasks (orienting in DPC vs. detection in VPC), although on different types of information (mnemonic vs. sensory).
doi:10.1162/jocn_a_00065
PMCID: PMC3518433  PMID: 21568633
23.  Sandwich masking eliminates both visual awareness of faces and face-specific brain activity through a feed-forward mechanism 
Journal of vision  2011;11(7):10.1167/11.7.3 3.
It is generally agreed that considerable amounts of low-level sensory processing of visual stimuli can occur without conscious awareness. On the other hand, the degree of higher-level visual processing that occurs in the absence of awareness is as yet unclear. Here, event-related potential (ERP) measures of brain activity were recorded during a sandwich-masking paradigm, a commonly used approach for attenuating conscious awareness of visual stimulus content. In particular, the present study used a combination of ERP activation contrasts to track both early sensory-processing ERP components and face-specific N170 ERP activations, in trials with versus without awareness. The electrophysiological measures revealed that the sandwich masking abolished the early face-specific N170 neural response (onset at ~170 ms post-stimulus), an effect that paralleled the abolition of awareness of face stimuli. Furthermore, however, the masking appeared to render a strong attenuation of earlier feed-forward visual sensory-processing signals. This early attenuation presumably resulted in insufficient information being fed into the higher level visual system pathways specific to object category processing, thus leading to unawareness of the visual object content. These results support a coupling of visual awareness and neural indices of face processing, while also demonstrating an early low-level mechanism of interference in sandwich masking.
doi:10.1167/11.7.3
PMCID: PMC3513353  PMID: 21669859
24.  Video Game Players Show More Precise Multisensory Temporal Processing Abilities 
Recent research has demonstrated enhanced visual attention and visual perception in individuals with extensive experience playing action video games. These benefits manifest in several realms, but much remains unknown about the ways in which video game experience alters perception and cognition. The current study examined whether video game players’ benefits generalize beyond vision to multisensory processing by presenting video game players and non-video game players auditory and visual stimuli within a short temporal window. Participants performed two discrimination tasks, both of which revealed benefits for video game players: In a simultaneity judgment task, video game players were better able to distinguish whether simple visual and auditory stimuli occurred at the same moment or slightly offset in time, and in a temporal-order judgment task, they revealed an enhanced ability to determine the temporal sequence of multisensory stimuli. These results suggest that people with extensive experience playing video games display benefits that extend beyond the visual modality to also impact multisensory processing.
doi:10.3758/APP.72.4.1120
PMCID: PMC3314265  PMID: 20436205
25.  The multifaceted interplay between attention and multisensory integration 
Trends in Cognitive Sciences  2010;14(9):400-410.
Multisensory integration has often been characterized as an automatic process. Recent findings suggest that multisensory integration can occur across various stages of stimulus processing that are linked to, and can be modulated by, attention. Stimulus-driven, bottom-up mechanisms induced by cross-modal interactions can automatically capture attention towards multisensory events, particularly when competition to focus elsewhere is relatively low. Conversely, top-down attention can facilitate the integration of multisensory inputs and lead to a spread of attention across sensory modalities. These findings point to a more intimate and multifaceted interplay between attention and multisensory integration than was previously thought. We review developments in our understanding of the interactions between attention and multisensory processing, and propose a framework that unifies previous, apparently discordant findings.
doi:10.1016/j.tics.2010.06.008
PMCID: PMC3306770  PMID: 20675182

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