[show abstract][hide abstract] ABSTRACT: 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 100 ms were temporally linked to an attended visual stimulus, as reflected by robust cross-modal spreading-of-attention activity, but not when delayed by 300 ms. 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.
Journal of Neuroscience 06/2011; 31(22):7982-90. · 6.91 Impact Factor
[show abstract][hide abstract] ABSTRACT: 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.
[show abstract][hide abstract] ABSTRACT: Previously, we have shown that spatial attention to a visual stimulus can spread across both space and modality to a synchronously presented but task-irrelevant sound arising from a different location, reflected by a late-onsetting, sustained, negative-polarity event-related potential (ERP) wave over frontal-central scalp sites, probably originating in part from the auditory cortices. Here we explore the influence of cross-modal conflict on the amplitude and temporal dynamics of this multisensory spreading-of-attention activity. Subjects attended selectively to one of two concurrently presented lateral visually-presented letter streams to perform a sequential comparison task, while ignoring task-irrelevant, centrally presented spoken letters that could occur synchronously with either the attended or unattended lateral visual letters and could be either congruent or incongruent with them. Extracted auditory ERPs revealed that, collapsed across congruency conditions, attentional spreading across modalities started at approximately 220 ms, replicating our earlier findings. The interaction between attentional spreading and conflict occurred beginning at approximately 300 ms, with attentional-spreading activity being larger for incongruent trials. Thus, the increased processing of an incongruent, task-irrelevant sound in a multisensory stimulation appeared to occur some time after attention has spread from the attended visual part to the ignored auditory part, presumably reflecting the conflict detection and associated attentional capture requiring accrual of some multisensory interaction processes at a higher-level semantic processing stage.
European Journal of Neuroscience 05/2010; 31(10):1744-54. · 3.75 Impact Factor
[show abstract][hide abstract] ABSTRACT: Moderate doses of alcohol (blood alcohol concentration [BAC] of about 0.05%) may result in acute impairments at various levels of information processing. A number of reports have documented detrimental effects of moderate alcohol on the mismatch negativity (MMN), the electrocortical manifestation of a rapid (100 ms poststimulus) mechanism dedicated to the detection of unexpected auditory change (e.g., Jääskeläinen, et al., 1995). Recently, we and others identified a partial visual counterpart of the MMN, sometimes called the rareness-related negativity (RRN). Analogous to the MMN, the RRN evolves at about 100 ms after the unexpected change and was localized in visual cortex (Kenemans, et al., 2003). Rapid detection of unexpected events is important for everyday-life conditions like driving, prompting the question whether the visual RRN shows sensitivity to moderate alcohol similar to the MMN. In all, 16 subjects were tested either under moderate alcohol or under placebo. Unexpected visual change was implemented by presenting 2.4 versus 0.6 c/d gratings in pseudorandom sequences according to a deviant (10%)/standard (90%) schedule. The alcohol effects on MMN reported before were replicated. Furthermore, the RRN, defined as the difference between deviant and standard event-related potentials between 120 and 170 ms at Oz, was present under placebo but not under alcohol. It is concluded that moderate alcohol does indeed impair the rapid detection in visual cortex of unexpected changes. In contrast, electrocortical correlates of lower level sensory processing were still significantly present under alcohol.
Journal of Psychopharmacology 12/2008; 24(6):839-45. · 3.37 Impact Factor
[show abstract][hide abstract] ABSTRACT: Recent brain imaging studies using functional magnetic resonance imaging (fMRI) have implicated a frontal-parietal network in the top-down control of attention. However, little is known about the timing and sequence of activations within this network. To investigate these timing questions, we used event-related electrical brain potentials (ERPs) and a specially designed visual-spatial attentional-cueing paradigm, which were applied as part of a multi-methodological approach that included a closely corresponding event-related fMRI study using an identical paradigm. In the first 400 ms post cue, attention-directing and control cues elicited similar general cue-processing activity, corresponding to the more lateral subregions of the frontal-parietal network identified with the fMRI. Following this, the attention-directing cues elicited a sustained negative-polarity brain wave that was absent for control cues. This activity could be linked to the more medial frontal-parietal subregions similarly identified in the fMRI as specifically involved in attentional orienting. Critically, both the scalp ERPs and the fMRI-seeded source modeling for this orienting-related activity indicated an earlier onset of frontal versus parietal contribution ( approximately 400 versus approximately 700 ms). This was then followed ( approximately 800-900 ms) by pretarget biasing activity in the region-specific visual-sensory occipital cortex. These results indicate an activation sequence of key components of the attentional-control brain network, providing insight into their functional roles. More specifically, these results suggest that voluntary attentional orienting is initiated by medial portions of frontal cortex, which then recruit medial parietal areas. Together, these areas then implement biasing of region-specific visual-sensory cortex to facilitate the processing of upcoming visual stimuli.
[show abstract][hide abstract] ABSTRACT: Event-related potential (ERP) studies have shown that emotional stimuli elicit greater amplitude late positive-polarity potentials (LPPs) than neutral stimuli. This effect has been attributed to arousal, but emotional stimuli are also more semantically coherent than uncategorized neutral stimuli. ERPs were recorded during encoding of positive, negative, uncategorized neutral, and categorized neutral words. Differences in LPP amplitude elicited by emotional versus uncategorized neutral stimuli were evident from 450 to 1000 ms. From 450 to 700 ms, LPP effects at midline and right hemisphere frontal electrodes indexed arousal, whereas LPP effects at left hemisphere centro-parietal electrodes indexed semantic cohesion. This dissociation helps specify the processes underlying emotional stimulus encoding, and suggests the need to control for semantic cohesion in emotional information processing studies.
Brain and Cognition 11/2006; 62(1):43-57. · 2.82 Impact Factor
[show abstract][hide abstract] ABSTRACT: In the present study, we investigated control of selective attention to spatial frequency patterns, using a cueing paradigm. Subjects either used the instruction embedded in a word cue to prepare for the upcoming test stimulus (transient attention condition) or used the instruction they received before a block of trials (sustained reference condition), under completely similar stimulus conditions. The pattern of differential cue responses between these two conditions, reflecting top-down attentional control processes, was different between two groups of subjects, effectively canceling each other out. Despite comparable behavioral performance on both cues and targets, one group (n = 4) elicited a fronto-central-parietal positivity, starting 500 ms postcue over frontal and prefrontal areas, later including more central and posterior scalp sites, whereas another group (n = 8) started 400 ms postcue over central sites with a negativity, growing in strength over time and stabilizing over fronto-central sites. Only the group of eight subjects showed some evidence of occipital pretarget biasing activity. Independent of group, source modeling of the attentional control activity showed that attentional control was initiated in anterior, not posterior, parts of the brain. Furthermore, different underlying sources were found for both groups, in addition to signs of differential processing of target stimuli. Possible individual differences in attentional control ability and its relation to usage of different brain areas to deal with the task demands are discussed in more detail.
Brain Research 09/2006; 1105(1):46-60. · 2.88 Impact Factor
[show abstract][hide abstract] ABSTRACT: The effects of selective attention on the neural response to the violation of musical syntax were investigated in the present study. Musical chord progressions were played to nonmusicians while Event-Related Potentials (ERPs) were recorded. The five-chord progressions included 61% harmonically expected cadences (I-I(6)-IV-V-I), 26% harmonically unexpected cadences (I-I(6)-IV-V-N(6)), and 13% with one of the five chords having an intensity fadeout across its duration. During the attended condition, subjects responded by pressing a button upon detecting a fadeout in volume; during the unattended condition, subjects were given reading comprehension materials and instructed to ignore all auditory stimuli. In response to the harmonic deviant, an Early Anterior Negativity (EAN) was observed at 150-300 ms in both attention conditions, but it was much larger in amplitude in the attended condition. A second scalp-negative deflection was also identified at 380-600 ms following the harmonic deviants; this Late Negativity onset earlier during the attended condition. These results suggest strong effects of attention on the neural processing of harmonic syntax.
Cognitive Brain Research 01/2006; 25(3):678-87. · 3.77 Impact Factor