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In scrutinizing a scene, the eyes alternate between fixations and saccades. During a fixation, two component processes can be distinguished: visual encoding and selection of the next fixation target. We aimed to distinguish the neural correlates of these processes in the electrical brain activity prior to a saccade onset. Participants viewed color photographs of natural scenes, in preparation for
Analyzing single trial brain activity remains a challenging problem in the neurosciences. We gain purchase on this problem by focusing on globally synchronous fields in within-trial evoked brain activity, rather than on localized peaks in the trial-averaged evoked response (ER). We analyzed data from three measurement modalities, each with different spatial resolutions: magnetoencephalogram (MEG),
Adaptation is widely used as a tool for studying selectivity to visual features. In these studies it is usually assumed that the loci of feature selective neural responses and adaptation coincide. We used an adaptation paradigm to investigate the relationship between response and adaptation selectivity in event-related potentials (ERPs). ERPs were evoked by the presentation of colored Glass patter
Perceptual interpretation of the same multisensory stimuli may rely upon influence of attention on multisensory integration. We tested this hypothesis by recording the brain activity using magnetoencephalography in a passing-bouncing illusion with sound. Early activation of the attention-related brain areas and subsequent involvement of the multisensory areas were associated with the bouncing perc
We considered the hypothesis that spontaneous dissociation between the direction of attention and eye movement causes encoding failure in change detection. We tested this hypothesis by analyzing eye fixation-related potentials (EFRP) at the encoding stage of a change blindness task; when participants freely inspect a scene containing an unmarked target region, in which a change will occur in a sub
We investigated the relationship between visual experience and temporal intervals of synchronized brain activity. Using high-density scalp electroencephalography, we examined how synchronized activity depends on visual stimulus information and on individual observer sensitivity. In a perceptual grouping task, we varied the ambiguity of visual stimuli and estimated observer sensitivity to this vari
We investigated the brain responses to the transitions from the static to moving audiovisual stimuli using magnetoencephalography. The spatially congruent auditory and visual stimuli moved in the same direction whereas the incongruent stimuli moved in the opposite directions. Using dipole modeling we found that the static-to-moving transitions evoked a neural response in the primary auditory corte
Selection of visual short-term memory content takes place during perceptual and postperceptual processing. We studied postperceptual selection in a change detection task, in which spatially distributed cues preceding the memory array marked potential change targets. In the 550-730ms interval after the memory array onset but not in the following retention interval, event-related potentials showed l
Visual integration between target and irrelevant features leads to effects of irrelevant feature congruency (Stroop) or variation (Garner) on target classification performance. Presenting closed geometrical shapes as stimuli, we obtained Stroop and Garner effects of one part of their contour on another, in response times and error rates. The correlates of these effects in brain activity were obser
We studied an effect of predictability in an audio-visual apparent motion task using magnetoencephalography. The synchronous sequences of audio-visual stimuli were self-triggered by subjects. The task was to detect the direction of the apparent motion in experimental blocks in which the motion either started from the side selected by subjects (predictable condition) or was random (unpredictable co
We used high-density event-related potentials (ERP) in a modified flanker paradigm to study the role of anticipated action consequences in action planning and the role of anticipation in the perception of action consequences. Prior to the experiment, participants were trained to classify target letters in a four-alternative forced-choice task; another letter was presented as an effect following ea
Perceptual grouping is a multi-stage process, irreducible to a single mechanism localized anatomically or chronometrically. To understand how various grouping mechanisms interact, we combined a phenomenological report paradigm with high-density event-related potential (ERP) measurements, using a 256-channel electrode array. We varied the relative salience of competing perceptual organizations in m
Phase patterns of human scalp alpha EEG activity show spontaneous transitions between different globally phase-synchronized states. We studied the dynamical properties of these transitions using the method of symbolic dynamics. We found greater predictability (deterministicity) and heterogeneity in the dynamics than what was expected from corresponding surrogate series in which linear correlations
We investigate patterns of collective phase synchronization in brain activity in awake, resting humans with eyes closed. The alpha range of human electroencephalographic activity is characterized by ever-changing patterns, with strong fluctuations in both time and overall level of phase synchronization. The correlations of these patterns are reflected in power-law scaling of these properties. We p
In three experiments, participants determined the orientation of a global triangle formed by three Gabor patches of a target spatial frequency in a field of distracters. The orientation of the target patches and their proximity were varied between conditions. When all the target patches had the same orientation this facilitated the response compared to random orientations. This effect occurred onl
The attentional blink (AB) phenomenon occurs when perceivers must report two targets embedded in a sequence of distracters; if the first target precedes the second by 200-600 msec, the second one is often missed. We investigated AB by measuring dynamic cross-lag phase synchronization for 565 electrode pairs in 40-Hz-range EEG. Phase synchrony, on average, was higher in experimental conditions, whe
Objective: Data from a previous event-related potential (ERP) study in visual-perceptual grouping [Nikolaev AR, van Leeuwen C. Flexibility in spatial and non-spatial feature grouping: an event-related potentials study. Brain Res Cogn Brain Res 2004;22:13-25] were re-analyzed to identify event-related dynamics of phase-synchronization. Methods: In 20 Hz activity, uniform spreading of phase synchron
Spatiotemporal characteristics of spontaneous alpha EEG activity patterns are analyzed in terms of large-scale phase synchronization. During periods with strong phase synchronization over the entire scalp, phase patterns take either of two forms; one is a gradual phase shift between frontal and occipital regions and the other is a stepwise pattern with a sudden phase shift in the central region. T
In a visual task using 12 healthy subjects, spread of evoked phase-synchronized activity was studied in local cortical areas. The areas were identified in a previous study of the same data set using event-related potentials (ERP). Chains of closely spaced (∼2 cm) scalp electrodes covering these areas were selected for phase synchronization analysis in which task and control conditions were compare
Early perceptual grouping was studied using 256-channels event-related potentials in a choice response task. The task involved the detection of a triangle configuration of Gabor patches among patches of different spatial frequencies. The influence of two task-irrelevant factors was compared. One was the spatial proximity relation between the target patches and the other their relative orientation,
