Previous studies of visual search in humans using event-related potentials (ERPs) have revealed an ERP component called ‘N2pc’ (180–280 ms) that reflects the focusing attention onto potential target items array. The present study was designed to localize neuroanatomical sources this by means magnetoencephalographic (MEG) recordings, which provide greater spatial precision than recordings. MEG recordings were obtained with array 148 magnetometers from six normal adult subjects, one whom...

The spatial focus of attention has traditionally been envisioned as a simple gradient enhanced activity that falls off monotonically with increasing distance. Here, we show high-density magnetoencephalographic recordings in human observers the is not monotonic but instead contains an excitatory peak surrounded by narrow inhibitory region. To demonstrate this center-surround profile, asked subjects to onto color pop-out target and then presented probe stimuli at various distances from target....

Previous studies of visual processing in humans using event-related potentials (ERPs) have demonstrated that task-related modulations an early component called the “N1” wave (140–200 ms) reflect operation a voluntary discrimination process. Specifically, this is larger tasks requiring target than simple detection. The present study was designed to localize discriminative process both time and space by means combined magnetoencephalographic (MEG) ERP recordings. Discriminative led...

Single-unit recordings in macaque extrastriate cortex have shown that attentional selection of nonspatial features can operate a location-independent manner. Here, we investigated analogous neural correlates at the population level human observers by using simultaneous event-related potential (ERP) and magnetic field (ERMF) recordings. The goals were to determine (1) whether task-relevant are selected before attention is allocated location target, (2) this reflects locations relevant...

Visual awareness has been proposed to depend on recurrent processing in early visual cortex areas including the primary (V1). Here, we address this hypothesis with high spatiotemporal resolution magnetoencephalographic recordings subjects performing a substitution masking paradigm. Neural activity reflecting is assessed by directly comparing neuromagnetic response elicited effectively and ineffectively masked targets after proportion of trials leading was individually adjusted match without...

Objects in the environment may be attended selectively and perceived as unified ensembles of their constituent features. To investigate timing cortical localization feature-integration mechanisms object-based attention, recordings event-related potentials magnetic fields were combined with functional MRI while subjects to one two superimposed transparent surfaces formed by arrays dots moving opposite directions. A spatiotemporal analysis revealed evidence for a rapid increase neural activity...

THE present study addresses phonological processing in children with developmental dyslexia. Following the hypothesis of a core deficit assembled phonology dyslexia set hierarchically structured tasks was applied that specifically control for different kinds coding (assembled versus addressed strategies). Seventeen dyslexics and 17 normal reading were scanned during four tasks: (1) passive viewing letter strings (control condition), (2) non-words, (3) legal words, (4) task requiring...

The cortical mechanisms of feature-selective attention to color and motion cues were studied in humans using combined electrophysiological, magnetoencephalographic, hemodynamic (functional magnetic resonance imaging) measures brain activity. Subjects viewed a display random dots that periodically either changed or moved coherently. When was directed the change it elicited enhanced neural activity visual area V4v, previously shown be specialized for processing information. In contrast, when...

What is the neural locus of visual attention? Here we show that not fixed but instead changes rapidly to match spatial scale task-relevant information in current scene. To accomplish this, obtained electrical, magnetic, and hemodynamic measures attention from human subjects while they detected large-scale or small-scale targets within multiscale stimulus patterns. Subjects did know target before onset, yet attention-related activity between 250 300 ms varied according target. Specifically,...

Dopamine release in cortical and subcortical structures plays a central role reward-related neural processes. Within this context, dopaminergic inputs are commonly assumed to play an activating role, facilitating behavioral cognitive operations necessary obtain prospective reward. Here, we provide evidence from human fMRI that can also be mediated by task-demand-related processes thus extends beyond situations only entail extrinsic motivating factors. Using visual discrimination task which...

In the present study magnetoencephalographic recordings were performed to investigate neural mechanisms underlying stopping of manual responses. Subjects in a Stop-signal task which Go-stimuli (S1), requiring rapid motor response, sometimes rapidly followed by Stop-stimulus (S2) indicating withhold already initiated response S1. Success strongly depended on early perceptual processing S1 and S2 reflected magnetic N1 component. Enhanced facilitated execution movement, whereas enhanced favored...

We recently demonstrated with magnetoencephalographic recordings in human observers that the focus of attention visual search has a spatial profile consisting center enhancement surrounded by narrow zone sensory attenuation. Here, we report new data from 2 experiments providing insights into cortical processes cause surround show suppression appears tasks require scrutiny, is precise binding search-relevant features at target's location but not permit target discrimination without...

When a stimulus is associated with reward, it becomes prioritized, and the allocation of attention to that increases. For low-level features, such as color, this reward-based can manifest early in time faster stronger shift targets reflected by N2pc (a parieto-occipital electrophysiological component peaking at ∼250 msec). It unknown, however, if reward associations similarly modulate attentional shifts complex objects or object categories, reward-related modulation stimuli would occur later...

Visual attention biases relevant processing in the visual system by amplifying or attenuating irrelevant sensory input. A potential signature of latter operation, referred to as surround attenuation, has recently been identified electromagnetic brain response human observers performing search. It was found that a zone attenuated cortical excitability surrounds target when search required increased spatial resolution for item discrimination. Here we address obvious hypothesis attenuation...

Abstract The pulvinar nuclei of the thalamus are hypothesized to coordinate attentional selection in visual cortex. Different models have, however, been proposed for precise role attention. One proposal is that mediates shifts spatial attention; a different it serves filtering distractor information. At present, relation between these possible operations and their relative importance remains unresolved. We address this issue by contrasting proposals two fMRI experiments. used search paradigm...