Isolating the Neural Substrates of Visually Guided Attention Orienting in Humans.

The neural processes that enable healthy humans to orient attention to sudden visual events are poorly understood because they are tightly intertwined with purely sensory processes. Here we isolated visually guided orienting activity from sensory activity using event-related potentials (ERPs). By recording ERPs to a lateral stimulus and comparing waveforms obtained under conditions of attention and inattention, we identified an early positive deflection over the ipsilateral visual cortex that was associated with the covert orienting of visual attention to the stimulus.

Inability to suppress salient distractors predicts low visual working memory capacity.

According to contemporary accounts of visual working memory (vWM), the ability to efficiently filter relevant from irrelevant information contributes to an individual's overall vWM capacity. Although there is mounting evidence for this hypothesis, very little is known about the precise filtering mechanism responsible for controlling access to vWM and for differentiating low- and high-capacity individuals. Theoretically, the inefficient filtering observed in low-capacity individuals might be specifically linked to problems enhancing relevant items, suppressing irrelevant items, or both.

Object-substitution masking modulates spatial attention deployment and the encoding of information in visual short-term memory: insights from occipito-parietal ERP components.

If object-substitution masking (OSM) arises from mask representations replacing target representations, OSM should impede the formation of representations in visual short-term memory (VSTM). We utilized event-related potentials to examine the effect of OSM on target processing. An N2pc was observed on trials with delayed-offset masks, indicating that focused attention was directed to the target.

Mental rotation requires visual short-term memory: evidence from human electric cortical activity.

The purpose of the present study was to seek evidence that mental rotation is accomplished by transforming a representation held in visual short-term memory (VSTM). In order to accomplish this goal, we utilized the sustained posterior contralateral negativity (SPCN), an electrophysiological index of the maintenance of information in VSTM. We hypothesized that if mental rotation is accomplished by transforming a representation held in VSTM, then the duration that this representation is maintained in VSTM should be related to the degree to which the representation must be rotated to reach the desired orientation.

On the relationship between occipital cortex activity and inhibition of return.

The present study explored the relationship between inhibition of return (IOR) and visual processes by seeking evidence that IOR and changes in event-related potential (ERP) indices of occipital cortex activity covary in response to experimental manipulation. The presence or absence of a central reorienting event was manipulated within the context of a cue-target experiment. When a reorienting event was presented in the interval between cue and target, IOR was accompanied by reductions in the amplitudes of early occipital ERP peaks on validly cued trials relative to invalidly cued trials.

When cross-modal spatial attention fails.

There is now convincing evidence that an involuntary shift of spatial attention to a stimulus in one modality can affect the processing of stimuli in other modalities, but inconsistent findings across different paradigms have led to controversy. Such inconsistencies have important implications for theories of cross-modal attention. The authors investigated why orienting attention to a visual event sometimes influences responses to subsequent sounds and why it sometimes fails to do so.

Response-selection conflict contributes to inhibition of return.

Here we examined the relationship between inhibition of return (IOR) and response-selection conflict. In two go/no-go and spatial-cueing experiments, we measured the amplitude of the fronto-central N2 event-related potential component to estimate the degree of response-selection conflict for validly cued and invalidly cued targets. When the probability of a go target was high (Experiment 1), both the amplitude of the N2 elicited on no-go trials and the number of false alarm errors were greater on invalid-cue than on valid-cue trials.

Tracking the location of visuospatial attention in a contingent capture paradigm.

Currently, there is considerable controversy regarding the degree to which top-down control can affect attentional capture by salient events. According to the contingent capture hypothesis, attentional capture by a salient stimulus is contingent on a match between the properties of the stimulus and top-down attentional control settings. In contrast, bottom-up saliency accounts argue that the initial capture of attention is determined solely by the relative salience of the stimulus, and the effect of top-down attentional control is limited to effects on the duration of attentional engagement on the capturing stimulus.

Lateralized readiness potentials reveal motor slowing in the aging brain.

Older adults consistently show slower reaction times (RTs) to the onset of motion. Both cognitive slowing and motor slowing have been suggested as causes of this effect. The lateralized readiness potential (LRP) of the electroencephalogram can be used to separate perceptual and decision processes from motor programming and execution as causes of RT differences.

Reorienting attention and inhibition of return.

In experiments examining inhibition of return (IOR), it is common practice to present a second cue at fixation during the cue-target interval. The purpose of this fixation cue is to reorient attention away from the cued location to ensure that the facilitative effects of spatial attention do not obscure IOR. However, despite their frequent use, relatively little is known about the relationship between fixation cues and IOR.

Cortical expressions of inhibition of return.

Inhibition of return (IOR) is a phenomenon that has been thought to be closely associated with attention mechanisms. In particular, it might arise from the operation of an attentional mechanism that facilitates visual search by inhibiting both covert attention and eye movements from returning to recently inspected locations. Although IOR has received a great deal of research interest, and mechanisms involving sensory, perceptual, and motor consequences have been proposed, no consensus has yet been reached regarding the stages of information processing at which IOR operates.

Inhibition of return and response repetition within and between modalities.

Inhibition of return (IOR) refers to slower responding to stimuli at previously occupied spatial locations. IOR has been vigorously studied because of its possible deep involvement with attention mechanisms. Although IOR occurs both within and across modalities in several experimental paradigms for simple stimulus detection tasks, it has sometimes been difficult to demonstrate in perceptual discrimination tasks.

Inhibition of return from stimulus to response.

In a standard inhibition-of-return (IOR) paradigm using a manual key-press response, we examined the effect of IOR both on the amplitude of early sensory event-related brain potential (ERP) components and on the motor-related lateralized readiness potential (LRP). IOR was associated with a delay of premotor processes (target-locked LRP latency) and reduced sensory ERP activity. No effect of IOR was found on motor processes (response-locked LRP latency).

Event-related potential evidence for attentional inhibition of return in audition.

Orienting attention to a spatial location facilitates responding to a subsequent target at that location, but inhibits the response if attention is oriented away from that location before the target appears there. This inhibitory effect of attention re-orienting, called inhibition of return (IOR), occurs in vision, hearing, touch, and cross-modally, and has been well studied behaviorally. However, little is known about its underlying neural mechanism(s).

Auditory frequency-based inhibition differs from spatial IOR.

Uninformative auditory frequency cues have a facilitatory effect on reaction time and accuracy of detection and intensity discrimination of target tones for cue-target intervals of up to 3 sec (Green & McKeown, 2001; Ward, 1997). Under some conditions, however, this facilitatory effect can reverse to an inhibitory effect at cue-target intervals longer than 450 msec (Mondor, Breau, & Milliken, 1998). Thepresent work demonstrates that such inhibitory effects are not found in target-target experiments (Experiment 1) or in cue-target experiments requiring a go-no-go discrimination of the target (Experiment 2), whereas they do appear in the paradigm used by Mondor et al.