Visual masking during the attentional blink: tests of the object substitution hypothesis.

When 2 masked targets are presented in a rapid sequence, correct identification of the 1st hinders identification of the 2nd. Visual masking of the 2nd target plays a critical role during this 2nd-target deficit, or "attentional blink" (AB). The object substitution hypothesis (B.

Orienting attention in aging and Parkinson's disease: distinguishing modes of control.

Past research on attentional orienting and Parkinson's disease (PD) has been compromised because the experimental paradigms tended to confound different forms of orienting. We sought to overcome this by examining the attentional orienting of three distinct groups (PD-patients, age-matched controls, and young controls) on five different tasks, four of which isolated pure forms of orienting. On two covert orienting tasks PD patients oriented volitional (Experiment 1) and reflexive (Experiment 2) covert attention in a healthy and normal manner for their age.

Covert and overt orienting to gaze direction cues and the effects of fixation offset.

We examined covert and overt orienting in response to non-predictive gaze direction cues and investigated whether the subcortical superior colliculus (SC) plays a role in this type of orienting. Participants viewed a centrally presented gazing schematic face and responded to targets appearing at gazed-at or non-gazed-at locations either by making a keypress response while maintaining central fixation or by making an eye movement to the target. For both response conditions, the fixation stimulus (the gazing face) either remained on the screen or was extinguished at the time of target presentation, a manipulation known to engage and disengage the SC.

A crossmodal attentional blink between vision and touch.

There is currently a great deal of interest regarding the possible existence of a crossmodal attentional blink (AB) between audition and vision. The majority of evidence now suggests that no such crossmodal deficit exists unless a task switch is introduced. We report two experiments designed to investigate the existence of a crossmodal AB between vision and touch.

Why are antisaccades slower than prosaccades? A novel finding using a new paradigm.

Eye movements away from a new object (antisaccades) are slower than towards it (prosaccades). This finding is assumed to reflect the fact that prosaccades to new objects are made reflexively, and that for antisaccades, reflexive eye movements have to be inhibited and antisaccades are generated volitionally. Experiment 1 investigated the relative contribution of saccade inhibition by comparing the latency difference between pro- and antisaccades obtained in the traditional blocked paradigm and in a new paradigm in which oculomotor inhibition across pro- and antisaccades was matched.

Abrupt onsets and gaze direction cues trigger independent reflexive attentional effects.

The present study investigated whether the direction of visual signals is influenced independently by two automatic visual orienting phenomena: orienting to a gazed-at location and inhibition of return (IOR) to the location of an abrupt onset. A schematic face served as both a nonpredictive gaze direction cue and an abrupt onset cue. Results indicated that target detection was facilitated at the gazed-at location, and that it was inhibited at the abrupt onset location.

Are eyes special? It depends on how you look at it.

Recent behavioral data have shown that central nonpredictive gaze direction triggers reflexive shifts of attention toward the gazed-at location (e.g., Friesen & Kingstone, 1998).

Hemispheric encoding asymmetry is more apparent than real.

Previous neuroimaging studies have claimed a left hemisphere specialization for episodic "encoding" and a right hemisphere specialization for episodic "retrieval." Yet studies of split-brain patients indicate relatively minor memory impairment after disconnection of the two hemispheres. This suggests that both hemispheres are capable of encoding and retrieval.

Tactile "capture" of audition.

Previous research has demonstrated that the localization of auditory or tactile stimuli can be biased by the simultaneous presentation of a visual stimulus from a different spatial position. We investigated whether auditory localization judgments could also be affected by the presentation of spatially displaced tactile stimuli, using a procedure designed to reveal perceptual interactions across modalities. Participants made left-right discrimination responses regarding the perceived location of sounds, which were presented either in isolation or together with tactile stimulation to the fingertips.

The ventriloquist in motion: illusory capture of dynamic information across sensory modalities.

Integrating dynamic information across the senses is crucial to survival. However, most laboratory studies have only examined sensory integration for static events. Here we demonstrate that strong crossmodal integration can also occur for an emergent attribute of dynamic arrays, specifically the direction of apparent motion.

Attentional momentum does not underlie the inhibition of return effect.

J. Pratt, T. M.

Inhibition of return at multiple locations in visual search: when you see it and when you don't.

Using a novel sequential task, Danziger, Kingstone, and Snyder (1998) provided conclusive evidence that inhibition of return (IOR) can co-occur at multiple non-contiguous locations. They argued that their findings depended crucially on the allocation of attention to cued locations. Specifically, they hypothesized that because subjects could not predict whether an onset event was a target or a non-target, all onset events had to be attended.

Cued shifts of attention and memory encoding in partial report: a dual-task approach.

This study explores how cued shifts of visual attention and rapid encoding of visual information relate to limited-capacity processing mechanisms. Three experiments were conducted placing a partial-report task within a dual-task paradigm. Experiments 1 and 2 involved a simple speeded visual discrimination (Task 1) and then an unspeeded partial-report task (Task 2).

Failure to remap visuotactile space across the midline in the split-brain.

We examined the effect of posture change on the representation of visuotactile space in a split-brain patient using a cross-modal congruency task. Split-brain patient J.W.

Environmentally defined frames of reference: their time course and sensitivity to spatial cues and attention.

In a Simon task the effects of spatial cues and attention on spatial stimulus coding were explored. Participants made speeded responses corresponding to the direction of target arrows that were preceded by peripherally presented cues. Cue validity varied across experiments as did the percentage of trials on which the target appeared peripherally or centrally.

Representation of visuotactile space in the split brain.

Recent neurophysiological research in the monkey has revealed bimodal neuronal cells with both tactile receptive fields on the hand and visual receptive fields that follow the hands as they move, suggesting the existence of a bimodal map of visuotactile space. Using a cross-modal congruency task, we examined the representation of visuotactile space in normal people and in a split-brain patient (J. W.

Reflexive joint attention depends on lateralized cortical connections.

Joint attention, the tendency to spontaneously direct attention to where someone else is looking, has been thought to occur because eye direction provides a reliable cue to the presence of important events in the environment. We have discovered, however, that adults will shift their attention to where a schematic face is looking--even when gaze direction does not predict any events in the environment. Research with 2 split-brain patients revealed that this reflexive joint attention is lateralized to a single hemisphere.

Competition-induced visual field differences in search.

Do visual field effects point to differences in cortical representation, or do they reflect differences in the way these representations are used by other brain regions? This study explored three attributes of visual search that provide strong evidence in favor of differences in use. Competition refers to the finding that visual field differences in search efficiency are larger in whole- than in half-field displays (both left-right and upper-lower half-fields). Task specialization refers to the finding that some tasks favor one hemisphere whereas other tasks favor the other hemisphere, even though the same stimulus displays are used in both tasks.

Inhibition of return and visual search: how many separate loci are inhibited?

Using a novel sequential visual search paradigm Danziger, Kingstone, and Snyder (1998) demonstrated that inhibition of return (IOR) can reside at three spatial locations. In the present study, we extended the work of Danziger et al. by investigating whether there is a limit to the number of locations that can be inhibited in a sequential visual search task.

Inhibition of return is composed of attentional and oculomotor processes.

Response time can be delayed if a target stimulus appears at a location or object that was previously cued. This inhibition of return (IOR) phenomenon has been attributed to a delay in activating attentional or motor processes to a previously cued stimulus. Two experiments required subjects to localize or identify a target stimulus.

Unmasking the inhibition of return phenomenon.

Conventional wisdom holds that a nonpredictive peripheral cue produces a biphasic response time (RT) pattern: early facilitation at the cued location, followed by an RT delay at that location. The latter effect is called inhibition of return (IOR). In two experiments, we report that IOR occurs at a cued location far earlier than was previously thought, and that it is distinct from attentional orienting.

Inhibition of return to successively stimulated locations in a sequential visual search paradigm.

The inhibition of return (IOR) effect refers to a slowing in response time for a target that appears at a previously attended location. Many investigators have speculated that IOR's inherent ecological validity may be to ensure an efficient search of a complex environment by creating a bias against returning to locations that have already been investigated. Unfortunately, this intriguing idea has lacked compelling empirical support.

The psychological refractory period effect following callosotomy: uncoupling of lateralized response codes.

A callosotomy patient was tested in 2 dual-task experiments requiring successive speeded responses to lateralized stimuli. The patient showed a robust psychological refractory period (PRP) effect. Three aspects of the data indicate that, unlike for the control participants, the PRP effect for the split-brain patient should not be attributed to a response selection bottleneck.

Inhibition of return in location- and identity-based choice decision tasks.

Three experiments were conducted to determine whether inhibition of return can be best characterized as an attentional or a motor phenomenon. In the first experiment, subjects made choice keypress responses to the location of a target (left or right) or the identity of the target (X or +) by pressing a left or right response key. In the second experiment, the display was rotated 90 degrees so that there was no direct spatial mapping between the vertically aligned stimulus display and the horizontally aligned response keys.

Response channel activation and the lateral prefrontal cortex.

The role of lateral prefrontal cortex in transducing perception into action was studied in 10 patients with chronic, unilateral lesions. They identified colors in the center of a visual display, while a flanking, distractor color was presented simultaneously in either the ipsilesional or contralesional field. The flanker could be either the same color as the target, or incompatible with the correct response.