Deciding where to attend: Large-scale network mechanisms underlying attention and intention revealed by graph-theoretic analysis.

The neural mechanisms by which intentions are transformed into actions remain poorly understood. We investigated the network mechanisms underlying spontaneous voluntary decisions about where to focus visual-spatial attention (willed attention). Graph-theoretic analysis of two independent datasets revealed that regions activated during willed attention form a set of functionally-distinct networks corresponding to the frontoparietal network, the cingulo-opercular network, and the dorsal attention network.

Attention induced neural response trade-off in retinotopic cortex under load.

The effects of perceptual load on visual cortex response to distractors are well established and various phenomena of 'inattentional blindness' associated with elimination of visual cortex response to unattended distractors, have been documented in tasks of high load. Here we tested an account for these effects in terms of a load-induced trade-off between target and distractor processing in retinotopic visual cortex. Participants were scanned using fMRI while performing a visual-search task and ignoring distractor checkerboards in the periphery.

The neural correlates of volitional attention: A combined fMRI and ERP study.

Studies of visual-spatial attention typically use instructional cues to direct attention to a relevant location, but in everyday vision, attention is often focused volitionally, in the absence of external signals. Although investigations of cued attention comprise hundreds of behavioral and physiological studies, remarkably few studies of voluntary attention have addressed the challenging question of how spatial attention is initiated and controlled in the absence of external instructions, which we refer to as willed attention. To explore this question, we employed a trial-by-trial spatial attention task using electroencephalography and functional magnetic resonance imaging (fMRI).

Spontaneous neural fluctuations predict decisions to attend.

Ongoing variability in neural signaling is an intrinsic property of the brain. Often this variability is considered to be noise and ignored. However, an alternative view is that this variability is fundamental to perception and cognition and may be particularly important in decision-making.

The impact of distractor congruency on stimulus processing in retinotopic visual cortex.

The brain is frequently confronted with sensory information that elicits conflicting response choices. While much research has addressed the top down control mechanisms associated with detection and resolution of response competition, the effects of response competition on sensory processing in the primary visual cortex remain unclear. To address this question we modified a typical 'flanker task' (Eriksen and Eriksen, 1974) so that the effects of response competition on human early retinotopic visual cortex could be assessed.

Enhanced visual perception with occipital transcranial magnetic stimulation.

Transcranial magnetic stimulation (TMS) over the occipital pole can produce an illusory percept of a light flash (or 'phosphene'), suggesting an excitatory effect. Whereas previous reported effects produced by single-pulse occipital pole TMS are typically disruptive, here we report the first demonstration of a location-specific facilitatory effect on visual perception in humans. Observers performed a spatial cueing orientation discrimination task.

Neural correlates of learning to attend.

Recent work has shown that training can improve attentional focus. Little is known, however, about how training in attention and multitasking affects the brain. We used functional magnetic resonance imaging (fMRI) to measure changes in cortical responses to distracting stimuli during training on a visual categorization task.

Working memory load modulates distractor competition in primary visual cortex.

When stimuli compete for sensory processing and response selection, coherent goal-guided behavior requires cognitive control so that task-relevant "targets" rather than irrelevant distractors are selected. It has been shown that reduced cognitive control under high working memory load increases distractor competition for selection. It remains unknown, though, whether cognitive control by working memory has an effect on the earliest levels of sensory processing in primary visual cortex.

Learning to attend: effects of practice on information selection.

Though practice can lead to improved performance in many domains, it is currently unknown how practice affects the deployment of selective attention to filter distracting information. We conducted a series of experiments to address this issue by examining how performance on a task changed after repeated exposure to distractors. Distraction initially slowed response time during task performance, an effect that diminished with repeated exposure to the distractors.

Cortical mechanisms for shifting and holding visuospatial attention.

Access to visual awareness is often determined by covert, voluntary deployments of visual attention. Voluntary orienting without eye movements requires decoupling attention from the locus of fixation, a shift to the desired location, and maintenance of attention at that location. We used event-related functional magnetic resonance imaging to dissociate these components while observers shifted attention among 3 streams of letters and digits, one located at fixation and 2 in the periphery.

Attentional modulation of repetition attenuation is anatomically dissociable for scenes and faces.

Repeating a stimulus generally leads to a decreased response in neural activity compared to that for novel items. This neural attenuation provides a marker for stimulus-specific perceptual encoding and memory that can be detected using functional magnetic resonance imaging (fMRI). Although previously assumed to occur automatically whenever a stimulus is repeated, recent studies have begun to show that the repetition attenuation effect is task-specific and modulated by attention.

Effects of scene inversion on change detection of targets matched for visual salience.

This work examines how context may influence the detection of changes in flickering scenes. Each scene contained two changes that were matched for low-level visual salience. One of the changes was of high interest to the meaning of the scene, and the other was of lower interest.