How Attention Changes in Response to Incentives.

Although the performance of simple cognitive tasks can be enhanced if an incentive is provided, the mechanisms enabling such motivational control are not known. This study sought to uncover how mechanisms of attention and readiness are altered by reward-associated incentive stimuli. We measured EEG/ERP activity as human adults viewed a high- or low-incentive cue, experienced a short preparation interval, and then performed a simple visual search task to gain the predicted reward. Search performance was faster with high versus low incentives, and this was accompanied by distinct incentive-related EEG/ERP patterns at each phase of the task (incentive, preparation, and search). First, and most surprisingly, attention to high but not low incentive cues was actively suppressed, as indexed by a PD component in response to the incentive display. During the subsequent preparation interval, neural oscillations in the alpha frequency range were reduced after high-incentive cues, indicating heightened visual readiness. Finally, attentional orienting to the target in the search array was deployed with relatively little effort on high-incentive trials, as indexed by a reduced N2pc component. These results reveal the chain of events by which the brain's executive control mechanisms respond to incentives by altering the operation of multiple processing systems to produce optimal performance.

Effective connectivity during feature-based attentional capture: evidence against the attentional reorienting hypothesis of TPJ.

The most prevalent neurobiological theory of attentional control posits 2 distinct brain networks: The dorsal and ventral attention networks. The role of the dorsal attentional network in top-down attentional control is well established, but there is less evidence for the putative role of the ventral attentional network in initiating stimulus-driven reorienting. Here, we used functional magnetic resonance imaging and dynamic causal modeling (DCM) to test the role of the ventral and dorsal networks in attentional reorienting during instances of attentional capture by a target-colored distracter. In the region of interest analyses, we found that frontal eye field (FEF) was selectively activated by conditions where attention was reoriented (i.e. to spatial cues and target-colored distracters). In contrast, temporoparietal junction (TPJ) responded positively to all stimulus conditions. The DCM results indicated that FEF received sensory inputs earlier than TPJ, and that only the connection from FEF to TPJ was modulated by the appearance of the target-colored distracter. The results provide novel empirical evidence against the idea that TPJ generates stimulus-driven reorientations of attention. We conclude that our results are incompatible with existing theories of TPJ involvement in the stimulus-driven reorientation of attention and discuss alternative explanations such as contextual updating.

A common neural mechanism for preventing and terminating the allocation of attention.

Much is known about the mechanisms by which attention is focused to facilitate perception, but little is known about what happens to attention after perception of the attended object is complete. One possibility is that the focus of attention passively fades. A second possibility is that attention is actively terminated after the completion of perception so that the brain can be prepared for the next target. The present study investigated this issue with event-related potentials in humans, focusing on the N2pc component (a neural measure of attentional deployment) and the Pd component (a neural measure of attentional suppression). We found that active suppression occurred both to prevent the allocation of attention to known distractors and to terminate attention after the perception of an attended object was complete. In addition, the neural measure of active suppression was correlated with a behavioral measure of trial-to-trial variations in the allocation of attention. Active suppression therefore appears to be a general-purpose mechanism that both prevents and terminates the allocation of attention.

Distractor P3 is associated with attentional capture by stimulus deviance.

OBJECTIVE: A simple distractor elicits a large P3 when the standard and target are difficult to discriminate in the three-stimulus oddball paradigm. This study investigated whether the distractor P3 reflects attentional capture by stimulus deviance or cognitive interference with maintaining the standard representation. METHODS: Event-related brain potentials were recorded from 12 participants who performed a visual three-stimulus oddball paradigm. Four task conditions were defined by a combination of two presentation types of distractor stimuli (central or bilateral) and two levels of standard/target discrimination difficulty (easy or difficult). Bilateral distractors had stimulus deviance but did not interfere with maintenance of the standard representation. RESULTS: Central distractors elicited a P3, the amplitude of which was larger in the difficult task than in the easy task. In contrast, bilateral distractors elicited a large P3 in both the easy and difficult tasks. CONCLUSIONS: Distractor P3 reflects attentional capture by stimulus deviance, rather than cognitive interference with maintaining the standard representation. SIGNIFICANCE: This is the first report showing that simple distractors can elicit large anteriorly distributed P3 in an easy task. The present findings contribute to the clinical application of distractor P3 to assess the cognitive function of deviant processing.

Top-down directed attention to stimulus features and attentional allocation to bottom-up deviations.

One highly controversial issue with respect to visual selective attention concerns the degree to which the top-down attentional mechanism modulates attentional allocation to bottom-up deviation. We investigated whether top-down directed attention to a stimulus feature modulates attentional allocation to task-irrelevant, bottom-up deviation. The P3 event-related potential was measured as an electrophysiological marker of attentional allocation. Target and non-target objects were serially presented in random order. Bottom-up deviations occurred as a change in task-irrelevant features of target or non-target objects, or as the appearance of task-irrelevant distractor objects around target or non-target objects. When task-irrelevant features were changed, the P3 deviant effect was greater in target than in non-target trials. In contrast, when distractor objects appeared, the P3 deviant effect was smaller in target than in non-target trials. These findings suggest that top-down directed attention to a stimulus feature modulates attentional allocation to bottom-up deviation such that attentional allocation is enhanced when bottom-up deviation and an attended feature share the same object but is inhibited when bottom-up deviation occurs outside an object with an attended feature. Thus, the top-down attentional mechanism has a strong influence even for deviant processing and provides a competitive advantage for objects with an attended feature.

Hyperfocusing of attention on goal-related information in schizophrenia: Evidence from electrophysiology.

Schizophrenia clearly involves impairments of attention, but the precise nature of these impairments has been difficult to determine. One possibility is that the deficit in attention is a secondary consequence of a deficit in goal maintenance. However, recent research suggests that people with schizophrenia (PSZ) actually focus attention more strongly on objects containing goal-relevant features. To test these competing hypotheses, we recorded event-related potentials (ERPs) from PSZ (N = 20) and healthy control subjects (HCS; N = 20) while they looked for a particular target color at fixation and tried to ignore lateral distractors that sometimes matched the target color (target-color distractors). Goal maintenance was made trivially easy by the continual presentation of a goal reminder. We found that HCS were able to successfully suppress target-color distractors (leading to a distractor positivity ERP component), whereas PSZ focused attention on these items (leading to an N2-posterior-contralateral ERP component). This suggests that, when maintaining a task set, PSZ engage in aberrant focusing of attention, or hyperfocusing, on goal-relevant features. (PsycINFO Database Record

Stimulus context determines whether non-target stimuli are processed as task-relevant or distractor information.

OBJECTIVE: The P300 event-related brain potential (ERP) was elicited using a visual three-stimulus oddball paradigm (standard 0.70, target 0.15, non-target 0.15) to examine how target/standard stimulus context affects non-target processing. METHODS: Target/standard discrimination difficulty (easy or difficult) and non-target /target similarity (similar or dissimilar) were manipulated orthogonally. Participants (N=13) were instructed to respond to each infrequent target stimulus by pressing a button. RESULTS: Target stimuli in all task conditions elicited P3b, which was affected only by the difficulty of target/standard discrimination. When target/standard discrimination was easy, the amplitude of non-target P3 was larger for similar than for dissimilar non-target. In contrast, when target/standard discrimination was difficult, non-target stimuli elicited P3a, the amplitude of which was larger for dissimilar than for similar non-target. Thus, the P300 component for non-target stimuli and the pattern of the effect of target similarity on each P300 component varied as a function of the target/standard stimulus context. CONCLUSIONS: The target/standard stimulus context influences the attentional set for stimulus processing such that it determines whether non-target stimuli are processed as task-relevant or distractor information. SIGNIFICANCE: The present results are important for understanding the mechanism of cognitive modification in non-target processing.

Severity of AD/HD symptoms and efficiency of attentional resource allocation.

This study investigated the mechanism that underlies the inefficient allocation of attentional resources in Attention-Deficit/Hyperactivity Disorder (AD/HD). The P300 event-related brain potential (ERP) was elicited from 24 healthy adults using a visual three-stimulus oddball paradigm (standard, 70%; target, 15%; non-target, 15%) and the degree of their AD/HD symptoms was assessed by using AD/HD symptom scales. Target stimulus was a circle and standard stimulus was an "X". Two task conditions were defined according to the non-target stimulus type (typical or novel): a triangle for the typical condition and colored non-repetitive novel stimuli for the novel condition. In both conditions, target and non-target elicited P300s. A ratio of non-target P300 to target P300 amplitude was used to assess the efficiency of attentional resource allocation; low ratio indicates the efficient allocation of attentional resource. The correlation analysis revealed a strong positive correlation between the AD/HD symptom score and the P300 amplitude ratio in the typical condition (r=.80), while only a weak positive correlation was observed in the novel condition (r=.23). The present study found that the commonality of task-relevant and task-irrelevant information, rather than the stimulus novelty of task-irrelevant information, induces the inefficient allocation of attentional resources in AD/HD.

Active suppression after involuntary capture of attention.

After attention has been involuntarily captured by a distractor, how is it reoriented toward a target? One possibility is that attention to the distractor passively fades over time, allowing the target to become attended. Another possibility is that the captured location is actively suppressed so that attention can be directed toward the target location. The present study investigated this issue with event-related potentials (ERPs), focusing on the N2pc component (a neural measure of attentional deployment) and the Pd component (a neural measure of attentional suppression). Observers identified a color-defined target in a search array, which was preceded by a task-irrelevant cue array. When the cue array contained an item that matched the target color, this item captured attention (as measured both behaviorally and with the N2pc component). This capture of attention was followed by active suppression (indexed by the Pd component), and this was then followed by a reorienting of attention toward the target in the search array (indexed by the N2pc component). These findings indicate that the involuntary capture of attention by a distractor is followed by an active suppression process that presumably facilitates the subsequent voluntary orienting of attention to the target.

Active suppression of distractors that match the contents of visual working memory.

The biased competition theory proposes that items matching the contents of visual working memory will automatically have an advantage in the competition for attention. However, evidence for an automatic effect has been mixed, perhaps because the memory-driven attentional bias can be overcome by top-down suppression. To test this hypothesis, the Pd component of the event-related potential waveform was used as a marker of attentional suppression. While observers maintained a color in working memory, task-irrelevant probe arrays were presented that contained an item matching the color being held in memory. We found that the memory-matching probe elicited a Pd component, indicating that it was being actively suppressed. This result suggests that sensory inputs matching the information being held in visual working memory are automatically detected and generate an "attend-to-me" signal, but this signal can be overridden by an active suppression mechanism to prevent the actual capture of attention.

Capture versus suppression of attention by salient singletons: electrophysiological evidence for an automatic attend-to-me signal.

There is considerable controversy about whether salient singletons capture attention in a bottom-up fashion, irrespective of top-down control settings. One possibility is that salient singletons always generate an attention capture signal, but this signal can be actively suppressed to avoid capture. In the present study, we investigated this issue by using event-related potential recordings, focusing on N2pc (N2-posterior-contralateral; a measure of attentional deployment) and Pd (distractor positivity; a measure of attentional suppression). Participants searched for a specific letter within one of two regions, and irrelevant color singletons were sometimes present. We found that the irrelevant singletons did not elicit N2pc but instead elicited Pd; this occurred equally within the attended and unattended regions. These findings suggest that salient singletons may automatically produce an attend-to-me signal, irrespective of top-down control settings, but this signal can be overridden by an active suppression process to prevent the actual capture of attention.

Difficulty of discrimination modulates attentional capture by regulating attentional focus.

Attentional capture for distractors is enhanced by increasing the difficulty of discrimination between the standard and the target in the three-stimulus oddball paradigm. In this study, we investigated the cognitive mechanism of this modulation of attentional capture. Event-related brain potentials were recorded from participants while they performed a visual three-stimulus oddball paradigm (frequent standard, rare target, and rare distractor). The discrimination difficulty between standard and target was manipulated in the central location. Distractor stimuli were presented in the central or surrounding locations. The P3a component was elicited by distractor stimuli and was used as a measure of attentional capture. The results revealed that discrimination difficulty had opposite effects on the P3a response between central and surrounding locations. With an increase in the difficulty of discrimination, the P3a response was enhanced when distractor stimuli were presented in the central location. In contrast, the P3a response was reduced when distractor stimuli were presented in a surrounding location. This finding suggests that spatial attention was focused by the difficulty of discrimination, and deviant processing was increased within its focus but decreased outside its focus. Therefore, attentional capture for deviant distractors is modulated by top-down controlled attentional focus.

Difficulty of discrimination modulates attentional capture for deviant information.

It has been reported that an increased difficulty of discrimination between standard and target enhances P3a for typical nontarget. To elucidate the mechanism of this effect on deviant processing, the P300 event-related brain potential (ERP) was elicited using a visual three-stimulus oddball paradigm (standard circle, .70, target circle, .15, and nontarget/target square, .15). Four task conditions were defined by a combination of two category types of rare square (nontarget or target) and two levels of discrimination difficulty between standard and target circles (easy or difficult). In the difficult conditions, P3a was elicited by both nontarget and target square. Our findings suggest that the difficulty of discrimination between standard and target enhances attentional capture, rather than inhibition, for deviant information. This study has implications for understanding the attentional mechanisms of deviant processing.