Distractor Stimuli Research Articles

Lateralized lexical decision in schizophrenia: hemispheric specialization and interhemispheric lexicality priming.

Reports of left-hemisphere dysfunction and abnormal interhemispheric transfer in schizophrenia are mixed. The authors used a unified paradigm, the lateralized lexical decision task, to assess hemispheric specialization in word recognition, hemispheric error monitoring, and interhemispheric transfer in male, right-handed participants with schizophrenia (n=34) compared with controls (n=20). Overall, performance and error monitoring were worse in patients. However, patients like controls showed left-hemisphere superiority for lexical processing and right-hemisphere superiority for error monitoring. Only patients showed selective-interhemispheric lexicality priming for accuracy, in which performance improved when the lexical status of target and distractor stimuli presented to each hemifield was congruent. Results suggest that schizophrenia is associated with impaired monitoring and with increased interhemispheric automatic information transfer rather than with changed hemispheric specialization for language or error monitoring.

Cross-modal congruency and visual capture in a visual elevation-discrimination task.

Participants in this experiment were required to discriminate the elevation of visual target stimuli (upper versus lower) presented to either side of fixation, while simultaneously trying to ignore vibrotactile distracters presented independently from the index finger (up) or thumb (lower) of either hand. The participants' hands were occluded from view under an opaque screen while the visual targets were situated directly over the hands above the screen. Participants responded more slowly on this elevation-discrimination task when the vibrotactile distracters were incongruent with the elevation of the visual targets (i.e. a "lower" vibration to the thumb during the presentation of an upper visual target) than when they were congruent (presumably due to the competing responses primed by the target and distracter stimuli on incongruent trials). The vibrotactile distracters had less of an effect on performance when a pair of rubber hands was placed on top of the screen, "holding" the target lights, in a posture consistent with that of the participant. Those participants who agreed most strongly with a statement about feeling the vibrations at the location of the rubber hands in a post-congruency task questionnaire evidenced the greatest reduction in the magnitude of the cross-modal congruency effect.

Reduction in distractibility with AF102B and THA in the macaque

Distractibility in primates may be influenced by central cholinergic systems. Two cholinomimetics, the m-1 muscarinic agonist (±)- cis-2-methyl-spiro(1,3-oxathiolane-5,3′)quinuclidine (AF102B, civemeline) and the cholinesterase inhibitor tetrahydroaminoacridine (THA, tacrine), were compared to vehicle controls for effects on distractibility in an automated visuospatial attention task. The task required visual pursuit of a moving target amongst distractor stimuli that acted to impair performance and was executed by seven healthy adult bonnet macaque monkeys. Task accuracy and reaction time were measured 1.5 h after systemic administration of each substance. For the seven-subject group at individually titrated best doses, accuracy increased significantly relative to vehicle for both drugs. Reaction time at best dose decreased for both drugs, but not significantly. Muscarinic agonists and cholinesterase inhibitors may reduce distractibility in primates.

The role of perceptual load in processing distractor faces.

It has been established that successful ignoring of irrelevant distractors depends on the extent to which the current task loads attention. However, the previous load studies have typically employed neutral distractor stimuli (e.g., letters). In the experiments reported here, we examined whether the perception of irrelevant distractor faces would show the same effects. We manipulated attentional load in a relevant task of name search by varying the search set size and found that whereas congruency effects from meaningful nonface distractors were eliminated by higher search load, interference from distractor faces was entirely unaffected by search load. These results support the idea that face processing may be mandatory and generalize the load theory to the processing of meaningful and more complex nonface distractors.

Distractor heterogeneity, attention, and color in visual search

Experiments were designed to investigate the effects of set size and variation in the chromaticity of distractor stimuli on thresholds for detecting a target stimulus that differed from distractors only in chromaticity. Distractor chromaticities were selected from a line in the isoluminant color plane and targets were selected from lines approximately orthogonal to the distractor line. With uniform distractors thresholds increased with set size as predicted by a signal detection model. When targets and distractors were selected from lines parallel to the Cardinal directions in color space, thresholds were lower with variable distractors than with uniform distractors and variations in the location of the target along the distractor line had no effect on threshold. Results with diagonally oriented distractor lines were similar. Results suggest that many pairs of orthogonal directions in the isoluminant color plane represent independent color coding mechanisms that mediate search. Results also show that information in independent color coding mechanisms tuned to orthogonal directions in the isoluminant plane can be combined to facilitate detection of the target.

Nociceptive processing in the human brain of infrequent task-relevant and task-irrelevant noxious stimuli. A study with event-related potentials evoked by CO 2 laser radiant heat stimuli

Laser evoked potentials (LEPs) are nociceptive-related brain responses to activation of cutaneous nociceptors by laser radiant heat stimuli. We previously showed that LEP amplitude during the P2 period (∼400 ms) was increased by rare noxious stimuli, inside and outside the focus of spatial attention. It was postulated that this effect reflected a P3a response indexing an involuntary shift of attention. In the present study, LEPs were recorded in a three-stimulus oddball paradigm, commonly used to evoke P3a (or novelty-P3). CO 2 laser-induced noxious stimuli were delivered on one hand (80%, frequent). Two series of rare stronger-intensity deviant stimuli were randomly intermixed: target stimuli (10%) were delivered on the same hand while distractor stimuli (10%) were delivered on the other hand. Subjects were instructed to count targets. During an additional session, strong stimuli were delivered alone on one hand without instruction (100%, no-task stimuli). All stimulus types evoked a first positivity around 360 ms (P360). Targets and distractors elicited a late positive complex (LPC) around 465–500 ms. Topography of LPC to distractors was central and significantly more anterior than that of LPC to targets. Distractor LPC corresponds to P3a (or novelty-P3) indexing an involuntary orientation of attention toward an unexpected new/deviant event. It suggests that at least an early part of the LEP positivity (P360) is independent of P3-activities.

Usefulness of semi-structured support groups in schizophrenia

There are few and controversial findings about adverse effects between the low frequency noise (LFN) and high frequency noise (HFN) on human. Although noise is presumed as a distracting stimulus, regarding controversial findings between performance effects of LFN and HFN, and scarcely studies on dissimilar effects of them, the present study was conducted to answer the following questions: is there any difference between LFN and HFN impacts on mental performance at a moderate noise level? And, how do LFN and HFN affect mental performance?This experimental study was carried out with 89 students (54 males and 35 females) of Tehran University of Medical Sciences. All participants performed the Stroop and Cognitrone tests in quiet condition, when exposing to LFN and HFN at both 50 and 70 dBA.It was found that both LFN and HFN augmented the performance through increasing sum hits and sum correct rejection and also decreasing working time of the Cognitrone test. The findings of the present study showed that not only LFN and HFN had no negative effects on the performance but also performance speed improved.This experiment study showed no differences between LFN and HFN effects on the performance; moreover, both LFN and HFN improved the participants’ performance. Of course, more researches are suggested in this issue.

Influence of terminal action requirements on action-centered distractor effects.

Tipper (1985; Q J Exp Psychol A 37:571-590) has suggested that competing responses programmed to distracting stimuli are inhibited based on their relationship to the action being performed. The present paper reports two experiments designed to examine the influence of the terminal action of a task on the allocation of visual attention. Taken together the results suggest that when engaging targets in an environment, which includes distracting stimuli, competing responses are likely to be programmed in parallel and that the relationship between competing responses can include both spatial position and action characteristics.

Exercise Maintenance Following Pulmonary Rehabilitation: Effect of Distractive Stimuli.

Exercise Maintenance Following Pulmonary Rehabilitation: Effect of Distractive Stimuli.

A Role for Top-Down Attentional Orienting during Interference between Global and Local Aspects of Hierarchical Stimuli

Various models of selective attention propose that greater attention is allocated toward target stimuli when conflicting distracters make selection more difficult, but compelling evidence to support this view is scarce. In the present experiment, 15 participants performed a cued global/local selective attention task while brain activity was recorded with event-related functional magnetic resonance imaging. The presence of conflicting versus nonconflicting distracters during target processing activated regions of frontal, parietal, and visual cortices that were also activated when participants oriented attention in response to global- and local-task cues. These findings support models in which conflict between target and distracter stimuli is resolved by more selectively focusing attention upon target stimuli.

Orthogonal Polynomial Regression for the Detection of Response Variability in Event-Related fMRI

Previous studies using event-related potentials (ERPs) have identified a variety of brain regions that respond to rare nontarget distractor stimuli presented in the visual oddball task. By contrast, event-related functional magnetic resonance imaging (ER-fMRI) studies using similar stimuli have found little or no response in these same regions, suggesting that ER-fMRI may be less sensitive than ERPs for detecting stimulus-evoked activity. It was hypothesized here that variations in ER-fMRI response amplitude evoked by successive stimuli may have reduced detection sensitivity in these previous studies. Multiple regression with orthogonal polynomials (OPR) was used to increase detection sensitivity by employing orthogonal polynomial equations to model such variations in response amplitude. ER-fMRI data was collected from 17 subjects during performance of the visual oddball task, which included frequent nontarget, rare nontarget distractor, and rare target block letter stimuli, to which subjects made a speeded button press response. When compared with multiple regression using main effect regressors alone, OPR identified an increased volume of significant target and distractor evoked main effect response due to reduced error variance. In addition, distractor-evoked activity was found to correlate with orthogonal polynomial regressors but not main effect regressors across a large volume of prefrontal and paralimbic brain regions including dorsal-lateral prefrontal, inferior-lateral prefrontal, and cingulate cortex. These results illustrate that considerable variability is present in ER-fMRI responses evoked by rare distractor stimuli in the oddball task. Such variability can be modeled using OPR, leading to increased detection sensitivity and better anatomical correspondence between the findings of ER-fMRI and ERP studies.

Exercise Maintenance Following Pulmonary Rehabilitation: Effect of Distractive Stimuli

To determine if distractive auditory stimuli (DAS) in the form of music would promote adherence to a walking regimen following completion of a pulmonary rehabilitation program (PRP) and, thereby, maintenance of gains achieved during the program. Experimental, randomized, two-group design with testing at baseline, 4 weeks, and 8 weeks. Outpatient. Twenty-four patients (4 men and 20 women) with moderate-to-severe COPD (FEV(1) 41.3 +/- 13% predicted [mean +/- SD]). Experimental group subjects (n = 12) were instructed to walk at their own pace for 20 to 45 min, two to five times a week, using DAS with a portable audiocassette player. The control group (n = 12) received the same instructions, but no DAS. Primary outcome measures were perceived dyspnea during activities of daily living (ADL) and 6-min walk (6MW) distance. Secondary outcome measures were anxiety, depressive symptoms, health-related quality of life (QoL), global QoL, and breathlessness and fatigue at completion of the 6MW. In addition, all subjects recorded the distance and time walked using self-report (pedometers and daily logs). There was a significant decrease in perceived dyspnea during ADL (p = 0.0004) and a significant increase in 6MW distance (p = 0.0004) over time in the DAS group compared to the control group. DAS subjects increased 6MW distance 445 +/- 264 feet (mean +/- SD) from baseline to 8 weeks, whereas control subjects decreased 6MW distance to 169 +/- 154 feet. No significant differences were noted for the remaining variables. The cumulative distance walked by the DAS group was 19.1 +/- 16.7 miles compared to 15.4 +/- 8.0 miles for the control group, a 24% difference (p = 0.49). Despite this difference, self-report exercise log data were similar for the two groups. Subjects who used DAS while walking had improved functional performance and decreased perceptions of dyspnea, whereas control subjects could not maintain post-PRP gains. DAS is a simple, cost-effective strategy that may have the potential to augment the effectiveness of post-PRP maintenance training.

Attentional recruitment of inter-areal recurrent networks for selective gain control.

There is strong anatomical and physiological evidence that neurons with large receptive fields located in higher visual areas are recurrently connected to neurons with smaller receptive fields in lower areas. We have previously described a minimal neuronal network architecture in which top-down attentional signals to large receptive field neurons can bias and selectively read out the bottom-up sensory information to small receptive field neurons (Hahnloser, Douglas, Mahowald, & Hepp, 1999). Here we study an enhanced model, where the role of attention is to recruit specific inter-areal feedback loops (e.g., drive neurons above firing threshold). We first illustrate the operation of recruitment on a simple example of visual stimulus selection. In the subsequent analysis, we find that attentional recruitment operates by dynamical modulation of signal amplification and response multistability. In particular, we find that attentional stimulus selection necessitates increased recruitment when the stimulus to be selected is of small contrast and of small distance away from distractor stimuli. The selectability of a low-contrast stimulus is dependent on the gain of attentional effects; for example, low-contrast stimuli can be selected only when attention enhances neural responses. However, the dependence of attentional selection on stimulus-distractor distance is not contingent on whether attention enhances or suppresses responses. The computational implications of attentional recruitment are that cortical circuits can behave as winner-take-all mechanisms of variable strength and can achieve close to optimal signal discrimination in the presence of external noise.

Can’t shake that feeling: event-related fMRI assessment of sustained amygdala activity in response to emotional information in depressed individuals

Background: Previous research suggests that depressed individuals engage in prolonged elaborative processing of emotional information. A computational neural network model of emotional information processing suggests this process involves sustained amygdala activity in response to processing negative features of information. This study examined whether brain activity in response to emotional stimuli was sustained in depressed individuals, even following subsequent distracting stimuli. Methods: Seven depressed and 10 never-depressed individuals were studied using event-related functional magnetic resonance imaging during alternating 15-sec emotional processing (valence identification) and nonemotional processing (Sternberg memory) trials. Amygdala regions were traced on high-resolution structural scans and co-registered to the functional data. The time course of activity in these areas during emotional and nonemotional processing trials was examined. Results: During emotional processing trials, never-depressed individuals displayed amygdalar responses to all stimuli, which decayed within 10 sec. In contrast, depressed individuals displayed sustained amygdala responses to negative words that lasted throughout the following nonemotional processing trials (25 sec later). The difference in sustained amygdala activity to negative and positive words was moderately related to self-reported rumination. Conclusions: Results suggest that depression is associated with sustained activity in brain areas responsible for coding emotional features.

Lateral prefrontal damage affects processing selection but not attention switching

A challenge for cognitive neuroscience is to determine how the prefrontal cortex (PFC) contributes to the cognitive control operations that oversee thought and action. We studied the effects of damage to the lateral PFC in two types of attentional control. Subjects performed a choice reaction time task that required attention switching and processing selection. The performance of individuals with PFC or parietal cortex damage was compared with that of age-matched and young control subjects. Damage to the lateral PFC did not significantly impair the switch from attending to one color to attending to another. PFC damage did, however, significantly increase the effects of distractor stimuli, implicating the lateral PFC in processing selection. Individual subjects’ performance suggested that the left inferior posterior PFC was the most critical for processing selection. Our data are consistent with the view that the lateral PFC contributes to the top-down control of the information flow along pathways from sensory input to motor output.

Enhanced negative priming in Parkinson's disease.

In the ignored repetition paradigm, negative priming (NP) is defined as the increase in response time that occurs when the current target stimulus served as a distractor stimulus in the previous trial. In this study, 25 Parkinson's disease (PD) participants and 17 age-matched healthy controls (HCs) were tested using a touchscreen version of the ignored repetition task that allowed response time to be partitioned into response initiation and response execution segments. In both groups, NP effects were stronger in the response execution than in the response initiation segments. The most striking result was that the PD group showed larger NP effects overall than the HC group. In PD, clinical ratings of bradykinesia, but not tremor, were related to larger NP effects. Results indicate that in PD, disruption of dopamine neuromodulation diminishes response efficiency when action must be directed toward previously ignored information.

The neural substrate of orientation short‐term memory and resistance to distractor items

We used Positron Emission Tomography to map the neural substrate of human short-term memory for orientation, defined as retaining a single orientation in memory over a long delay, by comparing a successive discrimination task with a 6-s delay to the same task with a brief 0.3 s delay and to an identification control task. Short-term memory engaged the superior parietal lobe bilaterally, the middle occipital gyrus bilaterally and the left dorsolateral prefrontal cortex. In addition, we studied the resistance to a distractor item by comparing the successive discrimination task with long delay, with and without an intervening distractor stimulus. This manipulative process engaged left ventral premotor cortex and left dorsolateral prefrontal cortex. The activation of left dorsolateral prefrontal cortex is interpreted as reflecting co-ordination between task components. These results, combined with those of two previous studies using an identical reduction strategy, underscore the functional heterogeneity in the prefrontal cortex during short-term and working memory.

Data-driven recognition memory: a new technique and some data on age differences.

In this study, we investigate the effect on recognition memory of having target and distractor stimuli consisting of different combinations of low-level elements (letters), relative to when targets and distractors consist of combinations of the same elements (nonoverlap and overlap conditions, respectively). It was found that recognition memory was enhanced in the nonoverlap condition, even though subjects reported being unaware of this experimental manipulation. This confirms the importance of perceptually driven processing in the implicit memory component of recognition memory. The extent to which this effect occurs is found to be age dependent, with elderly subjects benefiting more from having targets and distractors consisting of nonoverlapping elements. This is consistent with the notion that elderly subjects show less reliance on item-specific/contextual detail to support recognition memory.

P3a from a passive visual stimulus task

Objective: Visual event-related brain potentials (ERPs) were elicited using a 3-stimulus oddball paradigm to assess the P3a with passive stimulus processing. Methods: Young adults ( n=12) were presented with a series of visual stimuli consisting of a solid circle standard stimulus ( P=0.76) that was difficult to discriminate from a larger target circle ( P=0.12), with a large square distractor stimulus ( P=0.12) presented randomly in the series. Subjects were instructed in the passive condition to simply look at the stimuli and in the active condition to press a mouse key only to the target stimulus. ERPs were recorded from 15 scalp electrodes, with the amplitude and latency of the P300 from the distractor and target stimuli assessed. Results: The P3a from the distractor stimulus was similar in amplitude, scalp topography, and peak latency across the passive and active task conditions. The P3b from the target stimulus demonstrated much smaller amplitude, highly altered scalp topography, and longer latency for the passive compared to active task conditions. Conclusions: The P3a can be obtained with visual stimuli in the 3-stimulus paradigm under passive viewing conditions. Theoretical implications and clinical applications are discussed.

Influence of Competing Distractors on Response Selection in Huntington's Disease and Parkinson's Disease

Current theories of the basal ganglia suggest a functional role in filtering stimuli that are competing for response selection. We hypothesised that damage to the basal ganglia, as occurs in Huntington's disease (HD) and Parkinson's disease (PD), may alter the effects of distractors on this filtering process. Fourteen HD subjects, 16 PD subjects, and age-matched healthy controls performed an ignored repetition test of negative priming. Negative priming was defined as a significant time cost in responding to a target that shared features with the distractor from the previous trial. Results indicated that whereas healthy controls and PD subjects showed normal negative priming, HD subjects failed to show negative priming. The results indicate that disruption to cells in the neostriatum, but not necessarily to cells in the substantia nigra, may affect selective attention by altering the influence of distractor stimuli competing for action.