High Attentional Load Research Articles

Compensating for failed attention while driving

While operating a motor vehicle, drivers must pay attention to other moving vehicles and the roadside environment in order to detect and process critical information related to the driving task. Using a driving simulator, this study investigated the effects of an unexpected event on driver performance in environments of more or less clutter and under situations of high attentional load. Attentional load was manipulated by varying the number of neighboring vehicles participants tracked for lane changes. After baseline-driving behavior was established, the unexpected event occurred: a pedestrian ran into the driver’s path. Tracking-accuracy, brake initiation, swerving, and verbal report of the unexpected pedestrian were used to assess driver performance. All participants verbally reported noticing the pedestrian. However, analyses of driving behavior revealed differences in the reactions to the pedestrian: drivers braked faster and had significantly less deviation in their steering heading with a lower attentional load, and participants in low clutter environments had a larger overall change in velocity. This research advances the understanding of how drivers allocate attention between various stimuli and the trade-offs between a driver’s focus on an assigned task and external objects within the roadway environment. Moreover, the results of this research lend insight into how to construct roadway environments that encourage driver attention toward the most immediate and relevant information to reduce both vehicle-to-vehicle and vehicle-to-pedestrian interactions.

Theta phase coherence in affective picture processing reveals dysfunctional sensory integration in psychopathic offenders

Psychopathic offenders are described as emotionally cold, displaying deficits in affective responding. However, research demonstrates that many of the psychopathy-related deficits are moderated by attention, such that under conditions of high attentional and perceptual load psychopathic offenders display deficits in affective responses, but do not in conditions of low load. To date, most studies use measures of defensive reflex (i.e., startle) and conditioning manipulations to examine the impact of load on psychopathy-related processing, but have not examined more direct measures of attention processing. In a sample of adult male offenders, the present study examined time-frequency EEG phase coherence in response to a picture-viewing paradigm that manipulated picture familiarity to assess neural changes in processing based on perceptual demands. Results indicated psychopathy-related differences in the theta response, an index of readiness to perceive and integrate sensory information. These data provide further evidence that psychopathic offenders have disrupted integration of sensory information.

The effects of tDCS upon sustained visual attention are dependent on cognitive load

Transcranial Direct Current Stimulation (tDCS) modulates the excitability of neuronal responses and consequently can affect performance on a variety of cognitive tasks. However, the interaction between cognitive load and the effects of tDCS is currently not well-understood. We recorded the performance accuracy of participants on a bilateral multiple object tracking task while undergoing bilateral stimulation assumed to enhance (anodal) and decrease (cathodal) neuronal excitability. Stimulation was applied to the posterior parietal cortex (PPC), a region inferred to be at the centre of an attentional tracking network that shows load-dependent activation. 34 participants underwent three separate stimulation conditions across three days. Each subject received (1) left cathodal / right anodal PPC tDCS, (2) left anodal / right cathodal PPC tDCS, and (3) sham tDCS. The number of targets-to-be-tracked was also manipulated, giving a low (one target per visual field), medium (two targets per visual field) or high (three targets per visual field) tracking load condition. It was found that tracking performance at high attentional loads was significantly reduced in both stimulation conditions relative to sham, and this was apparent in both visual fields, regardless of the direction of polarity upon the brain’s hemispheres. We interpret this as an interaction between cognitive load and tDCS, and suggest that tDCS may degrade attentional performance when cognitive networks become overtaxed and unable to compensate as a result. Systematically varying cognitive load may therefore be a fruitful direction to elucidate the effects of tDCS upon cognitive functions.

Theta burst stimulation improves overt visual search in spatial neglect independently of attentional load

Visual neglect is considerably exacerbated by increases in visual attentional load. These detrimental effects of attentional load are hypothesised to be dependent on an interplay between dysfunctional inter-hemispheric inhibitory dynamics and load-related modulation of activity in cortical areas such as the posterior parietal cortex (PPC).Continuous Theta Burst Stimulation (cTBS) over the contralesional PPC reduces neglect severity. It is unknown, however, whether such positive effects also operate in the presence of the detrimental effects of heightened attentional load.Here, we examined the effects of cTBS on neglect severity in overt visual search (i.e., with eye movements), as a function of high and low visual attentional load conditions. Performance was assessed on the basis of target detection rates and eye movements, in a computerised visual search task and in two paper-pencil tasks. cTBS significantly ameliorated target detection performance, independently of attentional load. These ameliorative effects were significantly larger in the high than the low load condition, thereby equating target detection across both conditions. Eye movement analyses revealed that the improvements were mediated by a redeployment of visual fixations to the contralesional visual field.These findings represent a substantive advance, because cTBS led to an unprecedented amelioration of overt search efficiency that was independent of visual attentional load.

The Effects of High Stress on Attention

Attentional narrowing – the involuntary reduction in the range of cues that can be utilized by an individual – represents a major threat in many complex data-rich domains. Still, very little empirical research has been conducted to better understand and overcome the problem, in large part because it is difficult to reliably induce the phenomenon in controlled settings. The present study examined the effectiveness of two factors – high attentional load and ego-threat - for inducing high levels of stress and attentional narrowing in the context of a simplified air traffic control (ATC) task. Five participants were asked to complete two simultaneous noticing tasks - one presented centrally, the other in the periphery of the screen. In the high stress condition, they also had to perform a concurrent paced addition task (high attentional load) and received false feedback on their performance (ego-threat). Performance on the two main ATC tasks and the addition task was measured. Subjective ratings were collected to assess participants’ anxiety levels. High attentional load and ego-threat increased participants’ anxiety level. Overall, performance on the ATC tasks suffered slightly during high stress, suggesting a reduction in the spread of attention. Also, performance on the addition was significantly reduced when performed concurrently with the ATC tasks, as compared to the training phase. The findings from this study represent an important step towards being able to induce and study attentional narrowing systematically and to develop countermeasures to this significant safety threat.

Perceptual load of divided attention modulates auditory-motor integration of voice control

The present study sought to examine how the auditory-motor processing of feedback errors during vocal pitch regulation is modulated as a function of divided attention. Subjects were exposed to pitch perturbations in voice auditory feedback and flashing lights on the computer screen, during which they were asked to divide their attention to both auditory and visual stimuli by counting the number of both of them. The presentation rate of the visual stimuli (inter-stimulus intervel) was manipulated to produce a low, intermediate, and high attentional load. The results revealed that, as compared to the low and intermediate attentional load conditions, the high attentional load condition elicited significantly smaller magnitudes of vocal responses but larger amplitudes of N1 and P2 responses to pitch feedback perturbations. These findings demonstrate the effect of attentional load on the auditory-motor processing of pitch feedback errors during divided attention, suggesting that perceptual load of visual attention interferes the attentional modulation of auditory-motor integration in voice control.

Default mode network connectivity during task execution

Initially described as task-induced deactivations during goal-directed paradigms of high attentional load, the unresolved functionality of default mode regions has long been assumed to interfere with task performance. However, recent evidence suggests a potential default mode network involvement in fulfilling cognitive demands. We tested this hypothesis in a finger opposition paradigm with task and fixation periods which we compared with an independent resting state scan using functional magnetic resonance imaging and a comprehensive analysis pipeline including activation, functional connectivity, behavioural and graph theoretical assessments. The results indicate task specific changes in the default mode network topography. Behaviourally, we show that increased connectivity of the posterior cingulate cortex with the left superior frontal gyrus predicts faster reaction times. Moreover, interactive and dynamic reconfiguration of the default mode network regions' functional connections illustrates their involvement with the task at hand with higher-level global parallel processing power, yet preserved small-world architecture in comparison with rest. These findings demonstrate that the default mode network does not disengage during this paradigm, but instead may be involved in task relevant processing.

Attentional Modulation of Brain Responses to Primary Appetitive and Aversive Stimuli.

Studies of subjective well-being have conventionally relied upon self-report, which directs subjects’ attention to their emotional experiences. This method presumes that attention itself does not influence emotional processes, which could bias sampling. We tested whether attention influences experienced utility (the moment-by-moment experience of pleasure) by using functional magnetic resonance imaging (fMRI) to measure the activity of brain systems thought to represent hedonic value while manipulating attentional load. Subjects received appetitive or aversive solutions orally while alternatively executing a low or high attentional load task. Brain regions associated with hedonic processing, including the ventral striatum, showed a response to both juice and quinine. This response decreased during the high-load task relative to the low-load task. Thus, attentional allocation may influence experienced utility by modulating (either directly or indirectly) the activity of brain mechanisms thought to represent hedonic value.

Audio dilation in real time speech communication

Algorithmically decreasing speech tempo, or “audio dilation,” can improve speech perception in attentionally demanding tasks [Gygi & Shafiro (2014), Hear. Res. 310, pp. 76–86]. On-line audio dilation [Novak, et al. (2013), Interspeech 1869–1871] is a recently developed technique that decreases the tempo of audio signals as they are generated. This pilot study investigated effects of on-line audio dilation on performance in interactive problem solving tasks. We used a Diapix task [Baker & Hazan (2011), Behav. Res. Methods 43(3), 761–770] to elicit and record spontaneous speech from pairs of participants under various dilation conditions: participants, seated in different rooms, were asked to find ten differences on two similar pictures, while their speech was either transmitted as spoken or dilated. Conditions tested include stretching one, both, or neither audio signal by 40%. Subsequent analysis shows that the technique, even using this substantial increase, did not interfere with interactive problem solving tasks, and did not lead to changes in speech production rate, measured as number of syllables per second. The lack of negative effects of on-line speech dilation provides a preliminary basis for further assessment of this method in speech perception tasks with high attentional and memory load.

FMRI identifies chronotype-specific brain activation associated with attention to motion — Why we need to know when subjects go to bed

Human cognition relies on attentional capacities which, among others, are influenced by factors like tiredness or mood. Based on their inherent preferences in sleep and wakefulness, individuals can be classified as specific “chronotypes”. The present study investigated how early, intermediate and late chronotypes (EC, IC, LC) differ neurally on an attention-to-motion task.Twelve EC, 18 IC and 17 LC were included into the study. While undergoing functional magnetic resonance imaging (fMRI) scans, subjects looked at vertical bars in an attention-to-motion task. In the STATIONARY condition, subjects focused on a central fixation cross. During Fix-MOVING and Attend-MOVING, bars were moving horizontally. Only during the Attend-MOVING, subjects were required to attend to changes in the velocity of bars and indicate those by button presses. A two-way repeated measures ANOVA probed group by attentional load effects.The dorsolateral prefrontal cortex (DLPFC), insula and anterior cingulate cortex showed group by attention specific activations. Specifically, EC and LC presented attenuated DLPFC activation under high attentional load (Attend-MOVING), while EC showed less anterior insula activation than IC. LC compared to IC exhibited attenuation of superior parietal cortex.Our study reveals that individual sleep preferences are associated with characteristic brain activation in areas crucial for attention and bodily awareness. These results imply that considering sleep preferences in neuroimaging studies is crucial when administering cognitive tasks. Our study also has socio-economic implications. Task performance in non-optimal times of the day (e.g. shift workers), may result in cognitive impairments leading to e.g. increased error rates and slower reaction times.

Attention modulates cortical processing of pitch feedback errors in voice control.

Considerable evidence has shown that unexpected alterations in auditory feedback elicit fast compensatory adjustments in vocal production. Although generally thought to be involuntary in nature, whether these adjustments can be influenced by attention remains unknown. The present event-related potential (ERP) study aimed to examine whether neurobehavioral processing of auditory-vocal integration can be affected by attention. While sustaining a vowel phonation and hearing pitch-shifted feedback, participants were required to either ignore the pitch perturbations, or attend to them with low (counting the number of perturbations) or high attentional load (counting the type of perturbations). Behavioral results revealed no systematic change of vocal response to pitch perturbations irrespective of whether they were attended or not. At the level of cortex, there was an enhancement of P2 response to attended pitch perturbations in the low-load condition as compared to when they were ignored. In the high-load condition, however, P2 response did not differ from that in the ignored condition. These findings provide the first neurophysiological evidence that auditory-motor integration in voice control can be modulated as a function of attention at the level of cortex. Furthermore, this modulatory effect does not lead to a general enhancement but is subject to attentional load.

Vision and Haptics Share Spatial Attentional Resources and Visuotactile Integration Is Not Affected by High Attentional Load.

Human information processing is limited by attentional resources. Two questions that are discussed in multisensory research are (1) whether there are separate spatial attentional resources for each sensory modality and (2) whether multisensory integration is influenced by attentional load. We investigated these questions using a dual task paradigm: Participants performed two spatial tasks (a multiple object tracking ['MOT'] task and a localization ['LOC'] task) either separately (single task condition) or simultaneously (dual task condition). In the MOT task, participants visually tracked a small subset of several randomly moving objects. In the LOC task, participants either received visual, tactile, or redundant visual and tactile location cues. In the dual task condition, we found a substantial decrease in participants' performance and an increase in participants' mental effort (indicated by an increase in pupil size) relative to the single task condition. Importantly, participants performed equally well in the dual task condition regardless of whether they received visual, tactile, or redundant multisensory (visual and tactile) location cues in the LOC task. This result suggests that having spatial information coming from different modalities does not facilitate performance, thereby indicating shared spatial attentional resources for the tactile and visual modality. Also, we found that participants integrated redundant multisensory information optimally even when they experienced additional attentional load in the dual task condition. Overall, findings suggest that (1) spatial attentional resources for the tactile and visual modality overlap and that (2) the integration of spatial cues from these two modalities occurs at an early pre-attentive processing stage.

Prestimulus Alpha Oscillations as an Index of Increased Cognitive Control Under the Auditory Condensation Task

Attentional lapses are usually viewed as a result of deterioration in cognitive control. Current theories suggest that deterioration in the cognitive control may be related to an increase in alpha rhythm power, although it is not clear whether this notion can be generalized outside of the visual task modality. In the current study power of prestimulus alpha-band oscillations was analyzed during performance of the modified auditory condensation task, which creates high attentional load. Prestimulus lower alpha-band power was found to decrease before erroneous responses, which can be viewed as attentional lapses related to decreased cognitive control, compared with correct responses. Prestimulus lower alpha-band power also gradually increased within continuous sequences of distractor stimuli separating adjacent target stimuli, thus reflecting gradual increase in the level of cognitive control mirroring increasing expectancy of the target stimuli. These findings demonstrate that the relation of alpha power to cognitive control level critically depends on the experimental task modality, and under conditions of the auditory attentional task higher alpha power may be an index of increased rather than decreased level of cognitive control.

Attentional demands influence vocal compensations to pitch errors heard in auditory feedback.

Auditory feedback is required to maintain fluent speech. At present, it is unclear how attention modulates auditory feedback processing during ongoing speech. In this event-related potential (ERP) study, participants vocalized/a/, while they heard their vocal pitch suddenly shifted downward a ½ semitone in both single and dual-task conditions. During the single-task condition participants passively viewed a visual stream for cues to start and stop vocalizing. In the dual-task condition, participants vocalized while they identified target stimuli in a visual stream of letters. The presentation rate of the visual stimuli was manipulated in the dual-task condition in order to produce a low, intermediate, and high attentional load. Visual target identification accuracy was lowest in the high attentional load condition, indicating that attentional load was successfully manipulated. Results further showed that participants who were exposed to the single-task condition, prior to the dual-task condition, produced larger vocal compensations during the single-task condition. Thus, when participants’ attention was divided, less attention was available for the monitoring of their auditory feedback, resulting in smaller compensatory vocal responses. However, P1-N1-P2 ERP responses were not affected by divided attention, suggesting that the effect of attentional load was not on the auditory processing of pitch altered feedback, but instead it interfered with the integration of auditory and motor information, or motor control itself.

Effects of tinnitus and hearing loss on functional brain networks involved in auditory and visual short-term memory

Brain imaging data were acquired from three subject groups—persons with hearing loss and tinnitus (TIN), individuals with similar hearing loss without tinnitus (HL) and those with normal hearing without tinnitus (NH)—to test the hypothesis that TIN and control subjects use different functional brain networks for short-term memory. Previous studies have provided evidence of a link between hearing disorders such as tinnitus and the reorganization of auditory and extra-auditory functional networks. Greater knowledge of this reorganization could lead to the development of more effective therapies. Data analysis was conducted on fMRI data obtained while subjects performed short-term memory tasks with low or high attentional loads, using both auditory and visual stimuli in separate scanning sessions. Auditory stimuli were pure tones with frequencies between 500 and 1000 Hz. Visual stimuli were Korean fonts, unfamiliar to the subjects. We found similar behavioral response across the three groups for both modalities and tasks. However, the groups differed in their brain response, with these differences being more marked for the auditory tasks and not for the tasks involving visual stimuli.

Attentional load and the consciousness of one's own name.

We investigated how the location of one's own name in a visual display influences its conscious awareness using recall and recognition tests in an inattentional blindness paradigm. The participant's own name or another person's name appeared unexpectedly in the center or the periphery of the display during a critical trial under low- or high-attentional search load. The results showed that the majority of participants detected their names under low load regardless of location and test method. Under high load, the majority of the participants could recognize or recall their names presented in the center of the display. When the person's name was in the periphery, most of the participants did not recall their names, and approximately half recognized their names. In contrast, conscious awareness of another person's name was low in all conditions. A person's own name is processed with high priority, even under a high-attentional load.

Genetics of preparation and response control in ADHD: the role of DRD4 and DAT1

Difficulties with performance and brain activity related to attentional orienting (Cue-P3), cognitive or response preparation (Cue-CNV) and inhibitory response control (Nogo-P3) during tasks tapping executive functions are familial in ADHD and may represent endophenotypes. The aim of this study was to clarify the impact of dopamine receptor D4 (DRD4) and dopamine transporter (DAT1) gene polymorphisms on these processes in ADHD and control children. Behavioural and electrophysiological parameters from cued continuous performance tests with low and high attentional load were assessed in boys with ADHD combined type (N=94) and controls without family history of ADHD (N=31). Both groups were split for the presence of at least one DRD4 7-repeat allele and the DAT1 10-6 haplotype. Children with ADHD showed diminished performance and lower Cue-P3, CNV and Nogo-P3 amplitudes. Children with DRD4 7R showed similar performance problems and lower Cue-P3 and CNV, but Nogo-P3 was not reduced. Children with the DAT1 10-6 haplotype had no difficulties with performance or Cue-P3 and CNV, but contrary to expectations increased Nogo-P3. There were no Genotype by ADHD interactions. This study detected specific effects of DRD4 7R on performance and brain activity related to attentional orienting and response preparation, while DAT1 10-6 was associated with elevated brain activity related to inhibitory response control, which potentially compensates increased impulsivity. As these genotype effects were additive to the impact of ADHD, the current results indicate that DRD4 and DAT1 polymorphisms are functionally relevant risk factors for ADHD and presumably other disorders sharing these endophenotypes.

Earliest stages of visual cortical processing are not modified by attentional load.

This study investigated the effects of attentional load on neural responses to attended and irrelevant visual stimuli by recording high-density event-related potentials (ERPs) from the scalp in normal adult subjects. Peripheral (upper and lower visual field) and central stimuli were presented in random order at a rapid rate while subjects responded to targets among the central stimuli. Color detection and color-orientation conjunction search tasks were used as the low- and high-load tasks, respectively. Behavioral results showed significant load effects on both accuracy and reaction time for target detections. ERP results revealed no significant load effect on the initial C1 component (60-100 ms) evoked by either central-relevant or peripheral-irrelevant stimuli. Source analysis with dipole modeling confirmed previous reports that the C1 includes the initial evoked response in primary visual cortex. Source analyses indicated that high attentional load enhanced the early (70-140 ms) neural response to central-relevant stimuli in ventral-lateral extrastriate cortex, whereas load effects on peripheral-irrelevant stimulus processing started at 110 ms and were localized to more dorsal and anterior extrastriate cortical areas. These results provide evidence that the earliest stages of visual cortical processing are not modified by attentional load and show that attentional load affects the processing of task relevant and irrelevant stimuli in different ways.

OP 12. Effects of transcranial static magnetic field stimulation (tSMS) over the human visual cortex: Behavioural and electrophysiological effects

We previously reported that continuous application of Transcranial Static Magnetic Field Stimulation (tSMS) over the motor cortex induces a reduction of cortical excitability lasting several minutes after the end of tSMS. In the present study, we further explore static magnetic field effects on EEG oscillations in the visual cortex and during visual attentional performance in healthy humans. We specifically test a hypothesis that our previous tSMS effects in motor cortex could be related to an increase of alpha band activity, and therefore, associated with an “inhibitory” effect. Thus, we investigated the effects of tSMS (real or sham) placed over visual cortex in two studies: a first experiment, in which tSMS was simultaneous applied during ten minutes eyes-open resting EEG recording; a second experiment, in which visual attention was measured in the context of tSMS during performance of a visual search paradigm. In both experiments, EEG and behavioural measurements were made during, and 10 min following, tSMS application. As predicted, the application of real, but not sham, tSMS over the visual cortex resulted in a significant increase in alpha band power. In the visual search task, real and sham tSMS groups displayed a similar behavioural profile, with reaction times (RTs) increasing with increasing task demands. Critically, however, a significant slowing of RTs emerged on trials with the highest difficulty levels during real in comparison to sham tSMS . Our results therefore suggest that tSMS has a profound influence on oscillatory alpha activity, which we suggest reflects a modulation of visual cortical excitability. Secondly, our behavioural results indicate that tSMS over the occiput alters visual search performance, slowing responses to stimulus detection. Importantly, this was not a general task impairment, but a tSMS-induced slowing of visual search specific to high attentional load levels. We speculate that this slowing is secondary to a decrease in underlying alpha oscillations. Further studies using tSMS are required to extend the knowledge of the functional significance of brain oscillations changes induced by the application of small magnets over the scalp.

Compensatory Effort Parallels Midbrain Deactivation during Mental Fatigue: An fMRI Study

Fatigue reflects the functioning of our physiological negative feedback system, which prevents us from overworking. When fatigued, however, we often try to suppress this system in an effort to compensate for the resulting deterioration in performance. Previous studies have suggested that the effect of fatigue on neurovascular demand may be influenced by this compensatory effort. The primary goal of the present study was to isolate the effect of compensatory effort on neurovascular demand. Healthy male volunteers participated in a series of visual and auditory divided attention tasks that steadily increased fatigue levels for 2 hours. Functional magnetic resonance imaging scans were performed during the first and last quarter of the study (Pre and Post sessions, respectively). Tasks with low and high attentional load (Low and High conditions, respectively) were administrated in alternating blocks. We assumed that compensatory effort would be greater under the High-attentional-load condition compared with the Low-load condition. The difference was assessed during the two sessions. The effect of compensatory effort on neurovascular demand was evaluated by examining the interaction between load (High vs. Low) and time (Pre vs. Post). Significant fatigue-induced deactivation (i.e., Pre>Post) was observed in the frontal, temporal, occipital, and parietal cortices, in the cerebellum, and in the midbrain in both the High and Low conditions. The interaction was significantly greater in the High than in the Low condition in the midbrain. Neither significant fatigue-induced activation (i.e., Pre<Post), nor its interaction with factor Load, was identified. The observed midbrain deactivation ([PreH – PostH]>[PreE– PostE]) may reflect suppression of the negative feedback system that normally triggers recuperative rest to maintain homeostasis.