Blink-related EEG activity measures cognitive load during proactive and reactive driving.

Assessing drivers' cognitive load is crucial for driving safety in challenging situations. This research employed the occurrence of drivers' natural eye blinks as cues in continuously recorded EEG data to assess the cognitive workload while reactive or proactive driving. Twenty-eight participants performed either a lane-keeping task with varying levels of crosswind (reactive) or curve road (proactive). The blink event-related potentials (bERPs) and spectral perturbations (bERSPs) were analyzed to assess cognitive load variations. The study found that task load during reactive driving did not significantly impact bERPs or bERSPs, possibly due to enduring alertness for vehicle control. The proactive driving revealed significant differences in the occipital N1 component with task load, indicating the necessity to adapt the attentional resources allocation based on road demands. Also, increased steering complexity led to decreased frontal N2, parietal P3, occipital P2 amplitudes, and alpha power, requiring more cognitive resources for processing relevant information. Interestingly, the proactive and reactive driving scenarios demonstrated a significant interaction at the parietal P2 and occipital N1 for three difficulty levels. The study reveals that EEG measures related to natural eye blink behavior provide insights into the effect of cognitive load on different driving tasks, with implications for driver safety.

Decoding Eye Blink and Related EEG Activity in Realistic Working Environments.

Accurately evaluating cognitive load during work-related tasks in complex real-world environments is challenging, leading researchers to investigate the use of eye blinking as a fundamental pacing mechanism for segmenting EEG data and understanding the neural mechanisms associated with cognitive workload. Yet, little is known about the temporal dynamics of eye blinks and related visual processing in relation to the representation of task-specific information. Therefore, we analyzed EEG responses from two experiments involving simulated driving (re-active and pro-active) with three levels of task load for each, as well as operating a steam engine (active vs. passive), to decode the temporal dynamics of eye blink activity and the subsequent neural activity that follows blinking. As a result, we successfully decoded the binary representation of difficulty levels for pro-active driving using multivariate pattern analysis. However, the decoding level varied for different re-active driving conditions, which could be attributed to the required level of alertness. Furthermore, our study revealed that it was possible to decode both driving types as well as steam engine operating conditions, with the most significant decoding activity observed approximately 200 ms after a blink. Additionally, our findings suggest that eye blinks have considerable potential for decoding various cognitive states that may not be discernible through neural activity, particularly near the peak of the blink. The findings demonstrate the potential of blink-related measures alongside EEG data to decode cognitive states during complex tasks, with implications for improving evaluations of cognitive and behavioral states during tasks, such as driving and operating machinery.

Tracking drivers' minds: Continuous evaluation of mental load and cognitive processing in a realistic driving simulator scenario by means of the EEG.

Driving safety strongly depends on the driver's mental states and attention to the driving situation. Previous studies demonstrate a clear relationship between EEG measures and mental states, such as alertness and drowsiness, but often only map their mental state for a longer period of time. In this driving simulation study, we exploit the high temporal resolution of the EEG to capture fine-grained modulations in cognitive processes occurring before and after eye activity in the form of saccades, fixations, and eye blinks. A total of 15 subjects drove through an approximately 50-km course consisting of highway, country road, and urban passages. Based on the ratio of brain oscillatory alpha and theta activity, the total distance was classified into 10-m-long sections with low, medium, and high task loads. Blink-evoked and fixation-evoked event-related potentials, spectral perturbations, and lateralizations were analyzed as neuro-cognitive correlates of cognition and attention. Depending on EEG-based estimation of task load, these measures showed distinct patterns associated with driving behavior parameters such as speed and steering acceleration and represent a temporally highly resolved image of specific cognitive processes during driving. In future applications, combinations of these EEG measures could form the basis for driver warning systems which increase overall driving safety by considering rapid fluctuations in driver's attention and mental states.

Removing the cardiac field artifact from the EEG using neural network regression.

When EEG recordings are used to reveal interactions between central-nervous and cardiovascular processes, the cardiac field artifact (CFA) poses a major challenge. Because the electric field generated by cardiac activity is also captured by scalp electrodes, the CFA arises as a heavy contaminant whenever EEG data are analyzed time-locked to cardio-electric events. A typical example is measuring stimulus-evoked potentials elicited at different phases of the cardiac cycle. Here, we present a nonlinear regression method deploying neural networks that allows to remove the CFA from the EEG signal in such scenarios. We train neural network models to predict R-peak centered EEG episodes based on the ECG and additional CFA-related information. In a second step, these trained models are used to predict and consequently remove the CFA in EEG episodes containing visual stimulation occurring time-locked to the ECG. We show that removing these predictions from the signal effectively removes the CFA without affecting the intertrial phase coherence of stimulus-evoked activity. In addition, we provide the results of an extensive grid search suggesting a set of appropriate model hyperparameters. The proposed method offers a replicable way of removing the CFA on the single-trial level, without affecting stimulus-related variance occurring time-locked to cardiac events. Disentangling the cardiac field artifact (CFA) from the EEG signal is a major challenge when investigating the neurocognitive impact of cardioafferent traffic by means of the EEG. When stimuli are presented time-locked to the cardiac cycle, both sources of variance are systematically confounded. Here, we propose a regression-based approach deploying neural network models to remove the CFA from the EEG. This approach effectively removes the CFA on a single-trial level and is purely data-driven, providing replicable results.

Operator State in a Workplace Simulation Modulates Eye-Blink Related EEG Activity.

Evaluating and understanding the cognitive demands of natural activities has been difficult using neurocognitive approaches like mobile EEG. While task-unrelated stimuli are commonly added to a workplace simulation to estimate event-related cognitive processes, using eyeblink activity poses an alternative as it is inherent to human behavior. This study aimed to investigate the eye blink event-related EEG activity of fourteen subjects while working in a power-plant operator simulation - actively operating (active condition) or observing (passive condition) a real-world steam engine. The changes in event-related potentials, event-related spectral perturbations, and functional connectivity under both conditions were analyzed. Our results indicated several cognitive changes in relation to task manipulation. Posterior N1 and P3 amplitudes revealed alterations associated with task complexity, with increased N1 and P3 amplitudes for the active condition, indicating greater cognitive effort than the passive condition. Increased frontal theta power and suppressed parietal alpha power were observed during the active condition reflecting high cognitive engagement. Additionally, higher theta connectivity was seen in fronto-parieto-centro-temporo-occipital regions as task demands increased, showing increased communication between brain regions. All of these results suggest using eye blink-related EEG activity to acquire a comprehensive understanding of neuro-cognitive processing while working in realistic environments.

Neuroergonomics on the Go: An Evaluation of the Potential of Mobile EEG for Workplace Assessment and Design.

OBJECTIVE: We demonstrate and discuss the use of mobile electroencephalogram (EEG) for neuroergonomics. Both technical state of the art as well as measures and cognitive concepts are systematically addressed. BACKGROUND: Modern work is increasingly characterized by information processing. Therefore, the examination of mental states, mental load, or cognitive processing during work is becoming increasingly important for ergonomics. RESULTS: Mobile EEG allows to measure mental states and processes under real live conditions. It can be used for various research questions in cognitive neuroergonomics. Besides measures in the frequency domain that have a long tradition in the investigation of mental fatigue, task load, and task engagement, new approaches-like blink-evoked potentials-render event-related analyses of the EEG possible also during unrestricted behavior. CONCLUSION: Mobile EEG has become a valuable tool for evaluating mental states and mental processes on a highly objective level during work. The main advantage of this technique is that working environments don't have to be changed while systematically measuring brain functions at work. Moreover, the workflow is unaffected by such neuroergonomic approaches.

Using visual speech at the cocktail-party: CNV evidence for early speech extraction in younger and older adults.

The comprehension of spoken language benefits from visual speech information. One reason for this is the temporal lead of mouth and lip movements over the onset of acoustic speech utterance. Here, we investigated EEG event-related potentials preceding acoustic speech, focusing on a fronto-central contingent negative variation (CNV) prior to the onset of acoustic speech. We explored influences of expectation and visual speech content as well as age-related differences. In a multi-talker two-alternative speech discrimination task, younger and older subjects responded to short words presented simultaneously to competing speech under free-field conditions. Subjects were always presented with audiovisual speech stimuli, while the modality containing the task-relevant information was modulated in a block-wise fashion. Thus, task-relevant speech information was either available as audio-visually congruent stimuli or only in the visual (visual-valid) or the auditory (auditory-valid) modality. Subjects were instructed to fixate a pre-specified position in the left or right hemispace. In each task block, task-relevant stimuli appeared either at the pre-specified position (standard trials, 80%) or at a rare deviant position (20%). Target words were recognized faster and more accurately when visual speech information was available. The CNV prior to the acoustic speech onset was more pronounced with visual-informative than with visually non-informative speech. Especially in the younger group, a less pronounced CNV occurred with purely visual speech in deviant trials, that is, when a task-irrelevant speech stimulus appeared instead of the expected target stimulus. The results indicate that processes preceding the onset of acoustic speech are modulated by expectations and visual speech content, while age differences are rather small.

Task prioritization modulates alpha, theta and beta EEG dynamics reflecting proactive cognitive control.

Most neuroscientific studies investigating mental effort apply unspecific effort allocation paradigms. In contrast, the present EEG study targets specific effort allocation during task prioritization. Twenty-eight participants performed a cued number classification task during the retention interval of a working memory task including retrospective cues. One of two possible number classifications was done per trial. Each trial started with a cue indicating which of the two tasks would be more important in the upcoming trial. Subjects were told to engage in both tasks, but to concentrate on the important one. Feedback given at the end of each trial was calculated based on task performance, with scores obtained from the relevant task being tripled. Participants performed significantly better in either task when it was important compared to when not. Task prioritization modulates theta, alpha and beta oscillations, predominantly during task preparation. Multivariate pattern analysis revealed that the exact type of the two possible number classifications was decodable, however, decoding accuracy did not depend on task importance. Hemispheric alpha power asymmetries indicating attentional orienting between working memory representations also did not depend on task importance. The findings suggest that task prioritization primarily affects proactive cognitive control on a superordinate level.

Mental chronometry in big noisy data.

Temporal measures (latencies) in the event-related potentials of the EEG (ERPs) are a valuable tool for estimating the timing of mental processes, one which takes full advantage of the high temporal resolution of the EEG. Especially in larger scale studies using a multitude of individual EEG-based tasks, the quality of latency measures often suffers from high and low frequency noise residuals due to the resulting low trial counts (because of compressed tasks) and because of the limited feasibility of visual inspection of the large-scale data. In the present study, we systematically evaluated two different approaches to latency estimation (peak latencies and fractional area latencies) with respect to their data quality and the application of noise reduction by jackknifing methods. Additionally, we tested the recently introduced method of Standardized Measurement Error (SME) to prune the dataset. We demonstrate that fractional area latency in pruned and jackknifed data may amplify within-subjects effect sizes dramatically in the analyzed data set. Between-subjects effects were less affected by the applied procedures, but remained stable regardless of procedure.

Did you even see that? visual sensory processing of single stimuli under different locomotor loads.

Modern living and working environments are more and more interspersed with the concurrent execution of locomotion and sensory processing, most often in the visual domain. Many job profiles involve the presentation of visual information while walking, for example in warehouse logistics work, where a worker has to manage walking to the correct aisle to pick up a package while being presented with visual information over data-glasses concerning the next order. Similar use-cases can be found in manufacturing jobs, for example in car montage assembly lines where next steps are presented via augmented reality headsets while walking at a slow pace. Considering the overall scarcity of cognitive resources available to be deployed to either the cognitive or motor processes, task performance decrements were found when increasing load in either domain. Interestingly, the walking motion also had beneficial effects on peripheral contrast detection and the inhibition of visual stream information. Taking these findings into account, we conducted a study that comprised the detection of single visual targets (Landolt Cs) within a broad range of the visual field (-40° to +40° visual angle) while either standing, walking, or walking with concurrent perturbations. We used questionnaire (NASA-TLX), behavioral (response times and accuracy), and neurophysiological data (ERPs and ERSPs) to quantify the effects of cognitive-motor interference. The study was conducted in a Gait Real-time Analysis Interactive Laboratory (GRAIL), using a 180° projection screen and a swayable and tiltable dual-belt treadmill. Questionnaire and behavioral measures showed common patterns. We found increasing subjective physical workload and behavioral decrements with increasing stimulus eccentricity and motor complexity. Electrophysiological results also indicated decrements in stimulus processing with higher stimulus eccentricity and movement complexity (P3, Theta), but highlighted a beneficial role when walking without perturbations and processing more peripheral stimuli regarding earlier sensory components (N1pc/N2pc, N2). These findings suggest that walking without impediments can enhance the visual processing of peripheral information and therefore help with perceiving non-foveal sensory content. Also, our results could help with re-evaluating previous findings in the context of cognitive-motor interference, as increased motor complexity might not always impede cognitive processing and performance.

Stress effects on the top-down control of visuospatial attention: Evidence from cue-dependent alpha oscillations.

Stress is assumed to inhibit the top-down control of attention and to facilitate bottom-up processing. Evidence from human experiments, however, remains scarce. Previous studies have addressed how stress affects the interplay of bottom-up and top-down mechanisms of attention. A key open question is in how far such effects can actually be attributed to a stress-induced modulation of top-down attention control. We sought to isolate top-down from bottom-up effects by assessing stress effects on anticipatory changes in alpha oscillations that precede stimulus processing. Participants performed in a cued target detection task in which a cue prompted them to covertly shift their attention to left or right screen positions, 20 min after being exposed to the bilateral feet cold pressor test or a warm water control procedure. The stressor led to a substantial increase in cortisol, peaking 20 min post stressor, along with rises in heart rate, blood pressure, and subjective ratings of stress and arousal. As expected, cued attention deployment led to higher alpha power over posterior electrodes contralateral versus ipsilateral to the attended hemifield during the cue-target interval. Importantly, this purely endogenous effect was potentiated by stress, however, significant differences were restricted to the middle of the cue-target interval and thus temporally separated from the appearance of the target. These results indicate that stress does not impair top-down attentional control per se but may introduce a qualitative change modulating the way attention is deployed to meet action goals.

When long appears short: Effects of auditory distraction on event-related potential correlates of time perception.

Attentional models of time perception assume that the perceived duration of a stimulus depends on the extent to which attentional resources are allocated to its temporal information. Here, we studied the effects of auditory distraction on time perception, using a combined attentional-distraction duration-discrimination paradigm. Participants were confronted with a random sequence of long and short tone stimuli, most of which having a uniform (standard) pitch and only a few a different (deviant) pitch. As observed in previous studies, pitch-deviant tones impaired the discrimination of tone duration and triggered a sequence of event-related potentials (ERPs) reflecting a cycle of deviance detection, involuntary attentional distraction and reorientation (MMN, P3a, RON). Contrasting ERPs of short and long tone durations revealed that long tones elicited a more pronounced fronto-central contingent negative variation (CNV) in the time interval after the expected offset of the short tone as well as a more prominent centro-parietal late positive complex (LPC). Relative to standard-pitch tones, deviant-pitch tones especially impaired the correct discrimination of long tones, which was associated with a reduction of the CNV and LPC. These results are interpreted within the theoretical framework of resource-based models of time perception, in which involuntary distraction due to a deviant event led to a withdrawal of attentional resources from the processing of time information.

Decoding of cognitive processes involved in the continuous performance task.

Decoding of electroencephalogram brain representations is a powerful data driven technique to assess the stream of cognitive information processing. It could promote a more thorough understanding of cognitive control networks. For many years, the continuous performance task has been utilized to investigate impaired proactive and reactive cognitive functions. So far, mainly task performance and univariate electroencephalogram were involved in such investigations. In this study, we benefit from multi-variate pattern analysis of continuous performance task variations to provide a more complete spatio-temporal outline of information processing flow involved in sustained and transient attention and response preparation. Besides effects that are well in line with previous EEG research but could be described in more spatial and temporal detail by the used methods, our results could suggest the presence of a higher order feedback control system when expectations are violated. Such a feedback control is related to modulations of behavior both intra- and inter-individually.

Inverse effects of time-on-task in task-related and task-unrelated theta activity.

The phenomenon of mental fatigue has recently been investigated extensively by means of the EEG. Studies deploying spectral analysis consistently reported an increase of spectral power in the lower frequencies with increasing time-on-task, whereas event-related studies observed decreases in various measures related to task engagement and attentional resources. The results from these two lines of research cannot be aligned easily. (Frontal) theta power has been linked to cognitive control and was found to increase with time-on-task. In contrast, theoretical frameworks on mental fatigue suggest a decline in task-engagement as causal for the performance decline observed in mental fatigue. The goal of the present study was to investigate mental fatigue in time-frequency space using linear regression on single-trial data in order to obtain a better understanding about how time-on-task affects theta oscillatory activity. A data-driven analysis approach indicated an increase of alpha and theta power during the intertrial interval. In contrast, task-related theta activity declined. This reduction of stimulus-locked theta power may be interpreted as a reduction of task engagement with increasing mental fatigue. The increase of theta spectral power in the intertrial interval, moreover, could possibly be explained by an increased idling of cognitive control networks. Alternatively, it might be the case that the increase of theta power with time-on-task is a by-product an alpha power increase. As alpha peak frequency systematically decreases with time-on-task, the theta band might be affected as well.

A chronometric model of the relationship between frontal midline theta functional connectivity and human intelligence.

Individual differences in cognitive control have been suggested to act as a domain-general bottleneck constraining performance in a variety of cognitive ability measures, including but not limited to fluid intelligence, working memory capacity, and processing speed. However, owing to psychometric problems associated with the measurement of individual differences in cognitive control, it has been challenging to empirically test the assumption that individual differences in cognitive control underlie individual differences in cognitive abilities. In the present study, we addressed these issues by analyzing the chronometry of intelligence-related differences in midfrontal global theta connectivity, which has been shown to reflect cognitive control functions. We demonstrate in a sample of 98 adults, who completed a cognitive control task while their electroencephalogram was recorded, that individual differences in midfrontal global theta connectivity during stages of higher-order information-processing explained 65% of the variance in fluid intelligence. In comparison, task-evoked theta connectivity during earlier stages of information processing was not related to fluid intelligence. These results suggest that more intelligent individuals benefit from an adaptive modulation of theta-band synchronization during the time-course of information processing. Moreover, they emphasize the role of interregional goal-directed information-processing for cognitive control processes in human intelligence and support theoretical accounts of intelligence, which propose that individual differences in cognitive control processes give rise to individual differences in cognitive abilities. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Cognitive-motor interference in the wild: Assessing the effects of movement complexity on task switching using mobile EEG.

Adaptively changing between different tasks while in locomotion is a fundamental prerequisite of modern daily life. The cognitive processes underlying dual tasking have been investigated extensively using EEG. Due to technological restrictions, however, this was not possible for dual-task scenarios including locomotion. With new technological opportunities, this became possible and cognitive-motor interference can be studied, even in outside-the-lab environments. In the present study, participants carried out a cognitive-motor interference task as they responded to cued, auditory task-switch stimuli while performing locomotive tasks with increasing complexity (standing, walking, traversing an obstacle course). We observed increased subjective workload ratings as well as decreased behavioural performance for increased movement complexity and cognitive task difficulty. A higher movement load went along with a decrease of parietal P2, N2 and P3 amplitudes and frontal Theta power. A higher cognitive load, on the other hand, was reflected by decreased frontal CNV amplitudes. Additionally, a connectivity analysis using inter-site phase coherence revealed that higher movement as well as cognitive task difficulty had an impairing effect on fronto-parietal connectivity. In conclusion, subjective ratings, behavioural performance and electrophysiological results indicate that less cognitive resources were available to be deployed towards the execution of the cognitive task when in locomotion compared to standing still. Connectivity results also show a scarcity of attentional resources when switching a task during the highest movement complexity condition. Summarized, all findings indicate a central role of attentional control regarding cognitive-motor dual tasking and an inherent limitation of cognitive resources.

Boosting working memory with accelerated clocks.

Our perception of time varies with the degree of cognitive engagement in tasks. The perceived passage of time accelerates while working on demanding tasks, whereas time appears to drag during boring situations. Our experiment aimed at investigating whether this relationship is mutual: Can manipulated announcements of elapsed time systematically affect the attentional resources applied to a cognitive task? We measured behavioral performance and the EEG in a whole report working memory paradigm with six items of different colors that each had to be reported after a short delay period. The 32 participants were informed about the current time after each 20 trials, while the clock was running at either 100% (normal), 120% (fast), or 80% (slow) of normal clock speed depending on the experimental block. The mean number of correctly reported colors per trial was significantly increased in the fast as compared to the slow and normal clock conditions. In the EEG, we focused on neural oscillations during working memory encoding and storage. As an electrophysiological correlate of task engagement, frontal theta power during the storage interval was increased in the fast clock condition. Also, the power of frontal theta oscillations predicted the number of correctly reported colors on a single-trial basis. This shows that a covert manipulation of clock speed can lead to an improvement in cognitive performance, presumably mediated by a higher allocation of attentional resources resulting from an adaptation of the subjective passage of time during an experiment.

No effect of target probability on P3b amplitudes.

Event probability has been traditionally regarded as the major determinant of P3b amplitudes, with amplitudes increasing when stimuli are less likely. Here we show in a simple variant of the continuous performance task that this "oddball effect" does not universally apply. Stimuli were a continuous series of (A or B) -> (X or Y) pairs, with the letter X requiring a key-press response and occurring in 80% of trials after A and in 20% after B (vice versa the Y). P3b amplitudes were equally large with probable and improbable occurrence of X. This was in contrast to visual Mismatch Negativity which was consistently larger with less probable stimuli, and also in contrast to no-go P3 amplitudes, which were larger with improbable than probable Y. The only effect on P3b amplitude was due to stimulus onset asynchronies (SOA): P3b was larger with SOAs of 2000 ms compared to 1500 ms. This result dovetails with previous evidence in the oddball task that the main determinant of the oddball effect is not event probability but rather time interval between stimuli. The absence of probability effects on P3b was in sharp contrast to the presence of these effects on no-go P3. Implications are discussed for theories about the psychological meaning of the P3b component.

Inter-trial alpha power indicates mind wandering.

Mind wandering during ongoing tasks can impede task performance and increase the risk of failure in the laboratory as well as in daily-life tasks and work environments. Neurocognitive measures like the electroencephalography (EEG) offer the opportunity to assess mind wandering non-invasively without interfering with the primary task. However, the literature on electrophysiological correlates of mind wandering is rather inconsistent. The present study aims toward clarifying this picture by breaking down the temporal dynamics of mind wandering encounters using a cluster-based permutation approach. Participants performed a switching task during which mind wandering was occasionally assessed via thought probes applied after trial completion at random time points. In line with previous studies, response accuracy was reduced during mind wandering. Moreover, alpha power during the inter-trial interval was a significantly increased on those trials on which participants reported that they had been mind-wandering. This spatially widely distributed effect is theoretically well in line with recent findings linking an increased alpha power to an internally oriented state of attention. Measurements of alpha power may, therefore, be used to detect mind wandering online during critical tasks in traffic and industry in order to prevent failures.

The spatial orienting of the focus of attention in working memory makes use of inhibition: Evidence by hemispheric asymmetries in posterior alpha oscillations.

Retroactive cuing of information after encoding improves working memory performance. However, there is an ongoing debate on the contribution of target enhancement vs. distractor inhibition attentional sub-processes to this behavioral benefit. We investigated the electrophysiological correlates of retroactive attentional orienting by means of oscillatory EEG parameters. In order to disentangle excitatory and inhibitory attentional processes, the to-be-memorized information was presented in a way that posterior hemispheric asymmetries in oscillatory power could be unambiguously linked to lateral target vs. distractor processing. We found an increase of posterior alpha power (8-14 Hz) contralateral to the position of non-cued working memory content and a decrease of alpha power contralateral to cued positions. These effects were insensitive to the number of cued or non-cued items, supporting their relation to the spatial orienting of attention. Importantly, only the alpha power increase contralateral to non-cued positions differed reliably from the asymmetry in a neutral control condition, highlighting the importance of an inhibitory mechanism for the retroactive focusing of attention. Furthermore, the alpha power asymmetries relative to the positions of cued and non-cued items predicted the individual susceptibility to interference by irrelevant information during working memory retrieval. These findings indicate that the retroactive orienting of the focus of attention can bias the mental representations of non-spatial stimulus features stored in working memory and thereby promote a target-oriented retrieval process.