Levels Of Task Difficulty Research Articles

Timing and amplitude of gamma-band deactivation in default-mode network is correlated with behavior

Event Abstract Back to Event Timing and amplitude of gamma-band deactivation in default-mode network is correlated with behavior Tomas Ossandon1*, Karim Jerbi1, Juan R. Vidal1, Dimitri Bayle1, Olivier Bertrand11, Philippe Kahane2 and Jean-Philippe Lachaux1 1 Lyon Neuroscience Research Center, France 2 Neurology Department, Grenoble University Hospital, France Task-related deactivations, described in the default mode network (DMN) literature, have been predominantly reported with functional imaging studies (Raichle et al., 2001). Therefore, the electrophysiological correlates and the fine-scale temporal dynamics of this phenomenon are still poorly understood. Given that recent animal studies as well as recent findings in humans (Niessing et al., 2005) suggest correlations between the BOLD signal and gamma-band activity, we posit that gamma deactivation may provide an electrophysiological correlate of the DMN. To test this hypothesis we examine the spatial and temporal pattern of high gamma (60-140 Hz) power suppression using intracranial EEG recordings simultaneously from widespread cortical structures in subjects performing a visual search task. We used direct recordings of neural activity in 15 epileptic patients implanted with depth electrodes for therapeutic purposes. The subjects performed a visual search paradigm with variable levels of task difficulty. We use time-frequency analysis to assess the presence, duration and intensity of gamma band power induced by the display of the search array. We found that all DMN areas displayed transient suppressions of gamma (60-140 Hz) power during task performance and, critically, the duration and extent of this broadband suppression were correlated with task complexity and subject performance. Furthermore, trial-by-trial correlations revealed that spatially distributed gamma activations and deactivations formed distinct anticorrelated networks. These findings facilitate our understanding of the relationship between electrophysiology and neuroimaging studies in humans and indicate that neural deactivations encode the duration and efficiency of our engagement with the external world. Funding: Fondation pour la Recherche Medicale (FRM) and BrainSync FP7 European Project (Grant HEALTH-F2-2008-200728). Keywords: gamma band, Intra-cranial Electrophysiology Conference: XI International Conference on Cognitive Neuroscience (ICON XI), Palma, Mallorca, Spain, 25 Sep - 29 Sep, 2011. Presentation Type: Poster Presentation Topic: Abstracts Citation: Ossandon T, Jerbi K, Vidal JR, Bayle D, Bertrand1 O, Kahane P and Lachaux J (2011). Timing and amplitude of gamma-band deactivation in default-mode network is correlated with behavior. Conference Abstract: XI International Conference on Cognitive Neuroscience (ICON XI). doi: 10.3389/conf.fnhum.2011.207.00065 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 15 Nov 2011; Published Online: 25 Nov 2011. * Correspondence: Dr. Tomas Ossandon, Lyon Neuroscience Research Center, Lyon, France, tossandon@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Tomas Ossandon Karim Jerbi Juan R Vidal Dimitri Bayle Olivier Bertrand1 Philippe Kahane Jean-Philippe Lachaux Google Tomas Ossandon Karim Jerbi Juan R Vidal Dimitri Bayle Olivier Bertrand1 Philippe Kahane Jean-Philippe Lachaux Google Scholar Tomas Ossandon Karim Jerbi Juan R Vidal Dimitri Bayle Olivier Bertrand1 Philippe Kahane Jean-Philippe Lachaux PubMed Tomas Ossandon Karim Jerbi Juan R Vidal Dimitri Bayle Olivier Bertrand1 Philippe Kahane Jean-Philippe Lachaux Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Fluid intelligence allows flexible recruitment of the parieto-frontal network in analogical reasoning.

Fluid intelligence is the ability to think flexibly and to understand abstract relations. People with high fluid intelligence (hi-fluIQ) perform better in analogical reasoning tasks than people with average fluid intelligence (ave-fluIQ). Although previous neuroimaging studies reported involvement of parietal and frontal brain regions in geometric analogical reasoning (which is a prototypical task for fluid intelligence), however, neuroimaging findings on geometric analogical reasoning in hi-fluIQ are sparse. Furthermore, evidence on the relation between brain activation and intelligence while solving cognitive tasks is contradictory. The present study was designed to elucidate the cerebral correlates of geometric analogical reasoning in a sample of hi-fluIQ and ave-fluIQ high school students. We employed a geometric analogical reasoning task with graded levels of task difficulty and confirmed the involvement of the parieto-frontal network in solving this task. In addition to characterizing the brain regions involved in geometric analogical reasoning in hi-fluIQ and ave-fluIQ, we found that blood oxygenation level dependency (BOLD) signal changes were greater for hi-fluIQ than for ave-fluIQ in parietal brain regions. However, ave-fluIQ showed greater BOLD signal changes in the anterior cingulate cortex and medial frontal gyrus than hi-fluIQ. Thus, we showed that a similar network of brain regions is involved in geometric analogical reasoning in both groups. Interestingly, the relation between brain activation and intelligence is not mono-directional, but rather, it is specific for each brain region. The negative brain activation–intelligence relationship in frontal brain regions in hi-fluIQ goes along with a better behavioral performance and reflects a lower demand for executive monitoring compared to ave-fluIQ individuals. In conclusion, our data indicate that flexibly modulating the extent of regional cerebral activity is characteristic for fluid intelligence.

Self-focused attention, performance expectancies, and the intensity of effort: Do people try harder for harder goals?

Many theories argue that goal striving is more intense when people have optimistic expectancies for achieving the goal and when attention is self-focused. Brehm’s motivational intensity theory, however, predicts that the intensity of motivation is only as high as necessary, so people will try harder for difficult tasks than for easy tasks, all else equal. The present experiment compared these two approaches by manipulating two levels of self-focused attention (low and high self-awareness, via a mirror) and two levels of task difficulty (easy and difficult). Effort was assessed as cardiovascular reactivity, particularly change in systolic blood pressure. Neither high self-focus nor an easy task per se caused increased effort; instead, high self-focus significantly increased systolic reactivity when the task was difficult. Effort was thus higher despite less optimistic goal expectancies, a finding that is predicted by Brehm’s motivational intensity theory but not by traditional self-regulation models.

Kognitive Reservekapazität und ihre Bedeutung für Auftreten und Verlauf der Demenz

Progressive brain damage is undoubtedly the main cause of clinical symptoms of dementia in neurodegenerative disorders such as Alzheimer's disease. However, the association between brain damage and cognitive symptoms is not linear. Certain interindividual differences such as a good school education or a greater brain volume are associated with a higher resilience against brain damage that is usually referred to as cognitive reserve (CR). Individuals with high CR have a diminished risk for dementia and both active and passive concepts for this phenomenon are discussed. In the concept of passive CR, peculiarities of brain structure such as higher synapse or neuron counts are regarded as buffers against brain damage. Symptoms of dementia do not occur until a certain threshold of damage is passed. In addition to the passive concepts, active mechanisms are also discussed that are associated with the ability to maintain a certain level of cognitive performance in the face of progressive neurodegeneration for a longer period. In subjects with healthy cognitive function, these active mechanisms contribute to the adaptation of brain activity when task difficulty level is increased. Confronted with progressive neurodegeneration, these active mechanisms help to compensate for brain damage. Individuals with higher CR show more efficient activation for solving the same task, which helps them to preserve normal levels of cognitive performance for a longer period.

Smoking withdrawal shifts the spatiotemporal dynamics of neurocognition

Smoking withdrawal is associated with significant deficits in the ability to initiate and maintain attention for extended periods of time (i.e. sustained attention; SA). However, the effects of smoking abstinence on the temporal dynamics of neurocognition during SA have not been evaluated. Twenty adult smokers underwent functional magnetic resonance imaging scans following smoking as usual and after 24-hours abstinence. During scanning they completed a SA task with two levels of task difficulty, designed to measure both sustained (i.e. over the duration of the task) and transient (i.e. event-related) activation. Smoking abstinence significantly decreased task accuracy regardless of task difficulty. Compared to smoking as usual, abstinence resulted in decreased sustained activation in right inferior and middle frontal gyri but increased transient activation across dispersed cortical areas including precuneus and right superior frontal gyrus. Greater task difficulty was associated with even greater transient activation during abstinence in mostly right hemisphere regions including right inferior frontal gyrus. These findings suggest smoking withdrawal shifts the temporal and spatial dynamics of neurocognition from sustained, right prefrontal activation reflecting proactive cognitive control (Braver, Gray & Burgess 2009) to more dispersed and transient activation reflecting reactive control.

Challenges to attention: A continuous arterial spin labeling (ASL) study of the effects of distraction on sustained attention

Maintaining attention and performance over time is an essential part of many activities, and effortful cognitive control is required to avoid vigilance decrements and interference from distraction. Regions at or near right middle frontal gyrus (Brodmann's area (BA) 9), as well as in other prefrontal and parietal areas, are often activated in studies of sustained attention (e.g., Cabeza and Nyberg, 2000; Kim et al., 2006; Lim et al., 2010). This activation has often been interpreted as representing the engagement of cognitive control processes. However, such studies are typically implemented at one level of task difficulty, without an experimental manipulation of control demands. The present study used the distractor condition sustained attention task (dSAT), which has been used extensively in animals to determine the role of neuromodulator systems in attentional performance, to test the hypotheses that BA 9 is sensitive to changes in the demand for cognitive control and that this sensitivity reflects an increased engagement of attentional effort. Continuous arterial spin labeling (ASL) was used to measure neural activity in sixteen healthy, young adults performing a sustained attention task under standard conditions and under a distraction condition that provided an experimental manipulation of demands on cognitive control. The distractor impaired behavioral performance and increased activation in right middle frontal gyrus. Larger increases in right middle frontal gyrus activity were associated with greater behavioral vulnerability to the distractor. These findings indicate that while right middle frontal gyrus regions are sensitive to demands for attentional effort and control, they may not be sufficient to maintain performance under challenge. In addition, they demonstrate the sensitivity of ASL methods to variations in task demands, and suggest that the dSAT may be a useful tool for translational cross-species and clinical research.

How Does Day-to-Day Variability in Psychophysiological Data Affect Classifier Accuracy?

Combined psychophysiological measures have been used to determine mental workload in operators, but the day-to-day reliability of these measures has not been determined. Data were collected four times over a one month period. Two classifiers were trained with these data and their ability to correctly discriminate between two levels of task difficulty with new data was tested. Both classifiers very accurately discriminated between the two levels of task difficulty using data collected on the same day as the training data. However, the accuracy was considerably reduced when tested on data from days different from the training data. The implications for application of these procedures are discussed.

Older Adults' Experiences and Perceptions of Dual Tasking

There is no consensus on which dual task (DT) test best assesses mobility or balance deficits in older adults. This study aimed to explore older adults' experiences and perceptions of dual tasking to identify DTs relevant to their everyday life and that they perceive as difficult or risky. Two gender-specific focus groups were conducted. Six males and nine females, aged 70 years or above, participated. The topics posed to the groups included structured and open questions designed to explore experiences of combining two activities and the consequences of that for balance. The results were subjected to content analysis to identify DT examples, task difficulty levels and balance-threatening tasks. Most participants were able to identify DT examples and some identified a concurrent impact on balance. There were gender differences in the examples: the females focused more on household tasks and the males more on outdoor activities. Many tasks that were considered difficult or risky by the participants do not feature sufficiently in the literature, such as stair negotiation and avoiding moving obstacles accompanied by secondary tasks. The views of older adults should be taken into consideration to help to develop tests that are more sensitive and have face validity.

Accuracy and speed trade‐off in robot‐assisted surgery

Controlling surgical task speed and maintaining accuracy are vital components of robotic surgical skills. This study was designed to investigate the relationship between accuracy and speed for robot-assisted surgical skills. Ten participants were asked to alternately touch two circular targets with various dimensions and distances between two targets, using the da Vinci Surgical System. The design of this study was based on Fitt's law. Statistical correlations between the index of difficulty (ID) and the movement time (MT), as well as the ID and the smoothness of the movement, were analysed. A significant linear correlation between MT and ID was shown. Speed was reduced to maintain accuracy as the level of task difficulty increased. There was no significant correlation between the smoothness of the movement and ID. The trade-off between speed and accuracy plays an important role in robot-assisted surgical proficiency.

Changes in fMRI BOLD response to increasing and decreasing task difficulty during auditory perception of temporal order

We have discovered changes in brain activation during difficult and easy milliseconds timing. Structures engaged in difficult and easier auditory temporal-order judgment were identified in 17 young healthy listeners presented with paired-white-noises of different durations. Within each pair, a short (10ms) and a long (50ms) noise was separated by a silent gap of 10, 60 or 160ms, corresponding to three levels of task difficulty, i.e. difficult, moderate and easy conditions, respectively. A block design paradigm was applied. In temporal-order judgment task subjects were required to define the order of noises within each pair, i.e. short–long or long–short. In the control task they only detected the presentation of the stimulus pair. A multiple regression with ‘task difficulty’ as a regressor (‘difficult’, ‘moderate’, ‘easy’) showed dynamic changes in neural activity. Increasing activations accompanying increased task difficulty were found in both bilateral inferior parietal lobuli and inferior frontal gyri, thus, in classic regions related to attentional and working memory processes. Conversely, decreased task difficulty was accompanied by increasing involvement of more specific timing areas, namely bilateral medial frontal gyri and left cerebellum. These findings strongly suggest engagement of different neural networks in difficult or easier timing and indicate a framework for understanding timing representation in the brain.

Analysis of individual and occupational risk factors on task performance and biomechanical demands for a simulated drilling task

The purpose of this study was to evaluate age- and gender-dependent effects of shoulder fatigue on task performance and muscular responses of a drilling task commonly observed within the construction industry. Twelve younger (18–35 years) and ten older (45–60 years) participants, balanced by gender, were recruited from the local community. Task performance (task completion times and errors made), muscle activity of the anterior deltoid (static, mean, and peak amplitude probability density function), coactivity indices of the upper and lower arm, and perceived discomfort ratings were obtained for a series of drilling tasks at three levels of task difficulty, before and after manifestation of shoulder fatigue. To induce fatigue, participants performed a sustained sub-maximal fatigue task at 40% of their maximum voluntary shoulder exertion. Fatigue decreased task completion times, irrespective of age and gender. Higher errors were observed in the fatigued condition, especially for younger participants. Females showed higher shoulder muscle activity compared to men. Additionally, fatigue resulted in lower shoulder APDF measures compared to the no-fatigue condition. Muscle recruitment patterns differed within the fatigue condition, with higher coactivity indices in the upper and lower arm muscles compensating for decreases in shoulder muscle activity. Task difficulty was not found to affect any dependent measures. Participants reported higher discomfort in the fatigued state; this effect was more prominent in females. Overall, this study demonstrated, through objective and subjective measures, that task performance and biomechanical demands are affected by fatigue, and that this effect varies with individual factors such as gender and age. Relevance to industry This paper explored the influence of task demands (fatigue and task difficulty) and individual factors (gender and age) of a drilling task on the development of musculoskeletal injuries of construction workers. The results may contribute towards an understanding of the interplay of certain occupational task demands and worker characteristics on common construction tasks.

Theta frequency band activity and attentional mechanisms in visual and proprioceptive demand

In a companion manuscript we reported reduced electroencephalographic (EEG) activation at traditional sensorimotor areas in knee movements with high levels of task difficulty modulated by varying visual and proprioceptive sensory demands. Given that reduced cortical activity with more complex tasks is counter-intuitive, we suggested that high order cognitive-motor areas may show increased EEG activation to compensate for the observed decrease in sensorimotor regions. To test this hypothesis, we evaluated theta band activation at anterior frontal regions in a secondary analysis of our previous data. Unlike activation at sensorimotor areas, anterior frontal responses increased with each level of task difficulty as modulated by precision of visual targeting and/or proprioceptive demands from adding masses to the leg. Activity was increased as both unimodal visual and proprioceptive requirements became more demanding, but showed greater sensitivity to visual over proprioceptive processing requirements. Each level of bimodal task demands showed increasing activation, which was consistently greater when modulated through visual demands. These results are consistent with our hypothesis of increased contribution of anterior frontal regions for motor control in lower extremity movements with increasing sensory demands and further support different mechanisms for internally and externally guided movement.

‘Pain inhibits pain’ mechanisms: Is pain modulation simply due to distraction?

‘Diffuse noxious inhibitory controls’ (DNIC), a form of supraspinal descending endogenous analgesia, requires a noxious conditioning stimulus for pain attenuation. This may be partly dependent on a distraction effect. The term “conditioned pain modulation” (CPM) has recently been introduced to describe the psychophysical paradigm to test DNIC. The present study aimed to determine whether distraction and tonic heat stimulation inhibit pain through the same or different mechanisms by looking at whether there is a similar or even an additive effect on pain attenuation. Test pain was brief heat stimulation applied to the left volar of 34 healthy volunteers. For conditioning, the right hand was immersed in 46.5 °C water. Distraction was provided by three different difficulty levels of continuous cognitive visual tasks. Experimental blocks consisted of test pain: (1) alone; ‘ baseline’, (2) with conditioning pain; ‘CPM’, (3) with distraction; ‘ distraction’ and (4) with conditioning pain and distraction; ‘ combined’. They were randomized and repeated three times and pain intensity and unpleasantness rated. Results showed an overall effect of experimental block on test pain intensity ( P = 0.0125). Post-hoc tests revealed a significant reduction in pain intensity ratings under Combined (21.2 ± 2.3; mean ± SEM) compared to CPM alone (16.0 ± 2.3) ( P < 0.05). Furthermore, at all levels of distraction there were always a few subjects who were not distracted despite expressing CPM. Based on the additive effect of CPM and distraction on pain inhibition, and the cases of no distraction despite CPM, we suggest that CPM acts independently from distraction.

The long-term effects of traumatic brain injury on the coordinative function of the central executive

The objective of this study was to compare the coordinative function of the central executive of working memory in matched groups of controls and persons with traumatic brain injury (TBI) with long-term impairments in functioning, using a dual-task paradigm. The dual-task procedure required participants to complete digit span and tracing tasks separately and then together to produce a change index that reflects loss of productivity on the dual trial. A TBI group and a matched group of controls were compared on this task and on ratings of social competency and neuropsychological tests. The two groups were found to differ in social competence, in the number of dysexecutive symptoms, and on dual-task performance, but not on any other measures of cognitive ability. Poor performance on the dual task was found only in persons with initial very severe TBI. There was no evidence that the group difference on the dual task was the consequence of increased task difficulty level, distribution of attention, or other within-task biases. Performance on the dual task was correlated with dysexecutive symptoms and social competency (in particular interpersonal and cognitive competence), but not with other tests of executive functioning. The findings suggest that deficits in the coordinative function persist in long-term survivors of TBI after other deficits in executive functioning may have resolved and are associated with lower ratings of current interpersonal competence.

A test of engagement versus disengagement in catastrophe models

The present study explored the interactive effects of self-efficacy and increasing/decreasing task difficulty upon engagement and disengagement within a cusp-catastrophe model framework. Using a closed motor skill aiming task participants (N=60) were required to compete in conditions where task difficulty increased and then decreased (or vice versa) where they were rewarded for good performance but penalized for bad. Participants who reported low levels of self-efficacy disengage at an earlier level of task difficulty than their high self-efficacy counterparts. Furthermore, this group did not re-engage with the task until task difficulty had significantly decreased. Although task disengagement occurred with high difficulty in the high self-efficacy group, this group re-engaged in a similar manner in which they disengaged. Findings support and extend those of previous tests of catastrophe models by directly allowing for task disengagement.

Effects of the α4β2 Partial Agonist Varenicline on Brain Activity and Working Memory in Abstinent Smokers

Cognitive alterations are a core symptom of nicotine withdrawal, contributing to smoking relapse. In rodents and humans, cognitive deficits can be reversed by treatment with the alpha4beta2 nicotinic receptor partial agonist varenicline. This neuroimaging study examined the neural mechanisms that underlie these effects. Twenty-two smokers completed 13 days of varenicline and placebo treatment in a double-blind crossover study with two functional magnetic resonance imaging sessions: after 3 days of abstinence while on varenicline and after 3 days of abstinence while on placebo (counterbalanced randomized order, 2-week washout). Blood oxygenation level-dependent (BOLD) data were acquired during performance of a visual N-back working memory task. In a region of interest analysis, significant effects of treatment on mean percent signal change (varenicline > placebo) were observed in the dorsal anterior cingulate/medial frontal cortex, left dorsolateral prefrontal cortex, and right dorsolateral prefrontal cortex. In a cross-region model, there was a significant interaction of treatment by memory load, indicating significant increases in BOLD signal for varenicline versus placebo at the 2-back and 3-back levels but not the 1-back level. Varenicline improved performance (correct response time) in highly dependent smokers with no effect among less dependent smokers. In highly dependent smokers, faster correct response time was associated with increased BOLD signal. This study provides novel evidence that the alpha4beta2 partial agonist varenicline increases working memory-related brain activity after 3 days of nicotine abstinence, particularly at high levels of task difficulty, with associated improvements in cognitive performance among highly dependent smokers.

Ego depletion effects on mathematics performance in primary school students: why take the hard road?

Reduction in performance level following on from brief periods of self‐control is referred to as ego depletion. This study aimed to investigate if a brief ego depletion experience would impact upon primary school students working through an online mathematics exercise involving 40 computational trials. Seventy‐two students participated in the control group, and 80 students participated in the ego depletion group. The students were 10–14 years of age. A three‐minute task involving resistance to distraction was used as the depletion experience. Before each trial, participants selected task difficulty level. Control group students began by working at a moderate difficulty level and then progressed to work on more difficult items. Ego‐depleted students chose to work on easy problems throughout. Ego depletion did not markedly affect error rate after the first trial. Depletion effects can be evident in students’ academic application through encouraging students to undertake easier options.

Can people with Parkinson's disease improve dual tasking when walking?

Background Gait disorders in people with Parkinson's disease (PD) are accentuated when they perform another task simultaneously. This study examines whether practice enables people with PD to walk with large steps while performing added tasks, and to determine if training people with PD to walk with added working memory tasks leads to improvements in gait when walking and performing other tasks simultaneously. Methods Walking patterns were recorded pre and post a 20 min dual task training session in 20 people with PD. Participants performed a series of 10 m walking trials under seven conditions: gait only, and with six different added tasks varying by task type (e.g. motor, cognitive), domain (e.g. postural, manual manipulation, language, calculation, auditory, visuospatial), and difficulty level. Dual task training aimed to improve step length while simultaneously undertaking a variety of language and counting working memory tasks that were different to those used in assessment. Results Following training, step length increased when performing five of the six added tasks, indicating transfer of dual task training when walking occurred across task types and domains. Improvements in gait speed occurred in three of the six added tasks. When other gait variables were examined, such as step length variability, few improvements with training were found. Conclusions Training can lead to larger steps when walking under dual task conditions in people with PD. The gait variable emphasised during dual task training appears to be an important factor in enabling the transfer of training improvements across tasks.

Changes in gamma- and theta-band phase synchronization patterns due to the difficulty of auditory oddball task

We analyze the pattern of inter-regional functional association between cortical activities during auditory oddball tasks, and the influence of task difficulty on it. Event-related electroencephalograms were recorded from 17 subjects during auditory oddball tasks with two task difficulty levels. The task difficulty was controlled by changing the difference between the frequencies of standard and target tones. The changes in behavioral response and P300 component due to the difficulty were consistent with previous findings, whereby successful control of difficulty was verified. Significant gamma- and theta-band phase synchronization (PS) was observed primarily between frontal and posterior electrodes along the midline, which is interpreted as functional connectivity among cortical regions devoted to the task execution. Apparent differences in PS were identified between two difficulties in both gamma- and theta-bands. On the whole, the number of electrode pairs showing significant PS was much smaller for higher task difficulty. The overall result is in agreement with our recent study which reported similar difference in PS due to the difficulty of 'visual' oddball task.

Using Saccadic Intrusions To Quantify Mental Workload

This study proposes a new method to quantify mental workload (MWL) automatically, without interfering with the operator's primary task performance. An unobtrusive Tobii eye tracker recorded eye movements while participants were engaged in a cognitively demanding N-back task. Original algorithms automatically analyzed the eye data, detected specific eye deviation movements called saccadic intrusions (SIs), and automatically quantified the eye deviation accounted for SIs. This SI measure was strongly correlated with the task difficulty levels in the N-back tasks and with pupil diameter. This indicates that the SI measure appeared to reflect MWL and may be used as a measure of MWL.