What was the eye of vigilance

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Favorite Favorited We want you to love your art! If you are not completely satisfied with your purchase you can return it free within 14 days, no questions asked. We found that saccade amplitude and saccade velocity are negatively correlated with relative delta power whereas blink rate is positively correlated. Conversely, saccade amplitude and saccade velocity are positively correlated with frontal midline theta and frontal theta to parietal alpha ratio whereas blink rate is negatively correlated.

These results suggest that saccade measures saccade amplitude and saccade velocity of eye tracking and frontal midline theta and frontal theta to parietal alpha ratio of EEG correlate positively with vigilance level while blink rate from eye tracking and relative delta power from EEG correlate negatively with vigilance level.

The correlations are similar to the observations made by the studies described in the literature in Section 1. Correlation analysis between EEG relative delta power, frontal midline theta and frontal theta to parietal alpha ratio and eye tracking saccade velocity, saccade amplitude and blink rate measures.

The correlation coefficient r and significance value p are also shown in each case. All the correlations are statistically significant. The saccade velocity for the sessions with and without challenge integration was analyzed of all the four subjects who participated in the control study.

Variation of saccade velocity of all the four subjects is presented in Figure The saccade velocity of a subject during without challenge session is compared against saccade velocity during challenge session of that subject. The mean saccade velocity of the last 5 min of phase 1 is taken as the baseline in each session for each subject.

The baselines of both the sessions are also shown. These baselines indicate the level of vigilance before the beginning of phase 2. For 3 out of 4 control subjects controls 2, 3, and 4 , the saccade velocity is relatively higher for the challenge session than the session without challenge during phase 2. However, for control 1 Figure 9A , the variation of saccade velocity appears to be similar for both the sessions, except that the saccade velocity peaks are comparatively higher for the challenge session than for the session without challenge.

Variation of saccade velocity across time for all the subjects A—D of the control study. Solid red line indicates saccade velocity during challenge session and solid blue line indicates saccade velocity during no challenge session. Dashed red line indicates baseline for challenge session and dashed blue line indicates baseline for no challenge session. Gray bars indicate challenge stimulation periods. We observed that eye movements and rhythmic oscillations in brain activity are modulated by challenging stimuli.

From the eye tracking data, we found that challenging stimuli cause increasing peaks in saccade measures saccade velocity and saccade amplitude and suppression in blink rate See Figure 3.

Di Stasi et al. Blink rate suppression in the case of interesting tasks is also observed in Yamada Hence, the reverse change in the variation of these measures due to challenging events suggest an increase in vigilance.

Similarly, challenging stimuli caused suppression of relative delta power and augmentation in frontal midline theta and frontal theta to parietal alpha ratio in phase 2 showing an enhancement in the vigilance level. Delta power as investigated by Chuang et al. Suppression of relative delta power due to challenge integration therefore suggests fatigue inhibition and increase in vigilance levels. Frontal midline theta also increases due to challenge integration indicating vigilance enhancement Yamada, The increase in frontal theta to parietal alpha ratio suggests cortical arousal as studied by Smith and Gevins and Gevins et al.

Significant correlations between the EEG and eye tracking measures confirms the evidence of vigilance enhancement. The variation of saccade velocity of the subjects from control study are shown in Figure 12 for both challenge and no challenge sessions. Since saccade velocity is shown to decrease with vigilance decrement and vice versa, the results imply that the vigilance levels are higher for the sessions with challenge stimulation for 3 out of 4 subjects controls 2, 3, and 4 during phase 2.

Also, for the challenge session indicated in red , the saccade velocity in phase 2 peaks higher than the indicated baseline dashed red line which suggests that the challenge stimulation leads to an increase in the vigilance levels of the subjects.

This is consistent with the observations made in Figure 3 with respect to saccade velocity. However no such observations were made in the case of control 1. The reason for this behavior in control 1 may be due to subject to subject variation toward the challenge and needs further investigation.

With respect to eye tracking data, blink suppression and increase in saccade velocity and amplitude are observed. As discussed in Di Stasi et al. This main sequence is found to be affected by time-on-task. However, the modulation of this relation due to the challenge integration has to be studied yet. In our task, the challenge integration results in a reverse change in delta power which suggests fatigue inhibition and improved attention. Increase in vigilance levels due to challenge integration suggests increased engagement of attentional resources due to increase in mental workload as supported by underload hypothesis of vigilance decrement.

Fatigue and vigilance decrement mechanisms are compared and debated by several studies. Fatigue is believed to be an accumulated effect over time and can be ameliorated through breaks or rest during the tasks. However, vigilance decrement can be a result of either lack of motivation or increase of fatigue or both Langner et al. It has been found that fatigue is accompanied by an increase in delta oscillations Lal and Craig, ; Chuang et al. It could be that vigilance is a short-term state that can be altered by external stimulation while fatigue is a long-term state that can be temporarily altered but reverts back even though external stimulation can cause a transient adjustment in attention.

This may be the reason why some subjects do not show a clear enhancement effect during challenge stimulation. Therefore, it might be necessary to inhibit fatigue in addition to providing external stimulation to improve sustained attention for performance enhancement.

This aspect will be explored in detail in our future experiments where we plan to study the after effects of the challenge stimulation. The effect of challenge stimulation to sustain performance and inhibit increasing fatigue after the withdrawal of challenge has to be investigated further. The strategies of enhancing vigilance should also tend to increase the whole stimulus-response chain rather than simply enhancing perceptual sensibility of the stimulus.

Hence in our future studies we plan to build a closed loop cognition enhancing strategies to take into account the enhancement of both stimulus perception and response to the stimulus. In this study, we investigated the possibility of enhancing vigilance in a monotonous task using challenge integration. Challenge integration is achieved using noisy visual stimuli.

The results obtained from EEG relative delta power, frontal midline theta and frontal theta to parietal alpha ratio and eye tracking measures saccade velocity, saccade amplitude and blink rate , demonstrate with statistical significance, an increase in vigilance level due to challenge integration.

Furthermore, we found strong correlations between EEG and eye tracking measures used to measure vigilance. Saccade velocity, saccade amplitude, frontal midline theta and frontal theta to parietal alpha ratio correlate positively while blink rate and relative delta power correlate negatively with vigilance levels.

Therefore, challenge integration lead to increase in saccade velocity, saccade amplitude, frontal midline theta and frontal theta to parietal alpha ratio and suppression in blink rate and relative delta power. This study should find its application in fields like military surveillance, health monitoring and industrial watch-keeping where the primary task can be integrated with challenging stimuli to reduce vigilance decrement and enhance task performance.

IB performed the experiments. IB and JL performed the data analysis. All the authors made vital contributions in drafting the manuscript and have approved the final version. The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Anguera, J. Video game training enhances cognitive control in older adults.

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