Alpha spindles as neurophysiological correlates indicating attentional shift in a simulated driving task.

The intention of this paper is to describe neurophysiological correlates of driver distraction with highly robust parameters in the EEG (i.e. alpha spindles). In a simulated driving task with two different secondary tasks (i.e. visuomotor, auditory), N=28 participants had to perform full stop brakes reacting to appearing stop signs and red traffic lights. Alpha spindle rate was significantly higher during an auditory secondary task and significantly lower during a visuomotor secondary task as compared to driving only. Alpha spindle duration was significantly shortened during a visuomotor secondary task. The results are consistent with the assumption that alpha spindles indicate active inhibition of visual information processing. Effects on the alpha spindles while performing secondary tasks on top of the driving task indicate attentional shift according to the task modality. As compared to alpha band power, both the measures of alpha spindle rate and alpha spindle duration were less vulnerable to artifacts and the effect sizes were larger, allowing for a more accurate description of the current driver state.

EEG alpha spindle measures as indicators of driver fatigue under real traffic conditions.

OBJECTIVE: The purpose of this study is to show the effectiveness of EEG alpha spindles, defined by short narrowband bursts in the alpha band, as an objective measure for assessing driver fatigue under real driving conditions. METHODS: An algorithm for the identification of alpha spindles is described. The performance of the algorithm is tested based on simulated data. The method is applied to real data recorded under real traffic conditions and compared with the performance of traditional EEG fatigue measures, i.e. alpha-band power. As a highly valid fatigue reference, the last 20 min of driving from participants who aborted the drive due to heavy fatigue were used in contrast to the initial 20 min of driving. RESULTS: Statistical analysis revealed significant increases from the first to the last driving section of several alpha spindle parameters and among all traditional EEG frequency bands, only of alpha-band power; with larger effect sizes for the alpha spindle based measures. An increased level of fatigue over the same time periods for drop-outs, as compared to participants who did not abort the drive, was observed only by means of alpha spindle parameters. CONCLUSIONS: EEG alpha spindle parameters increase both fatigue detection sensitivity and specificity as compared to EEG alpha-band power. SIGNIFICANCE: It is demonstrated that alpha spindles are superior to EEG band power measures for assessing driver fatigue under real traffic conditions.

Drivers' misjudgement of vigilance state during prolonged monotonous daytime driving.

To investigate the effects of monotonous daytime driving on vigilance state and particularly the ability to judge this state, a real road driving study was conducted. To objectively assess vigilance state, performance (auditory reaction time) and physiological measures (EEG: alpha spindle rate, P3 amplitude; ECG: heart rate) were recorded continuously. Drivers judged sleepiness, attention to the driving task and monotony retrospectively every 20 min. Results showed that prolonged daytime driving under monotonous conditions leads to a continuous reduction in vigilance. Towards the end of the drive, drivers reported a subjectively improved vigilance state, which was contrary to the continued decrease in vigilance as indicated by all performance and physiological measures. These findings indicate a lack of self-assessment abilities after approximately 3h of continuous monotonous daytime driving.

The right supratemporal plane hears the distance of objects: neuromagnetic correlates of virtual reality.

The neural mechanisms of auditory distance perception, a function of great biological importance, are poorly understood. Where not overruled by conflicting factors such as echoes or visual input, sound intensity is perceived as conveying distance information. We recorded neuromagnetic responses to amplitude variations over both supratemporal planes, with and without auditory spatial simulations. In the absence of other cues for distance, including those provided by auditory virtual reality, amplitude changes elicited enhanced preattentive responses over the right temporal lobe, indicating hemispheric lateralization of the 'where' pathway in the human. Lesion studies in monkeys and humans have shown that the rostral part of the right superior temporal cortex contributes to spatial awareness in the visual domain. Our data indicate that the distance to a sound source is processed within the adjacent right auditory cortex, thus extending the recent model of a right-hemisphere temporal multisensory matrix that subserves the integration of space-related data across visual and auditory modalities.