Anke Marks

Event-related awakenings caused by nocturnal transportation noise.

The present study focussed on awakenings caused by nocturnal noises emitted from aircraft, road and rail vehicles with maximum levels ranging from 40 to 76 dBA. A laboratory study with 24 participants (12 male, 12 female, 19-28 years) was performed with polysomnographic recordings during 13 nights (including a preceding habituation night). Multivariable random subject effect logistic regression models containing acoustical, situational and individual parameters were used to determine the probability of event-related awakenings for each traffic mode. Awakening probability increased significantly with maximum sound pressure level (SPL), slope of rise (dB/s), noise duration and the noise-free interval between noise events. Gender, noise sensitivity and age did not influence awakening probability significantly (the latter only in a combined model). Awakening probability increased with elapsed time after sleep onset, and was significantly lower during slow wave sleep compared to S2 sleep, but not during REM sleep. After adjusting for differences in study design (acoustical macrostructure), awakening probability decreased in the order rail, road and air traffic noise, but only rail and air traffic noise differed significantly (p= 0.002). After further adjusting for slope of rise and noise duration (acoustical microstructure), differences between traffic modes decreased, but rail and air traffic noise still differed significantly (p=0.044). Acoustical properties other than slope of rise and noise duration may account for the residual difference. The results of this study suggest that the reduction of maximum SPLs, rise slopes, and traffic volume during the second part of the night might reduce the number of noise-induced awakenings.

PRACTICE-RELATED EFFECTS IN A GO-NOGO TASK '

Comparison of an incoming stimulus with a memory template and the inhibition of an irrelevant response representation assumes these are separable processes differently affected by practice. Practice effects were studied in a visual Go-Nogo task which contained stimuli either compatible or incompatible with a response. Eight participants (19–28 years old, M = 23.3, SD = 3.6) performed the task with simultaneous EEG recording every morning during three consecutive weeks except weekends. Short-term, long-term, as well as weekday effects were analyzed. As a short-term effect, the false alarm rate became smaller; this was accompanied by an enhancement of the frontal N2 component of the event-related potential (ERP). As a long-term effect, the shortening of reaction time to incompatible stimuli and increase of the blink rate for Go trials was observed. Within the N2 two subcomponents, the early (N2e) and late (N2l) could be distinguished. N2e and N2l varied differently with the experimental manipulations. First, they showed different effects of stimulus compatibility. Second, the N2e was enhanced with practice irrespective of trial type, while the practice-related increase of the N2l was obtained for Nogo trials only. Third, the practice-related effects on components differed in scalp topography. The results suggest N2e reflects the comparison process and N2l the inhibition of an irrelevant response representation. Both processes improved with practice.

The relationship between poor sleep and inhibitory functions indicated by event-related potentials

The present study focused on the relationship between normal variations of sleep and inhibitory functions as reflected in event-related potentials. For this reason one night of 21 healthy participants was analysed. After waking up all participants completed a visual Go/Nogo task. On the basis of a sleep disturbance index (SDI) the participants were separated into 8 SDI-good and 13 SDI-poor sleepers using a cluster analysis. The results showed that Nogo-N2 amplitude was smaller and Nogo-P3 latency longer in SDI-poor sleepers. Moreover, Go-P3 amplitude was smaller in SDI-poor sleepers. Performance parameters were not influenced by poor sleep. We concluded that poor sleep specifically affects the intensity of pre-motor inhibitory processes (Nogo-N2 amplitude), the speed to inhibit a motor response (Nogo-P3 latency) and the intensity of task-relevant information processing (Go-P3 amplitude). In further studies, it should be explored under which conditions such subliminal deficits also become relevant for overt behaviour.

Noise Aftereffects and Brain Processes Mediating Role of Achievement Motivation

Abstract. Aftereffects of noise-induced sleep disturbance on executive functions were investigated with motivational traits as mediating variables. Thirty-two healthy young subjects performed a visual Go/Nogo task with simultaneous EEG recording after a quiet night and after 3 nights with railway noise at different noise levels. As motivational traits, the “hope of success” (HS) and “fear of failure” (FF) were assessed. Subjective sleep rating worsened with increased noise level, but, noise-induced sleep disturbances did not affect performance immediately following sleep. However, in the event-related potential (ERP) an attenuation of the N2 and P3 amplitude as well as an increase in N2 latency in Noise conditions were found. Only subjects who scored low in HS showed a reduction of the N2 after Noise, while subjects who scored high in HS did not. The N2 and P3 were larger in high HS than in low HS subjects in Nogo trials only. Similarly, low FF subjects had larger N2 and P3 than high FF subjects in Nogo t...

Blink rate during tests of executive performance after nocturnal traffic noise.

This analysis is on the hypothesis that nocturnal traffic noise affects sleep quality whereas performance decrement is avoided by increased effort expressed by a decrease in blink rates (BRs) during a visual task. Twenty-four persons (12 women, 12 men; 19-28 years, 23.56+/-2.49 years) slept during three consecutive weeks in the laboratory while exposed to road, rail, or aircraft noise with weekly permuted changes. Each week consisted of a random sequence of a quiet night (32 dBA) and three nights with equivalent noise levels of 39, 44 and 50 dBA respectively. The polysomnogram was recorded during all nights. Every morning the participants rated their sleep quality and then completed two executive tasks (Go/Nogo-, Switch-task). Neither of the two performance tests was affected by nocturnal noise. Sleep efficiency and subjective sleep quality decreased with increasing noise levels but were not associated with the type of noise. In contrast, BRs were associated with the type of noise, not with noise levels. The results do not support the hypothesis concerning the BR. The possible reasons are discussed. However, the results do not exclude that other physiological parameters such as heart rate or brain potentials measured during the tests might have revealed alterations associated with nocturnal noise exposure.