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.

Autonomic arousals related to traffic noise during sleep.

AIM: To analyze the heart rate (HR) response to traffic noise during sleep and the influence of acoustic parameters, time of night, and momentary sleep stage on these responses. PARTICIPANTS: Twelve women and 12 men (19-28 years). MEASUREMENTS AND RESULTS: The participants slept in the laboratory for 4 consecutive nights in each of 3 consecutive weeks and were exposed to aircraft, road, or rail traffic noise with weekly permutations. The 4 nights of each week consisted of a random sequence of a quiet night (32 dBA) and 3 nights during which aircraft, rail traffic, or road traffic noises occurred with maximum levels of 45-77 dBA. The polysomnogram and the electrocardiogram were recorded during all nights. In case of awakenings, the HR alterations consisted of monophasic elevations for >1 min, with mean maximum HR elevations of 30 bpm. Though obviously triggered by the noise events, the awakenings per se rather than the acoustical parameters determined the extent and pattern of the response. Without awakenings, HR responses were biphasic and consisted of initial accelerations with maximum HR elevations of about 9 bpm followed by decelerations below the baseline. These alterations were clearly influenced by the acoustic parameters (traffic mode, maximum level, rate of rise) as well as by the momentary sleep stage. CONCLUSIONS: Cardiac responses did not habituate to traffic noise within the night and may therefore play a key role in promoting traffic noise induced cardiovascular disease. If so, these consequences are more likely for responses accompanied by awakenings than for situations without awakenings.

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.

The development of the noise sensitivity questionnaire.

The existing questionnaires for determining the noise sensitivity of individuals provide information only about global noise sensitivity, although empirical data suggest that measuring noise sensitivity for different situations in daily life might be more logical. Therefore, the "Noise-Sensitivity-Questionnaire" (NoiSeQ) was developed to measure global noise sensitivity as well as the sensitivity of five domains of daily life, namely, leisure, work, habitation, communication, and sleep. The assessment of the measurement characteristics was based on the Generalizability (G) theory. The results of the G-study (N=66) proved that a single application of the questionnaire is sufficient for determining an individual's noise sensitivity. Furthermore, the ratings are age and gender independent. The subsequently conducted Decision (D)-study (N=288) provides information on the reliability of NoiSeQ. If the questionnaire is used for measuring global noise sensitivity, the reliability (relative and absolute G-coefficient) reaches a value above 0.90. According to ISO 10075-3, the questionnaire satisfies the precision level 1 "accurate measurement" in this case. The G-coefficients for all the subscales exceed the lower limit 0.70, with the exception of subscale leisure, which did not prove satisfactory. However, this subscale can reach a reliability of more than 0.70 if additional items are included. The validity of the instrument was proven for the subscales habitation (N=72) and work (N=72). In both the studies, the participants were asked to rate the annoyance in the presence of several rail and traffic noise scenarios. The subjects were characterized as low and high noise sensitive according to their sensitivity values obtained from NoiSeQ. In conclusion, a significant difference in annoyance rates was observed between the low and high noise sensitive groups for both the subscales habitation and work. This data support the validity of NoiSeQ.

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.

Executive brain functions after exposure to nocturnal traffic noise: effects of task difficulty and sleep quality.

The after-effects of nocturnal traffic noise on cognitive performance and inhibitory brain activity were investigated. Twenty participants (18-30 years) performed an easy and a difficult visual Go/Nogo task with simultaneous EEG recording after a quiet night and then during three nights when aircraft noise was presented with equivalent noise levels of 39, 44, and 50 dBA, respectively, between 11 p.m. to 7 a.m. Based on subjective sleep quality rating, participants were separated into "good" versus "bad" sleepers. The performance and inhibition-related components (N2, P3) of event-related potentials were analysed. The N2 and P3 amplitudes were smaller and latencies were prolonged in the difficult than in the easy task. This effect was more pronounced for Nogo than for Go trials. The Nogo-P3 amplitude was smaller in Noise than in "Quiet" conditions in the difficult task only. In the difficult task, the Nogo-P3 latency was prolonged in bad sleepers than in good sleepers. The Nogo-P3 amplitude was reduced in Noise as compared to "Quiet" conditions in bad sleepers only. Sleep quality in bad sleepers worsened steadily with increasing noise levels. No effects of noise or subjective sleep quality on performance were found. Inhibitory processes appear to be selectively impaired after nocturnal noise exposure. The task difficulty and perceived sleep quality are important factors modulating noise effects. The results suggest that nocturnal traffic noise increase physiological costs for inhibitory functioning on the day even if no overt performance decrement is observed.

After effects of noise-induced sleep disturbances on inhibitory functions.

The study focuses on possible after effects of noise-induced sleep disturbances on inhibitory brain processes reflecting in performance changes and alternations of inhibition-related components of event-related potentials (ERPs). Following a quiet night and three nights, in which railway noise was presented with different levels, twelve women and ten men (19-28 years) performed a visual Go/Nogo task that contained stimuli either compatible or incompatible with a response. Noise-induced sleep disturbances are highly evident in worsening of subjective sleep quality but did not show up in significant changes of reaction time and error rate. A smaller N2 amplitude and longer latency to incompatible than to compatible stimuli as well as an unspecific attenuation of N2 amplitude under Noise were found. The amplitude of the fronto-central P3 was reduced under Noise compared to baseline only in Nogo trials. The amplitude of the parietal P3 in Go trials was smaller to incompatible than to compatible stimuli but was not affected by Noise. Disturbed sleep was associated with a decreased blink rate during task performance. The results suggest that physiological costs to maintain performance are increased after noisy nights. Decisional processes underlying overt responses (Go-P3) are less vulnerable to noise-disturbed sleep than those related to inhibition (Nogo-N2, NoGo-P3). The deficits may have been compensated by increased on-task concentration and thereby did not become apparent in the performance data. Inhibition-related ERPs may be more sensitive indicators of moderate sleep disturbances caused by noise than performance measures.