No abstract

The data suggest that older workers as compared with younger ones are impaired in tasks requiring WM, which is accompanied by enhanced cardiovascular "costs" in terms of increased SBP and reduced vagal control over HR.

No abstract

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.

The study investigated the neuronal mechanisms of age-related changes in mixing costs during memory-based task switching with two levels of working memory (WM) load. Forty-eight healthy younger and 45 healthy older participants performed a memory based (high WM load) and a memory plus cue based (low WM load) switching task while event-related brain potentials (ERPs) were registered. Older adults revealed larger mixing costs in both reaction time (RT) and accuracy at higher WM loads than younger adults. The presence of explicit cues substantially reduced age differences in mixing costs for accuracy but not for RT. Similarly, no age differences regarding local switch costs were found at lower WM load. Surprisingly, larger RT local costs in younger adults than in older adults were found in the memory-based block. The CNV was reduced under high WM load and positively correlated with accuracy mixing costs in older adults. The target-locked occipital N1 and fronto-central P2 were larger in older adults relative to younger adults irrespective of WM load. The P2 latency reflected the pattern of switch costs observed in behavioral data. Moreover, P2 latency positively correlated with RT mixing costs in older adults. Elderly also showed a delayed N2 and a delayed and reduced P3b. The results suggest that age-related differences in mixing costs may be partially due to a less efficient task preparation and task set maintenance (CNV) in elderly. However, elderly attempted to compensate for these deficits by permanent activation of mechanisms relating to stimulus encoding (N1) and task-set retrieval (P2). Finally, the delayed fronto-central N2 as well as the delayed and reduced parietal P3b strongly suggest delays of response selection and working memory updating in elderly due to an increase in selection threshold or in response selection variability constituting the performance decline.

The present study aimed to examine EEG correlates of cognitive load in a task, in which multiple stimulus-response mappings have to be maintained in working memory (WM) combined with selective inhibition of irrelevant stimulus-response mappings on every trial. Twenty-four healthy younger adults had to perform choice reaction tasks differed in the number of S-R mappings and motor response requirements. Performance was lower in the high load than in the low load condition. Performance decline at higher WM loads was accompanied by an increase of EEG power in delta, theta, and beta frequency bands and by a reduction in alpha band. The effect on alpha was generalized across all the electrodes. Correlations between EEG and performance were observed in the high load condition but not in the low load condition. Theta activity negatively correlated with reaction time, whereas positive correlations between beta activity and reaction time were found. The two frequency bands negatively correlated with each other at all electrodes. The results suggest that changes in alpha and theta power may be considered as the most sensitive indicators of cognitive load. The alpha reduction may be related to activation of widespread cortical areas which were recruited for performance of complex WM tasks. The beta increase, especially in the beta-2 range, may partly be associated with activation of motor cortex due to difficulties in preparation and execution of motor responses. Theta increases may be considered as an index of facilitation of information processing in WM and improvements in higher-order executive control, which in turn facilitates motor processes.

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.

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.