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Introduction: Slow-wave sleep (SWS) slow waves and sleep spindle activity have been shown to be crucial for memory consolidation. Recently, memory consolidation has been causally facilitated in human participants via auditory stimuli phase-locked to SWS slow waves. Aims: Here, we aimed to develop a new acoustic stimulus protocol to facilitate learning and to validate it using different memory tasks. Most importantly, the stimulation setup was automated to be applicable for ambulatory home use. Methods: Fifteen healthy participants slept 3 nights in the laboratory. Learning was tested with 4 memory tasks (word pairs, serial finger tapping, picture recognition, and face-name association). Additional questionnaires addressed subjective sleep quality and overnight changes in mood. During the stimulus night, auditory stimuli were adjusted and targeted by an unsupervised algorithm to be phase-locked to the negative peak of slow waves in SWS. During the control night no sounds were presented. Results: Results showed that the sound stimulation increased both slow wave (p = .002) and sleep spindle activity (p < .001). When overnight improvement of memory performance was compared between stimulus and control nights, we found a significant effect in word pair task but not in other memory tasks. The stimulation did not affect sleep structure or subjective sleep quality. Conclusions: We showed that the memory effect of the SWS-targeted individually triggered single-sound stimulation is specific to verbal associative memory. Moreover, the ambulatory and automated sound stimulus setup was promising and allows for a broad range of potential follow-up studies in the future.

How is morphological and morphosyntactic information processed during sentence reading? Are the neural mechanisms underlying word- and phrase-level combinatorial processing overlapping or distinct? Here, electroencephalography (EEG) and magnetoencephalography (MEG) responses were recorded simultaneously during silent reading of Finnish sentences. The experimental conditions included 1) well-formed grammatical sentences (correct condition), 2) sentences containing morphosyntactic violations (adjective–noun number agreement violations), 3) morphological violations (incorrect stem allomorph and inflectional suffix combination), and 4) combined violations, containing both morphosyntactic and morphological violations. Signal space and source modeling results showed that morphosyntactic violations elicited a left anterior negativity effect, generated particularly in the left inferior frontal area. Morphological violations elicited a widespread negativity, resembling the N400. The neural sources of this negativity were localized most prominently to the right temporal cortical networks. Furthermore, all violations elicited P600 effects with similar widespread bilateral fronto-temporal neural generators that did not differ between morphosyntactic and morphological conditions. Our findings suggest at least partially distinct subnetworks in the fronto-temporal cortices for morphological and morphosyntactic parsing during the earlier stages of processes (∼400 ms post stimulus onset) and shared neural generators for the later processing stages.

The present study investigates age-related changes in duration discrimination in millisecond time domain. We tested young (N = 20, mean age = 24.5, SD = 2.97) and elderly (N = 20, mean age = 65.2, SD = 2.94) subjects using the mismatch negativity (MMN) paradigm. White-noise bursts of two different durations (50 and 10 ms) were presented in two oddball blocks. In one block (Increment Condition), the repetitive sequence of 10 ms standards was interspersed by occasional 50 ms deviants. In the Decrement Condition, the roles of the two stimuli were reversed. We analyzed the P1-N1 complex, MMN and P3a and found the effect of age for all these components. Moreover, the impact of stimulus presentation condition (increment/decrement) was observed for MMN and P3a. Our results confirmed the previous evidence for deteriorated duration discrimination in elderly people. Additionally, we found that this effect may be influenced by procedural factors.

Hazard and risk perception has been studied extensively among car drivers, and their link to crash involvement is established. Bicyclists, in particular, are vulnerable road users. Better understanding of their risk and hazard perception could help to improve their traffic safety. In this study, we investigated the risk perception of bicyclists in a city environment. Two groups of bicyclists were compared: 19 frequent and 19 infrequent bicyclists. Participants were shown video clips taken with a camera attached to the handlebar of a bicycle, and they were asked to continuously indicate with a slider how much caution the situation needed. The frequent cyclists had more frequent rises in the caution estimate, which suggest that they anticipated or detected more hazards than infrequent cyclists. This is in line with the classical hazard perception results, which link the car driving experience to faster and more accurate hazard perception. The overall level or caution was not directly related to the rise event rate or bicycling frequency. Those cyclists who reported typically cycling faster than others showed elevated overall level of caution on sidewalks compared with others, but there was no difference on bike paths. Hazard and risk perception has been studied extensively among car drivers, and their link to crash involvement is established. Bicyclists, in particular, are vulnerable road users. Better understanding of their risk and hazard perception could help to improve their traffic safety. In this study, we investigated the risk perception of bicyclists in a city environment. Two groups of bicyclists were compared: 19 frequent and 19 infrequent bicyclists. Participants were shown video clips taken with a camera attached to the handlebar of a bicycle, and they were asked to continuously indicate with a slider how much caution the situation needed. The frequent cyclists had more frequent rises in the caution estimate, which suggest that they anticipated or detected more hazards than infrequent cyclists. This is in line with the classical hazard perception results, which link the car driving experience to faster and more accurate hazard perception. The overall level or caution was not directly related to the rise event rate or bicycling frequency. Those cyclists who reported typically cycling faster than others showed elevated overall level of caution on sidewalks compared with others, but there was no difference on bike paths. (C) 2015 Elsevier Ltd. All rights reserved.

The spatiotemporal dynamics of the neural processing of spoken morphologically complex words are still an open issue. In the current study, we investigated the time course and neural sources of spoken inflected and derived words using simultaneously recorded electroencephalography (EEG) and magnetoencephalography (MEG) responses. Ten participants (native speakers) listened to inflected, derived, and monomorphemic Finnish words and judged their acceptability. EEG and MEG responses were time-locked to both the stimulus onset and the critical point (suffix onset for complex words, uniqueness point for monomorphemic words). The ERP results showed that inflected words elicited a larger left-lateralized negativity than derived and monomorphemic words approximately 200 ms after the critical point. Source modeling of MEG responses showed one bilateral source in the superior temporal area ∼100 ms after the critical point, with derived words eliciting stronger source amplitudes than inflected and monomorphemic words in the right hemisphere. Source modeling also showed two sources in the temporal cortex approximately 200 ms after the critical point. There, inflected words showed a more systematic pattern in source locations and elicited temporally distinct source activity in comparison to the derived word condition. The current results provide electrophysiological evidence for at least partially distinct cortical processing of spoken inflected and derived words. In general, the results support models of morphological processing stating that during the recognition of inflected words, the constituent morphemes are accessed separately. With regard to derived words, stem and suffix morphemes might be at least initially activated along with the whole word representation.

Reliable measurements are mandatory in clinically relevant auditory event-related potential (AERP)-based tools and applications. The comparability of the results gets worse as a result of variations in the remaining measurement error. A potential method is studied that allows optimization of the length of the recording session according to the concurrent quality of the recorded data. In this way, the sufficiency of the trials can be better guaranteed, which enables control of the remaining measurement error. The suggested method is based on monitoring the signal-to-noise ratio (SNR) and remaining measurement error which are compared to predefined threshold values. The SNR test is well defined, but the criterion for the measurement error test still requires further empirical testing in practice. According to the results, the reproducibility of average AERPs in repeated experiments is improved in comparison to a case where the number of recorded trials is constant. The test-retest reliability is not significantly changed on average but the between-subject variation in the value is reduced by 33–35%. The optimization of the number of trials also prevents excessive recordings which might be of practical interest especially in the clinical context. The efficiency of the method may be further increased by implementing online tools that improve data consistency.