Biology subjects

Wascher, E.

Publications and source records attributed to Wascher, E..

24 records · Page 2Linked to original sources

bioRxiv2020

Congruent lip movements facilitate speech processing in a dynamic audiovisual multi-talker scenario: An ERP study with older and younger adults

In natural conversations, visible mouth and lip movements play an important role in speech comprehension. There is evidence that visual speech information improves speech comprehension, especially for older adults and under difficult listening conditions. However, the neurocognitive basis is still poorly understood. The present EEG experiment investigated the benefits of audiovisual speech in a dynamic cocktail-party scenario with 22 (aged 20 to 34 years) younger and 20 (aged 55 to 74 years) older participants. We presented three simultaneously talking faces with a varying amount of visual speech input (still faces, visually unspecific and audiovisually congruent). In a two-alternative forced-choice task, participants had to discriminate target words ("yes" or "no") among two distractors (one-digit number words). In half of the experimental blocks, the target was always presented from a central position, in the other half, occasional switches to a lateral position could occur. We investigated behavioral and electrophysiological modulations due to age, location switches and the content of visual information, analyzing response times and accuracy as well as the P1, N1, P2, N2 event-related potentials (ERPs) and the contingent negative variation (CNV) in the EEG. We found that audiovisually congruent speech information improved performance and modulated ERP amplitudes in both age groups, suggesting enhanced preparation and integration of the subsequent auditory input. In the older group, larger amplitude measures were found in early phases of processing (P1-N1). Here, amplitude measures were reduced in response to audiovisually congruent stimuli. In later processing phases (P2-N2) we found decreased amplitude measures in the older group, while an amplitude reduction for audiovisually congruent compared to visually unspecific stimuli was still observable. However, these benefits were only observed as long as no location switches occurred, leading to enhanced amplitude measures in later processing phases (P2-N2). To conclude, meaningful visual information in a multi-talker setting, when presented from the expected location, is shown to be beneficial for both younger and older adults.

neuroscience↗

bioRxiv2019

The Electrophysiological Signature of Mind Wandering

Mind wandering during ongoing tasks can impede task performance and increase the risk of failure in laboratory as well as in daily-life tasks and work environments. Neurocognitive measures like the electroencephalography (EEG) offer the opportunity to assess mind wandering non-invasively without interfering with the primary task. However, the literature on electrophysiological correlates of mind wandering is rather inconsistent. The present study aims towards clarifying this picture by breaking down the temporal dynamics of mind-wandering encounters using a cluster-based permutation approach. Participants performed a switching task during which mind wandering was occasionally assessed via thought probes applied after trial completion at random time points. In line with previous studies, response accuracy was reduced during mind wandering. Moreover, alpha power during the inter-trial interval was significantly increased on those trials on which participants reported that they had been mind-wandering. This spatially widely distributed effect is theoretically well in line with recent findings linking an increased alpha power to an internally oriented state of attention. Measurements of alpha power may therefore be used to detect mind wandering online during critical tasks in traffic and industry in order to prevent failures.

neuroscience↗

bioRxiv2019

The role of working memory for bridging the gap between perception and goal-directed actions - Evidence by mu and beta oscillations in sensorimotor cortex

What mechanisms are at work when transferring a visual representation in working memory into a higher-level code for guiding future actions? We investigated the underlying attentional and motor selection processes in working memory by means of oscillatory EEG parameters. Participants stored two, three or four objects in working memory and subsequent retroactive cues indicated one or two items as task-relevant. The oscillatory response in mu (10-14 Hz) and beta (15-25 Hz) frequencies with an estimated source in sensorimotor cortex contralateral to response side was used as a correlate of motor planning. There was a stronger suppression of oscillatory power when only one item was cued. Importantly, this effect appeared although the required response could not be anticipated at this point in time. This suggests that working memory can store multiple item-specific motor plans and the selection of a stored visual item leads to an automatic updating of associated response alternatives.

neuroscience↗

bioRxiv2019

Excitatory and inhibitory attentional mechanisms involved in the control of distractor interference in working memory: A neural oscillations perspective

There is an ongoing debate on the contribution of target enhancement and distractor inhibition processes to selective attention. In a working memory task, we presented to-be-memorized information in a way that posterior hemispheric asymmetries in oscillatory power could be unambiguously linked to lateral target vs. distractor processing. Alpha power asymmetries (8-14 Hz) were insensitive to the number of cued or non-cued items, supporting their relation to spatial attention. Furthermore, we found an increase in alpha power contralateral to non-cued working memory content and an alpha power suppression contralateral to relevant information. These oscillatory patterns relative to the positions of cued and non-cued items were related to the participants ability to control for the impact of irrelevant information on working memory retrieval. Based on these results, we propose that spatially specific modulations of posterior alpha power are related to accessing vs. inhibiting the spatial context of information stored in working memory.

neuroscience↗

bioRxiv2019

Unraveling the relation between EEG-correlates of attentional orienting and sound localization performance: a diffusion model approach

Understanding the contribution of cognitive processes and their underlying neurophysiological signals to behavioral phenomena has been a key objective in recent neuroscience research. Using a diffusion-model framework, we investigated to what extent well-established correlates of spatial attention in the electro-encephalogram contribute to behavioral performance in an auditory free-field sound-localization task. Younger and older participants were instructed to indicate the horizontal position of a pre-defined target among three simultaneously presented distractors. The central question of interest was whether posterior alpha lateralization and amplitudes of the anterior contralateral N2 subcomponent (N2ac) predict sound localization performance (accuracy, mean reaction time) and/or diffusion model parameters (drift rate, boundary separation, non-decision time). Two age groups were compared to explore whether in older adults, who struggle with multi-speaker environments, the brain-behavior relationship would differ from younger adults. Regression analyses revealed that N2ac amplitudes predicted drift rate and accuracy, whereas alpha lateralization was not related to behavioral or diffusion modeling parameters. This was true irrespective of age. The results indicate that a more efficient attentional filtering and selection of information within an auditory scene, reflected by increased N2ac amplitudes, was associated with a higher speed of information uptake (drift rate) and better localization performance (accuracy), while the underlying response criteria (threshold separation), mean reaction times, and non-decisional processes remained unaffected. The lack of a behavioral correlate of post-stimulus alpha power lateralization constrast the well-established notion that pre-stimulus alpha power reflects a functionally relevant attentional mechanism. This highlights the importance of distinguishing anticipatory from post-stimulus alpha power modulations.

neuroscience↗

bioRxiv2017

Distractor inhibition contributes to retroactive attentional orienting within working memory: Evidence by lateralized event-related parameters of the EEG

Shifts of attention within mental representations based on retroactive cues (retro-cues) facilitate performance in working memory tasks. It was suggested that this retro-cue benefit is related to the concentration of working memory resources on a subset of representations, thereby improving storage and retrieval at the cost of non-cued items. However, the attentional mechanisms underlying this updating of working memory representations remain unknown. Here, we present EEG data for distinguishing between target enhancement and distractor suppression processes in the context of retroactive attentional orienting. Therefore, we used a working memory paradigm with retro-cues indicating a shift of attention to either a lateralized or non-lateralized item. There was an increase of posterior alpha power contralateral compared to ipsilateral to the irrelevant item when a non-lateralized mental representation was cued and a contralateral suppression of posterior alpha power when a lateralized item had to be selected. This suggests that both inhibition of the non-cued information and enhancement of the target representation are important features of attentional orienting within working memory. By further presenting cues to either remember or to forget a working memory representation, we give a first impression of these retroactive attentional sub-processes as two separable cognitive mechanisms.

neuroscience↗