Adverse Listening Conditions and Memory Load Drive a Common Alpha Oscillatory Network

“4, top row; bottom row shows the same data being plotted onto brain areas as outlined in the automatic anatomical labeling atlas; Tzourio-Mazoyer et al., 2002).”

“Offline, the data were analyzed using MATLAB and the FieldTrip toolbox (Oostenveld et al., 2011).”

“At the second or group level, we submitted the individual z-maps to a massed cluster-based permutation t test (testing for significant differences from zero, two-sided, dependent samples, with 1000 iterations; as outlined by Maris and Oostenveld, 2007).”

“The alpha enhancement attributable to more severe acoustic degradation was found to be additive to the alpha enhancement attributable to more stored items: acoustic degradation (a perceptual challenge) and memory load (a capacity challenge) both draw on a neural system subserving “functional inhibition” (Klimesch et a…”

“Noise vocoding is an effective technique to manipulate the spectral detail while preserving the temporal envelope of the speech signal (Drullman, 1995; Shannon et al., 1995) and render it more or less intelligible in a graded and controlled way, depending on the number of bands used.”

“The alpha enhancement attributable to more severe acoustic degradation was found to be additive to the alpha enhancement attributable to more stored items: acoustic degradation (a perceptual challenge) and memory load (a capacity challenge) both draw on a neural system subserving “functional inhibition” (Klimesch et a…”

“As illustrated in Figure 4, the significant cluster extends into the SMG and the temporoparietal junction (TPJ), both being hotspots in verbal working memory (Paulesu et al., 1993; Jacquemot et al., 2003; Jacquemot and Scott, 2006; Obleser and Eisner, 2009).”

“…to overcome this and other inherent limitations when interpreting sensor-space topographies (Lopes da Silva, 2004), alpha activity during delay was projected to source space using an adaptive spatial filter in the frequency domain [dynamic imaging of coherent sources (DICS); Gross et al., 2001].”

“Enhanced alpha oscillations have become a welldocumented neural substrate of increased cognitive effort, in line with a functional, inhibitory role of alpha in controlling or gating local circuits of neural activity (Klimesch et al., 2007; Jensen and Mazaheri, 2010; Foxe and Snyder, 2011; Weisz et al., 2011).”

“…a function of memory load has been demonstrated unanimously in the Sternberg task, in which items have to be briefly retained in short-term memory, and higher memory load is known to elicit longer response times (Jensen et al., 2002; Leiberg et al., 2006; Nenert et al., 2012; Sander et al., 2012).”

“Alpha rhythms reflects the cognitive system’s pre-stimulus preparation for incoming stimuli, enabling efficient processing (Babiloni et al., 2006), and have been associated with both WM load and processing of acoustically degraded stimuli (Obleser et al., 2011).”

“Obleser et al. (2012) used magnetoencephalography to compare the effects of increasing memory load during an explicit memory task and during degraded speech understanding.”

“…found modulations in alpha power in a variety of auditory tasks prompted by degraded spectral detail (Obleser and Weisz, 2012), missing temporal expectations (Wilsch et al., 2014), working memory load (Leiberg et al., 2006; Obleser et al., 2012), or syntactic complexity (Meyer et al., 2013).”

“…additional executive resources to specific neural systems by identifying increased neural activity resulting from acoustic challenge during speech comprehension (Davis and Johnsrude, 2003; Eckert et al., 2008, 2009; Adank, 2012; Hervais-Adelman et al., 2012; Obleser et al., 2012; Erb et al., 2013).”

“…on the effect of adverse listening conditions on alpha oscillations (which are often interpreted as a measure for attention or memory load) (Obleser et al. 2012; Petersen et al. 2015), or studying the relationship between hearing impairment, hearing aid use, and sentence processing delay…”

“Individuals with normal hearing show greater pupil dilation (Zekveld et al. 2018) and increasing alpha power (Obleser et al. 2012), both established indices of cognitive load, with increasing degradation of the speech signal.”

“Based on previous localizations of alpha power effects in auditory tasks (Obleser and Weisz, 2012; Obleser et al., 2012), the current parietal distributions of alpha power likely originate from parietal cortex, which belongs to the “dorsal attention network” (Sadaghiani et al.”

“To extract significant spatio-temporal deflections in the TRFs at an SNR of 0 dB, we applied a two-level statistical analysis (two-level clustertest; e.g. Obleser et al., 2012).”

“Max Planck Research Group “Auditory Cognition”, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany Edited by: Jonathan E. Peelle, Washington University in St. Louis, USA Reviewed by: Jonathan E. Peelle, Washington University in St. Louis, USA Stefanie E. Kuchinsky,…”

“Data were analysed using MATLAB (The MathWorks, Inc.), including external toolboxes, such as FieldTrip (Oostenveld et al., 2011), and custom-written routines.”

“…paradigms or reaction time measures 70 (Fraser et al., 2010; Houben et al., 2013; Tun et al., 2009); and physiological measures, such as the 71 pupil response and functional magnetic resonance imaging (fMRI) or EEG measures (Kuchinsky et al., 72 2013; Obleser et al., 2012; Petersen et al., 2015).”

“Source localization for resulting clusters followed the Fieldtrip protocol on source reconstruction using beamformer techniques (e.g., Haegens et al., 2010; Medendorp et al., 2007; Obleser and Weisz, 2012; Obleser et al., 2012).”

“Band-pass filtering was used instead of high-pass filtering as in Obleser et al. (2012).”

“…7 February 2017 | Volume 11 | Article 88 The alpha ERS we observed is qualitatively similar to previously reported alpha ERS in a variety of experimental masking paradigms (Obleser et al., 2012; Petersen et al., 2015; Wilsch et al., 2015; Wöstmann et al., 2015; McMahon et al., 2016).”

“…retention (Klimesch et al., 1999; Jensen et al., 2002; Tuladhar et al., 2007; Haegens et al., 2010; Johnson et al., 2011; Bonnefond & Jensen, 2012; Obleser et al., 2012; Spitzer & Blankenburg, 2012), with larger increases in amplitude (e.g. Jensen et al., 2002; Tuladhar et al., 2007) as well as…”

“2012), ERPs (Obleser & Kotz 2011), and EEG alpha power (Obleser et al. 2012; see McGarrigle et al. 2014, for a summary of listening effort studies using physiological measures published between 2008 and 2013).”

“…and oscillations in the alpha frequency band (8–12 Hz) have independently been shown to be associated with changes in speech intelligibility (Obleser et al., 2012; Becker et al., 2013; Zekveld and Kramer, 2014; Petersen et al., 2015) and seem to be sensitive to hearing loss during a speech…”

“Note that this tentative explanation is also supported by analyses conducted over the single contrasts: In line with previous auditory literature (Obleser et al., 2012; Weisz et al., 2011) we observed enhanced alpha power in response to degraded speech, which has been suggested, in line with the…”

“Recently using magnetoencephalography, we showed increased right auditory alpha activity when attention was cued ipsilaterally.”

“On the other hand, the posterior supramarginal gyrus (SMG) and temporoparietal junction (TPJ) are mainly responsible for generating alpha activity during effortful listening [21], [30].”

“These findings have been taken as evidence for resource models of WM in general and the ELU model for language processing in particular (Obleser et al., 2012; Petersen et al., 2015; Peelle, 2018; Rönnberg et al., 2019).”

“Word frequency in particular affects lexical retrieval times (e.g., Oldfield and Wingfield, 1965; Murray and Forster, 2004) and recognition accuracy for words presented in noise (Howes, 1957).”

“…separation of relevant and distracting auditory inputs, higher alpha power was associated with more adverse conditions and decreased speech intelligibility (Obleser and Weisz, 2012; Obleser et al., 2012; Becker et al., 2013; Strauß et al., 2014; Dimitrijevic et al., 2017; Wisniewski et al., 2017) .”

“Second, alpha power has been repeatedly found to increase parametrically with memory load, such as number of items (Jensen et al., 2002; Leiberg et al., 2006b; Obleser et al., 2012).”

“Time–frequency representations (TFRs) of each trial were computed by convolving the single-trial time-domain EEG data with a family of sevencycle Morlet wavelets for frequencies of 1– 40 Hz (with 1 Hz resolution).”

“For group-level statistical analysis, the distribution of these first-level, subject-specific statistics can be tested for significant deviation from zero or an otherwise hypothesised value (e.g. Obleser et al., 2012; Wöstmann, Herrmann, Wilsch, et al., 2015; Wöstmann, Schröger, & Obleser, 2015).”

“2015), and magnetoencephalography (Obleser et al. 2012).”

“…EEG studies, evidence for higher cognitive load (represented by alpha power enhancement) in listening to degraded signals was found for young, normal-hearing listeners (20–32 years, Obleser et al., 2012) as well as older listeners (62–86 years) with and without hearing loss (Petersen et al., 2015).”

“The EEG data were analysed using MATLAB and the FieldTrip toolbox (Oostenveld et al., 2011).”

“Several have proposed that enhancements of theta and alpha power (Eckert, Teubner-Rhodes, & Vaden, 2016; McMahon et al., 2016; Obleser et al., 2012; Wisniewski et al., 2015; Wisniewski, 2017) can be used as indices of listening effort—“the mental exertion required to attend to, and understand, an…”

“This modulation occurs when short degraded stimuli are used (Obleser & Weisz, 2012; Obleser et al., 2012).”

“In contrast, previous studies suggesting sensitivity of univariate alpha power modulations to task difficulty or subjective effort did find such a correlation between the two measures (Obleser et al., 2012; Wöstmann et al., 2015).”

“By now, it is well established that alpha desynchronization facilitates attention and memory processes (e.g., Klimesch et al., 1997), with empirical evidence for the visual (e.g., Friese et al., 2013), and the auditory domain (e.g., Obleser et al., 2012).”

“Firstly, studies have shown an association between changes in these measures and changes in listening effort (alpha: Obleser et al., 2012; phase: Bernarding et al., 2014).”

“…to distinguish from other related constructs such as “mental effort” (Panico & Healey, 2009), “perceptual effort” (Tun et al., 2009), “cognitive effort” (Obleser et al., 2012; Piquado et al., 2010), “cognitive load” (Zekveld et al., 2011), and “processing load” (Kramer et al., 2012; Zekveld et…”

“Specific to the measurement of listening effort, investigators have used pupillometery, skin conductance, heart rate variability, and electroencephalography (e.g. Zekveld and Kramer 2014; Obleser et al. 2012; Mackersie, Macphee, and Heldt 2015).”

“…task, during which pupillometry was recorded, was a modified version of the Sternberg paradigm (Sternberg 1966) in which participants are asked to recall speech material presented during a stimulus-free retention period, based on similar paradigms (e.g. Obleser et al. 2012; Petersen et al. 2015).”

“For the to-be-memorized stimuli, we used recordings of German spoken digits from 1 to 9 from a previous study (Obleser et al., 2012).”

“It is thus conceivable, in line with previous research, that degraded acoustic conditions automatically increase the allocation of attention (Obleser et al., 2012; Obleser & Weisz, 2012) even if the degradation applies only to task-irrelevant materials (Winkler, Teder-Salejarvi, Horvath, Näätänen, & Sussman, 2003).”

“…because of speech degradation (Drijvers, Mulder, & Ernestus, 2016; Wilsch, Henry, Herrmann, Maess, & Obleser, 2015; Strauß, Wöstmann, & Obleser, 2014; Weisz & Obleser, 2014; Becker, Pefkou, Michel, & Hervais-Adelman, 2013; Obleser & Weisz, 2012; Obleser, Wöstmann, Hellbernd, Wilsch, & Maess, 2012).”

“…Zekveld et al., 2010; Zekveld et al., 2014; Ohlenforst et al., 2017b; Wendt et al., 2017), various physiological indices (e.g., Hicks and Tharpe, 2002; Mackersie and Cones, 2011), and/or electroencephalographic (EEG) responses (e.g., Obleser et al., 2012) (for a review, see Klink et al., 2012a,b).”

“…suppression reflects a state that allows for an increase of mental operations that can be performed on the incoming speech signal, thus, active cognitive processing (e.g,. Shanin et al., 2009; Obleser & Weisz, 2012; Obleser et al., 2012; Strauß, Kotz, et al., 2014; Strauß, Wostmann, et al., 2014).”

“leads to parametric increases in alpha power (Jensen et al., 2002; Tuladhar et al., 2007; Obleser et al., 2012).”

“The power of alpha oscillations in the posterior parietal cortex, right superior parietal cortex, right SMA, and superior temporal gyrus has been reported to be positively correlated with the number of retained items (Leiberg et al., 2006; Obleser et al., 2012), and it decreases as the load dissolves (Wilsch et al.”

“As outlined earlier, previous studies have reported an increase in alpha activity in cognitively more demanding tasks (Jensen et al., 2002; Obleser et al., 2012).”

“…perception, the enhancement of alpha activity is often inversely related to signal intelligibility (Becker et al., 2013; McMahon et al., 2016; Obleser et al., 2012; Obleser and Weisz, 2012; Scharinger et al., 2014; Wostmann et al., 2015), possibly reflecting age-related changes in…”

“However, with the emergence of body-worn biosensors such as electroencephalograph (EEG), it is possible to extract meaningful perceptual measures such as speech intelligibility, speech quality and listening efforts directly from the EEG signal [15].”

“In particular, posterior alpha (8–12 Hz) power changes have been related to attentional shifts and WM load during retention (e.g., Obleser et al., 2012; Sander et al., 2012b; Sauseng et al., 2009).”

“In contrast, NH seem to need an additional allocation of attention only in adverse auditory listening conditions (Zekveld et al., 2006; Obleser et al., 2012; Rönnberg et al., 2013).”

“To draw a clean line separating visual encoding and memory processes, we opted to record the EEG during a modified Sternberg working memory task (Obleser et al., 2012) in which stimuli were visual characters presented sequentially (visual stimulus encoding) followed by a period where participants…”

“The interpretation of negative correlations of alpha power with BOLD activations follows the functional inhibition hypothesis (Foxe et al., 1998; Klimesch et al., 2007; Foxe and Snyder, 2011; Weisz et al., 2011, 2013; Klimesch, 2012; Obleser and Weisz, 2012; Obleser et al., 2012).”

“Brain activity, as an objective measure, is examined using electroencephalography (EEG; Obleser et al., 2012).”

“The SMG has previously been observed to be crucial for stimulus maintenance in auditory short-term memory (see Paulesu et al., 1993; van Dijk et al., 2010; Obleser et al., 2012 for increased alpha power in SMG during auditory short-term memory).”

“…changes in the synchronization of alpha and theta oscillations during electroencephalogram (EEG) recordings (Deng et al., 2019; Miles et al., 2017; Obleser et al., 2012; Wisniewski, 2017; Wisniewski et al., 2018), changes in the topography, latency, or amplitude of event-related potentials (ERPs)…”

“…synchronisation in the working memory processes responsible for mapping online auditory inputs to specific linguistic predictions (i.e. hypotheses about sentence content induced by prior information; cf. Obleser et al., 2012; Meyer et al., 2013; Sedley et al., 2016; Wilsch and Obleser, 2016).”

“…alpha increases have been reported during the retention period in the visual (e.g. Jensen et al., 2002; Klimesch et al., 1999), somatosensory (e.g. Haegens et al., 2009) and auditory modalities (e.g. Obleser et al., 2012), putatively protecting the to-be-remembered information against interference.”

“A similar effect has been found for working memory for spoken words using alpha power as an index of working Frontiers in Psychology | www.frontiersin.org 7 May 2018 | Volume 9 | Article 679 memory load (Obleser et al., 2012).”

“Applied to speech perception, it has been proposed that alpha oscillations might be actively enhanced in order to cope with a demanding task, particularly listening to speech in the presence of background noise (Obleser et al., 2012; Strauß et al., 2014b; Wöstmann et al., 2015).”

“…in auditory processing: on the one hand, it has been shown to be suppressed to reinforce acoustic intelligibility, but on the other hand, alpha rhythm is enhanced during auditory memory retention (Knecht et al., 2000; Jensen et al., 2002; Obleser et al., 2012; Theofanopoulou and Boeckx, 2015).”

“The balance between top-down processes of template matching and functional inhibition (Gazzaley and Nobre, 2012; Obleser et al., 2012), reflected by theta and alpha oscillations, is modulated by attentional control (Klimesch et al., 1999; Kerlin et al., 2010; Keller et al., 2017; Fiebelkorn and…”

“The alpha inhibition hypothesis is contrasted by an alternative interpretation that alpha synchronization enhances stimulus maintenance at the network level (Leiberg et al., 2006; Obleser et al., 2012; Palva and Palva, 2007; Wilsch and Obleser, 2016).”

“…independent component analysis; lWMN, left WMN; RT, reaction time; rWMN, right WMN; TCT, Topographic consistency tests; TCNs, temporally coherent networks; WM, working memory; WMN, working memory network; 3T, 3 Tesla. demands on storage and inhibition of irrelevant stimuli (Obleser et al., 2012).”

“The second neurophysiological measure that may enable segregating different contributions associated with cognitive demand is neural alpha power (8–12 Hz; Dimitrijevic et al., 2017; 2021; Petersen et al., 2015; Wöstmann et al., 2017).”

“EEG has been widely used in the literature to measure effort objectively, whether in auditory [7], [8], [9], [10], [11] or nonauditory [12], [13], [14] studies.”

“Together with other evidence from the auditory domain this suggests a common neural mechanism for degradation and load (Obleser et al. 2012; Alain et al. 2018; Peelle 2018; Rönnberg et al. 2019), supporting resource models of working memory (Ma et al. 2014) and language processing (e.g., the ELU…”