Auditory Selective Attention Research Articles

Rejection positivity predicts trial-to-trial reaction times in an auditory selective attention task: a computational analysis of inhibitory control.

A series of computer simulations using variants of a formal model of attention (Melara and Algom, 2003) probed the role of rejection positivity (RP), a slow-wave electroencephalographic (EEG) component, in the inhibitory control of distraction. Behavioral and EEG data were recorded as participants performed auditory selective attention tasks. Simulations that modulated processes of distractor inhibition accounted well for reaction-time (RT) performance, whereas those that modulated target excitation did not. A model that incorporated RP from actual EEG recordings in estimating distractor inhibition was superior in predicting changes in RT as a function of distractor salience across conditions. A model that additionally incorporated momentary fluctuations in EEG as the source of trial-to-trial variation in performance precisely predicted individual RTs within each condition. The results lend support to the linking proposition that RP controls the speed of responding to targets through the inhibitory control of distractors.

Stress improves selective attention towards emotionally neutral left ear stimuli

Research concerning the impact of psychological stress on visual selective attention has produced mixed results. The current paper describes two experiments which utilise a novel auditory oddball paradigm to test the impact of psychological stress on auditory selective attention. Participants had to report the location of emotionally-neutral auditory stimuli, while ignoring task-irrelevant changes in their content. The results of the first experiment, in which speech stimuli were presented, suggested that stress improves the ability to selectively attend to left, but not right ear stimuli. When this experiment was repeated using tonal stimuli the same result was evident, but only for female participants. Females were also found to experience greater levels of distraction in general across the two experiments. These findings support the goal-shielding theory which suggests that stress improves selective attention by reducing the attentional resources available to process task-irrelevant information. The study also demonstrates, for the first time, that this goal-shielding effect extends to auditory perception.

Neural effects of cognitive control load on auditory selective attention

Whether and how working memory disrupts or alters auditory selective attention is unclear. We compared simultaneous event-related potentials (ERP) and functional magnetic resonance imaging (fMRI) responses associated with task-irrelevant sounds across high and low working memory load in a dichotic-listening paradigm. Participants performed n-back tasks (1-back, 2-back) in one ear (Attend ear) while ignoring task-irrelevant speech sounds in the other ear (Ignore ear). The effects of working memory load on selective attention were observed at 130–210ms, with higher load resulting in greater irrelevant syllable-related activation in localizer-defined regions in auditory cortex. The interaction between memory load and presence of irrelevant information revealed stronger activations primarily in frontal and parietal areas due to presence of irrelevant information in the higher memory load. Joint independent component analysis of ERP and fMRI data revealed that the ERP component in the N1 time-range is associated with activity in superior temporal gyrus and medial prefrontal cortex. These results demonstrate a dynamic relationship between working memory load and auditory selective attention, in agreement with the load model of attention and the idea of common neural resources for memory and attention.

Abstracts fromThe 32nd AnnualNational Neurotrauma SymposiumJune 29–July 2, 2014San Francisco, California

Abstracts fromThe 32^nd AnnualNational Neurotrauma SymposiumJune 29–July 2, 2014San Francisco, California

Impaired Facilitatory Mechanisms of Auditory Attention After Damage of the Lateral Prefrontal Cortex.

There is growing evidence that auditory selective attention operates via distinct facilitatory and inhibitory mechanisms enabling selective enhancement and suppression of sound processing, respectively. The lateral prefrontal cortex (LPFC) plays a crucial role in the top-down control of selective attention. However, whether the LPFC controls facilitatory, inhibitory, or both attentional mechanisms is unclear. Facilitatory and inhibitory mechanisms were assessed, in patients with LPFC damage, by comparing event-related potentials (ERPs) to attended and ignored sounds with ERPs to these same sounds when attention was equally distributed to all sounds. In control subjects, we observed 2 late frontally distributed ERP components: a transient facilitatory component occurring from 150 to 250 ms after sound onset; and an inhibitory component onsetting at 250 ms. Only the facilitatory component was affected in patients with LPFC damage: this component was absent when attending to sounds delivered in the ear contralateral to the lesion, with the most prominent decreases observed over the damaged brain regions. These findings have 2 important implications: (i) they provide evidence for functionally distinct facilitatory and inhibitory mechanisms supporting late auditory selective attention; (ii) they show that the LPFC is involved in the control of the facilitatory mechanisms of auditory attention.

Cortical alpha oscillations as a tool for auditory selective inhibition.

Listening to speech is often demanding because of signal degradations and the presence of distracting sounds (i.e., “noise”). The question how the brain achieves the task of extracting only relevant information from the mixture of sounds reaching the ear (i.e., “cocktail party problem”) is still open. In analogy to recent findings in vision, we propose cortical alpha (~10 Hz) oscillations measurable using M/EEG as a pivotal mechanism to selectively inhibit the processing of noise to improve auditory selective attention to task-relevant signals. We review initial evidence of enhanced alpha activity in selective listening tasks, suggesting a significant role of alpha-modulated noise suppression in speech. We discuss the importance of dissociating between noise interference in the auditory periphery (i.e., energetic masking) and noise interference with more central cognitive aspects of speech processing (i.e., informational masking). Finally, we point out the adverse effects of age-related hearing loss and/or cognitive decline on auditory selective inhibition. With this perspective article, we set the stage for future studies on the inhibitory role of alpha oscillations for speech processing in challenging listening situations.

Individual differences in attentional modulation of cortical responses correlate with selective attention performance

Many studies have shown that attention modulates the cortical representation of an auditory scene, emphasizing an attended source while suppressing competing sources. Yet, individual differences in the strength of this attentional modulation and their relationship with selective attention ability are poorly understood. Here, we ask whether differences in how strongly attention modulates cortical responses reflect differences in normal-hearing listeners' selective auditory attention ability. We asked listeners to attend to one of three competing melodies and identify its pitch contour while we measured cortical electroencephalographic responses. The three melodies were either from widely separated pitch ranges (“easy trials”), or from a narrow, overlapping pitch range (“hard trials”). The melodies started at slightly different times; listeners attended either the leading or lagging melody. Because of the timing of the onsets, the leading melody drew attention exogenously. In contrast, attending the lagging melody required listeners to direct top–down attention volitionally. We quantified how attention amplified auditory N1 response to the attended melody and found large individual differences in the N1 amplification, even though only correctly answered trials were used to quantify the ERP gain. Importantly, listeners with the strongest amplification of N1 response to the lagging melody in the easy trials were the best performers across other types of trials. Our results raise the possibility that individual differences in the strength of top–down gain control reflect inherent differences in the ability to control top–down attention.

Selective attention reduces physiological noise in the external ear canals of humans. I: Auditory attention

In this study, a nonlinear version of the stimulus-frequency OAE (SFOAE), called the nSFOAE, was used to measure cochlear responses from human subjects while they simultaneously performed behavioral tasks requiring, or not requiring, selective auditory attention. Appended to each stimulus presentation, and included in the calculation of each nSFOAE response, was a 30-ms silent period that was used to estimate the level of the inherent physiological noise in the ear canals of our subjects during each behavioral condition. Physiological-noise magnitudes were higher (noisier) for all subjects in the inattention task, and lower (quieter) in the selective auditory-attention tasks. These noise measures initially were made at the frequency of our nSFOAE probe tone (4.0 kHz), but the same attention effects also were observed across a wide range of frequencies. We attribute the observed differences in physiological-noise magnitudes between the inattention and attention conditions to different levels of efferent activation associated with the differing attentional demands of the behavioral tasks. One hypothesis is that when the attentional demand is relatively great, efferent activation is relatively high, and a decrease in the gain of the cochlear amplifier leads to lower-amplitude cochlear activity, and thus a smaller measure of noise from the ear.

A spatial approach of magnitude-squared coherence applied to selective attention detection

Auditory selective attention is the human ability of actively focusing in a certain sound stimulus while avoiding all other ones. This ability can be used, for example, in behavioral studies and brain-machine interface. In this work we developed an objective method - called Spatial Coherence - to detect the side where a subject is focusing attention to. This method takes into consideration the Magnitude Squared Coherence and the topographic distribution of responses among electroencephalogram electrodes. The individuals were stimulated with amplitude-modulated tones binaurally and were oriented to focus attention to only one of the stimuli. The results indicate a contralateral modulation of ASSR in the attention condition and are in agreement with prior studies. Furthermore, the best combination of electrodes led to a hit rate of 82% for 5.03 commands per minute. Using a similar paradigm, in a recent work, a maximum hit rate of 84.33% was achieved, but with a greater a classification time (20s, i.e. 3 commands per minute). It seems that Spatial Coherence is a useful technique for detecting focus of auditory selective attention.

Individual differences revealed by the challenges of listening in a complex, crowded scene

To extract content and meaning from a single source of sound in a quiet background, the auditory system can use a small subset of a very redundant range of spectral and temporal features. In stark contrast, communication in a complex, crowded scene places enormous demands on the auditory system. Spectrotemporal overlap between sounds reduces modulations in the signals at the ears and causes masking, with problems exacerbated by reverberation. Often, the more sensitive neurons in the early auditory pathway are driven to saturation, yet precise sensory representation is crucial for the ability to extract spatial, pitch, and cues that support source segregation and selective attention. Consistent with this idea, many patients seeking audiological treatment seek help precisely because they notice difficulties in environments requiring auditory selective attention. Consistent with this, in the laboratory, even listeners with normal hearing thresholds exhibit vast differences in the ability to selectively attend to a target. Here, we highlight the issues faced by the auditory system in a complex scene and describe recent behavioral and electrophysiological findings that hint at the mechanisms underlying individual differences in the ability to communicate in such adverse situations.

Behavioral and neural measures of auditory selective attention in blast-exposed veterans with traumatic brain injury

It is estimated that 15–20% of veterans returning from combat operations have experienced some sort of traumatic brain injury (TBI), a majority of which are the result of exposure to blast forces from military ordinance. Many of these veterans complain of complications when understanding speech in noisy environments, even when they have normal or near normal audiograms. Here, ten veterans diagnosed with mild TBI performed a selective auditory attention task in which they identified the shape of one of three simultaneously occurring ITD-spatialized melodies. TBI subject performance was significantly worse than that of 17 adult controls. Importantly, the veterans had hearing thresholds within 20 dB HL up to 8 kHz and brainstem responses indistinguishable from those of the controls. Cortical response potentials (measured on the scalp using electroencephalography) from correctly identified trials showed weaker attention-related modulation than in controls. These preliminary results suggest blast exposure dama...

Auditory attention in a dynamic scene: Behavioral and electrophysiological correlates

The ability to direct and redirect selective auditory attention varies substantially across individuals with normal hearing thresholds, even when sounds are clearly audible. We hypothesized that these differences can come from both differences in the spectrotemporal fidelity of subcortical sound representations and in the efficacy of cortical attentional networks that modulate neural representations of the auditory scene. Here, subjects were presented with an initial stream from straight ahead and a second stream (from either left or right), each comprised of four monotonized consonant-vowel syllables. Listeners were instructed to report the contents of either the first stream (holding attentional focus) or the second stream (switching attentional focus). Critically, the direction of the second stream informed subjects whether to hold or to switch attention. Pilot results suggest that when the lateral angle of the second stream is small, task performance is linked to subcortical encoding fidelity of suprathreshold sound (as measured using brainstem frequency-following responses obtained separately in the same subjects). Using a paradigm that allows simultaneous collection of behavioral measures, FFRs, and cortical responses, here we test whether differences in top-down attentional control explain subject variability when the second stream’s lateral angle is large and coding fidelity does not limit performance.

Editorial for special issue: “Auditory attention: merging paradigms and perspectives”

How can we be so absorbed into some activity that we fail to hear our name being called, while some minutes later we perfectly understand a whispering voice? Questions like this tap into the issue of auditory attention. As in any other modality, information processing in audition is shaped by the listener’s current goals. Consequently, perception of and responses to sound depend on inner states as much as on physical stimulus input. Diverse phenomena of auditory attention along the perception–action cycle have been addressed in various research groups. The field must, however, be described as somewhat scattered. In this special issue, we aim to provide an overview of the different research lines by bringing together 12 different perspectives on auditory attention. The 12 contributions comprise 5 review articles and 7 papers reporting original data. Seeing the links between the different research approaches is sometimes complicated by the fact that they come from fundamentally different traditions: some approach the problem of auditory attention with a strong focus on perceptual processes, others take an action-oriented perspective. Some base their investigation on the top-down allocation of attention in accordance with the listener’s goals, while others exploit the bottom-up capturing of attention resulting from stimulus saliency. While such dichotomies are difficult to avoid when structuring the available research material, we attempt to counteract them here by pointing out conceptual as well as methodological links between the various contributions. In everyday life, the need for (selective) auditory attention arguably arises most prominently from the presence of multiple objects producing sounds at the same time. What enables us to listen to our conversation partner in a busy cafeteria? We must be equipped with a powerful mechanism giving priority to the processing of some parts of the auditory input over others. This allows us to focus on a momentarily interesting signal (e.g., our conversation partner) while ignoring less relevant input (e.g., other speakers and the cafeteria noise). Many laboratory demonstrations of auditory selective attention in such scenarios rest on processing impairments for the unattended signals rather than on processing gains for the attended signals. The extent to which unattended signals are ignored is so surprisingly high that it has been termed inattentional deafness. This phenomenon is at the heart of the contribution by Koreimann, Gula, and Vitouch (2014). The authors provide an empirical demonstration of such perceptual failures in the ecologically valid case of listening to music: listeners, even musically trained ones, failed to notice an e-guitar improvisation in a piece by Richard Strauss when their attention was strongly focused on a certain aspect of the piece. This reflects a striking case of attentional over-selectivity. On the other hand, when the acoustic contrast between the e-guitar improvisation and the musical piece was increased, the inattentional deafness effect disappeared. Such findings illustrate a fine balance between attentional selectivity—allowing to focus on the task at hand— and the ‘‘breakthrough of the unattended’’ (Moray, 1959; Treisman, 1960)—allowing to check task-irrelevant but acoustically salient, potentially important information. The A. Bendixen (&) Auditory Psychophysiology Lab, Department of Psychology, Cluster of Excellence ‘‘Hearing4all’’, European Medical School, Carl von Ossietzky University of Oldenburg, Oldenburg, Germany e-mail: alexandra.bendixen@uni-oldenburg.de

Bottom-up influences of voice continuity in focusing selective auditory attention

Selective auditory attention causes a relative enhancement of the neural representation of important information and suppression of the neural representation of distracting sound, which enables a listener to analyze and interpret information of interest. Some studies suggest that in both vision and in audition, the "unit" on which attention operates is an object: an estimate of the information coming from a particular external source out in the world. In this view, which object ends up in the attentional foreground depends on the interplay of top-down, volitional attention and stimulus-driven, involuntary attention. Here, we test the idea that auditory attention is object based by exploring whether continuity of a non-spatial feature (talker identity, a feature that helps acoustic elements bind into one perceptual object) also influences selective attention performance. In Experiment 1, we show that perceptual continuity of target talker voice helps listeners report a sequence of spoken target digits embedded in competing reversed digits spoken by different talkers. In Experiment 2, we provide evidence that this benefit of voice continuity is obligatory and automatic, as if voice continuity biases listeners by making it easier to focus on a subsequent target digit when it is perceptually linked to what was already in the attentional foreground. Our results support the idea that feature continuity enhances streaming automatically, thereby influencing the dynamic processes that allow listeners to successfully attend to objects through time in the cacophony that assails our ears in many everyday settings.

Endogenous auditory frequency-based attention modulates electroencephalogram-based measures of obligatory sensory activity in humans

Auditory selective attention is the ability to enhance the processing of a single sound source, while simultaneously suppressing the processing of other competing sound sources. Recent research has addressed a long-running debate by showing that endogenous attention produces effects on obligatory sensory responses to continuous and competing auditory stimuli. However, until now, this result has only been shown under conditions where the competing stimuli differed in both their frequency characteristics and, importantly, their spatial location. Thus, it is unknown whether endogenous selective attention based only on nonspatial features modulates obligatory sensory processing. Here, we investigate this issue using a diotic paradigm, such that competing auditory stimuli differ in frequency, but had no separation in space. We find a significant effect of attention on electroencephalogram-based measures of obligatory sensory processing at several poststimulus latencies. We discuss these results in terms of previous research on feature-based attention and by comparing our findings with the previous work using stimuli that differed both in terms of spatial and frequency-based characteristics.

Probing the sensory effects of involuntary attention change by ERPs to auditory transients

An auditory selective attention set allows one to enhance the processing of goal-relevant sound events, which is reflected by the enhancement of the N1 event-related potential (ERP). The present study investigated whether the sensory consequences of distraction (i.e., involuntary attention changes triggered by infrequent sensory events) can be revealed as the removal of this attentional ERP enhancement. Continuous tones featuring occasional gaps were presented, and participants performed a gap-detection task. Independently from gaps, abrupt pitch changes (glides) were introduced, either rarely or frequently, in separate conditions. Whereas rare glides preceding gaps by 150 ms strongly impacted gap-detection performance and gap-related N1 amplitudes, their impact on gaps following rare glides by 650 ms was significantly smaller in both measures. This result demonstrates the utility of N1 in probing the sensory impact of auditory distraction.

Measuring auditory selective attention using frequency tagging

Frequency tagging of sensory inputs (presenting stimuli that fluctuate periodically at rates to which the cortex can phase lock) has been used to study attentional modulation of neural responses to inputs in different sensory modalities. For visual inputs, the visual steady-state response (VSSR) at the frequency modulating an attended object is enhanced, while the VSSR to a distracting object is suppressed. In contrast, the effect of attention on the auditory steady-state response (ASSR) is inconsistent across studies. However, most auditory studies analyzed results at the sensor level or used only a small number of equivalent current dipoles to fit cortical responses. In addition, most studies of auditory spatial attention used dichotic stimuli (independent signals at the ears) rather than more natural, binaural stimuli. Here, we asked whether these methodological choices help explain discrepant results. Listeners attended to one of two competing speech streams, one simulated from the left and one from the right, that were modulated at different frequencies. Using distributed source modeling of magnetoencephalography results, we estimate how spatially directed attention modulates the ASSR in neural regions across the whole brain. Attention enhances the ASSR power at the frequency of the attended stream in contralateral auditory cortex. The attended-stream modulation frequency also drives phase-locked responses in the left (but not right) precentral sulcus (lPCS), a region implicated in control of eye gaze and visual spatial attention. Importantly, this region shows no phase locking to the distracting stream. Results suggest that the lPCS in engaged in an attention-specific manner. Modeling results that take account of the geometry and phases of the cortical sources phase locked to the two streams (including hemispheric asymmetry of lPCS activity) help to explain why past ASSR studies of auditory spatial attention yield seemingly contradictory results.

Cortical response variability as a developmental index of selective auditory attention.

Attention induces synchronicity in neuronal firing for the encoding of a given stimulus at the exclusion of others. Recently, we reported decreased variability in scalp-recorded cortical evoked potentials to attended compared with ignored speech in adults. Here we aimed to determine the developmental time course for this neural index of auditory attention. We compared cortical auditory-evoked variability with attention across three age groups: preschoolers, school-aged children and young adults. Results reveal an increased impact of selective auditory attention on cortical response variability with development. Although all three age groups have equivalent response variability to attended speech, only school-aged children and adults have a distinction between attend and ignore conditions. Preschoolers, on the other hand, demonstrate no impact of attention on cortical responses, which we argue reflects the gradual emergence of attention within this age range. Outcomes are interpreted in the context of the behavioral relevance of cortical response variability and its potential to serve as a developmental index of cognitive skill.

Atypical vertical sound localization and sound-onset sensitivity in people with autism spectrum disorders.

Autism spectrum disorders (ASDs) are associated with auditory hyper- or hyposensitivity; atypicalities in central auditory processes, such as speech-processing and selective auditory attention; and neural connectivity deficits. We sought to investigate whether the low-level integrative processes underlying sound localization and spatial discrimination are affected in ASDs. We performed 3 behavioural experiments to probe different connecting neural pathways: 1) horizontal and vertical localization of auditory stimuli in a noisy background, 2) vertical localization of repetitive frequency sweeps and 3) discrimination of horizontally separated sound stimuli with a short onset difference (precedence effect). Ten adult participants with ASDs and 10 healthy control listeners participated in experiments 1 and 3; sample sizes for experiment 2 were 18 adults with ASDs and 19 controls. Horizontal localization was unaffected, but vertical localization performance was significantly worse in participants with ASDs. The temporal window for the precedence effect was shorter in participants with ASDs than in controls. The study was performed with adult participants and hence does not provide insight into the developmental aspects of auditory processing in individuals with ASDs. Changes in low-level auditory processing could underlie degraded performance in vertical localization, which would be in agreement with recently reported changes in the neuroanatomy of the auditory brainstem in individuals with ASDs. The results are further discussed in the context of theories about abnormal brain connectivity in individuals with ASDs.

Factors Influencing Individual Variation in Perceptual Directional Microphone Benefit

Large variations in perceptual directional microphone benefit, which far exceed the variation expected from physical performance measures of directional microphones, have been reported in the literature. The cause for the individual variation has not been systematically investigated. To determine the factors that are responsible for the individual variation in reported perceptual directional benefit. A correlational study. Physical performance measures of the directional microphones obtained after they had been fitted to individuals, cognitive abilities of individuals, and measurement errors were related to perceptual directional benefit scores. Fifty-nine hearing-impaired adults with varied degrees of hearing loss participated in the study. All participants were bilaterally fitted with a Motion behind-the-ear device (500 M, 501 SX, or 501 P) from Siemens according to the National Acoustic Laboratories' non-linear prescription, version two (NAL-NL2). Using the Bamford-Kowal-Bench (BKB) sentences, the perceptual directional benefit was obtained as the difference in speech reception threshold measured in babble noise (SRTn) with the devices in directional (fixed hypercardioid) and in omnidirectional mode. The SRTn measurements were repeated three times with each microphone mode. Physical performance measures of the directional microphone included the angle of the microphone ports to loudspeaker axis, the frequency range dominated by amplified sound, the in situ signal-to-noise ratio (SNR), and the in situ three-dimensional, articulation-index weighted directivity index (3D AI-DI). The cognitive tests included auditory selective attention, speed of processing, and working memory. Intraparticipant variation on the repeated SRTn's and the interparticipant variation on the average SRTn were used to determine the effect of measurement error. A multiple regression analysis was used to determine the effect of other factors. Measurement errors explained 52% of the variation in perceptual directional microphone benefit (95% confidence interval [CI]: 34-78%), while another 37% of variation was explained primarily by the physical performance of the directional microphones after they were fitted to individuals. The most contributing factor was the in situ 3D AI-DI measured across the low frequencies. Repeated SRTn measurements are needed to obtain a reliable indication of the perceptual directional benefit in an individual. Further, to obtain optimum benefit from directional microphones, the effectiveness of the microphones should be maximized across the low frequencies.