Spatial Selective Auditory Attention Research Articles

Spatial selective auditory attention is preserved in older age but is degraded by peripheral hearing loss

Interest in how ageing affects attention is long-standing, although interactions between sensory and attentional processing in older age are not fully understood. Here, we examined interactions between peripheral hearing and selective attention in a spatialised cocktail party listening paradigm, in which three talkers spoke different sentences simultaneously and participants were asked to report the sentence spoken by a talker at a particular location. By comparing a sample of older (N = 61; age = 55–80 years) and younger (N = 58; age = 18–35 years) adults, we show that, as a group, older adults benefit as much as younger adults from preparatory spatial attention. Although, for older adults, this benefit significantly reduces with greater age-related hearing loss. These results demonstrate that older adults with excellent hearing retain the ability to direct spatial selective attention, but this ability deteriorates, in a graded manner, with age-related hearing loss. Thus, reductions in spatial selective attention likely contribute to difficulties communicating in social settings for older adults with age-related hearing loss. Overall, these findings demonstrate a relationship between mild perceptual decline and attention in older age.

Brain Network Interconnectivity Dynamics Explain Metacognitive Differences in Listening Behavior.

Complex auditory scenes pose a challenge to attentive listening, rendering listeners slower and more uncertain in their perceptual decisions. How can we explain such behaviors from the dynamics of cortical networks that pertain to the control of listening behavior? We here follow up on the hypothesis that human adaptive perception in challenging listening situations is supported by modular reconfiguration of auditory-control networks in a sample of N = 40 participants (13 males) who underwent resting-state and task functional magnetic resonance imaging (fMRI). Individual titration of a spatial selective auditory attention task maintained an average accuracy of ∼70% but yielded considerable interindividual differences in listeners' response speed and reported confidence in their own perceptual decisions. Whole-brain network modularity increased from rest to task by reconfiguring auditory, cinguloopercular, and dorsal attention networks. Specifically, interconnectivity between the auditory network and cinguloopercular network decreased during the task relative to the resting state. Additionally, interconnectivity between the dorsal attention network and cinguloopercular network increased. These interconnectivity dynamics were predictive of individual differences in response confidence, the degree of which was more pronounced after incorrect judgments. Our findings uncover the behavioral relevance of functional cross talk between auditory and attentional-control networks during metacognitive assessment of one's own perception in challenging listening situations and suggest two functionally dissociable cortical networked systems that shape the considerable metacognitive differences between individuals in adaptive listening behavior.

The Spatial Selective Auditory Attention of Cochlear Implant Users in Different Conversational Sound Levels.

In multi-speaker environments, cochlear implant (CI) users may attend to a target sound source in a different manner from normal hearing (NH) individuals during a conversation. This study attempted to investigate the effect of conversational sound levels on the mechanisms adopted by CI and NH listeners in selective auditory attention and how it affects their daily conversation. Nine CI users (five bilateral, three unilateral, and one bimodal) and eight NH listeners participated in this study. The behavioral speech recognition scores were collected using a matrix sentences test, and neural tracking to speech envelope was recorded using electroencephalography (EEG). Speech stimuli were presented at three different levels (75, 65, and 55 dB SPL) in the presence of two maskers from three spatially separated speakers. Different combinations of assisted/impaired hearing modes were evaluated for CI users, and the outcomes were analyzed in three categories: electric hearing only, acoustic hearing only, and electric + acoustic hearing. Our results showed that increasing the conversational sound level degraded the selective auditory attention in electrical hearing. On the other hand, increasing the sound level improved the selective auditory attention for the acoustic hearing group. In the NH listeners, however, increasing the sound level did not cause a significant change in the auditory attention. Our result implies that the effect of the sound level on selective auditory attention varies depending on the hearing modes, and the loudness control is necessary for the ease of attending to the conversation by CI users.

Weak neural signatures of spatial selective auditory attention in hearing-impaired listeners.

Spatial attention may be used to select target speech in one location while suppressing irrelevant speech in another. However, if perceptual resolution of spatial cues is weak, spatially focused attention may work poorly, leading to difficulty communicating in noisy settings. In electroencephalography (EEG), the distribution of alpha (8–14 Hz) power over parietal sensors reflects the spatial focus of attention [Banerjee, Snyder, Molholm, and Foxe (2011). J. Neurosci. 31, 9923–9932; Foxe and Snyder (2011). Front. Psychol. 2, 154.] If spatial attention is degraded, however, alpha may not be modulated across parietal sensors. A previously published behavioral and EEG study found that, compared to normal-hearing (NH) listeners, hearing-impaired (HI) listeners often had higher interaural time difference thresholds, worse performance when asked to report the content of an acoustic stream from a particular location, and weaker attentional modulation of neural responses evoked by sounds in a mixture [Dai, Best, and Shinn-Cunningham (2018). Proc. Natl. Acad. Sci. U. S. A. 115, E3286]. This study explored whether these same HI listeners also showed weaker alpha lateralization during the previously reported task. In NH listeners, hemispheric parietal alpha power was greater when the ipsilateral location was attended; this lateralization was stronger when competing melodies were separated by a larger spatial difference. In HI listeners, however, alpha was not lateralized across parietal sensors, consistent with a degraded ability to use spatial features to selectively attend.

Updating of spatial selective auditory attention under-compensates for listener head movement

Listeners can use spatial selective auditory attention (SSAA) to focus on one talker in a complex acoustic scene. In our dynamic SSAA task, listeners oscillate their heads ~±40 deg at ~0.5 Hz while five different simultaneous sequences of four spoken digits are presented from loudspeakers at 0 deg azimuth (the target) and ±22.5 deg and ±45 deg azimuth (four distractors); listeners report the target sequence heard. We have observed [ASA, Minneapolis 2018] that listeners are more likely to misreport distractors that are centrally located in head-centered coordinates at the moment of presentation, and that under static conditions, performance declines with increasing target eccentricity—suggesting either that listeners cannot rapidly update the focus of their SSAA to compensate head motion (“lag” ) or that they have difficulty directing SSAA eccentrically (“low gain” ). To differentiate these alternatives, spatio-temporal maps of SSAA, conditioned on head orientation and direction of motion during each digit, were derived by computing the percentage of reported digits corresponding to those emitted by each loudspeaker. The spatial pattern of errors depended primarily on head orientation and not on direction of motion, suggesting that in this task SSAA tends to remain centrally focused in head-centered coordinates (low gain) rather than lagging dynamic head position.

Sensorineural hearing loss degrades behavioral and physiological measures of human spatial selective auditory attention

Listeners with sensorineural hearing loss often have trouble understanding speech amid other voices. While poor spatial hearing is often implicated, direct evidence is weak; moreover, studies suggest that reduced audibility and degraded spectrotemporal coding may explain such problems. We hypothesized that poor spatial acuity leads to difficulty deploying selective attention, which normally filters out distracting sounds. In listeners with normal hearing, selective attention causes changes in the neural responses evoked by competing sounds, which can be used to quantify the effectiveness of attentional control. Here, we used behavior and electroencephalography to explore whether control of selective auditory attention is degraded in hearing-impaired (HI) listeners. Normal-hearing (NH) and HI listeners identified a simple melody presented simultaneously with two competing melodies, each simulated from different lateral angles. We quantified performance and attentional modulation of cortical responses evoked by these competing streams. Compared with NH listeners, HI listeners had poorer sensitivity to spatial cues, performed more poorly on the selective attention task, and showed less robust attentional modulation of cortical responses. Moreover, across NH and HI individuals, these measures were correlated. While both groups showed cortical suppression of distracting streams, this modulation was weaker in HI listeners, especially when attending to a target at midline, surrounded by competing streams. These findings suggest that hearing loss interferes with the ability to filter out sound sources based on location, contributing to communication difficulties in social situations. These findings also have implications for technologies aiming to use neural signals to guide hearing aid processing.

Effects of vision, listener head movement, and target location on spatial selective auditory attention

Listeners can use spatial selective auditory attention (SSAA) to focus on one talker in a complex acoustic scene. We have reported [Macpherson & Ellis, ASA Salt Lake, 2016] that listeners’ ability to attend to a frontal target in the presence of spatially separated distractors is decreased in a head-movement condition, suggesting that listeners cannot rapidly update the focus of their SSAA to compensate fully for head motion. Participants reported anecdotally that being able to see the target loudspeaker seemed beneficial in directing SSAA. Here, we assessed the benefit of access to a visual reference frame in a similar task. Under lighted and dark conditions, on each trial, listeners either fixated toward 0 azimuth or oscillated their heads at ~0.5 Hz with an amplitude of ~±40 degrees while five different simultaneous equal-intensity sequences of four spoken digits were presented as target (at azimuths from 0 to 90 degrees) and four distractors (at azimuths ±22.5 and ±45 degrees relative to the central target). Listeners verbally reported the target sequence heard. Performance declined under head motion and with increasing target eccentricity, but not additionally in dark conditions, suggesting that a visual reference frame was not beneficial in directing SSAA in our task.Listeners can use spatial selective auditory attention (SSAA) to focus on one talker in a complex acoustic scene. We have reported [Macpherson & Ellis, ASA Salt Lake, 2016] that listeners’ ability to attend to a frontal target in the presence of spatially separated distractors is decreased in a head-movement condition, suggesting that listeners cannot rapidly update the focus of their SSAA to compensate fully for head motion. Participants reported anecdotally that being able to see the target loudspeaker seemed beneficial in directing SSAA. Here, we assessed the benefit of access to a visual reference frame in a similar task. Under lighted and dark conditions, on each trial, listeners either fixated toward 0 azimuth or oscillated their heads at ~0.5 Hz with an amplitude of ~±40 degrees while five different simultaneous equal-intensity sequences of four spoken digits were presented as target (at azimuths from 0 to 90 degrees) and four distractors (at azimuths ±22.5 and ±45 degrees relative to the central t...

Listener head motion can degrade spatial selective auditory attention

Listeners can use spatial selective auditory attention (SSAA) to focus on one talker in a complex acoustic scene. Although the dynamic binaural cues generated by listener head motion improve sound localization, and might therefore enhance the perceptual differences between separated targets and distractors, the effect of head motion on SSAA is unknown. We measured listeners’ ability to attend, with and without head motion, to a frontal target in the presence of two symmetrically separated distractors. During stationary trials, listeners visually fixated and oriented toward a target loudspeaker. On head-motion trials, listeners oscillated their heads at ~0.5 Hz with an amplitude of ~±40° while continuously directing their gaze toward the target. On each trial, three equal-intensity sequences of four spoken digits were presented simultaneously as target and distractors. Listeners reported the target sequence heard. With distractors at ±22.5°, 86% of target digits were reported correctly without motion, but only 72% were reported correctly with head motion. Correspondingly, the percentage of distractor digits reported as targets increased from 11% to 23%. For widely separated distractors, there was no performance penalty for head motion. These results suggest that listeners cannot rapidly update the focus of their SSAA to compensate for head motion.

Effects of dynamic range compression on spatial selective auditory attention in normal-hearing listeners

Many hearing aids introduce compressive gain to accommodate the reduced dynamic range that often accompanies hearing loss. However, natural sounds produce complicated temporal dynamics in hearing aid compression, as gain is driven by whichever source dominates at a given moment. Moreover, independent compression at the two ears can introduce fluctuations in interaural level differences (ILDs) important for spatial perception. While independent compression can interfere with spatial perception of sound, it does not always interfere with localization accuracy or speech identification. Here, normal-hearing listeners reported a target message played simultaneously with two spatially separated masker messages. We measured the amount of spatial separation required between the target and maskers for subjects to perform at threshold in this task. Fast, syllabic compression that was independent at the two ears increased the required spatial separation, but linking the compressors to provide identical gain to both ears (preserving ILDs) restored much of the deficit caused by fast, independent compression. Effects were less clear for slower compression. Percent-correct performance was lower with independent compression, but only for small spatial separations. These results may help explain differences in previous reports of the effect of compression on spatial perception of sound.

Normal hearing is not enough to guarantee robust encoding of suprathreshold features important in everyday communication

"Normal hearing" is typically defined by threshold audibility, even though everyday communication relies on extracting key features of easily audible sound, not on sound detection. Anecdotally, many normal-hearing listeners report difficulty communicating in settings where there are competing sound sources, but the reasons for such difficulties are debated: Do these difficulties originate from deficits in cognitive processing, or differences in peripheral, sensory encoding? Here we show that listeners with clinically normal thresholds exhibit very large individual differences on a task requiring them to focus spatial selective auditory attention to understand one speech stream when there are similar, competing speech streams coming from other directions. These individual differences in selective auditory attention ability are unrelated to age, reading span (a measure of cognitive function), and minor differences in absolute hearing threshold; however, selective attention ability correlates with the ability to detect simple frequency modulation in a clearly audible tone. Importantly, we also find that selective attention performance correlates with physiological measures of how well the periodic, temporal structure of sounds above the threshold of audibility are encoded in early, subcortical portions of the auditory pathway. These results suggest that the fidelity of early sensory encoding of the temporal structure in suprathreshold sounds influences the ability to communicate in challenging settings. Tests like these may help tease apart how peripheral and central deficits contribute to communication impairments, ultimately leading to new approaches to combat the social isolation that often ensues.

Spatial Selective Auditory Attention in the Presence of Reverberant Energy: Individual Differences in Normal-Hearing Listeners

Listeners can selectively attend to a desired target by directing attention to known target source features, such as location or pitch. Reverberation, however, reduces the reliability of the cues that allow a target source to be segregated and selected from a sound mixture. Given this, it is likely that reverberant energy interferes with selective auditory attention. Anecdotal reports suggest that the ability to focus spatial auditory attention degrades even with early aging, yet there is little evidence that middle-aged listeners have behavioral deficits on tasks requiring selective auditory attention. The current study was designed to look for individual differences in selective attention ability and to see if any such differences correlate with age. Normal-hearing adults, ranging in age from 18 to 55years, were asked to report a stream of digits located directly ahead in a simulated rectangular room. Simultaneous, competing masker digit streams were simulated at locations 15° left and right of center. The level of reverberation was varied to alter task difficulty by interfering with localization cues (increasing localization blur). Overall, performance was best in the anechoic condition and worst in the high-reverberation condition. Listeners nearly always reported a digit from one of the three competing streams, showing that reverberation did not render the digits unintelligible. Importantly, inter-subject differences were extremely large. These differences, however, were not significantly correlated with age, memory span, or hearing status. These results show that listeners with audiometrically normal pure tone thresholds differ in their ability to selectively attend to a desired source, a task important in everyday communication. Further work is necessary to determine if these differences arise from differences in peripheral auditory function or in more central function.

Reverberation and bottom-up cues in spatial selective auditory attention.

Given multiple, competing speech streams, listeners can selectively attend to a desired stream using spatial cues made available by fine timing information arriving at the ears and passing to progressively higher regions of auditory processing. Reverberation smears fine temporal information needed for encoding important spatial cues, which may interfere with the ability to selectively attend to a target from a particular direction. To test this hypothesis, subjects were asked to focus spatial attention toward a location simulated directly in front of them and report a stream of digits from that location while ignoring two masker streams symmetrically positioned at 15 deg left and right. Three levels of reverberation were simulated to measure the influence of reverberant energy on performance. Results show that spatial selective attention degrades as reverberation increases and that overall performance varies dramatically from listener to listener in ways that are not predicted by age or memory span. Performance is highly correlated with absolute sensitivity to frequency modulation. Ongoing studies are exploring whether individual differences in performance on the spatial selection task are predicted by physiological frequency-following responses in the brain stem or by the process of aging.

Reverberation disrupts spatial selective auditory attention.

When there are multiple, competing speech streams, listeners can selectively attend to a desired target using spatial cues like interaural time differences (ITDs). However, reverberation smears fine temporal information needed to encode ITDs. Reverberation may therefore interfere with the ability to selectively attend to a target from a particular direction. Subjects were asked to report a stream of digits simulated to be directly in front of them in the presence of two masker streams symmetrically positioned at 15 deg left and right. Because the maskers were statistically identical to the target (except in direction), listeners had to focus spatial attention on the target while ignoring the masker streams. Three levels of reverberation were simulated using a rectangular room model to measure the influence of reverberation on performance. Initial results showed that spatial selective attention degraded as reverberation increased. However, overall performance varied dramatically from listener to listener in ways that were not predicted by age or memory span. The current study explores whether individual differences are predicted by performance on two discrimination tasks that rely on signal fine temporal structure: frequency modulation (a monaural task) and ITD (a binaural task). [NIDCD, ONR, and NSF provided funding to support this work.]