Auditory Localization Task Research Articles

The relationship between sustained hamstring pain and reorganisation of somatosensory representations: a randomised, controlled study.

Recurrent hamstring injuries are highly prevalent amongst sporting populations. It has been hypothesised that pain from an initial hamstring injury may induce reorganisation of somatosensory representations that could contribute to reinjury. However, because of the cross-sectional nature of existing research, it remains unknown whether somatosensory changes are a cause or effect of pain or if they are driven by other potentially confounding factors. Here, we explored the effect of experimentally induced sustained hamstring pain on tasks that interrogate somatosensory and spatial representations. Fifty healthy participants were randomly allocated to an experimental group that performed an eccentric exercise protocol on the right hamstring to induce delayed onset muscle soreness or a control group performing a repetition-matched concentric exercise protocol. The tactile cortical representation was assessed using two-point discrimination and tactile localisation, whereas the proprioceptive representation was assessed using a left-right judgement task. Peripersonal spatial representations were assessed using an auditory localisation task. Assessments were performed at baseline and day 2. No between-group differences in tactile acuity were observed. However, improvements in left-right judgments and worsening of auditory localisation occurred in the experimental group compared with the control group. This study provides preliminary evidence showing that somatosensory changes occur in response to sustained hamstring pain. Experimentally induced, sustained hamstring pain elicited enhancements in proprioceptive processing and deficits in peripersonal spatial processing, suggesting a shift in the allocation of attentional resources from the external (peripersonal) to internal (body) environment. These findings may hold important implications for reinjury risk and rehabilitation following hamstring pain.

No effect of 10-week training in click-based echolocation on auditory localization in people who are blind

What factors are important in the calibration of mental representations of auditory space? A substantial body of research investigating the audiospatial abilities of people who are blind has shown that visual experience might be an important factor for accurate performance in some audiospatial tasks. Yet, it has also been shown that long-term experience using click-based echolocation might play a similar role, with blind expert echolocators demonstrating auditory localization abilities that are superior to those of people who are blind and who do not use click-based echolocation by Vercillo et al. (Neuropsychologia 67: 35–40, 2015). Based on this hypothesis we might predict that training in click-based echolocation may lead to improvement in performance in auditory localization tasks in people who are blind. Here we investigated this hypothesis in a sample of 12 adult people who have been blind from birth. We did not find evidence for an improvement in performance in auditory localization after 10 weeks of training despite significant improvement in echolocation ability. It is possible that longer-term experience with click-based echolocation is required for effects to develop, or that other factors can explain the association between echolocation expertise and superior auditory localization. Considering the practical relevance of click-based echolocation for people who are visually impaired, future research should address these questions.

The association between audio-visual spatial integration and hallucinations in Schizophrenia

It has been suggested that patients with schizophrenia (SZs) show impairment in multisensory integration (De Gelder et al., 2003; Stevenson et al., 2017; Williams et al., 2010). A work in our group examined the audio-visual temporal integration with sound-induced flash illusion and found a lengthened temporal binding window for the bisensory information in SZs (Kim et al., IMRF 2017). The present study investigated the audio-visual spatial integration in schizophrenia by using the ventriloquist illusion paradigm. Ventriloquist illusion indicates biased perception of the spatial position of an auditory stimulus toward the position of a temporally synchronized visual stimulus. A group of 22 SZs and a group of 22 healthy controls performed an auditory localization task when a beep sounded with or without a synchronized LED flash. Eight loudspeakers with attached LEDs were arranged in a semicircular array, half of which were on the left, and the other half were on the right side of the central fixation LED. Each loudspeaker was 14-deg away from its adjacent one. The audio-visual stimuli were presented 0-deg, 14-deg or 28-deg apart. The ventriloquist effect was defined as the ratio of biased sound localization towards the visual stimulus to the spatial disparity between audio-visual stimuli. Following the experiment, SZs were given a structured psychiatric interview to assess the severity of positive and negative symptoms with SAPS and SANS respectively. Results showed a typical ventriloquist effect in both groups with no statistically significant difference. However, in SZs, the ventriloquist effect showed a negative correlation with the severity of visual hallucinations, and a marginally significant negative correlation with the global ratings of hallucinations. There was no correlation between hallucinations and unisensory auditory localization performance. These results demonstrate that hallucinations were implicated in reduced audio-visual spatial integration, which might be related to impaired multisensory processing, not unisensory processing.

Auditory processing in schizophrenia: Behavioural evidence of abnormal spatial awareness

ABSTRACT Spatial processing deficits are the reason for many daily life problems of schizophrenia (SCZ) patients. In this study, we aimed to examine the possibility of abnormal bias to one hemifield, in form of hemispatial neglect and extinction, in auditory modality in SCZ. Twenty-five SCZ patients and 25 healthy individuals were compared on speech tasks to study the auditory neglect and extinction, as well as an auditory localization task for studying neglect. In the speech tasks, participants reproduced some nonsense syllables, played from one or two speakers on the right and/or left sides. On the localization task, examinees discriminated the subjective location of the noise stimuli presented randomly from five speakers. On the speech task, patients had significantly lower hit rates for the right ear compared with controls (p = 0.01). While healthy controls showed right ear advantage, SCZs showed a left ear priority. In the localization task, although both groups had a left-side bias, this bias was much more prominent for the patients (all p < 0.05). SCZ could potentially alter the auditory spatial function, which may appear in the form of auditory neglect and extinction on the right side, depending on the characteristics of patient population.

A Polarity Alignment Method for Group-Averaging of Event-Related Neural Signals at Source Level in MEG Beamforming Applications.

Brain waveforms reconstructed at source level, like in beamforming, suffer polarity indeterminacy, which precludes direct group averaging of associated waveforms. We describe a polarity alignment method as an alternative of averaging rectified (i.e. absolute value) waveforms. Using MEG from an auditory localisation task, we compare the ability of the two approaches to enable signal detection in the primary auditory cortex over increasing sample size. The two methods are comparable in signal detection sensitivity, but the alignment method preserves group-average polarity alternation.

Superior side sound localisation performance in a full-chassis driving simulator

Alerts presented through the auditory modality improve drivers’ crash avoidance performance in driving simulations, but drivers’ ability to accurately localise the source of the auditory alerts is understudied. Because the results of driving simulation studies may hinge on assumptions that sound locations are accurately perceived by drivers, this study used a sound localisation task in a full-chassis driving simulator. Twenty-nine participants engaged in a sound localisation task while seated in the driving simulator. Performance was assessed by sound localisation accuracy, relative directional error, and participant confidence across seven sound sources surrounding the simulator. Performance was best when sounds were presented in left and right cardinal regions, and poorest when presented from the front and rear. Participants were less confident in their localisation judgments when sounds were presented from the rear. Practitioner summary: Drivers’ ability to accurately localise auditory alerts is understudied. Participants performed an auditory localisation task with external sounds while seated in a full-chassis driving simulator. Participants were better detecting sounds from the sides instead of the front and rear. This has implications for external auditory alarms during driving. Abbreviations: ANOVA: analysis of variance; dB: decibel; f: frequency; Hz: hertz; LHD: left hand drive; ms: milliseconds; RTI: realtime technologies; s: seconds; SPL: sound pressure level

The Effects of Blast-Related Neurotrauma on Aurally Aided Visual Search While Standing and Walking.

Service members (SMs) who have suffered mild traumatic brain injury due to blast exposure (b/TBI) often report post-concussive symptoms consistent with auditory, visual, or vestibular impairments even when they score within the normal range on traditional clinical tests of sensory function. One possible explanation for this discrepancy is that patients who score in the low normal range in more than one sensory modality may be severely impaired in tasks that require multisensory integration. This study evaluated unimodal and multimodal sensory performance in SMs with b/TBI and healthy controls by having them conduct four tasks while walking or standing in an immersive virtual environment: an Auditory Localization task (AL) where they moved a cursor to the perceived location of a sound; a Visual Discrimination task (VD) where they distinguished between two visual targets; an Aurally-Aided Visual Search Task (AAVS) where they used an auditory cue to locate and identify a visual target hidden in a field of visual distractors; and a Visual-Only Visual Search task (VOVS) where they located and identified a visual target in a field of distractors with no auditory cue. The results show the b/TBI and healthy control groups performed equivalently in the AL and VD tasks, but that the b/TBI group responded roughly 15% slower in the AAVS task and 50% slower in the VOVS task. Walking had no effect on performance in the visual-only tasks, but both groups responded faster while walking in the AL and AAVS tasks without any reduction in accuracy.

The Effect of Walking on Auditory Localization, Visual Discrimination, and Aurally Aided Visual Search.

The present study was designed to examine the impact that walking has on performance in auditory localization, visual discrimination, and aurally aided visual search tasks. Auditory localization and visual search are critical skills that are frequently conducted by moving observers, but most laboratory studies of these tasks have been conducted on stationary listeners who were either seated or standing during stimulus presentation. Thirty participants completed three different tasks while either standing still or while walking at a comfortable self-selected pace on a treadmill: (1) an auditory localization task, where they identified the perceived location of a target sound; (2) a visual discrimination task, where they identified a visual target presented at a known location directly in front of the listener; and (3) an aurally aided visual search task, where they identified a visual target that was presented in the presence of multiple visual distracters either in isolation or in conjunction with a spatially colocated auditory cue. Participants who were walking performed auditory localization and aurally aided visual search tasks significantly faster than those who were standing, with no loss in accuracy. The improved aurally aided visual search performance found in this experiment may be related to enhanced overall activation caused by walking. It is also possible that the slight head movements required may have provided auditory cues that enhanced localization accuracy. The results have potential applications in virtual and augmented reality displays where audio cues might be presented to listeners while walking.

Effects of noise exposure on young adults with normal audiograms II: Behavioral measures

An estimate of lifetime noise exposure was used as the primary predictor of performance on a range of behavioral tasks: frequency and intensity difference limens, amplitude modulation detection, interaural phase discrimination, the digit triplet speech test, the co-ordinate response speech measure, an auditory localization task, a musical consonance task and a subjective report of hearing ability. One hundred and thirty-eight participants (81 females) aged 18–36 years were tested, with a wide range of self-reported noise exposure. All had normal pure-tone audiograms up to 8 kHz. It was predicted that increased lifetime noise exposure, which we assume to be concordant with noise-induced cochlear synaptopathy, would elevate behavioral thresholds, in particular for stimuli with high levels in a high spectral region. However, the results showed little effect of noise exposure on performance. There were a number of weak relations with noise exposure across the test battery, although many of these were in the opposite direction to the predictions, and none were statistically significant after correction for multiple comparisons. There were also no strong correlations between electrophysiological measures of synaptopathy published previously and the behavioral measures reported here. Consistent with our previous electrophysiological results, the present results provide no evidence that noise exposure is related to significant perceptual deficits in young listeners with normal audiometric hearing. It is possible that the effects of noise-induced cochlear synaptopathy are only measurable in humans with extreme noise exposures, and that these effects always co-occur with a loss of audiometric sensitivity.

The open virtual auditory-localization environment: Towards a common methodology for objectively evaluating head-related transfer function personalization methods

Despite the fact that individualized head-related transfer functions (HRTFs) are critical for achieving high-fidelity virtual audio representation, the techniques for measuring them, which have been around for decades, are too costly for most potential users. As such, many strategies have been proposed that aim to improve virtual audio fidelity by personalizing a non-individualized HRTF based on input (or anthropometric information) from the user. Unfortunately, evaluations of these methodologies have varied widely from purely computational to purely subjective, making comparisons across studies or to objective behavioral performance metrics difficult. The current work presents the Open Virtual Auditory-Localization Environment (OpenVALE), a software toolkit for providing a common, objective, HRTF-based auditory localization task via new, relatively low-cost, commercial VR headsets. The heart of OpenVALE is a server application that allows researchers to dynamically load custom HRTFs, present spatialized auditory stimuli, collect hand- or head-slaved, cursor-based localization responses, and provide visual feedback, all through simple string-based IP socket messages from any compatible client application (e.g., Matlab, Java, Python, etc.). An initial validation of the task environment, based on individualized HRTF measurements, will be described along with a discussion of the remaining challenges for creating an accepted standard methodology.

The Impact of Early Visual Deprivation on Spatial Hearing: A Comparison between Totally and Partially Visually Deprived Children.

The specific role of early visual deprivation on spatial hearing is still unclear, mainly due to the difficulty of comparing similar spatial skills at different ages and to the difficulty in recruiting young blind children from birth. In this study, the effects of early visual deprivation on the development of auditory spatial localization have been assessed in a group of seven 3–5 years old children with congenital blindness (n = 2; light perception or no perception of light) or low vision (n = 5; visual acuity range 1.1–1.7 LogMAR), with the main aim to understand if visual experience is fundamental to the development of specific spatial skills. Our study led to three main findings: firstly, totally blind children performed overall more poorly compared sighted and low vision children in all the spatial tasks performed; secondly, low vision children performed equally or better than sighted children in the same auditory spatial tasks; thirdly, higher residual levels of visual acuity are positively correlated with better spatial performance in the dynamic condition of the auditory localization task indicating that the more residual vision the better spatial performance. These results suggest that early visual experience has an important role in the development of spatial cognition, even when the visual input during the critical period of visual calibration is partially degraded like in the case of low vision children. Overall these results shed light on the importance of early assessment of spatial impairments in visually impaired children and early intervention to prevent the risk of isolation and social exclusion.

Comparison of congruence judgment and auditory localization tasks for assessing the spatial limits of visual capture.

Vision typically has better spatial accuracy and precision than audition and as a result often captures auditory spatial perception when visual and auditory cues are presented together. One determinant of visual capture is the amount of spatial disparity between auditory and visual cues: when disparity is small, visual capture is likely to occur, and when disparity is large, visual capture is unlikely. Previous experiments have used two methods to probe how visual capture varies with spatial disparity. First, congruence judgment assesses perceived unity between cues by having subjects report whether or not auditory and visual targets came from the same location. Second, auditory localization assesses the graded influence of vision on auditory spatial perception by having subjects point to the remembered location of an auditory target presented with a visual target. Previous research has shown that when both tasks are performed concurrently they produce similar measures of visual capture, but this may not hold when tasks are performed independently. Here, subjects alternated between tasks independently across three sessions. A Bayesian inference model of visual capture was used to estimate perceptual parameters for each session, which were compared across tasks. Results demonstrated that the range of audiovisual disparities over which visual capture was likely to occur was narrower in auditory localization than in congruence judgment, which the model indicates was caused by subjects adjusting their prior expectation that targets originated from the same location in a task-dependent manner.

Brain stem auditory evoked potentials in normal and congenitally blind individuals

Background: Understanding the effects of visual loss on remaining senses has been a matter of interest since long. Neuroplasticity in the form of cross-modal plasticity occurs to compensate for the loss of function and to enhance remaining functions in the event of sensory deprivation. In congenitally blind individuals, auditory localization tasks can activate the visual cortex. Studies have shown that blind subjects perform as well or even better than normal controls with auditory stimuli. Objectives: To compare the auditory evoked potentials in congenitally blind individuals with those of normal subjects so as to look for any compensatory increased activity in auditory functions. Materials and Methods: Auditory evoked potentials were recorded in 33 normal subjects and 37 congenitally blind subjects using a single fiber electromyography. Recording was done in both ears by giving clicks into test ear. Latencies, amplitudes, and waveforms were recorded. Result: A significant decrease (p < 0.05) in latencies of left I and V wave was seen both ipsilateral and contralateral. One-way ANOVA showed a significant difference in the mean between the two groups. Conclusion: A compensatory neural reorganization may occur in blind individuals which may be influenced by corticofugal connections with the auditory system.

Effect of stimulus intensity on response time distribution in multisensory integration

To increase the efficiency of multimodal user interfaces, one has to design them according to how multimodal features appear in the real world. Although spatial coincidence and matching intensity levels are important for perception, these factors received little attention in human–computer interaction studies. In our present study we aimed to map how spatial coincidence and different intensity levels influence response times. Sixteen participants performed a simple auditory localization task, where sounds were presented either alone or together with visual non-targets. We found that medium intensity visual stimuli facilitated responses to low intensity sounds. Analyses of response time distributions showed that intensity of target and non-target stimuli affected different parameters of the ex-Gaussian distribution. Our results suggest that multisensory integration and response facilitation may occur even if the non-target has low predictive power to the location of the target. Furthermore, we show that the parameters of the ex-Gaussian distribution can be related to distinct cognitive processes. The current results are potentially applicable in the design of an intelligent warning system that employs the user’s reaction time to adapt the warning signal for optimal results.

Touch the sound: The role of audio-tactile and audio-proprioceptive interaction on the spatial orientation in virtual scenes

Being able to localize objects in the space close to the body is an important prerequisite for precise object interaction. It is also very important for the spatial orientation in virtual scenes. Since sound is usually produced by the vibrations of a body, sound emitting objects, such as shaver or hair dryer, provide both auditory and haptic information. This study focuses on auditory-haptic localization in the spatial domain. We carried out two experiments to investigate the interaction effects. In the first experiment, the influence of tactile signals on auditory localization task was investigated. Similar to the ventriloquist effect from auditory-visual interaction, the results of the first experiment show that the perceived location of auditory stimuli is influenced by tactile stimulation. The results also indicate some hints that there may be an audiotactile precedence effect. In the second experiment, the influence of auditory signals on proprioception was investigated. The results show that the auditory and proprioceptive information can be combined in such a way that the localization errors in a virtual scene are minimized.

Neural correlates of sound externalization

When we listen to sounds through headphones without utilizing special transforms, sound sources seem to be located inside our heads. The sound sources are said to be lateralized to one side or the other to varying degree. This internal lateralization is different than sound source localization in the natural environment in which the sound is localized distal to the head. We used fMRI to investigate difference in neural responses between lateralization and localization. Individualized binaural recordings were used as externalized auditory stimuli and stereo recordings were used as internalized auditory stimuli. Brain activity was measured while 14 participants performed an active auditory localization task and while 12 participants performed a stimulus type identification task. Irrespective of the task condition, we observed enhanced activity in the bilateral posterior temporal gyri (pSTG) for the externalized stimuli relative to the internalized stimuli. Region of interest analysis indicated that both left and right pSTG were more sensitive to sound sources in contra- than ipsilateral hemifields. Moreover, greater back than front activity was also found in the left pSTG. Compared to impoverished spatial auditory stimuli, realistic spatial auditory stimuli enhance neural responses in the pSTG. This may be why we could observe contralateral hemifield preference in bilateral pSTG that many previous studies have failed to observe. Overall, the results indicate the importance of using ecologically valid stimuli for investigating neural processes in human cortex.

Event-related responses and rhythmic activity of the human brain during auditory localization task

Event-related responses and rhythmic activity of the human brain during auditory localization task

Independent mechanisms for ventriloquism and multisensory integration as revealed by theta‐burst stimulation

The visual and auditory systems often concur to create a unified perceptual experience and to determine the localization of objects in the external world. Co-occurring auditory and visual stimuli in spatial coincidence are known to enhance performance of auditory localization due to the integration of stimuli from different sensory channels (i.e. multisensory integration). However, auditory localization of audiovisual stimuli presented at spatial disparity might also induce a mislocalization of the sound towards the visual stimulus (i.e. ventriloquism effect). Using repetitive transcranial magnetic stimulation we tested the role of right temporoparietal (rTPC), right occipital (rOC) and right posterior parietal (rPPC) cortex in an auditory localization task in which indices of ventriloquism and multisensory integration were computed. We found that suppression of rTPC excitability by means of continuous theta-burst stimulation (cTBS) reduced multisensory integration. No similar effect was found for cTBS over rOC. Moreover, inhibition of rOC, but not of rTPC, suppressed the visual bias in the contralateral hemifield. In contrast, cTBS over rPPC did not produce any modulation of ventriloquism or integrative effects. The double dissociation found in the present study suggests that ventriloquism and audiovisual multisensory integration are functionally independent phenomena and may be underpinned by partially different neural circuits.

Concurrent sound segregation based on inharmonicity and onset asynchrony

To explore the neural processes underlying concurrent sound segregation, auditory evoked fields (AEFs) were measured using magnetoencephalography (MEG). To induce the segregation of two auditory objects we manipulated harmonicity and onset synchrony. Participants were presented with complex sounds with (i) all harmonics in-tune (ii) the third harmonic mistuned by 8% of its original value (iii) the onset of the third harmonic delayed by 160ms compared to the other harmonics. During recording, participants listened to the sounds and performed an auditory localisation task whereas in another session they ignored the sounds and performed a visual localisation task. Active and passive listening was chosen to evaluate the contribution of attention on sound segregation. Both cues – inharmonicity and onset asynchrony – elicited sound segregation, as participants were more likely to report correctly on which side they heard the third harmonic when it was mistuned or delayed compared to being in-tune with all other harmonics. AEF activity associated with concurrent sound segregation was identified over both temporal lobes. We found an early deflection at ∼75ms (P75m) after sound onset, probably reflecting an automatic registration of the mistuned harmonic. Subsequent deflections, the object-related negativity (ORNm) and a later displacement (P230m) seem to be more general markers of concurrent sound segregation, as they were elicited by both mistuning and delaying the third harmonic. Results indicate that the ORNm reflects relatively automatic, bottom-up sound segregation processes, whereas the P230m is more sensitive to attention, especially with inharmonicity as the cue for concurrent sound segregation.

Repetitive transcranial magnetic stimulation over frontal eye fields disrupts visually cued auditory attention

Voluntary eye movements and covert shifts of visual attention activate the same brain regions. Specifically, the intraparietal sulcus and the frontal eye fields (FEF) appear to be involved both with generating voluntary saccades as well with attending to a peripheral spatial location. Furthermore, these regions appear to be required by both tasks--functional disruption of these regions impairs both tasks. Therefore, it appears that the targeting system that allows us to plan saccades is the same system that allows us to covertly track peripheral visual information. Recent neuroimaging studies suggest that these brain regions are also activated when participants engage in auditory spatial attention tasks. However, it remains unclear whether these regions are required by these tasks. We used repetitive transcranial magnetic stimulation (rTMS) to disrupt the FEF while participants performed an auditory localization task. On each trial, a visual cue directed attention to the probable laterality of the auditory target, and the participant decided whether the subsequent target sound came from an upper or lower speaker. In the absence of TMS, individuals were faster to respond to targets that occurred on the cued side (valid trials) than when the target appears contralaterally to the cued side (invalid side). TMS interfered with this effect, such that the costs associated with ipsilateral invalidly cued targets were substantially reduced. These results suggest that the eye-movement system is needed for normal auditory attention.