A Multimodal Investigation of Listening Effort in Single-Sided Deafness.

PURPOSE: For patients with single-sided deafness (SSD), choosing between bone conduction devices (BCDs) and contralateral routing of signal hearing aids (CROS) is challenging due to mixed evidence on their benefits. The lack of clear guidelines complicates clinical decision making. This study explores whether realistic spatial listening measures can reveal a clinically valid benefit and if the optimal choice varies among patients. By assessing listening effort through objective and subjective measures, this research evaluates the efficacy of BCD and CROS, seeking to provide evidence-based recommendation anchored in the effectiveness of these devices in real-world scenarios. METHOD: Thirteen participants with SSD performed the Hearing-in-Noise Test while using a BCD, CROS hearing aids, and no hearing device (unaided). Subjective listening effort was assessed using the National Aeronautics and Space Administration Task Load Index (NASA-TLX) questionnaire after each testing block. An objective measurement of listening effort was obtained by measuring the peak pupil dilation (PPD) during the task using eye tracking glasses. RESULTS: No significant difference of either PPD or NASA-TLX scores was observed between the three device conditions (BCD, CROS, and unaided). However, a trend is noted toward reduced PPD in the BCD and CROS conditions. The lack of significance in pupillometry results does not stem from technical issues, as the study's findings confirm its effectiveness in measuring task difficulty, and validate its use for assessing listening effort. CONCLUSIONS: Although the results from the present study cannot significantly differentiate the hearing devices, we observe a trend that points toward reduced listening effort when using hearing devices. Future investigations should aim to optimize metrics of listening effort, perhaps making them clinically useful on an individual level.

Pupillometry reveals effects of pitch manipulation within and across words on listening effort and short-term memory.

For individuals with hearing loss, even successful speech communication comes at a cost. Cochlear implants transmit degraded information, specifically for voice pitch, which demands extra and sustained listening effort. The current study hypothesized that abnormal pitch patterns contribute to the additional listening effort, even in non-tonal language native speaking normally hearing listeners. We manipulated the fundamental frequency (F0) within and across words, while participants listen and repeat (simple intelligibility task), or listen, repeat, and later recall (concurrent encoding task) the words. In both experiments, the F0 manipulations resulted in small changes in intelligibility but no difference in free recall or subjective effort ratings. Pupillary metrics were yet sensitive to these manipulations: pupil dilations were larger when words were monotonized (flat contour) or inverted (the natural contour flipped upside-down), and larger when successive words were organized into a melodic pattern. The most likely interpretation is that the natural or expected F0 contour of a word contributes to its identity and facilitate its matching and retrieval from the phonological representation stored in long-term memory. Consequently, degrading words' F0 contour can result in extra listening effort. Our results call for solutions to improve pitch saliency and naturalness in future development of cochlear implants' signal processing strategies, even for non-tonal languages.

Differences Between French and English in the Use of Suprasegmental Cues for the Short-Term Recall of Word Lists.

PURPOSE: Greater recognition of the impact of hearing loss on cognitive functions has led speech/hearing clinics to focus more on auditory memory outcomes. Typically evaluated by scoring participants' recall on a list of unrelated words after they have heard the list read out loud, this method implies pitch and timing variations across words. Here, we questioned whether these variations could impact performance differentially in one language or another. METHOD: In a series of online studies evaluating auditory short-term memory in normally hearing adults, we examined how pitch patterns (Experiment 1), timing patterns (Experiment 2), and interactions between the two (Experiment 3) affected free recall of words, cued recall of forgotten words, and mental demand. Note that visual memory was never directly tested; written words were only used after auditory encoding in the cued recall part. Studies were administered in both French and English, always conducted with native listeners. RESULT: Confirming prior work, grouping mechanisms facilitated free recall, but not cued recall (the latter being only affected by longer presentation time) or ratings of mental demand. Critically, grouping by pitch provided more benefit for French than for English listeners, while grouping by time was equally beneficial in both languages. CONCLUSION: Pitch is more useful to French- than to English-speaking listeners for encoding spoken words in short-term memory, perhaps due to the syllable-based versus stress-based rhythms inherent to each language. SUPPLEMENTAL MATERIAL: https://doi.org/10.23641/asha.27048328.

Integrating Emotion Perception in Rehabilitation Programs for Cochlear Implant Users: A Call for a More Comprehensive Approach.

PURPOSE: Postoperative rehabilitation programs for cochlear implant (CI) recipients primarily emphasize enhancing speech perception. However, effective communication in everyday social interactions necessitates consideration of diverse verbal social cues to facilitate language comprehension. Failure to discern emotional expressions may lead to maladjusted social behavior, underscoring the importance of integrating social cues perception into rehabilitation initiatives to enhance CI users' well-being. After conventional rehabilitation, CI users demonstrate varying levels of emotion perception abilities. This disparity notably impacts young CI users, whose emotion perception deficit can extend to social functioning, encompassing coping strategies and social competence, even when relying on nonauditory cues such as facial expressions. Knowing that emotion perception abilities generally decrease with age, acknowledging emotion perception impairments in aging CI users is crucial, especially since a direct correlation between quality-of-life scores and vocal emotion recognition abilities has been observed in adult CI users. After briefly reviewing the scope of CI rehabilitation programs and summarizing the mounting evidence on CI users' emotion perception deficits and their impact, we will present our recommendations for embedding emotional training as part of enriched and standardized evaluation/rehabilitation programs that can improve CI users' social integration and quality of life. CONCLUSIONS: Evaluating all aspects, including emotion perception, in CI rehabilitation programs is crucial because it ensures a comprehensive approach that enhances speech comprehension and the emotional dimension of communication, potentially improving CI users' social interaction and overall well-being. The development of emotion perception training holds promises for CI users and individuals grappling with various forms of hearing loss and sensory deficits. Ultimately, adopting such a comprehensive approach has the potential to significantly elevate the overall quality of life for a broad spectrum of patients.

Improving emotion perception in cochlear implant users: insights from machine learning analysis of EEG signals.

BACKGROUND: Although cochlear implants can restore auditory inputs to deafferented auditory cortices, the quality of the sound signal transmitted to the brain is severely degraded, limiting functional outcomes in terms of speech perception and emotion perception. The latter deficit negatively impacts cochlear implant users' social integration and quality of life; however, emotion perception is not currently part of rehabilitation. Developing rehabilitation programs incorporating emotional cognition requires a deeper understanding of cochlear implant users' residual emotion perception abilities. METHODS: To identify the neural underpinnings of these residual abilities, we investigated whether machine learning techniques could be used to identify emotion-specific patterns of neural activity in cochlear implant users. Using existing electroencephalography data from 22 cochlear implant users, we employed a random forest classifier to establish if we could model and subsequently predict from participants' brain responses the auditory emotions (vocal and musical) presented to them. RESULTS: Our findings suggest that consistent emotion-specific biomarkers exist in cochlear implant users, which could be used to develop effective rehabilitation programs incorporating emotion perception training. CONCLUSIONS: This study highlights the potential of machine learning techniques to improve outcomes for cochlear implant users, particularly in terms of emotion perception.

The Montreal model: an integrative biomedical-psychedelic approach to ketamine for severe treatment-resistant depression.

Background: Subanesthetic ketamine has accumulated meta-analytic evidence for rapid antidepressant effects in treatment-resistant depression (TRD), resulting in both excitement and debate. Many unanswered questions surround ketamine's mechanisms of action and its integration into real-world psychiatric care, resulting in diverse utilizations that variously resemble electroconvulsive therapy, conventional antidepressants, or serotonergic psychedelics. There is thus an unmet need for clinical approaches to ketamine that are tailored to its unique therapeutic properties. Methods: This article presents the Montreal model, a comprehensive biopsychosocial approach to ketamine for severe TRD refined over 6 years in public healthcare settings. To contextualize its development, we review the evidence for ketamine as a biomedical and as a psychedelic treatment of depression, emphasizing each perspectives' strengths, weaknesses, and distinct methods of utilization. We then describe the key clinical experiences and research findings that shaped the model's various components, which are presented in detail. Results: The Montreal model, as implemented in a recent randomized clinical trial, aims to synergistically pair ketamine infusions with conventional and psychedelic biopsychosocial care. Ketamine is broadly conceptualized as a brief intervention that can produce windows of opportunity for enhanced psychiatric care, as well as powerful occasions for psychological growth. The model combines structured psychiatric care and concomitant psychotherapy with six ketamine infusions, administered with psychedelic-inspired nonpharmacological adjuncts including rolling preparative and integrative psychological support. Discussion: Our integrative model aims to bridge the biomedical-psychedelic divide to offer a feasible, flexible, and standardized approach to ketamine for TRD. Our learnings from developing and implementing this psychedelic-inspired model for severe, real-world patients in two academic hospitals may offer valuable insights for the ongoing roll-out of a range of psychedelic therapies. Further research is needed to assess the Montreal model's effectiveness and hypothesized psychological mechanisms.

Grouping by Time and Pitch Facilitates Free but Not Cued Recall for Word Lists in Normally-Hearing Listeners.

Auditory memory is an important everyday skill evaluated more and more frequently in clinical settings as there is recently a greater recognition of the cost of hearing loss to cognitive systems. Testing often involves reading a list of unrelated items aloud; but prosodic variations in pitch and timing across the list can affect the number of items remembered. Here, we ran a series of online studies on normally-hearing participants to provide normative data (with a larger and more diverse population than the typical student sample) on a novel protocol characterizing the effects of suprasegmental properties in speech, namely investigating pitch patterns, fast and slow pacing, and interactions between pitch and time grouping. In addition to free recall, and in line with our desire to work eventually with individuals exhibiting more limited cognitive capacity, we included a cued recall task to help participants recover specifically the words forgotten during the free recall part. We replicated key findings from previous research, demonstrating the benefits of slower pacing and of grouping on free recall. However, only slower pacing led to better performance on cued recall, indicating that grouping effects may decay surprisingly fast (over a matter of one minute) compared to the effect of slowed pacing. These results provide a benchmark for future comparisons of short-term recall performance in hearing-impaired listeners and users of cochlear implants.

Changes in Spoken and Sung Productions Following Adaptation to Pitch-shifted Auditory Feedback.

OBJECTIVE: Using voice to speak or to sing is made possible by remarkably complex sensorimotor processes. Like any other sensorimotor system, the speech motor controller guides its actions with maximum performance at minimum cost, using available sources of information, among which, auditory feedback plays a major role. Manipulation of this feedback forces the speech monitoring system to refine its expectations for further actions. The present study hypothesizes that the duration of this refinement and the weight applied on different feedbacks loops would depend on the intended sounds to be produced, namely reading aloud versus singing. MATERIAL AND METHODS: We asked participants to sing "Happy Birthday" and read a paragraph of Harry Potter before and after experiencing pitch-shifted feedback. A detailed fundamental frequency (F0) analysis was conducted for each note in the song and each segment in the paragraph (at the level of a sentence, a word, or a vowel) to determine whether some aspects of F0 production changed in response to the pitch perturbations experienced during the adaptation paradigm. RESULTS: Our results showed that changes in the degree of F0-drift across the song or the paragraph was the metric that was the most consistent with a carry-over effect of adaptation, and in this regard, reading new material was more influenced by recent remapping than singing. CONCLUSION: The motor commands used by (normally-hearing) speakers are malleable via altered-feedback paradigms, perhaps more so when reading aloud than when singing. But these effects are not revealed through simple indicators such as an overall change in mean F0 or F0 range, but rather through subtle metrics, such as a drift of the voice pitch across the recordings.

Luminance effects on pupil dilation in speech-in-noise recognition.

There is an increasing interest in the field of audiology and speech communication to measure the effort that it takes to listen in noisy environments, with obvious implications for populations suffering from hearing loss. Pupillometry offers one avenue to make progress in this enterprise but important methodological questions remain to be addressed before such tools can serve practical applications. Typically, cocktail-party situations may occur in less-than-ideal lighting conditions, e.g. a pub or a restaurant, and it is unclear how robust pupil dynamics are to luminance changes. In this study, we first used a well-known paradigm where sentences were presented at different signal-to-noise ratios (SNR), all conducive of good intelligibility. This enabled us to replicate findings, e.g. a larger and later peak pupil dilation (PPD) at adverse SNR, or when the sentences were misunderstood, and to investigate the dependency of the PPD on sentence duration. A second experiment reiterated two of the SNR levels, 0 and +14 dB, but measured at 0, 75, and 220 lux. The results showed that the impact of luminance on the SNR effect was non-monotonic (sub-optimal in darkness or in bright light), and as such, there is no trivial way to derive pupillary metrics that are robust to differences in background light, posing considerable constraints for applications of pupillometry in daily life. Our findings raise an under-examined but crucial issue when designing and understanding listening effort studies using pupillometry, and offer important insights to future clinical application of pupillometry across sites.

Recording EEG in cochlear implant users: Guidelines for experimental design and data analysis for optimizing signal quality and minimizing artifacts.

Cochlear implants (CI) are neural prostheses that can restore hearing in individuals with severe to profound hearing loss. Although CIs significantly improve quality of life, clinical outcomes are still highly variable. An important part of this variability is explained by the brain reorganization following cochlear implantation. Therefore, clinicians and researchers are seeking objective measurements to investigate post-implantation brain plasticity. Electroencephalography (EEG) is a promising technique because it is objective, non-invasive, and implant-compatible, but is nonetheless susceptible to massive artifacts generated by the prosthesis's electrical activity. CI artifacts can blur and distort brain responses; thus, it is crucial to develop reliable techniques to remove them from EEG recordings. Despite numerous artifact removal techniques used in previous studies, there is a paucity of documentation and consensus on the optimal EEG procedures to reduce these artifacts. Herein, and through a comprehensive review process, we provide a guideline for designing an EEG-CI experiment minimizing the effect of the artifact. We provide some technical guidance for recording an accurate neural response from CI users and discuss the current challenges in detecting and removing CI-induced artifacts from a recorded signal. The aim of this paper is also to provide recommendations to better appraise and report EEG-CI findings.

Visual cortex plasticity in cochlear implant users revealed in a visual motion detection task.

OBJECTIVE: The aim of this study was to investigate brain reorganization following cochlear implantation using electroencephalography, an implant-compatible technique to record electrical brain activity. METHODS: We investigated cortical plasticity in cochlear implant (CI) users using visual evoked potentials in response to visual motion changes. We estimated visual and auditory neural sources in CI users (n = 20) and normal hearing (NH) matched control participants (n = 22). RESULTS: Results showed intra-modal plasticity in the visual cortex of CI users, revealed by higher P1 and visual mismatch negativity amplitude, and greater contribution of the visual cortex during visual motion changes compared to NH controls. CONCLUSIONS: Our results suggest more efficient processing of visual information in CI users that may reflect enhanced multimodal compensatory strategies during speech processing. SIGNIFICANCE: This study showcases an objective, implant-compatible method that could be used in a clinical setting to measure and longitudinally track cortical plastic changes, enabling a better understanding of the link between individual patterns of cortical plasticity and CI outcomes.

Accuracy of Tempo Judgments in Disk Jockeys Compared to Musicians and Untrained Individuals.

Professional disk jockeys (DJs) are an under-studied population whose performance involves creating new musical experiences by combining existing musical materials with a high level of temporal precision. In contemporary electronic dance music, these materials have a stable tempo and are composed with the expectation for further transformation during performance by a DJ for the audience of dancers. Thus, a fundamental aspect of DJ performance is synchronizing the tempo and phase of multiple pieces of music, so that over seconds or even minutes, they may be layered and transitioned without disrupting the rhythmic pulse. This has been accomplished traditionally by manipulating the speed of individual music pieces "by ear," without additional technological synchronization aids. However, the cumulative effect of this repeated practice on auditory tempo perception has not yet been evaluated. Well-known phenomena of experience-dependent plasticity in other populations, such as musicians, prompts the question of whether such effects exist in DJs in their domain of expertise. This pilot study examined auditory judgments of tempo in 10 professional DJs with experience mixing by ear, compared to 7 percussionists, 12 melodic instrumental musicians, and 11 untrained controls. Participants heard metronome sequences between 80 and 160 beats per minute (BPM) and estimated the tempo. In their most-trained tempo range, 120-139 BPM, DJs were more accurate (lower absolute percent error) than untrained participants. Within the DJ group, 120-139 BPM exhibited greater accuracy than slower tempos of 80-99 or 100-119 BPM. DJs did not differ in accuracy compared to percussionists or melodic musicians on any BPM range. Percussionists were more accurate than controls for 100-119 and 120-139 BPM. The results affirm the experience-dependent skill of professional DJs in temporal perception, with comparable performance to conventionally trained percussionists and instrumental musicians. Additionally, the pattern of results suggests a tempo-specific aspect to this training effect that may be more pronounced in DJs than percussionists and musicians. As one of the first demonstrations of enhanced auditory perception in this unorthodox music expert population, this work opens the way to testing whether DJs also have enhanced rhythmic production abilities, and investigating the neural substrates of this skill compared to conventional musicians.

Free-Field Cortical Steady-State Evoked Potentials in Cochlear Implant Users.

Auditory steady-state evoked potentials (SS-EPs) are phase-locked neural responses to periodic stimuli, believed to reflect specific neural generators. As an objective measure, steady-state responses have been used in different clinical settings, including measuring hearing thresholds of normal and hearing-impaired subjects. Recent studies are in favor of recording these responses as a part of the cochlear implant (CI) device-fitting procedure. Considering these potential benefits, the goals of the present study were to assess the feasibility of recording free-field SS-EPs in CI users and to compare their characteristics between CI users and controls. By taking advantage of a recently developed dual-frequency tagging method, we attempted to record subcortical and cortical SS-EPs from adult CI users and controls and measured reliable subcortical and cortical SS-EPs in the control group. Independent component analysis (ICA) was used to remove CI stimulation artifacts, yet subcortical responses of several CIs were heavily contaminated by these artifacts. Consequently, only cortical SS-EPs were compared between groups, which were found to be larger in the controls. The lower cortical SS-EPs' amplitude in CI users might indicate a reduction in neural synchrony evoked by the modulation rate of the auditory input across different neural assemblies in the auditory pathway. The brain topographies of cortical auditory SS-EPs, the time course of cortical responses, and the reconstructed cortical maps were highly similar between groups, confirming their neural origin and possibility to obtain such responses also in CI recipients. As for subcortical SS-EPs, our results highlight a need for sophisticated denoising algorithms to pinpoint and remove artifactual components from the biological response.

Modulation of hyperacusis and tinnitus loudness in tinnitus patients with and without hearing loss following 3 weeks of acoustic stimulation: A proof-of-concept study.

Tinnitus and hyperacusis are two debilitating conditions that are highly comorbid. It has been postulated that they may originate from similar pathophysiological mechanisms such as an increase in central gain. Interestingly, sound stimulation has been shown to reduce central gain and is currently used for the treatment of both conditions. This study investigates the effect of sound stimulation on both tinnitus and hyperacusis in the same patients. Two distinct series of tinnitus participants were tested: one with normal or near-normal hearing (n=16) and one with hearing loss (n=14). A broadband noise shaped to cover most of the tinnitus frequency spectrum was delivered through hearing aids using the noise generator feature (no amplification) and verified through real-ear measurements. Participants received sound stimulation for 3 weeks and were tested before (at baseline), then after 1 week and at the end of the 3 weeks of sound stimulation. There was also a 1-month follow-up after the end of the stimulation protocol. The measurements included self-reported measures of tinnitus and hyperacusis (VAS), validated questionnaires (THI, HQ) and psychoacoustic measurements (tinnitus battery and loudness functions). On both self-assessment (VAS of sound tolerance and tinnitus loudness) and psychoacoustic measures (loudness function and tinnitus loudness in dB), about 50% of tinnitus participants had a synchronous (either a decrease or an increase) modulation of hyperacusis and tinnitus loudness after 1 week and 3 weeks of acoustic stimulation and up to about 70% of participants at 1-M follow-up. The decrease of hyperacusis and tinnitus loudness was more prevalent in normal-hearing participants. There was a significant increase in tinnitus loudness during and following the stimulation in the group with hearing loss. Hyperacusis improvement as assessed by loudness function was significantly correlated with the intensity level of the acoustic stimulation (dB level of the noise produced by the noise generator) in tinnitus participants with normal/near-normal hearing thresholds. Our study partly supports the central gain hypothesis by showing synchronous modulation of hyperacusis and tinnitus loudness. It also shows beneficial effects of acoustic stimulation in some tinnitus individuals, in particular those with normal or near-normal hearing, while highlighting the importance of a careful fitting of sound generators to prevent increase. Since the amplification feature was not turned on in our study, future work should determine whether amplification alone, or in addition to acoustic stimulation (sound generators), would benefit to those with hearing loss.

Association of In-Ear Device Use With Communication Quality Among Individuals Wearing Personal Protective Equipment in a Simulated Operating Room.

Importance: The COVID-19 pandemic has brought forth new challenges for health care workers, such as the daily use of personal protective equipment, including reusable facial respirators. Poor communication while wearing respirators may have fatal complications for patients, and no solution has been proposed to date. Objective: To examine whether use of an in-ear communication device is associated with improved communication while wearing different personal protective equipment (N95 mask, half-face elastomeric respirator, and powered air-purifying respirator [PAPR]) in the operating room. Design, Setting, and Participants: This quality improvement study was conducted in June 2020. Surgical residents from the Department of Otolaryngology-Head and Neck Surgery at McGill University in Montreal, Quebec, Canada, were recruited. All participants had normal hearing, were fluent in English, and had access to the operating rooms at the Royal Victoria Hospital. Exposures: All participants performed the speech intelligibility tasks with and without an in-ear communication device. Main Outcomes and Measures: Speech intelligibility was measured using a word recognition task (Modified Rhyme Test) and a sentence recognition task (AzBio Sentence Test). A percentage correct score (0% to 100%) was obtained for each speech intelligibility test. Listening effort was assessed using the NASA Task Load Index. An overall workload score, ranging from 0 points (low workload) to 100 points (high workload), was obtained. Results: A total of 12 participants were included (mean [SD] age, 31.2 [1.9] years; 8 women [66.7%]). AzBio Sentence Test results revealed that, while wearing the N95 mask, the mean (SD) speech intelligibility was 98.8% (1.8%) without the in-ear device vs 94.3% (7.4%) with the device. While wearing the half-face elastomeric respirator, the mean speech intelligibility was 58.5% (12.4%) without the in-ear device vs 90.8% (8.9%) with the device. While wearing the PAPR, the mean speech intelligibility was 84.6% (9.8%) without the in-ear device vs 94.5% (5.5%) with the device. Use of the in-ear device was associated with a significant improvement in speech intelligibility while wearing the half-face elastomeric respirator (32.3%; 95% CI, 23.8%-40.7%; P < .001) and the PAPR (9.9%; 95% CI, 1.4%-18.3%; P = .01). Furthermore, use of the device was associated with decreased listening effort. The NASA Task Load Index results reveal that, while wearing the N95 mask, the mean (SD) overall workload score was 12.6 (10.6) points without the in-ear device vs 17.6 (9.2) points with the device. While wearing the half-face elastomeric respirator, the mean overall workload score was 67.7 (21.6) points without the in-ear device vs 29.3 (14.4) points with the in-ear device. While wearing the PAPR, the mean overall workload score was 42.2 (18.2) points without the in-ear device vs 23.8 (12.8) points with the in-ear device. Use of the in-ear device was associated with a significant decrease in overall workload score while wearing the half-face elastomeric respirator (38.4; 95% CI, 23.5-53.3; P < .001) and the PAPR (18.4; 95% CI, 0.4-36.4; P = .04). Conclusions and Relevance: This study found that among participants using facial respirators that impaired communication, a novel in-ear device was associated with improved communication and decreased listening effort. Such a device may be a feasible solution for protecting health care workers in the operating room while allowing them to communicate safely, especially during the COVID-19 pandemic.

Disentangling listening effort and memory load beyond behavioural evidence: Pupillary response to listening effort during a concurrent memory task.

Recent research has demonstrated that pupillometry is a robust measure for quantifying listening effort. However, pupillary responses in listening situations where multiple cognitive functions are engaged and sustained over a period of time remain hard to interpret. This limits our conceptualisation and understanding of listening effort in realistic situations, because rarely in everyday life are people challenged by one task at a time. Therefore, the purpose of this experiment was to reveal the dynamics of listening effort in a sustained listening condition using a word repeat and recall task. Words were presented in quiet and speech-shaped noise at different signal-to-noise ratios (SNR): 0dB, 7dB, 14dB and quiet. Participants were presented with lists of 10 words, and required to repeat each word after its presentation. At the end of the list, participants either recalled as many words as possible or moved on to the next list. Simultaneously, their pupil dilation was recorded throughout the whole experiment. When only word repeating was required, peak pupil dilation (PPD) was bigger in 0dB versus other conditions; whereas when recall was required, PPD showed no difference among SNR levels and PPD in 0dB was smaller than repeat-only condition. Baseline pupil diameter and PPD followed different variation patterns across the 10 serial positions within a block for conditions requiring recall: baseline pupil diameter built up progressively and plateaued in the later positions (but shot up when listeners were recalling the previously heard words from memory); PPD decreased at a pace quicker than in repeat-only condition. The current findings demonstrate that additional cognitive load during a speech intelligibility task could disturb the well-established relation between pupillary response and listening effort. Both the magnitude and temporal pattern of task-evoked pupillary response differ greatly in complex listening conditions, urging for more listening effort studies in complex and realistic listening situations.

Adaptation to pitch-altered feedback is independent of one's own voice pitch sensitivity.

Monitoring voice pitch is a fine-tuned process in daily conversations as conveying accurately the linguistic and affective cues in a given utterance depends on the precise control of phonation and intonation. This monitoring is thought to depend on whether the error is treated as self-generated or externally-generated, resulting in either a correction or inflation of errors. The present study reports on two separate paradigms of adaptation to altered feedback to explore whether participants could behave in a more cohesive manner once the error is of comparable size perceptually. The vocal behavior of normal-hearing and fluent speakers was recorded in response to a personalized size of pitch shift versus a non-specific size, one semitone. The personalized size of shift was determined based on the just-noticeable difference in fundamental frequency (F0) of each participant's voice. Here we show that both tasks successfully demonstrated opposing responses to a constant and predictable F0 perturbation (on from the production onset) but these effects barely carried over once the feedback was back to normal, depicting a pattern that bears some resemblance to compensatory responses. Experiencing a F0 shift that is perceived as self-generated (because it was precisely just-noticeable) is not enough to force speakers to behave more consistently and more homogeneously in an opposing manner. On the contrary, our results suggest that the type of the response as well as the magnitude of the response do not depend in any trivial way on the sensitivity of participants to their own voice pitch. Based on this finding, we speculate that error correction could possibly occur even with a bionic ear, typically even when F0 cues are too subtle for cochlear implant users to detect accurately.

Binaural Beats through the Auditory Pathway: From Brainstem to Connectivity Patterns.

Binaural beating is a perceptual auditory illusion occurring when presenting two neighboring frequencies to each ear separately. Several controversial claims have been attributed to binaural beats regarding their ability to entrain human brain activity and mood, in both the scientific literature and the marketing realm. Here, we sought to address those questions in a robust fashion using a single-blind, active-controlled protocol. To do so, we compared the effects of binaural beats with a control beat stimulation (monaural beats, known to entrain brain activity but not mood) across four distinct levels in the human auditory pathway: subcortical and cortical entrainment, scalp-level functional connectivity and self-reports. Both stimuli elicited standard subcortical responses at the pure tone frequencies of the stimulus [i.e., frequency following response (FFR)], and entrained the cortex at the beat frequency [i.e., auditory steady state response (ASSR)]. Furthermore, functional connectivity patterns were modulated differentially by both kinds of stimuli, with binaural beats being the only one eliciting cross-frequency activity. Despite this, we did not find any mood modulation related to our experimental manipulation. Our results provide evidence that binaural beats elicit cross frequency connectivity patterns, but weakly entrain the cortex when compared with monaural beat stimuli. Whether binaural beats have an impact on cognitive performance or other mood measurements remains to be seen and can be further investigated within the proposed methodological framework.

Middle Latency Responses to Optimized Chirps in Adult Cochlear Implant Users.

BACKGROUND: Cochlear implant (CI) outcomes can be assessed using objective measures that reflect the integrity of the auditory pathway. One such measure is the middle latency response (MLR), which can provide valuable information for clinicians. PURPOSE: Traditional stimuli for evoking MLRs, that is, clicks or tone bursts, do not stimulate all parts of the cochlea simultaneously, whereas chirp stimuli compensate for the cochlear neural delay and, therefore, produce more synchronous responses from the different neural elements of the cochlea. The purpose of the present study was to determine whether chirp stimuli can elicit reliable MLRs in CI users and whether those responses correlate with clinical outcomes and with deprivation-related factors. RESEARCH DESIGN: We presented 2,000 free-field optimized chirp stimuli to CI and control participants while their electroencephalography (EEG) was being recorded. STUDY SAMPLE: Twenty-four adult CI users and 24 matched normal-hearing (NH) individuals (age range from 18 to 63 years) participated in this study. DATA COLLECTIONS AND ANALYSIS: The EEG was recorded from 64 active electrodes placed on the scalp. EEG signals were processed using EEGLAB and ERPLAB toolboxes. We characterized the latencies and amplitudes of the different MLR components in both groups. RESULTS: Chirp stimuli reliably evoked qualitatively similar MLRs across all NH and CI participants with a couple of differences observed between the NH and CI group. Among the different MLR components, the Na latency was significantly shorter for the CI group. A significant amplitude difference was also found between groups for the Pa-Nb complex, with higher amplitudes observed in the NH group. Finally, there were no significant correlations between MLR latencies (or amplitudes) and clinical outcomes or deprivation-related measures. CONCLUSIONS: Free-field-presented optimized chirp stimuli were shown to evoke measurable and reliable MLRs in CI users. In this experiment, the MLR morphology in CI users was similar to those observed in NH participants. Even though we did not replicate here a significant relationship between MLR and speech perception measures, we were able to successfully collect acoustically evoked MLRs, which could constitute an important supplemental measure to the standard behavioral tests presently being used in postoperative clinical evaluation settings.