Simon Henin

Changes in amplitude and phase of distortion-product otoacoustic emission fine-structure and separated components during efferent activation

Medial olivocochlear (MOC) efferent fibers synapse directly on the outer hair cells (OHCs). Efferent activation evoked by contralateral acoustic stimulation (CAS) will affect OHC amplification and subsequent measures of distortion-product otoacoustic emissions (DPOAEs). The aim of this study was to investigate measures of total and separated DPOAEs during efferent activation. Efferent activation produces both suppression and enhancement of the total DPOAE level. Level enhancements occurred near fine-structure minima and were associated with consistent MOC evoked upward shifts in DPOAE fine-structure frequency. Examination of the phase of the separated components revealed that frequency shifts stemmed from increasing phase leads of the reflection component during CAS, while the generator component phase was nearly invariant. Separation of the two DPOAE components responsible for the fine-structure revealed more consistent reduction of the levels of both components. Using vector subtraction (which takes into account both level and phase) to estimate the changes in the unseparated DPOAE provided consistent evidence of DPOAE suppression. Including phase information provided a more sensitive, valid and consistent estimate of CAS function even if one does not know the position of the DPOAE in the fine-structure.

Sensitization to masked tones following notched-noise correlates with estimates of cochlear function using distortion product otoacoustic emissions

Neuronal gain adaptation has been proposed as the underlying mechanism leading to the perception of phantom sounds such as Zwicker tones and tinnitus. In this gain-adaptation theory, cochlear compression plays a significant role with weaker compression leading to stronger phantom percepts. The specific aim of this study was to find a link between the strength of neuronal gain adaptation and cochlear compression. Compression was assessed using distortion product otoacoustic emissions (DPOAEs). Gain adaptation is hypothesized to manifest itself in the sensitization observed for the detection of masked tones when preceded by notched noise. Perceptual thresholds for pure tones in notched noise were measured at multiple frequencies following various priming signals. The observed sensitization was larger than expected from the combined effect of the various maskers. However, there was no link between sensitization and compression. Instead, across subjects, stronger sensitization correlated with stronger DPOAEs evoked by low-level primaries. In addition, growth of DPOAEs correlated reliably with perceptual thresholds across frequencies within subjects. Together, the data suggest that short-term dynamic adaptation leading to perceptual sensitization is the result of an active process mediated by the outer hair cells, which are thought to modulate the gain of the cochlear amplifier via efferent feedback.

Wideband detection of middle ear muscle activation using swept-tone distortion product otoacoustic emissions

The measurement of efferent-induced suppression of otoacoustic emissions (OAEs) using contralateral acoustic stimulation (CAS) is complicated by potential contamination by the middle ear muscle reflex (MEMR), particularly at moderate to high CAS levels. When logarithmically sweeping primaries are used to measure distortion product otoacoustic emissions, the level and phase of the primaries at the entrance of the ear canal may be monitored simultaneously along with the OAEs elicited by the swept-tones. A method of detecting MEMR activation using swept-tones is presented in which the differences in the primaries in the ear canal with and without CAS are examined, permitting evaluation of MEMR effects over a broad frequency range. A range of CAS levels above and below expected contralateral acoustic reflex thresholds permitted evaluation of conditions with and without MEMR activation.

Engaging narratives evoke similar neural activity and lead to similar time perception

It is said that we lose track of time - that “time flies” - when we are engrossed in a story. How does engagement with the story cause this distorted perception of time, and what are its neural correlates? People commit both time and attentional resources to an engaging stimulus. For narrative videos, attentional engagement can be represented as the level of similarity between the electroencephalographic responses of different viewers. Here we show that this measure of neural engagement predicted the duration of time that viewers were willing to commit to narrative videos. Contrary to popular wisdom, engagement did not distort the average perception of time duration. Rather, more similar brain responses resulted in a more uniform perception of time across viewers. These findings suggest that by capturing the attention of an audience, narrative videos bring both neural processing and the subjective perception of time into synchrony.

The Effects of Compensatory Auditory Stimulation and High-Definition Transcranial Direct Current Stimulation (HD-tDCS) on Tinnitus Perception - A Randomized Pilot Study

Background Tinnitus correlates with elevated hearing thresholds and reduced cochlear compression. We hypothesized that reduced peripheral input leads to elevated neuronal gain resulting in the perception of a phantom sound. Objective The purpose of this pilot study was to test whether compensating for this peripheral deficit could reduce the tinnitus percept acutely using customized auditory stimulation. To further enhance the effects of auditory stimulation, this intervention was paired with high-definition transcranial direct current stimulation (HD-tDCS). Methods A randomized sham-controlled, single blind study was conducted in a clinical setting on adult participants with chronic tinnitus (n = 14). Compensatory auditory stimulation (CAS) and HD-tDCS were administered either individually or in combination in order to access the effects of both interventions on tinnitus perception. CAS consisted of sound exposure typical to daily living (20-minute sound-track of a TV show), which was adapted with compressive gain to compensate for deficits in each subjects individual audiograms. Minimum masking levels and the visual analog scale were used to assess the strength of the tinnitus percept immediately before and after the treatment intervention. Results CAS reduced minimum masking levels, and visual analog scale trended towards improvement. Effects of HD-tDCS could not be resolved with the current sample size. Conclusions The results of this pilot study suggest that providing tailored auditory stimulation with frequency-specific gain and compression may alleviate tinnitus in a clinical population. Further experimentation with longer interventions is warranted in order to optimize effect sizes.

Negative Middle Ear Pressure and Composite and Component Distortion Product Otoacoustic Emissions.

Objectives: Distortion product otoacoustic emissions (DPOAEs), a by-product of normal outer hair cell function, are used in research and clinical settings to noninvasively test cochlear health. The composite DPOAE recorded in the ear canal is the result of interactions of at least two components: a nonlinear distortion component (the generator component) and a linear reflection component. Negative middle ear pressure (NMEP) results in the tympanic membrane being pulled inward and increases middle ear impedance. This influences both the forward travel of stimuli used to induce distortion products and the reverse travel of the emissions back to the ear canal. NMEP may therefore limit the effectiveness of DPOAEs in clinical settings. Design: Twenty-six normal-hearing subjects were recruited, and eight were able to reliably and consistently induce NMEP using the Toynbee maneuver. Eight interleaved measures of tympanic peak pressure (TPP) were collected for each subject at normal pressure and NMEP. DPOAEs were then collected both when middle ear pressure was normal and during subject-induced NMEP. All measures were interleaved. Two primary tones were swept logarithmically across frequency (1 second per octave) from f1 = 410 to 6560 Hz and f2 = 500 to 8000 Hz (f1/f2 = 1.22), producing 2f1 − f2 DPOAEs from 320 to 5120 Hz. DPOAEs were collected at three equal-level primary level combinations (L65, L70, L75 dB SPL). Before composite and component DPOAE analysis, analysis of the f1 DPOAE primary confirmed that subjects had successfully induced NMEP. DPOAE and component magnitudes were separately analyzed using repeated measures analysis of variances with three factors, primary level (L65, L70, L75 dB SPL), middle ear pressure (normal pressure versus NMEP), and frequency (500 to 4000 Hz). Results: Mean subject-induced NMEP ranged from −65 to −324 daPa. Changes in the magnitude (dB) of the primary tones used to induce the DPOAE provided a reliable indicator of subject-induced NMEP. Composite DPOAE and component levels were significantly affected by NMEP for all the frequencies tested. Changes were most clearly observed for the generator component with one subject demonstrating a mean decrease of 12 dB in magnitude during NMEP. Results were subject-specific, and there was a correlation between the degree of negative TPP induced and the amount of change in DPOAE level. Conclusions: Mean TPPs collected during NMEP ranged from −65 to −324 daPa and significantly affected composite DPOAE, generator, and reflection component levels. Changes in the magnitude of the swept-primaries as a function of frequency were used to confirm that NMEP had been successfully induced. The patterns of change in the composite DPOAEs were clearer and easier to interpret when the components of the DPOAE were separated with evaluation of the generator component alone.

Total and component distortion product otoacoustic emission analysis in persons with induced negative middle ear pressure

Distortion product otoacoustic emissions (DPOAEs) are generated when two primary tones (f1, f2 with f2 > f1) are presented simultaneously to the ear. Inter-modulation between primary tones produces distortion products at predictable frequencies not present in the original signal (e.g., 2f1 − f2). In persons with negative middle ear pressure (NMEP), the tympanic membrane is retracted and pulled inward, compressing structures in the middle ear. NMEP is expected to modify DPOAE level and phase. Performing the Toynbee maneuver can artificially induce NMEP. Changes in DPOAE primary f1 and f2 level and phase and energy reflectance measures were used to confirm that 8 subjects had artificially induced NMEP using the Toynbee maneuver. DPOAEs were obtained using 1 s/octave duration logarithmic frequency sweeping primaries, f2/f1 = 1.22 producing 2f1 − f2 from 320–2560 Hz, L1 = L2 = 65, 70, 75 dB SPL. There was a significant effect of condition, primary level, and frequency on total DPOAE and component amplitude. S...

Age and sex modulate the variability of neural responses to naturalistic videos

Recent efforts have aimed to characterize clinical pediatric populations by using neurophysiological tests in addition to behavioral assays. Here we report on a data collection effort in which electroencephalography (EEG) was recorded in both juveniles and adults (N=114 participants, ages 6-44 years of age) during various stimulation protocols. The present analysis focuses on how neural responses during passive viewing of naturalistic videos vary with age and sex, and in particular, how similar they are within developmental groups. Similarity of neural responses was measured as the inter-subject correlation of the EEG. Stimulus-evoked neural responses are more similar among children and decrease in similarity with age. Among children, males respond more similarly to each other than females. This was uniformly true for a variety of videos. The decrease in group similarity with age may result from an overall decline in the magnitude of evoked responses, but this cannot explain the sex differences found in the young. We therefore propose that as children mature, neural function may become more variable.Neural development is generally marked by an increase in the efficiency and diversity of neural processes. In a large sample (N = 114) of children and adults with ages ranging from 5 - 44 years, we investigated the neural responses to naturalistic video stimuli. Videos from both real-life classroom settings and Hollywood feature films were used to probe different aspects of attention and engagement. For all stimuli, older ages were marked by more variable neural responses. Variability was assessed by the inter-subject correlation of evoked electroencephalographic (EEG) responses. Young males also had more variable responses than young females. These results were replicated in an independent cohort (N = 303). When interpreted in the context of neural maturation, we conclude that neural function becomes more variable with maturity, at least in during the passive viewing of real-world stimuli.

Neural engagement with online educational videos predicts learning performance for individual students

&NA; Online educational materials are largely disseminated through videos, and yet there is little understanding of how these videos engage students and fuel academic success. We hypothesized that components of the electroencephalogram (EEG), previously shown to reflect video engagement, would be predictive of academic performance in the context of educational videos. Two groups of subjects watched educational videos in either an intentional learning paradigm, in which they were aware of an upcoming test, or in an incidental learning paradigm, in which they were unaware that they would be tested. “Neural engagement” was quantified by the inter‐subject correlation (ISC) of the EEG that was evoked by the videos. In both groups, students with higher neural engagement retained more information. Neural engagement also discriminated between attentive and inattentive video viewing. These results suggest that this EEG metric is a marker of the stimulus‐related attentional mechanisms necessary to retain information. In the future, EEG may be used as a tool to design and assess online educational content.

A ressource for assessing information processing in the developing brain using EEG and eye tracking

We present a dataset combining electrophysiology and eye tracking intended as a resource for the investigation of information processing in the developing brain. The dataset includes high-density task-based and task-free EEG, eye tracking, and cognitive and behavioral data collected from 126 individuals (ages: 6-44). The task battery spans both the simple/complex and passive/active dimensions to cover a range of approaches prevalent in modern cognitive neuroscience. The active task paradigms facilitate principled deconstruction of core components of task performance in the developing brain, whereas the passive paradigms permit the examination of intrinsic functional network activity during varying amounts of external stimulation. Alongside these neurophysiological data, we include an abbreviated cognitive test battery and questionnaire-based measures of psychiatric functioning. We hope that this dataset will lead to the development of novel assays of neural processes fundamental to information processing, which can be used to index healthy brain development as well as detect pathologic processes.