Biology subjects

Epp, B.

Publications and source records attributed to Epp, B..

6 recordsLinked to original sources

bioRxiv2025

Entrainment effects and information processing in coupled oscillator models of auditory biomechanics

The ability to process sound as a means of gaining information about the environment is shared by many species of animals. The auditory system of many vertebrates contains non-linear and active elements, hair cells, in the inner ear. These are considered elementary for high sensitivity, high selectivity, and wide dynamic range. However, the implications of the complex interplay between active hair cell function and inner ear mechanics on information processing are not yet fully understood. Here we use the basic properties of vertebrate ears to develop a numerical approach that captures active and nonlinear elements with the goal of quantifying effects of entrainment on information processing. We show that entrainment and the generation of clusters affect information processing, and that inclusion of these phenomena extends the scope of commonly used models of hearing. The results show ubiquitous phenomena that are robust against variation of model parameters. We show that the encoding of information emerges as a global effect in the system rather than locally in individual elements. These findings have implications for our understanding of tonotopy in, e.g., the peripheral auditory system, and link active and nonlinear dynamic behavior with information encoding in the inner ear. This will help the identification of the key principles that underlie hearing in complex acoustical environments with strict physiological restrictions. The purpose of this study is to bridge entrainment effects with information processing in biological sensory systems. The results show the impact of self-organizing (spontaneous) and entrainment (externally driven) phenomena on the sensitivity, frequency selectivity, and information encoding capacity of the system. The frequency-specific sensitivity to external stimulation provides an explanation for physiological data recorded from the vertebrate auditory system. The link to information theory allows us to quantify the benefit of entrainment of sensory detection performance. Based on these results, acoustical, mechanical, and behavioral data can be evaluated within the same framework. This enables exploitation of the results for diagnostic and technological applications in, for example, audio signal processing.

biophysics↗

bioRxiv2021

Ecological validity of masking release with speech-like stimuli

The relevance of masking release by comodulation and interaural phase difference (IPD) for speech perception is still unclear. We used speech-like stimuli to link spectro-temporal properties of formants with masking release. The stimuli comprised a tone and three masker bands centered at formant frequencies F1, F2, and F3 derived from a consonant-vowel (/gu/, /fu/, and /pu/). The target was a diotic or dichotic frequency-modulated tone following F2 trajectories. Results showed no statistically significant comodulation masking release (CMR), while the binaural masking level difference (BMLD) was comparable to previous findings. The data suggest that factors other than comodulation may play a dominant role in grouping frequency components in speech.

animal behavior and cognition↗

bioRxiv2021

The effect of the preceding masking noise on monaural and binaural release from masking

Auditory stream segregation can be facilitated when the maskers share coherent amplitude modulations or by utilizing spatial cues. The effectiveness of each cue can be quantified as a decrease in masked thresholds, termed as comodulated masking release (CMR) and binaural masking level difference (BMLD). Prolonged exposure to the masker can influence following target segregation. However, the collective impact preceding noise on target segregation in the presence of comodulation and interaural phase difference (IPD) cues is unclear. Stimuli were used to induce noise streams by altering the duration and temporal coherence of the envelope of the preceding masker. The effect on following target detection with CMR and BMLD induced by an IPD of the target tone was investigated. The results indicate that the effect of the preceding stream formation on CMR operates on different time scales, extending beyond 200 ms, depending on the spectrotemporal characteristics of the maskers. However, the effect on IPD-induced BMLD was not significant across time. Under the simplifying assumption that peripheral processing operates on shorter time scales than cortical processing, the results of the present study may provide insights into auditory signal processing in the presence of beneficial cues for target stream segregation.

neuroscience↗

bioRxiv2021

Neural correlates of masked and unmasked tones: psychoacoustics and late auditory evoked potentials (LAEPs)

Hearing thresholds are commonly used to quantify a listeners ability to detect sound. In the presence of masking sounds, hearing thresholds can vary depending on the signal properties of the target and the masker, commonly referred to as auditory cues. Target detection can be facilitated with comodulated masking noise and interaural phase disparity (IPD). This can be quantified with a decrease in detection thresholds or masking release: comodulation masking release (CMR, for comodulation) and binaural masking level difference (BMLD, for IPD). As these measures only reflect the low limit of levels for target detection, the relevance of masking release at supra-threshold levels is still unclear. Here, we used psychoacoustic and electrophysiological measures to investigate the effect of masking release for a masked tone at supra-threshold levels. Behaviorally, we investigated how the amount of masking release affects the salience at supra-threshold levels. We used intensity just-noticeable difference (JND) to quantify level-dependent changes in the salience of the tonal signal. As a physiological correlate, we investigated late auditory evoked potentials (LAEPs) with electroencephalography (EEG). The results showed that the intensity JNDs were equal at the same physical target tone level, regardless of the presence or absence of masking release. Estimated salience was correlated with the amount of masking release. However, salience measures across conditions converged with the target tone level above 70 dB SPL. For the LAEPs, the P2 amplitudes were more closely linked to behavioral measures than the N1 amplitudes. Both behavioral and electrophysiological measures suggest that the salience of a masked tone at supra-threshold levels is correlated with the amount of masking release.

neuroscience↗

bioRxiv2019

Perceptual weighting of binaural lateralization cues across frequency bands

The auditory system uses interaural time- and level differences (ITD and ILD) as cues to localize and lateralize sounds. The availability of ITDs and ILDs in the auditory system is limited by neural phase-locking and by the head size, respectively. Although the frequency-specific limitations are well known, the relative contribution of ITDs and ILDs in individual frequency bands in broad-band stimuli are unknown. To determine these relative contributions, or spectral weights, listeners were asked to judge the lateralization of stimuli consisting of eleven simultaneously presented 1-ERB-wide noise bands centered between 442 Hz and 5544 Hz and separated by 1-ERB-wide gaps. Interaural disparities were applied to each noise band and were roved independently on every trial. The weights were obtained using a multiple linear regression analysis. In a second experiment the effect of temporal context on the spectral weights was investigated. Ten of the noise bands were used as pre- and postcursors and listeners were asked to lateralize the stimuli. Results show that only the lowest- or highest frequency band received highest weight for ITD and ILD, respectively. Temporal context led to significantly enhanced weights given to the band without the pre- and postcursor. The weight enhancement could only be observed at low frequencies, when determined with ITD cues and for low and high frequencies for ILDs. Hence, the auditory system seems to be able to change the spectral weighting of binaural information depending on the information content. PACS43.64.-q {middle dot} 43.64.+r {middle dot} 87.19.lt {middle dot} 43.66.-x {middle dot} 43.66.+y {middle dot} 43.64.Bt

neuroscience↗

bioRxiv2019

Supra-threshold perception and neural representation of tones presented in noise in conditions of masking release

The neural representation and perceptual salience of tonal signals presented in different noise maskers were investigated. The properties of the maskers and signals were varied such that they produced different amounts of either monaural masking release, binaural masking release, or a combination of both. The signals were then presented at different levels above their corresponding masked thresholds and auditory evoked potentials (AEPs) were measured. It was found that, independent of the masking condition, the amplitude of the P2 component of the AEP was similar for the same stimulus levels above masked threshold, suggesting that both monaural and binaural effects of masking release were represented at the level of P2 generation. The perceptual salience of the signal was evaluated at equal levels above masked threshold using a rating task. In contrast to the electrophysiological findings, the subjective ratings of the perceptual signal salience were less consistent with the signal level above masked threshold and varied strongly across listeners and masking conditions. Overall, the results from the present study suggest that the P2 amplitude of the AEP represents an objective indicator of the audibility of a target signal in the presence of complex acoustic maskers.

neuroscience↗