Biology subjects

Boothalingam, S.

Publications and source records attributed to Boothalingam, S..

2 recordsLinked to original sources

bioRxiv2020

Click evoked Middle Ear Muscle Reflex: Implications for Medial Olivocochlear System Assays

This study describes a time series-based method of middle ear muscle reflex (MEMR) detection using bilateral clicks. Although many methods can detect changes in the OAE evoking stimulus to monitor the MEMR, they do not discriminate between true MEMR-mediated vs. artifactual changes in the stimulus. We measured MEMR in 20 young clinically normal hearing individuals using 1-second-long click trains presented at six levels (65 to 95 dB peak-to-peak SPL in 6 dB steps). Changes in the stimulus levels over the 1 second period were well-approximated by two-term exponential functions. The magnitude of ear canal pressure changes due to MEMR increased monotonically as a function of click level but non-monotonically with frequency when separated into 1/3rd-octave wide bands between 1 and 3.2 kHz. MEMR thresholds estimated using this method were lower than that obtained from a clinical tympanometer in [~]94% of the participants. A time series-based method, along with statistical tests, may provide additional confidence in detecting the MEMR. MEMR effects were smallest at 2 kHz, between 1 and 3.2 kHz, which may provide avenues for minimizing the MEMR influence while measuring other responses (e.g., the medial olivocochlear reflex).

neuroscience↗

bioRxiv2020

Perceptual gating of a brainstem reflex facilitates speech understanding in humans

Navigating "cocktail party" situations by enhancing foreground sounds over irrelevant background information is typically considered from a cortico-centric perspective. However, subcortical circuits, such as the medial olivocochlear (MOC) reflex that modulates inner ear activity itself, have ample opportunity to extract salient features from the auditory scene prior to any cortical processing. To understand the contribution of auditory subcortical nuclei and the cochlea, physiological recordings were made along the auditory pathway while listeners differentiated non(sense)-words and words. Both naturally-spoken and intrinsically-noisy, vocoded speech -- filtering that mimics processing by a cochlear implant--significantly activated the MOC reflex, whereas listening to speech-in-background noise revealed instead engagement of midbrain and cortical resources. An auditory periphery model reproduced these speech degradation-specific effects, providing a rationale for goal-directed gating of the MOC reflex to enhance representation of speech features in the auditory nerve. Our data reveals the co-existence of two strategies in the auditory system that may facilitate speech understanding in situations where the speech signal is either intrinsically degraded or masked by extrinsic auditory information.

neuroscience↗