A Temporal Filter for Binaural Hearing Is Dynamically Adjusted by Sound Pressure Level.

Area of Science:

• Neuroscience
• Auditory System Physiology
• Sensory Processing

Background:

• The auditory system processes diverse sounds with fluctuating amplitudes in natural environments.
• Sound pressure level influences neuronal response patterns, necessitating adaptive temporal filtering.
• The dorsal nuclei of the lateral lemniscus (DNLL) may act as a temporal filter suppressing binaural fluctuations.

Purpose of the Study:

• To investigate how sound pressure levels affect temporal filters in mammalian binaural processing.
• To test the hypothesis that the mammalian binaural system dynamically adjusts temporal filters.
• To correlate physiological findings with human psychophysical perception of temporal sound events.

Main Methods:

• In vivo and in vitro electrophysiology in Mongolian gerbils.
• Investigated the integration of excitation and inhibition in the DNLL.
• Human psychophysical experiments on tone detection and localization at varying sound levels.

Main Results:

• The temporal properties of the DNLL inhibitory filter are defined by ascending excitation and contralateral inhibition.
• Synaptic drive, modulated by sound pressure level and N-methyl-D-aspartate receptor (NMDAR) signaling, shapes the filter's time course.
• Human temporal perception of sound detection and localization varies with sound pressure level, aligning with physiological data.

Conclusions:

• Mammalian binaural systems dynamically adjust temporal filtering based on sound level.
• This level-dependent adjustment optimizes the time window for sound detection and localization.
• NMDAR signaling plays a role in modulating these adaptive temporal filtering mechanisms.