Encoding sound in the cochlea: from receptor potential to afferent discharge

• Autores: Rutherford, Mark A.; von Gersdorff, Henrique; Goutman, Juan Diego
• Año de publicación: 2021
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: FIRST-SPIKE LATENCY; PHASE-LOCKING; RECEPTOR POTENTIAL; RIBBON SYNAPSE; SYNAPTIC DELAY; TEMPORAL CODE
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

Ribbon-class synapses in the ear achieve analog to digital transformation of a continuously graded membrane potential to all-or-none spikes. In mammals, several auditory nerve fibres (ANFs) carry information from each inner hair cell (IHC) to the brain in parallel. Heterogeneity of transmission among synapses contributes to the diversity of ANF sound-response properties. In addition to the place code for sound frequency and the rate code for sound level, there is also a temporal code. In series with cochlear amplification and frequency tuning, neural representation of temporal cues over a broad range of sound levels enables auditory comprehension in noisy multi-speaker settings. The IHC membrane time constant introduces a low-pass filter that attenuates fluctuations of the receptor potential above 1?2 kHz. The ANF spike generator adds a high-pass filter via its depolarization-rate threshold that rejects slow changes in the postsynaptic potential and its phasic response property that ensures one spike per depolarization. Synaptic transmission involves several stochastic subcellular processes between IHC depolarization and ANF spike generation, introducing delay and jitter that limits the speed and precision of spike timing. ANFs spike at a preferred phase of periodic sounds in a process called phase-locking that is limited to frequencies below a few kilohertz by both the IHC receptor potential and the jitter in synaptic transmission. During phase-locking to periodic sounds of increasing intensity, faster and facilitated activation of synaptic transmission and spike generation may be offset by presynaptic depletion of synaptic vesicles, resulting in relatively small changes in response phase. Here we review encoding of spike-timing at cochlear ribbon synapses.
Fil: Rutherford, Mark A.. Washington University in St. Louis; Estados Unidos
Fil: von Gersdorff, Henrique. Oregon Health and Sciences University; Estados Unidos
Fil: Goutman, Juan Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; Argentina