Phase synchronization in the cochlea at transition from mechanical waves to electrical spikes

Abstract

Measured auditory nervous spikes often show synchronization, phase-locking, or entrainment (P. Cariani, Neural Plast. 6(4), 142-172 (1999) and Kumaresana et al., J. Acoust. Soc. Am. 133(6), 4290-4310 (2013). Physiologically synchronization is found in the anteroventral cochlear nucleus (Joris et al., J. Neurophysiol. 71(3), 1022-1036 (1994)) or in the trapezoid body also between critical bandwidths (Louage et al., Auditory Signal Processing: Physiology, Psychoacoustics, and Models (Springer, New York, 2004), pp. 100-106). The effect is an enhancement of pitch detection, spatial localization, or speech intelligibility. To investigate the presence of synchronization already in the cochlea, in the present paper, a finite-difference time-domain model of the cochlea is implemented with conditions for spike excitation caused by mechanical basilar membrane displacement. This model shows synchronization already in the cochlea at the transition from mechanical waves to nerve spike excitation. Using a sound as model input consisting of ten harmonic overtones with random phase relations, the output spikes are strongly phase aligned after this transition. When using a two-sinusoidal complex as input, and altering the phase relations between the two sinusoidals, the output spikes show the higher sinusoidal shifting the phase of the lower one in its direction in a systematic way. Therefore, already during the transition from mechanical to electrical excitation within the cochlea, synchronization appears to be improving perception of pitch, speech, or localization.

Influence of music on empirical brain networks

“…The transformation of sound into neural spikes is the subject of much current research (Bader, 2015(Bader, , 2017(Bader, , 2018. Music, speech, or any sound enters through the outer and middle ear as sound pressure, then acting on the oval window of the cochlear.…”

Neural coincidence detection strategies during perception of multi-pitch musical tones

“…All sounds were processed using a cochlear model and post-processing the cochlear output. The cochlear model was used before in a study of phase-synchronization of partials in the transition between mechanical motion on the basilar membrane into neural spikes 5 , in a coincidence detection model using a Iszikevich neural model 3 , when studying cello surface sounds 2 , or as foundation of a pitch theory 4 .…”

Pitch and timbre discrimination at wave-to-spike transition in the cochlea

“…The present model has been discussed in detail before 3 . A phase synchronization of spikes appeared at the transition between mechanical energy on the BM and the spiks excited by this energy.…”

“…As until now no neural network has been found displaying an autocorrelation, which would need to be present in the nucleus cochlearis or the trapezoid body, pitch perception based on an autocorrelation is of doubt. Therefore a Finite-Difference Time Domain (FDTD) model of the cochlea with a transfer of mechanical energy into spikes is used as introduced before 3 . The cochleogram calculated is then further investigated in terms of Inerspike Interval (ISI) histograms and bark Periodicities (BP) to show the temporal and spatial coding of pitch and residue pitch.…”