Abstract: Objective To explore the characteristics of the evolution of auditory response signal-to-noise ratio at all levels of the ascending auditory pathway, its modulation by different brain states in different brain regions, and its potential value as an effective indicator for encoding sound characteristics. Methods Eighty C57BL/6J awake mice were used for recording the best frequency auditory response of the neurons in the inferior colliculus (n=20), medial geniculate body (n=20), and primary auditory cortex using a glass microelectrode. The probability density of spontaneous and evoked firing of the neurons was calculated to establish a distribution model of spontaneous and evoked firing, and the evolution of the auditory response signal-to-noise ratio was statistically analyzed. The changes in spontaneous and evoked firing of the neurons and the auditory response signal- to-noise ratio in different brain regions were analyzed at rest and during running. Results In different brain regions in the ascending auditory pathway, the spontaneous firing of the neurons all showed a Poisson distribution, and the evoked firing showed a lognormal distribution. The auditory response signal- to-noise ratio was significantly greater in the inferior colliculus than in the medial geniculate body and auditory cortex (P<0.001). The auditory response signal-to-noise ratio in the 3 brain regions remained stable irrespective of the states of motion (P>0.05). Conclusion Auditory response signal-to-noise ratio may serve as an effective indicator of encoding sound characteristics.

Key words: auditory response signal-to-noise ratio; ascending auditory neural pathway; brain states; auditory cortex