Characterization of Auditory Responsive Neurons in the Mouse Superior Colliculus to White Noise and Frequency-Restricted Sounds.

Locating the source of a specific sound in a complex environment and determining its saliency is critical for survival. The superior colliculus (SC), a sensorimotor midbrain structure, plays an important role in sound localization and has been shown to have a topographic map of the auditory space in a range of species. In mice, previous studies using broadband white noise stimuli found that high-frequency monaural spectral cues and interaural-level differences (ILDs) are used to generate a neuron's spatially restricted receptive field (RF) and that these RFs are organized topographically along the azimuth. However, in a naturalistic environment, the auditory stimuli that an animal encounters may have restricted spectral components, although these sound sources can still be localized efficiently. It remains unknown whether and how the SC neurons respond to frequency-restricted sounds and, in turn, how this changes the organization of their RFs into a topographic map. Here, we show results from large-scale in vivo physiological recordings of SC neurons from male and female mice in response to white noise, naturalistic ultrasonic pup call, and chirps. We find that mouse SC auditory neurons respond to a pup call and chirps with distinct temporal patterns and a spatial preference predominantly at ∼60° in contralateral azimuth. In addition, we categorized auditory SC neurons based on their spectrotemporal RF patterns and demonstrated that there are at least four classes of auditory-responsive neurons in the SC that lie in different locations along the anteroposterior axis of the SC.