Determining auditory-evoked activities from multiple cells in layer 1 of the dorsal cortex of the inferior colliculus of mice by in vivo calcium imaging

• An in vivo Ca2+ imaging method was established in the inferior colliculus (IC).
• Most layer 1 cells in the dorsal cortex of IC responded to both tone and noise.
• Most layer 1 cells in the dorsal cortex of IC tuned to low-frequency tones.

Layer 1 of the dorsal cortex of the inferior colliculus (DCIC) is distinguished from other layers by its cytoarchitecture and fiber connections. However, the information of the sound types represented in layer 1 of the DCIC remains unclear because placing electrodes on such thin structures is challenging. In this study, we utilized in vivo calcium imaging to assess auditory-evoked activities in multiple cells in layer 1 of DCIC and to characterize sound stimuli producing strong activity. Most cells examined showed strong responses to broad-band noise and low-frequency tone bursts of high sound intensity. In some cases, we successfully obtained frequency response areas, which are receptive fields to tone frequencies and intensities, and ~30% of these showed V-shape tunings. This is the first systematic study to record auditory responses of cells in layer 1 of DCIC. These results indicate that cells in this area are selective to tones with low frequency, implying the importance of such auditory information in the neural circuitry of layer 1 of DCIC.