The inferior colliculus (IC) is the major midbrain auditory integration center, where virtually all ascending auditory inputs converge. Although the IC has been extensively studied for sound processing, little is known about the neural activity of the IC in moving subjects, as frequently happens in natural hearing conditions. Here, by recording neural activity in walking mice, we show that the activity of IC neurons is strongly modulated by locomotion, even in the absence of sound stimuli. Similar modulation was also found in hearing-impaired mice, demonstrating that IC neurons receive non-auditory, locomotion-related neural signals. Sound-evoked activity was attenuated during locomotion, and this attenuation increased frequency selectivity across the neuronal population, while maintaining preferred frequencies. Our results suggest that during behavior, integrating movement-related and auditory information is an essential aspect of sound processing in the IC.

The inferior colliculus (IC) is the major midbrain auditory integration center, where virtually all ascending auditory inputs converge. Although the IC has been extensively studied for sound processing, little is known about the neural activity of the IC in moving subjects, as frequently happens in natural hearing conditions. Here we show, by recording the IC neural activity in walking mice, the activity of IC neurons is strongly modulated by locomotion in the absence of sound stimulus presentation. Similar modulation was also found in deafened mice, demonstrating that IC neurons receive non-auditory, locomotion-related neural signals.Sound-evoked activity was attenuated during locomotion, and the attenuation increased frequency selectivity across the population, while maintaining preferred frequencies. Our results suggest that during behavior, integrating movement-related and auditory information is an essential aspect of sound processing in the IC.The inferior colliculus (IC) is the major auditory integration center in the midbrain, where virtually all ascending inputs from the auditory brainstem and the descending cortical inputs converge (Adams, 1979(Adams, , 1980Malmierca, 2004;Winer and Schreiner, 2005). The IC plays a critical role in auditory processing, such as representing spectrotemporal features and communication sounds (Egorova et al.While auditory response properties have been extensively studied, most of neural recordings in the IC have been performed in stationary subjects, and little is known about the IC activity while subjects are engaged in locomotion.The central nucleus of the IC is considered a predominantly auditory structure. In contrast, the shell region of the IC (the lateral and dorsal cortex) receives non-auditory inputs such as somatosensory inputs (Cooper and Young, 1976;Morest and Oliver, 1984;Coleman and Clerici, 1987;Lesicko et al., 2016) and is thought to perform multi-sensory integration (Aitkin et al., 1978(Aitkin et al., , 1981 Jain and Shore, 2016). The shell region has also been implicated in generating sound-driven behavior by projecting to motor-related regions (Huffman and Henson, 1990;Xiong et al., 2015). Although this multi-modal integration may subserve a range of functions (Gruters and Groh, 2012), modulation of the IC activity during vocalization (Schuller, 1979;Tammer et al., 2004; ) or eye movements (Groh et al., 2001;Porter et al., 2006Porter et al., , 2007 suggests that a main role of the non-auditory inputs is providing motor-related information.Movement adds challenges to auditory processing such as recognizing sounds associated with movement itself or changing spatial relationships with a sound source. In order to Neural modulation precedes locomotion onsetWhen mice walk on a treadmill, the movements generate low intensity sounds. Therefore, NeurophysiologyMice were acclimated to head-fixing and walking on a passive disc-type treadmill for 2-4 days (one 30 min session per day) prior to neurophysiological recordings. On the day of significantly modulated by lo...

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