Sensing Movement: Encoding of Self and External Motion by Auditory Cortical Neuronal Ensembles

Abstract

In the world, humans and animals continuously receive sensory information, decode from it information about the environment and use that information to guide survival. For each sensory modality, continuous information can be produced by either the self, or an external source, and both are equally important for survival. Recent technological advances have allowed neuroscientists the ability to understand how neural populations encode continuous sensory information and how to localize the functional cortical region producing the behaviors. Across sensory modalities, self-generated locomotion, a ubiquitous and simple form of continuous sensory input, has been shown to have a direct effect on sensory processing and behavior. In the visual and somatosensory cortices, self-generated locomotion information is encoded by neural populations in each respective sensory cortex, but that has yet to be addressed in auditory neural populations. This dissertation addresses this gap by combining behavioral learning, cortical inactivation, two-photon calcium imaging, electrophysiology, and computational modeling to demonstrate that auditory neural populations encode self-generated locomotion and that it is necessary for learned adaptive behaviors. This finding, along with previous studies, suggests that the ability to integrate continuous sensory information and locomotive state is a fundamental property across sensory modalities, and necessary for quick adaptive behavioral processing and learning. While the ability to continuously integrate self-locomotion and sensory information has been studied, very little to no work has attempted to understand how and if sensory neural populations encode and integrate the movement of external sensory objects. In the visual and auditory modalities, studies have replicated external movement by using a VR system to play a moving video or increasing the sound intensity to mimic something approaching. However, in the real world, humans and animals move, and so do predators, prey, and mates. Thus, the ability to continuously track, or monitor the movement of an external object, is necessary for survival. This dissertation combines behavioral learning and two-photon calcium imaging to demonstrate that animals can be trained to understand the movement of external object, and auditory neural populations encode information about the movement of external sources. Beyond simply processing auditory information, primary auditory cortex, continuously monitors and integrates self-generated locomotion and external object motion information to guide behaviors.