Thesis defense Fei Ma

Rodents are whisker specialists; they gather tactile sensory information by rhythmically sweeping their whiskers back and forth to actively seek and palpate objects in their immediate surroundings and efficiently guide their navigation, locomotion, and exploration. To optimize tactile information collection, rodents are able to precisely control the spatial and temporal positioning of their whiskers depending on recent sensory experiences, a process known as active sensing. Effective sensorimotor coordination for active sensing requires the incorporation of bottom-up stimuli (i.e., the current state of the world) with top-down modulations (i.e., organismal goals, neural predictions, and beliefs about the current state of the world). Bottom-up control is a closed loop that involves constant interplay between sensory input and motor output. Top-down modulation, which is often accomplished by neuromodulators, permits the participation of attention, motivation, and expectation in altering the integration and perception of the sensory drive and, as a result, the resulting motor commands. In this thesis, we employ cutting-edge experimental approaches, such as high-speed behavioral monitoring, large-scale extracellular electrophysiological recording, pathwayspecific chemical genetic inactivation, and receptor-selective neuropharmacological intervention, to investigate sensorimotor control for object localization in freely behaving mice, as well as neural correlates for active tactile sensing.