The proposed research investigates how auditory neurons in the midbrain superior colliculus (SC) of the echolocating bat, Eptesicus fuscus, respond to the motion of sounds along the range axis (Aim I) and examines how the temporal features of sounds affect the spatial tuning of SC neurons (Aim II). The echolocating bat presents an excellent model system to study auditory motion processing because of the role the SC plays in its ability to track and capture moving insect prey. The experiments under Aim I use extracellular recordings from single SC neurons to test three hypotheses in a head-fixed, passively listening bats: (1) that SC neurons show selective responses to direction of motion along the range axis, (2) that SC neurons show response field shifts in the direction opposite of a sounds motion, and (3) that SC neurons are tuned to a sound's motion velocity. The experiments under Aim II use extracellular recording from single neurons to test two hypotheses of how auditory spatial tuning in the SC is affected by the pulse interval (PI) with which simulated echolocation cries and returning echoes are presented: (1) that the spatial tuning of SC neurons sharpens at lower PIs and (2) that stable PIs are necessary for echo-delay tuned responses. ? ? ?
