The spatial and temporal resolution of bat sonar

• Applicant: Professor Dr. Lutz Wiegrebe (†)
• Subject Area: Sensory and Behavioural Biology
• Term: from 2008 to 2013
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 73153028

Ultrasonic echo imaging enables bats not only to orient through complex environments in total darkness, but also to identify complex, three-dimensional objects in space. When a bat ensonifies a natural echo-acoustic scene, many echoes will impinge almost simultaneously from many different directions onto the bats’ ears. To date there is nothing known about the bats’ capability to spatially resolve single reflectors from this multitude of echoes. Within this grant proposal, the spatial resolution of bat sonar is investigated in a series of formal psychophysical phantomtarget experiments: In a six-channel, two-alternative, forced-choice setup, the echolocating bat Phyllostomus discolor will be trained to detect a rewarded phantomtarget surrounded by masking phantom targets. The recruitment of multiple maskers allows quantifying sonar spatial receptive fields perceptually and comparing these with the directionality of the sonar beam, the directionality of the bats’ outer ears, and electrophysiologically measured spatio-temporal receptive fields. The phantom-target technique allows manipulating not only spatial but also temporal and spectral characteristics of the target and masker reflections. Specifically, the contributions of differences in echo delay or spectral content between signal- and masker reflections onto spatial unmasking will be assessed. These experiments will gain a detailed insight into how echolocating bats exploit the spatial characteristics of their sonar system to inspect complex echo-acoustic scenes in space.

• DFG Programme: Research Grants