Auditory object analysis

The auditory analysis of the echoes reflected off objects in the bats' surrounding is the basis for a biosonar-based perception of the world. To understand the ecology of echolocation, we need to understand how object features are coded in echoes, how these echoes are analysed by the auditory system, and how a bat's perceptual strategies are adapted to its ecology.

The visual system possesses a spatially arranged sensory epithelium, the retina and can thus directly represent the spatial arrangement of an organisms' environment. In contrast, the sensory organ of the auditory domain, the cochlea, is arranged by frequency. Naturally, animals that orient themselves by echolocation can extract lots of information about the targeted objects from the returning echoes. However, there is no 1:1 relationship between the acoustic features of the echo and the spatial layout of the environment. Bats must use spectral and temporal echo cues to create an internal representation of their surroundings.

Here we aim to understand if and how bats perceive the spatial and temporal frequency of rippled surfaces, such as water. Many bat species forage above water bodies, even though a rippled surface can pose a challenge for prey detection due to additional echoes being reflected off the water ripples. We hypothesize that the the auditory system employs a mechanism for foreground/background separation that is functionally analogue to the analysis of spatial frequencies in the visual domain. We use both precisely controlled psychophysical training experiments, semi-natural experiments with free-flying bats foraging from rippled water surfaces, and observations of free-flying bats in the wild.

This project is a collaboration with Prof. Dr. Lutz Wiegrebe at the Ludwig-Maximilians-University Munich.