Biosonar spatial resolution along the distance axis: revisiting the clutter interference zone

Unlike all other remote senses like vision or hearing, echolocation allows estimating the distance of an object. Not only have echolocating bats and toothed whales been shown to measure distance by echolocation extremely precisely, distance information is even topographically represented by a neuro-computational map in bats auditory cortex. This topographic representation and the corresponding tuning of cortical cells to object distance suggests the bats may be able to perceptually resolve multiple, simultaneously present objects along the distance axis. Here we use a novel psychophysical paradigm with complex phantom targets to quantity spatial resolution along the distance axis in the echolocating bat Phyllostomus discolor. We show that our bats can indeed perceptually resolve objects along the distance axis when they are separated by about 40 cm (around a reference distance of 108 cm) along the distance axis. These results are well comparable to earlier work on bats clutter interference zone (Simmons et al., 1988) and confirm those results with a more robust psychophysical paradigm. Summary statementEcholocating bats perceive absolute distance to objects by measuring the time delay between call and echo. In addition, they possess spatial resolution along the distance axis.