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Published on: November 26, 2012
Neural coding of echo-envelope disparities in echolocating bats.
Frank Borina1, Uwe Firzlaff, Lutz Wiegrebe
1Division of Neurobiology, Department Biologie II, Ludwig-Maximilians-Universität München, Großhadernerstr. 2, 82152, Planegg-Martinsried, Germany.
Summary
Bats use interaural time differences (ITDs) in echo envelopes for echolocation. This study found neurons sensitive to envelope ITDs, crucial for locating objects, especially with complex natural reflectors like vegetation.
Area of Science:
- Neuroscience
- Bioacoustics
- Sensory Biology
Background:
- Echolocation in bats relies on processing echo delays and binaural cues (IIDs and ITDs) for object localization.
- While interaural intensity differences (IIDs) are well-established, the role of interaural time differences (ITDs) in echo envelopes for complex targets is less understood.
Purpose of the Study:
- To investigate the neural basis of echo envelope processing in bat echolocation.
- To determine if bats utilize envelope interaural time differences (ITDs) for navigating complex environments.
Main Methods:
- Extracellular recordings were performed on neurons in the auditory midbrain of the bat Phyllostomus discolor.
- Neuronal sensitivity to envelope ITDs was analyzed in response to simulated sonar echoes with varying temporal fluctuations.
Main Results:
- A population of auditory midbrain neurons sensitive to envelope ITDs was identified in Phyllostomus discolor.
- The sensitivity of these neurons to envelope ITDs increased with greater temporal fluctuations in echo envelopes.
- This finding correlates with the spatial statistics of complex natural reflectors, such as vegetation.
Conclusions:
- Bats may use envelope ITDs for echolocation, particularly when ensonifying complex natural targets.
- Temporal fluctuations in echo envelopes, generated by reflections from complex surfaces, enhance ITD-mediated echolocation.
- Envelope ITDs contribute to both the detection of external sounds and spatial awareness during echolocation.
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