Biosonar navigation above water II: exploiting mirror images

Area of Science:

• Bioacoustics
• Neuroethology
• Sensory Ecology

Background:

• Smooth surfaces like water create acoustic mirror images from sonar signals.
• Echolocating bats encounter these mirror images when flying over water bodies.
• Understanding bat navigation relies on how they process complex acoustic cues.

Purpose of the Study:

• To investigate if bats exploit echo-acoustic mirror images for navigation.
• To determine how the auditory cortex encodes these mirrorlike echo-acoustic cues.
• To provide behavioral and neurophysiological evidence for the use of acoustic mirror images in obstacle avoidance.

Main Methods:

• Combined electrophysiological recordings with a behavioral obstacle-avoidance task.
• Analyzed sonar ensonification patterns and echo delays.
• Recorded cortical spatiotemporal response maps (STRMs) to assess neural tuning.

Main Results:

• Most bats successfully used echo-acoustic mirror images for obstacle avoidance.
• Sonar analysis revealed changes in reflection patterns and increased target strengths for mirrored objects.
• Cortical neurons showed a preference for echoes with long delays and low elevations, consistent with mirrored reflections.

Conclusions:

• Bats can effectively exploit echo-acoustic mirror images for navigation and obstacle avoidance.
• Specific neural encoding in the auditory cortex supports the processing of these complex acoustic cues.
• This capability enhances echo-acoustic navigation in cluttered natural environments.