The sonar aperture and its neural representation in bats

Area of Science:

• Auditory neuroscience
• Animal behavior
• Sensory biology

Background:

• Biosonar imaging presents challenges for auditory systems due to the lack of spatial arrangement in sensory epithelia.
• Echolocating bats use echo intensity and sonar aperture to encode object width, but the relative importance of these cues is unclear.

Purpose of the Study:

• To investigate whether bats (Phyllostomus discolor) utilize echo intensity or sonar aperture, or both, to estimate object width.
• To determine the behavioral relevance and neural encoding of sonar aperture in bat biosonar.

Main Methods:

• Combined psychophysical experiments with electrophysiological recordings in bats.
• Virtual-object playback experiments to control echo intensity and sonar aperture independently.
• Analysis of neural unit responses in the auditory midbrain and cortex.

Main Results:

• Bat discrimination performance for object width was similar whether echo intensity and sonar aperture covaried naturally or when only sonar aperture was varied.
• Bats could detect changes in object width without echo intensity cues, demonstrating the importance of sonar aperture.
• Auditory midbrain and cortical neurons showed strongest responses to specific sonar apertures, irrespective of echo intensity variations.

Conclusions:

• Sonar aperture is a behaviorally relevant and reliably encoded cue for estimating object size in bat biosonar.
• The auditory system, particularly cortical units, effectively processes sonar aperture for spatial perception.
• This research clarifies the sensory mechanisms underlying spatial property estimation in biosonar.