Microseconds-level coding of echo delay in the auditory brainstem of an FM-echolocating bat
Andrea Megela Simmons1,2,3, Michaela Warnecke2, James A Simmons2,3
1Department of Cognitive and Psychological Sciences, Brown University, Providence, Rhode Island, United States.
Journal of Neurophysiology
|November 21, 2024
Summary
Big brown bats achieve precise echo delay detection using neural population responses. Latency jitter in brainstem nuclei approaches the bats' remarkable perceptual acuity.
Area of Science:
- Neuroscience
- Auditory Neuroscience
- Sensory Systems
Background:
- Echolocating bats, like the big brown bat (Eptesicus fuscus), exhibit extraordinary precision in detecting ultrasonic echo delays, reaching sensitivities of 1 microsecond or less.
- The neural mechanisms underlying this hyperacuity in echo delay detection remain largely unknown.
- Understanding these mechanisms is crucial for deciphering the neural basis of sensory perception.
Purpose of the Study:
- To investigate the precision of neural latency registration, specifically latency jitter, in population responses within the bat auditory system.
- To determine if neural population jitter could explain the bat's exceptional echo delay acuity.
- To compare latency jitter in different brainstem auditory nuclei.
Main Methods:
- Local field potentials were recorded from the cochlear nucleus and inferior colliculus of anesthetized big brown bats.
- Responses were measured to simulated echolocation sounds, including a frequency-modulated sweep and a four-echo cascade at varying delays.
- Latency jitter was quantified for neural responses to the initial sound and subsequent echoes.
Main Results:
- Mean latency jitter was found to be approximately 51 µs in the cochlear nucleus and 56 µs in the inferior colliculus for the initial sound.
- Latency jitter increased for successive echoes, with means of 125 µs and 111 µs, respectively.
- These population-level latency jitter values are significantly lower than those typically reported for single neurons and approach the bats' psychophysical acuity.
Conclusions:
- Neural population latency jitter in the cochlear nucleus and inferior colliculus is precise enough to potentially account for the big brown bat's high acuity in echo delay detection.
- The findings suggest that synchronized population activity, rather than individual neuron precision, may underlie this remarkable perceptual feat.
- Further systems-level research is needed to fully elucidate the neural computations involved in bat echolocation perception.
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