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Salles A, Loscalzo E, Montoya J, Mendoza R, Boergens KM, Moss CF. Auditory processing of communication calls in interacting bats. iScience 2024; 27:109872. [PMID: 38827399 PMCID: PMC11141141 DOI: 10.1016/j.isci.2024.109872] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Revised: 01/15/2024] [Accepted: 04/29/2024] [Indexed: 06/04/2024] Open
Abstract
There is strong evidence that social context plays a role in the processing of acoustic signals. Yet, the circuits and mechanisms that govern this process are still not fully understood. The insectivorous big brown bat, Eptesicus fuscus, emits a wide array of communication calls, including food-claiming calls, aggressive calls, and appeasement calls. We implemented a competitive foraging task to explore the influence of behavioral context on auditory midbrain responses to conspecific social calls. We recorded neural population responses from the inferior colliculus (IC) of freely interacting bats and analyzed data with respect to social context. Analysis of our neural recordings from the IC shows stronger population responses to individual calls during social events. For the first time, neural recordings from the IC of a copulating bat were obtained. Our results indicate that social context enhances neuronal population responses to social vocalizations in the bat IC.
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Affiliation(s)
- Angeles Salles
- Department of Biological Sciences, University of Illinois Chicago, Chicago, IL 60607, USA
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Emely Loscalzo
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Jessica Montoya
- Department of Biological Sciences, University of Illinois Chicago, Chicago, IL 60607, USA
| | - Rosa Mendoza
- Department of Biological Sciences, University of Illinois Chicago, Chicago, IL 60607, USA
| | - Kevin M. Boergens
- Department of Physics, University of Illinois Chicago, Chicago, IL 60607, USA
| | - Cynthia F. Moss
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD 21218, USA
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Oscillatory discharges in the auditory midbrain of the big brown bat contribute to coding of echo delay. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2023; 209:173-187. [PMID: 36383255 DOI: 10.1007/s00359-022-01590-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2022] [Revised: 10/17/2022] [Accepted: 10/20/2022] [Indexed: 11/17/2022]
Abstract
Subsequent to his breakthrough discovery of delay-tuned neurons in the bat's auditory midbrain and cortex, Albert Feng proposed that neural computations for echo delay involve intrinsic oscillatory discharges generated in the inferior colliculus (IC). To explore further the presence of these neural oscillations, we recorded multiple unit activity with a novel annular low impedance electrode from the IC of anesthetized big brown bats and Seba's short-tailed fruit bats. In both species, responses to tones, noise bursts, and FM sweeps contain long latency components, extending up to 60 ms post-stimulus onset, organized in periodic, oscillatory-like patterns at frequencies of 360-740 Hz. Latencies of this oscillatory activity resemble the wide distributions of single neuron response latencies in the IC. In big brown bats, oscillations lasting up to 30 ms after pulse onset emerge in response to single FM pulse-echo pairs, at particular pulse-echo delays. Oscillatory responses to pulses and evoked responses to echoes overlap extensively at short echo delays (5-7 ms), creating interference-like patterns. At longer echo delays, responses are separately evident to both pulses and echoes, with less overlap. These results extend Feng's reports of IC oscillations, and point to different processing mechanisms underlying perception of short vs long echo delays.
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Macias S, Bakshi K, Troyer T, Smotherman M. The prefrontal cortex of the Mexican free-tailed bat is more selective to communication calls than primary auditory cortex. J Neurophysiol 2022; 128:634-648. [PMID: 35975923 PMCID: PMC9448334 DOI: 10.1152/jn.00436.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Revised: 07/20/2022] [Accepted: 08/05/2022] [Indexed: 11/22/2022] Open
Abstract
In this study, we examined the auditory responses of a prefrontal area, the frontal auditory field (FAF), of an echolocating bat (Tadarida brasiliensis) and presented a comparative analysis of the neuronal response properties between the FAF and the primary auditory cortex (A1). We compared single-unit responses from the A1 and the FAF elicited by pure tones, downward frequency-modulated sweeps (dFMs), and species-specific vocalizations. Unlike the A1, FAFs were not frequency tuned. However, progressive increases in dFM sweep rate elicited a systematic increase of response precision, a phenomenon that does not take place in the A1. Call selectivity was higher in the FAF versus A1. We calculated the neuronal spectrotemporal receptive fields (STRFs) and spike-triggered averages (STAs) to predict responses to the communication calls and provide an explanation for the differences in call selectivity between the FAF and A1. In the A1, we found a high correlation between predicted and evoked responses. However, we did not generate reasonable STRFs in the FAF, and the prediction based on the STAs showed lower correlation coefficient than that of the A1. This suggests nonlinear response properties in the FAF that are stronger than the linear response properties in the A1. Stimulating with a call sequence increased call selectivity in the A1, but it remained unchanged in the FAF. These data are consistent with a role for the FAF in assessing distinctive acoustic features downstream of A1, similar to the role proposed for primate ventrolateral prefrontal cortex.NEW & NOTEWORTHY In this study, we examined the neuronal responses of a frontal cortical area in an echolocating bat to behaviorally relevant acoustic stimuli and compared them with those in the primary auditory cortex (A1). In contrast to the A1, neurons in the bat frontal auditory field are not frequency tuned but showed a higher selectivity for social signals such as communication calls. The results presented here indicate that the frontal auditory field may represent an additional processing center for behaviorally relevant sounds.
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Affiliation(s)
- Silvio Macias
- Department of Biology, Texas A&M University, College Station, Texas
| | - Kushal Bakshi
- Institute for Neuroscience, Texas A&M University, College Station, Texas
| | - Todd Troyer
- Department of Neuroscience, Developmental and Regenerative Biology, University of Texas at San Antonio, San Antonio, Texas
| | - Michael Smotherman
- Department of Biology, Texas A&M University, College Station, Texas
- Institute for Neuroscience, Texas A&M University, College Station, Texas
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Beetz MJ, Hechavarría JC. Neural Processing of Naturalistic Echolocation Signals in Bats. Front Neural Circuits 2022; 16:899370. [PMID: 35664459 PMCID: PMC9157489 DOI: 10.3389/fncir.2022.899370] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Accepted: 04/21/2022] [Indexed: 11/18/2022] Open
Abstract
Echolocation behavior, a navigation strategy based on acoustic signals, allows scientists to explore neural processing of behaviorally relevant stimuli. For the purpose of orientation, bats broadcast echolocation calls and extract spatial information from the echoes. Because bats control call emission and thus the availability of spatial information, the behavioral relevance of these signals is undiscussable. While most neurophysiological studies, conducted in the past, used synthesized acoustic stimuli that mimic portions of the echolocation signals, recent progress has been made to understand how naturalistic echolocation signals are encoded in the bat brain. Here, we review how does stimulus history affect neural processing, how spatial information from multiple objects and how echolocation signals embedded in a naturalistic, noisy environment are processed in the bat brain. We end our review by discussing the huge potential that state-of-the-art recording techniques provide to gain a more complete picture on the neuroethology of echolocation behavior.
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Affiliation(s)
- M. Jerome Beetz
- Zoology II, Biocenter, University of Würzburg, Würzburg, Germany
| | - Julio C. Hechavarría
- Institute of Cell Biology and Neuroscience, Goethe University Frankfurt, Frankfurt, Germany
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Yu C, Moss CF. Natural acoustic stimuli evoke selective responses in the hippocampus of passive listening bats. Hippocampus 2022; 32:298-309. [PMID: 35085416 PMCID: PMC9306857 DOI: 10.1002/hipo.23407] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Revised: 12/21/2021] [Accepted: 01/12/2022] [Indexed: 11/10/2022]
Abstract
A growing body of research details spatial representation in bat hippocampus, and experiments have yet to explore hippocampal neuron responses to sonar signals in animals that rely on echolocation for spatial navigation. To bridge this gap, we investigated bat hippocampal responses to natural echolocation sounds in a non‐spatial context. In this experiment, we recorded from CA1 of the hippocampus of three awake bats that listened passively to single echolocation calls, call‐echo pairs, or natural echolocation sequences. Our data analysis identified a subset of neurons showing response selectivity to the duration of single echolocation calls. However, the sampled population of CA1 neurons did not respond selectively to call‐echo delay, a stimulus dimension posited to simulate target distance in recordings from auditory brain regions of bats. A population analysis revealed ensemble coding of call duration and sequence identity. These findings open the door to many new investigations of auditory coding in the mammalian hippocampus.
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Affiliation(s)
- Chao Yu
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, Maryland, USA
| | - Cynthia F Moss
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, Maryland, USA
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Allen KM, Salles A, Park S, Elhilali M, Moss CF. Effect of background clutter on neural discrimination in the bat auditory midbrain. J Neurophysiol 2021; 126:1772-1782. [PMID: 34669503 PMCID: PMC8794058 DOI: 10.1152/jn.00109.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2021] [Revised: 09/22/2021] [Accepted: 10/12/2021] [Indexed: 11/22/2022] Open
Abstract
The discrimination of complex sounds is a fundamental function of the auditory system. This operation must be robust in the presence of noise and acoustic clutter. Echolocating bats are auditory specialists that discriminate sonar objects in acoustically complex environments. Bats produce brief signals, interrupted by periods of silence, rendering echo snapshots of sonar objects. Sonar object discrimination requires that bats process spatially and temporally overlapping echoes to make split-second decisions. The mechanisms that enable this discrimination are not well understood, particularly in complex environments. We explored the neural underpinnings of sonar object discrimination in the presence of acoustic scattering caused by physical clutter. We performed electrophysiological recordings in the inferior colliculus of awake big brown bats, to broadcasts of prerecorded echoes from physical objects. We acquired single unit responses to echoes and discovered a subpopulation of IC neurons that encode acoustic features that can be used to discriminate between sonar objects. We further investigated the effects of environmental clutter on this population's encoding of acoustic features. We discovered that the effect of background clutter on sonar object discrimination is highly variable and depends on object properties and target-clutter spatiotemporal separation. In many conditions, clutter impaired discrimination of sonar objects. However, in some instances clutter enhanced acoustic features of echo returns, enabling higher levels of discrimination. This finding suggests that environmental clutter may augment acoustic cues used for sonar target discrimination and provides further evidence in a growing body of literature that noise is not universally detrimental to sensory encoding.NEW & NOTEWORTHY Bats are powerful animal models for investigating the encoding of auditory objects under acoustically challenging conditions. Although past work has considered the effect of acoustic clutter on sonar target detection, less is known about target discrimination in clutter. Our work shows that the neural encoding of auditory objects was affected by clutter in a distance-dependent manner. These findings advance the knowledge on auditory object detection and discrimination and noise-dependent stimulus enhancement.
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Affiliation(s)
- Kathryne M Allen
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, Maryland
| | - Angeles Salles
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, Maryland
| | - Sangwook Park
- Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland
| | - Mounya Elhilali
- Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland
| | - Cynthia F Moss
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, Maryland
- Department of Neuroscience, Johns Hopkins University, Baltimore, Maryland
- Department of Mechanical Engineering, Johns Hopkins University, Baltimore, Maryland
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Warnecke M, Simmons JA, Simmons AM. Population registration of echo flow in the big brown bat's auditory midbrain. J Neurophysiol 2021; 126:1314-1325. [PMID: 34495767 DOI: 10.1152/jn.00013.2021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Echolocating big brown bats (Eptesicus fuscus) perceive their surroundings by broadcasting frequency-modulated (FM) ultrasonic pulses and processing returning echoes. Bats echolocate in acoustically cluttered environments containing multiple objects, where each broadcast is followed by multiple echoes at varying time delays. The bat must decipher this complex echo cascade to form a coherent picture of the entire acoustic scene. Neurons in the bat's inferior colliculus (IC) are selective for specific acoustic features of echoes and time delays between broadcasts and echoes. Because of this selectivity, different subpopulations of neurons are activated as the bat flies through its environment, while the physical scene itself remains unchanging. We asked how a neural representation based on variable single-neuron responses could underlie a cohesive perceptual representation of a complex scene. We recorded local field potentials from the IC of big brown bats to examine population coding of echo cascades similar to what the bat might encounter when flying alongside vegetation. We found that the temporal patterning of a simulated broadcast followed by an echo cascade is faithfully reproduced in the population response at multiple stimulus amplitudes and echo delays. Local field potentials to broadcasts and echo cascades undergo amplitude-latency trading consistent with single-neuron data but rarely show paradoxical latency shifts. Population responses to the entire echo cascade move as a unit coherently in time as broadcast-echo cascade delay changes, suggesting that these responses serve as an index for the formation of a cohesive perceptual representation of an acoustic scene.NEW & NOTEWORTHY Echolocating bats navigate through cluttered environments that return cascades of echoes in response to the bat's broadcasts. We show that local field potentials from the big brown bat's auditory midbrain have consistent responses to a simulated echo cascade varying across echo delays and stimulus amplitudes, despite different underlying individual neuronal selectivities. These results suggest that population activity in the midbrain can build a cohesive percept of an auditory scene by aggregating activity over neuronal subpopulations.
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Affiliation(s)
| | - James A Simmons
- Department of Neuroscience, Brown University, Providence, Rhode Island.,Carney Institute for Brain Science, Brown University, Providence, Rhode Island
| | - Andrea Megela Simmons
- Department of Neuroscience, Brown University, Providence, Rhode Island.,Carney Institute for Brain Science, Brown University, Providence, Rhode Island.,Department of Cognitive, Linguistic, and Psychological Sciences, Brown University, Providence, Rhode Island
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Chitradurga Achutha A, Peremans H, Firzlaff U, Vanderelst D. Efficient encoding of spectrotemporal information for bat echolocation. PLoS Comput Biol 2021; 17:e1009052. [PMID: 34181643 PMCID: PMC8270447 DOI: 10.1371/journal.pcbi.1009052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 07/09/2021] [Accepted: 05/07/2021] [Indexed: 12/04/2022] Open
Abstract
In most animals, natural stimuli are characterized by a high degree of redundancy, limiting the ensemble of ecologically valid stimuli to a significantly reduced subspace of the representation space. Neural encodings can exploit this redundancy and increase sensing efficiency by generating low-dimensional representations that retain all information essential to support behavior. In this study, we investigate whether such an efficient encoding can be found to support a broad range of echolocation tasks in bats. Starting from an ensemble of echo signals collected with a biomimetic sonar system in natural indoor and outdoor environments, we use independent component analysis to derive a low-dimensional encoding of the output of a cochlear model. We show that this compressive encoding retains all essential information. To this end, we simulate a range of psycho-acoustic experiments with bats. In these simulations, we train a set of neural networks to use the encoded echoes as input while performing the experiments. The results show that the neural networks’ performance is at least as good as that of the bats. We conclude that our results indicate that efficient encoding of echo information is feasible and, given its many advantages, very likely to be employed by bats. Previous studies have demonstrated that low-dimensional encodings allow for task resolution at a relatively high level. In contrast to previous work in this area, we show that high performance can also be achieved when low-dimensional filters are derived from a data set of realistic echo signals, not tailored to specific experimental conditions. We show that complex (and simple) echoes from real environments can be efficiently and effectively represented using a small set of filters. Critically, we show that high performance across a range of tasks can be achieved when low-dimensional filters are derived from a data set of realistic echo signals, not tailored to specific experimental conditions. The redundancy in echoic information opens up the opportunity for efficient encoding, reducing the computational load of echo processing as well as the memory load for storing the information. Therefore, we predict the auditory system of bats to capitalize on this opportunity for efficient coding by implementing filters with spectrotemporal properties akin to those hypothesized here. Indeed, the filters we obtain here are similar to those found in other animals and other sensing capabilities. Our results indicate that bats could exploit the redundancy in sonar signals to implement an efficient neural encoding of the relevant information.
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Affiliation(s)
- Adarsh Chitradurga Achutha
- Mechanical and Materials Engineering, University of Cincinnati, Cincinnati, Ohio, United States of America
| | - Herbert Peremans
- Department of Engineering Management, University of Antwerp, Antwerp, Belgium
| | - Uwe Firzlaff
- Chair of Zoology, School of Life Sciences, Technical University of Munich, Freising, Germany
| | - Dieter Vanderelst
- Department of Biological Sciences, University of Cincinnati, Cincinnati, Ohio, United States of America
- * E-mail:
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Natural Statistics as Inference Principles of Auditory Tuning in Biological and Artificial Midbrain Networks. eNeuro 2021; 8:ENEURO.0525-20.2021. [PMID: 33947687 PMCID: PMC8211468 DOI: 10.1523/eneuro.0525-20.2021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Revised: 03/10/2021] [Accepted: 04/27/2021] [Indexed: 12/04/2022] Open
Abstract
Bats provide a powerful mammalian model to explore the neural representation of complex sounds, as they rely on hearing to survive in their environment. The inferior colliculus (IC) is a central hub of the auditory system that receives converging projections from the ascending pathway and descending inputs from auditory cortex. In this work, we build an artificial neural network to replicate auditory characteristics in IC neurons of the big brown bat. We first test the hypothesis that spectro-temporal tuning of IC neurons is optimized to represent the natural statistics of conspecific vocalizations. We estimate spectro-temporal receptive fields (STRFs) of IC neurons and compare tuning characteristics to statistics of bat calls. The results indicate that the FM tuning of IC neurons is matched with the statistics. Then, we investigate this hypothesis on the network optimized to represent natural sound statistics and to compare its output with biological responses. We also estimate biomimetic STRFs from the artificial network and correlate their characteristics to those of biological neurons. Tuning properties of both biological and artificial neurons reveal strong agreement along both spectral and temporal dimensions, and suggest the presence of nonlinearity, sparsity, and complexity constraints that underlie the neural representation in the auditory midbrain. Additionally, the artificial neurons replicate IC neural activities in discrimination of social calls, and provide simulated results for a noise robust discrimination. In this way, the biomimetic network allows us to infer the neural mechanisms by which the bat’s IC processes natural sounds used to construct the auditory scene.
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Beetz MJ, Kössl M, Hechavarría JC. The frugivorous bat Carollia perspicillata dynamically changes echolocation parameters in response to acoustic playback. J Exp Biol 2021; 224:jeb.234245. [PMID: 33568443 DOI: 10.1242/jeb.234245] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Accepted: 01/30/2021] [Indexed: 11/20/2022]
Abstract
Animals extract behaviorally relevant signals from 'noisy' environments. Echolocation behavior provides a rich system testbed for investigating signal extraction. When echolocating in acoustically enriched environments, bats show many adaptations that are believed to facilitate signal extraction. Most studies to date focused on describing adaptations in insectivorous bats while frugivorous bats have rarely been tested. Here, we characterize how the frugivorous bat Carollia perspicillata adapts its echolocation behavior in response to acoustic playback. Since bats not only adapt their echolocation calls in response to acoustic interference but also with respect to target distances, we swung bats on a pendulum to control for distance-dependent call changes. Forward swings evoked consistent echolocation behavior similar to approach flights. By comparing the echolocation behavior recorded in the presence and absence of acoustic playback, we could precisely define the influence of the acoustic context on the bats' vocal behavior. Our results show that C. perspicillata decrease the terminal peak frequencies of their calls when echolocating in the presence of acoustic playback. When considering the results at an individual level, it became clear that each bat dynamically adjusts different echolocation parameters across and even within experimental days. Utilizing such dynamics, bats create unique echolocation streams that could facilitate signal extraction in noisy environments.
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Affiliation(s)
- M Jerome Beetz
- Institute for Cell Biology and Neuroscience, Goethe University, 60438 Frankfurt am Main, Germany
| | - Manfred Kössl
- Institute for Cell Biology and Neuroscience, Goethe University, 60438 Frankfurt am Main, Germany
| | - Julio C Hechavarría
- Institute for Cell Biology and Neuroscience, Goethe University, 60438 Frankfurt am Main, Germany
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Genzel D, Yartsev MM. The fully automated bat (FAB) flight room: A human-free environment for studying navigation in flying bats and its initial application to the retrosplenial cortex. J Neurosci Methods 2021; 348:108970. [PMID: 33065152 PMCID: PMC8857751 DOI: 10.1016/j.jneumeth.2020.108970] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 09/23/2020] [Accepted: 10/07/2020] [Indexed: 10/23/2022]
Abstract
BACKGROUND Bats can offer important insight into the neural computations underlying complex forms of navigation. Up to now, this had been done with the confound of the human experimenter being present in the same environment the bat was navigating in. NEW METHOD We, therefore, developed a novel behavioral setup, the fully automated bat (FAB) flight room, to obtain a detailed and quantitative understanding of bat navigation flight behavior while studying its relevant neural circuits, but importantly without human intervention. As a demonstration of the FAB flight room utility we trained bats on a four-target, visually-guided, foraging task and recorded neural activity from the retrosplenial cortex (RSC). RESULTS We find that bats can be efficiently trained and engaged in complex, multi-target, visuospatial behavior in the FAB flight room. Wireless neural recordings from the bat RSC during the task confirm the multiplexed characteristics of single RSC neurons encoding spatial positional information, target selection, reward obtainment and the intensity of visual cues used to guide navigation. COMPARISON WITH EXISTING METHODS In contrast to the methods introduced in previous studies, we now can investigate spatial navigation in bats without potential experimental biases that can be easily introduced by active physical involvement and presence of experimenters in the room. CONCLUSIONS Combined, we describe a novel experimental approach for studying spatial navigation in freely flying bats and provide support for the involvement of bat RSC in aerial visuospatial foraging behavior.
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Affiliation(s)
- Daria Genzel
- Helen Wills Neuroscience Institute, UC Berkeley, Berkeley, 94720, United States; Department of Bioengineering, UC Berkeley, Berkeley, 94720, United States
| | - Michael M Yartsev
- Helen Wills Neuroscience Institute, UC Berkeley, Berkeley, 94720, United States; Department of Bioengineering, UC Berkeley, Berkeley, 94720, United States.
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12
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Enhanced representation of natural sound sequences in the ventral auditory midbrain. Brain Struct Funct 2020; 226:207-223. [PMID: 33315120 PMCID: PMC7817570 DOI: 10.1007/s00429-020-02188-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Accepted: 11/24/2020] [Indexed: 11/30/2022]
Abstract
The auditory midbrain (inferior colliculus, IC) plays an important role in sound processing, acting as hub for acoustic information extraction and for the implementation of fast audio-motor behaviors. IC neurons are topographically organized according to their sound frequency preference: dorsal IC regions encode low frequencies while ventral areas respond best to high frequencies, a type of sensory map defined as tonotopy. Tonotopic maps have been studied extensively using artificial stimuli (pure tones) but our knowledge of how these maps represent information about sequences of natural, spectro-temporally rich sounds is sparse. We studied this question by conducting simultaneous extracellular recordings across IC depths in awake bats (Carollia perspicillata) that listened to sequences of natural communication and echolocation sounds. The hypothesis was that information about these two types of sound streams is represented at different IC depths since they exhibit large differences in spectral composition, i.e., echolocation covers the high-frequency portion of the bat soundscape (> 45 kHz), while communication sounds are broadband and carry most power at low frequencies (20–25 kHz). Our results showed that mutual information between neuronal responses and acoustic stimuli, as well as response redundancy in pairs of neurons recorded simultaneously, increase exponentially with IC depth. The latter occurs regardless of the sound type presented to the bats (echolocation or communication). Taken together, our results indicate the existence of mutual information and redundancy maps at the midbrain level whose response cannot be predicted based on the frequency composition of natural sounds and classic neuronal tuning curves.
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Salles A, Park S, Sundar H, Macías S, Elhilali M, Moss CF. Neural Response Selectivity to Natural Sounds in the Bat Midbrain. Neuroscience 2020; 434:200-211. [PMID: 31918008 DOI: 10.1016/j.neuroscience.2019.11.047] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Revised: 11/27/2019] [Accepted: 11/28/2019] [Indexed: 11/29/2022]
Abstract
Little is known about the neural mechanisms that mediate differential action-selection responses to communication and echolocation calls in bats. For example, in the big brown bat, frequency modulated (FM) food-claiming communication calls closely resemble FM echolocation calls, which guide social and orienting behaviors, respectively. Using advanced signal processing methods, we identified fine differences in temporal structure of these natural sounds that appear key to auditory discrimination and behavioral decisions. We recorded extracellular potentials from single neurons in the midbrain inferior colliculus (IC) of passively listening animals, and compared responses to playbacks of acoustic signals used by bats for social communication and echolocation. We combined information obtained from spike number and spike triggered averages (STA) to reveal a robust classification of neuron selectivity for communication or echolocation calls. These data highlight the importance of temporal acoustic structure for differentiating echolocation and food-claiming social calls and point to general mechanisms of natural sound processing across species.
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Affiliation(s)
- Angeles Salles
- Department of Psychological and Brain Sciences, Johns Hopkins University, United States.
| | - Sangwook Park
- Department of Electrical and Computer Engineering, Johns Hopkins University, United States
| | - Harshavardhan Sundar
- Department of Electrical and Computer Engineering, Johns Hopkins University, United States
| | - Silvio Macías
- Department of Psychological and Brain Sciences, Johns Hopkins University, United States
| | - Mounya Elhilali
- Department of Electrical and Computer Engineering, Johns Hopkins University, United States
| | - Cynthia F Moss
- Department of Psychological and Brain Sciences, Johns Hopkins University, United States
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Luo J, Simmons AM, Beck QM, Macías S, Moss CF, Simmons JA. Frequency-modulated up-chirps produce larger evoked responses than down-chirps in the big brown bat auditory brainstem. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2019; 146:1671. [PMID: 31590554 DOI: 10.1121/1.5126022] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Accepted: 08/22/2019] [Indexed: 06/10/2023]
Abstract
In many mammals, upward-sweeping frequency-modulated (FM) sounds (up-chirps) evoke larger auditory brainstem responses than downward-sweeping sounds (down-chirps). To determine if similar effects occur in FM echolocating bats, auditory evoked responses (AERs) in big brown bats in response to up-chirps and down-chirps at different chirp durations and levels were recorded. Even though down-chirps are the biologically relevant stimulus for big brown bats, up-chirps typically evoked larger peaks in the AER, but with some exceptions at the shortest chirp durations. The up-chirp duration that produced the largest AERs and the greatest differences between up-chirps and down-chirps varied between individual bats and stimulus levels. Cross-covariance analyses using the entire AER waveform confirmed that amplitudes were typically larger to up-chirps than down-chirps at supra-threshold levels, with optimal durations around 0.5-1 ms. Changes in response latencies with stimulus levels were consistent with previous estimates of amplitude-latency trading. Latencies tended to decrease with increasing up-chirp duration and increase with increasing down-chirp duration. The effects of chirp direction on AER waveforms are generally consistent with those seen in other mammals but with small differences in response patterns that may reflect specializations for FM echolocation.
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Affiliation(s)
- Jinhong Luo
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - Andrea Megela Simmons
- Department of Cognitive, Linguistic, and Psychological Sciences, Brown University, Providence, Rhode Island 02912, USA
| | - Quincy M Beck
- Department of Neuroscience, Brown University, Providence, Rhode Island 02912, USA
| | - Silvio Macías
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - Cynthia F Moss
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - James A Simmons
- Department of Neuroscience, Brown University, Providence, Rhode Island 02912, USA
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Fu Z, Xu N, Zhang G, Zhou D, Liu L, Tang J, Jen PHS, Chen Q. Evoked potential study of the inferior collicular response to constant frequency-frequency modulation (CF-FM) sounds in FM and CF-FM bats. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2019; 205:239-252. [DOI: 10.1007/s00359-019-01326-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Revised: 02/26/2019] [Accepted: 02/28/2019] [Indexed: 12/20/2022]
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Warnecke M, Macías S, Falk B, Moss CF. Echo interval and not echo intensity drives bat flight behavior in structured corridors. ACTA ACUST UNITED AC 2018; 221:jeb.191155. [PMID: 30355612 DOI: 10.1242/jeb.191155] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Accepted: 10/15/2018] [Indexed: 12/18/2022]
Abstract
To navigate in the natural environment, animals must adapt their locomotion in response to environmental stimuli. The echolocating bat relies on auditory processing of echo returns to represent its surroundings. Recent studies have shown that echo flow patterns influence bat navigation, but the acoustic basis for flight path selection remains unknown. To investigate this problem, we released bats in a flight corridor with walls constructed of adjacent individual wooden poles, which returned cascades of echoes to the flying bat. We manipulated the spacing and echo strength of the poles comprising each corridor side, and predicted that bats would adapt their flight paths to deviate toward the corridor side returning weaker echo cascades. Our results show that the bat's trajectory through the corridor was not affected by the intensity of echo cascades. Instead, bats deviated toward the corridor wall with more sparsely spaced, highly reflective poles, suggesting that pole spacing, rather than echo intensity, influenced bat flight path selection. This result motivated investigation of the neural processing of echo cascades. We measured local evoked auditory responses in the bat inferior colliculus to echo playback recordings from corridor walls constructed of sparsely and densely spaced poles. We predicted that evoked neural responses would be discretely modulated by temporally distinct echoes recorded from the sparsely spaced pole corridor wall, but not by echoes from the more densely spaced corridor wall. The data confirm this prediction and suggest that the bat's temporal resolution of echo cascades may drive its flight behavior in the corridor.
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Affiliation(s)
- Michaela Warnecke
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Silvio Macías
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Benjamin Falk
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Cynthia F Moss
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD 21218, USA
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Luo J, Macias S, Ness TV, Einevoll GT, Zhang K, Moss CF. Neural timing of stimulus events with microsecond precision. PLoS Biol 2018; 16:e2006422. [PMID: 30365484 PMCID: PMC6221347 DOI: 10.1371/journal.pbio.2006422] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2018] [Revised: 11/07/2018] [Accepted: 10/10/2018] [Indexed: 12/29/2022] Open
Abstract
Temporal analysis of sound is fundamental to auditory processing throughout the animal kingdom. Echolocating bats are powerful models for investigating the underlying mechanisms of auditory temporal processing, as they show microsecond precision in discriminating the timing of acoustic events. However, the neural basis for microsecond auditory discrimination in bats has eluded researchers for decades. Combining extracellular recordings in the midbrain inferior colliculus (IC) and mathematical modeling, we show that microsecond precision in registering stimulus events emerges from synchronous neural firing, revealed through low-latency variability of stimulus-evoked extracellular field potentials (EFPs, 200–600 Hz). The temporal precision of the EFP increases with the number of neurons firing in synchrony. Moreover, there is a functional relationship between the temporal precision of the EFP and the spectrotemporal features of the echolocation calls. In addition, EFP can measure the time difference of simulated echolocation call–echo pairs with microsecond precision. We propose that synchronous firing of populations of neurons operates in diverse species to support temporal analysis for auditory localization and complex sound processing. We routinely rely on a stopwatch to precisely measure the time it takes for an athlete to reach the finish line. Without the assistance of such a timing device, our measurement of elapsed time becomes imprecise. By contrast, some animals, such as echolocating bats, naturally perform timing tasks with remarkable precision. Behavioral research has shown that echolocating bats can estimate the elapsed time between sonar cries and echo returns with a precision in the range of microseconds. However, the neural basis for such microsecond precision has remained a puzzle to scientists. Combining extracellular recordings in the bat’s inferior colliculus (IC)—a midbrain nucleus of the auditory pathway—and mathematical modeling, we show that microsecond precision in registering stimulus events emerges from synchronous neural firing. Our recordings revealed a low-latency variability of stimulus-evoked extracellular field potentials (EFPs), which, according to our mathematical modeling, was determined by the number of firing neurons and their synchrony. Moreover, the acoustic features of echolocation calls, such as signal duration and bandwidth, which the bat dynamically modulates during prey capture, also modulate the precision of EFPs. These findings have broad implications for understanding temporal analysis of acoustic signals in a wide range of auditory behaviors across the animal kingdom.
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Affiliation(s)
- Jinhong Luo
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, Maryland, United States of America
- * E-mail: (JL); (CFM)
| | - Silvio Macias
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Torbjørn V. Ness
- Faculty of Science and Technology, Norwegian University of Life Sciences, Ås, Norway
| | - Gaute T. Einevoll
- Faculty of Science and Technology, Norwegian University of Life Sciences, Ås, Norway
- Department of Physics, University of Oslo, Oslo, Norway
| | - Kechen Zhang
- Department of Biomedical Engineering, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America
| | - Cynthia F. Moss
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, Maryland, United States of America
- * E-mail: (JL); (CFM)
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