Publications

Displaying 1 - 6 of 6
  • Vernes, S. C., Devanna, P., Hörpel, S. G., Alvarez van Tussenbroek, I., Firzlaff, U., Hagoort, P., Hiller, M., Hoeksema, N., Hughes, G. M., Lavrichenko, K., Mengede, J., Morales, A. E., & Wiesmann, M. (2022). The pale spear‐nosed bat: A neuromolecular and transgenic model for vocal learning. Annals of the New York Academy of Sciences, 1517, 125-142. doi:10.1111/nyas.14884.

    Abstract

    Vocal learning, the ability to produce modified vocalizations via learning from acoustic signals, is a key trait in the evolution of speech. While extensively studied in songbirds, mammalian models for vocal learning are rare. Bats present a promising study system given their gregarious natures, small size, and the ability of some species to be maintained in captive colonies. We utilize the pale spear-nosed bat (Phyllostomus discolor) and report advances in establishing this species as a tractable model for understanding vocal learning. We have taken an interdisciplinary approach, aiming to provide an integrated understanding across genomics (Part I), neurobiology (Part II), and transgenics (Part III). In Part I, we generated new, high-quality genome annotations of coding genes and noncoding microRNAs to facilitate functional and evolutionary studies. In Part II, we traced connections between auditory-related brain regions and reported neuroimaging to explore the structure of the brain and gene expression patterns to highlight brain regions. In Part III, we created the first successful transgenic bats by manipulating the expression of FoxP2, a speech-related gene. These interdisciplinary approaches are facilitating a mechanistic and evolutionary understanding of mammalian vocal learning and can also contribute to other areas of investigation that utilize P. discolor or bats as study species.

    Additional information

    supplementary materials
  • Hörpel, S. G., Baier, L., Peremans, H., Reijniers, J., Wiegrebe, L., & Firzlaff, U. (2021). Communication breakdown: Limits of spectro-temporal resolution for the perception of bat communication calls. Scientific Reports, 11: 13708. doi:10.1038/s41598-021-92842-4.

    Abstract

    During vocal communication, the spectro‑temporal structure of vocalizations conveys important
    contextual information. Bats excel in the use of sounds for echolocation by meticulous encoding of
    signals in the temporal domain. We therefore hypothesized that for social communication as well,
    bats would excel at detecting minute distortions in the spectro‑temporal structure of calls. To test
    this hypothesis, we systematically introduced spectro‑temporal distortion to communication calls of
    Phyllostomus discolor bats. We broke down each call into windows of the same length and randomized
    the phase spectrum inside each window. The overall degree of spectro‑temporal distortion in
    communication calls increased with window length. Modelling the bat auditory periphery revealed
    that cochlear mechanisms allow discrimination of fast spectro‑temporal envelopes. We evaluated
    model predictions with experimental psychophysical and neurophysiological data. We first assessed
    bats’ performance in discriminating original versions of calls from increasingly distorted versions of
    the same calls. We further examined cortical responses to determine additional specializations for
    call discrimination at the cortical level. Psychophysical and cortical responses concurred with model
    predictions, revealing discrimination thresholds in the range of 8–15 ms randomization‑window
    length. Our data suggest that specialized cortical areas are not necessary to impart psychophysical
    resilience to temporal distortion in communication calls.

    Additional information

    supplementary information
  • Lattenkamp, E. Z., Hörpel, S. G., Mengede, J., & Firzlaff, U. (2021). A researcher’s guide to the comparison of vocal production learning. Philosophical Transactions of the Royal Society of London, Series B: Biological Sciences, 376: 20200237. doi:10.1098/rstb.2020.0237.

    Abstract

    Vocal production learning (VPL) is the capacity to learn to produce new vocalizations, which is a rare ability in the animal kingdom and thus far has only been identified in a handful of mammalian taxa and three groups of birds. Over the last few decades, approaches to the demonstration of VPL have varied among taxa, sound production systems and functions. These discrepancies strongly impede direct comparisons between studies. In the light of the growing number of experimental studies reporting VPL, the need for comparability is becoming more and more pressing. The comparative evaluation of VPL across studies would be facilitated by unified and generalized reporting standards, which would allow a better positioning of species on any proposed VPL continuum. In this paper, we specifically highlight five factors influencing the comparability of VPL assessments: (i) comparison to an acoustic baseline, (ii) comprehensive reporting of acoustic parameters, (iii) extended reporting of training conditions and durations, (iv) investigating VPL function via behavioural, perception-based experiments and (v) validation of findings on a neuronal level. These guidelines emphasize the importance of comparability between studies in order to unify the field of vocal learning.
  • Hörpel, S. G., & Firzlaff, U. (2020). Post-natal development of the envelope following response to amplitude modulated sounds in the bat Phyllostomus discolor. Hearing Research, 388: 107904. doi:10.1016/j.heares.2020.107904.

    Abstract

    Bats use a large repertoire of calls for social communication, which are often characterized by temporal amplitude and frequency modulations. As bats are considered to be among the few mammalian species capable of vocal learning, the perception of temporal sound modulations should be crucial for juvenile bats to develop social communication abilities. However, the post-natal development of auditory processing of temporal modulations has not been investigated in bats, so far. Here we use the minimally invasive technique of recording auditory brainstem responses to measure the envelope following response (EFR) to sinusoidally amplitude modulated noise (range of modulation frequencies: 11–130 Hz) in three juveniles (p8-p72) of the bat, Phyllostomus discolor. In two out of three animals, we show that although amplitude modulation processing is basically developed at p8, EFRs maturated further over a period of about two weeks until p33. Maturation of the EFR generally took longer for higher modulation frequencies (87–130 Hz) than for lower modulation frequencies (11–58 Hz).
  • Mengede, J., Devanna, P., Hörpel, S. G., Firzla, U., & Vernes, S. C. (2020). Studying the genetic bases of vocal learning in bats. In A. Ravignani, C. Barbieri, M. Flaherty, Y. Jadoul, E. Lattenkamp, H. Little, M. Martins, K. Mudd, & T. Verhoef (Eds.), The Evolution of Language: Proceedings of the 13th International Conference (Evolang13) (pp. 280-282). Nijmegen: The Evolution of Language Conferences.
  • Hörpel, S. G., & Firzlaff, U. (2019). Processing of fast amplitude modulations in bat auditory cortex matches communication call-specific sound features. Journal of Neurophysiology, 121(4), 1501-1512. doi:10.1152/jn.00748.2018.

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