Scientific interests
Throughout my scientific career, I have sought ways to study how behaviors important to the life history of an animal are adapted by experience. As a master’s student with Dr. Peter Slater at the University of St. Andrews, I performed fieldwork to quantitatively study the similarity of songs in a population of chaffinches (Fringilla coelebs) inhabiting a small chain of islands. This research examined the interactions of geographic isolation upon song learning, and found that the acoustic structure of songs was learned on birth islands, while song sequencing was determined by the location of adult territories. My master’s work motivated a more mechanistic approach for my doctoral thesis with Dr. Michael Brainard at the University of California, San Francisco. I examined the relationship between motor neuron variability and song variability in the Bengalese finch (Lonchura striata domestica) by performing chronic neural recordings in a song motor nucleus of singing birds. Variation in neural activity was analyzed with respect to variation in the acoustics and sequencing of the bird’s songs, demonstrating how motor neuron variability contributes to sensorimotor learning for both song spectrotemporal structure (1) and song sequencing (2). As a postdoc with Dr. Cynthia Moss at Johns Hopkins University (and formerly at the University of Maryland), I extended my work on sensorimotor processing by examining the role of sensory feedback in audio-vocal integration in the echolocating bat. I conducted both behavioral (3,4) and neurophysiological studies(5) in bats performing natural tasks to determine how sensory feedback in the form of sonar echoes is used to modify subsequent sonar vocalizations, as well as head and ear movements. My postdoctoral work examined the role of the midbrain superior colliculus (SC) in sensorimotor processing for echolocation behaviors in the insectivorous big brown bat (Eptesicus fuscus). I first conducted an auditory physiology experiment examining response selectivity in the SC (5). This research identified neural response specificity in the SC to natural sounds (i.e. sonar vocalizations), that was not uncovered using artificial stimuli. This research demonstrated the importance of providing ethological relevant stimuli for assaying brain function. In order to understand the role of the SC in the bat’s active sensing behaviors, I developed a paradigm
where the bat is trained to track a moving target from a
stationary position (Fig 1), providing precise
experimental control over the target tracking conditions,
and an opportunity to make detailed measurements of
changes in echolocation behaviors (e.g. sonar
vocalizations, ear motion, head motion) with multi-
channel chronic neurophysiology. I found neural
signals in the SC related to each stage of audio-vocal
integration (i.e. echo responses and/or motor signals),
identifying species-specific signals for spatial orientation.
Additionally, in one important series of experiments in
free-flying bats that employed an RF telemetry system
to wirelessly record neural activity the SC, I
demonstrated for the first time the 3D receptive fields of sensory neurons in the SC, as well as the dynamic modulation of 3D spatial tuning with changes in the bat’s adaptive sonar behaviors. This work hints at the influence of the bat’s behaviors upon sensory representations, and these results would not have been realized without placing the bat in a natural context that encouraged the full suite of adaptive, spatial orienting behaviors. Future work will build upon the skills and questions I developed as a graduate student and postdoc to answer fundamental questions about sensorimotor integration in natural, adaptive behaviors.
Bibliography:
1. Sober, S. J., Wohlgemuth, M. J. & Brainard, M. S. Central contributions to acoustic variation in birdsong. J. Neurosci. 28, 10370–9 (2008).
2. Wohlgemuth, M. J., Sober, S. J. & Brainard, M. S. Linked control of syllable sequence and phonology in birdsong. J. Neurosci. 30, 12936–49 (2010).
3. M. J. et al. Action Enhances Acoustic Cues for 3-D Target Localization by Echolocating Bats. PLOS Biol. 14, e1002544 (2016).
4. N. B., Wohlgemuth, M. J., Hulgard, K., Surlykke, A. & Moss, C. F. Timing matters: sonar call groups facilitate target localization in bats. Front. Physiol. 5, 168 (2014).
5. M. J. & Moss, C. F. Midbrain auditory selectivity to natural sounds. Proc. Natl. Acad. Sci. U. S. A. 113, (2016).
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