Marc Schmidt

Associate Professor of Biology
Co-Director, Biological Basis of Behavior Program
312 Leidy Laboratory
marcschm@sas.upenn.edu
215-898-9375
Neurobiology, Behavior, and Physiology
Education: 
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B.A., Swarthmore College, Biology, 1986
PhD, Colorado State University, Neuroscience, 1993
Postdoc, California Institute of Technology, Neuroethology, 1993-1999
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Research Interests: 

Work in our laboratory uses songbirds to study the neural bases of vocal production and sensorimotor integration. Birdsong is one of the most tractable model systems for the study of complex learned behaviors. Much of the strength of the system lies in the ease with which the behavior can be quantified and the prominence of the highly specialized circuit, known as the song system, that is involved in song learning and production.

In addition, because song learning in birds and language acquisition in humans are both dependent on auditory feedback, the study of birdsong learning is likely to provide many insights into the mechanisms underlying vocal development in humans. [ Click here for an article highlighting work on the neural bases of birdsong.pdf]

Our work is divided into three main areas of investigation.

 

1. The "respiratory-thalamic" pathway and its role in motor sequencing and hemispheric coordination

The primary objective of this work is to use the highly stereotyped zebra finch (Figure 1) song to investigate how the brainstem might shape the generation of higher-order motor commands. In songbirds, the respiratory brainstem (RAm & PAm in figure 2), which shares many anatomical and functional characteristics with its mammalian counterpart (McLean et al., 2013), also contains a distinct population of neurons that is functionally connected, via a thalamic intermediary (Uva in figure 2), to vocal motor “cortex” (HVC & NIf in figure 2). This work tests the hypothesis that the “respiratory-thalamic” pathway sends precisely timed signals that directly shape the timing of the circuits that encode the moment-to-moment motor commands for song (Schmidt, McLean & Goller, 2011; Ashmore et al. 2008). Because this projection is bilateral in nature, we are also interested in the role of this pathway in synchronizing motor commands across hemispheres.

Because the corpus callosum is absent in birds, as it is in all non-mammalian vertebrates, this work directly addresses mechanisms of hemispheric coordination that occur in the absence of this major commissural system. We use neural recording methods (single and multi-unit) together with optogenetics (in collaboration with Brian Chow; Department of Bioengineering @ Penn) in awake birds to investigate the nature of the signal carried by the “respiratory-t halamic” pathway during song production. These measurements are coupled with detailed quantitative analysis of song acoustic and temporal features.

 This work is the primary research focus of the laboratory.

 

 

2. Cellular and network mechanisms underlying persistent gamma oscillations in a sensorimotor nucleus

Recent work in the lab (Lewandowski and Schmidt, 2011) observed pesisten fast gamma oscillations (90 - 150 Hz) of local field potentials and of single neuron firing following song production in a forebrain sensorimotor nucleus, nucleus Interface (NIf) in songbirds. These oscillations appear after singing has ended and accompany a rebound of spiking activity. They persist for up to 30 seconds following singing thereby outlasting teh event (song) thattriggered them by over an order of magnitude. NIf is at the top of the ascending auditory pathway, and provides input to the nucleus HVC, which is a key driver of song production. Therefore, NIf is ideally suited to link high sensory and motor pathways during song production and/or during replay during rest or sleep. It remains completely unknown how a nuclear structure can generate fast gamma oscillations and how these oscillations can persist for so long. This interdisciplinary project combines theoretical and experimental approaches. A modeling component (Hansel/Leblois Labs, Universite Paris Descartes, France) will determine the minimal neural network sufficient to drive fast and persistent gamma oscillations with spatiotemporal features consistent with available data. An in vitro component (Perkel Lab, University of Washington) will determine neuronal, synaptic and network properties in NIf. The in vivo component of the project will be performed in our lab where we will determine the source of the gamma oscillations and the mechanism(s) underlying their persistence.

3. Neural bases of song preference and reproductive behavior in a female songbird

For many decades, neuroscientists and evolutionary biologists have been interested in the mechanics and function of the songbirds’ song system: the interconnected neural circuit that connects the auditory forebrain with the brainstem via song-specific control nuclei. This work has predominantly focused on how the song system allows male songbirds to learn and produce song. The role of the song system in female songbirds, however, has been largely ignored. Rather than acting as a circuit that generates vocal behavior, some evidence suggests that the song system in females serves to organize preferences for males’ songs and guides their behavioral reactions to song in the form of a copulation solicitation display (CSD), that ensures survival of the species. Female brown-headed cowbirds show great selectivity in producing this behavior in reaction to variants of male song and disruption to the song system (nucleus HVC) eliminates this selectivity. Capitalizing on the robustness of the behavior, its selectivity and its social malleability, the aim of this work is investigate how the song system transforms a sensory stimulus (the song) into a motor command that controls a postural (CSD) response. This work is relatively new direction for the laboratory that started out as a collaboration between my laboratory and David White's laboratory (See Maguire, Schmidt and White, 2013). This work continues as a collaboration with David White (Wilfrid Laurier University, Canada) and Lori Flanagan-Cato (Department of Psychology @ Penn).


Selected Publications: 

Castelino C. B., C. Glaze, S. Bibu and M.F. Schmidt (2014) Norepinephrine regulates motor performance in a naturally occurring behavior. Submitted

Maguire S., M. F.  Schmidt and D. J. White (2013) Social brains in context: Lesions to the song control system in female cowbirds affect their social network. PLoS ONE 8(5): e63239. [Maguire et al. (PLOS ONE 2013).pdf]

Lewandowski B.C, Alexei A., Hahnloser R. and M.F.Schmidt (2013) At the interface between the auditory and vocal motor system: NIf and its role in vocal processing, production and learning J. Physiology (Paris) 107:178-192 [Lewandowski et al. (J. Physiol Paris 2013).pdf]

Mclean J., S. Bricault and M. F. Schmidt (2013) Characterization of respiratory neurons in the rostral ventrolateral medulla, an area critical for vocal production in songbirds. J. Neurophysiology 109: 948-957. [McLean et al (JNP 2013).pdf]

Raksin J. N., C. Glaze, S. Smith and M. F. Schmidt (2012) Linear and Nonlinear Auditory Response Properties of Interneurons in a High Order Avian Vocal Motor Nucleus During Wakefulness. J. Neurophysiology 107:2185-2201 [Raksin et al. (JNP 2012).pdf]

Schmidt, M. F., J. Mc Lean and F. Goller (2011) Breathing and Vocal Control: The Respiratory System as both a Driver and Target of Telencephalic Vocal Motor Circuits in Songbirds. J. Exp. Physiology 97 (4) 455-461 [Schmidt et al. (Exp Physiol-2012).pdf]

 Lewandowski B. C. and M. F. Schmidt (2011) Short bouts of vocalization induce long lasting fast gamma oscillations in a sensorimotor nucleus. J. Neuroscience 31(39): 13936-13948; doi: 10.1523/ JNEUROSCI.6809-10.2011 [Lewandowski and Schmidt (JN 2011).pdf]

Margoliash, D. and M.F. Schmidt (2010) Sleep, off-line processing, and vocal learning. Brain and Language 115: 45 – 58. [Margoliash ad Schmidt (Brain and Language 2009).pdf]

Castelino, C. B. and M. F. Schmidt (2010) What birdsong can teach us about the central noradrenergic system. J. Chem. Neuroanatomy 39: 96 – 111 [Castelino and Schmidt (J. Chem. Neuroanat. 2010).pdf]

Schmidt, M. F. (2008) Using Both Sides of Your Brain: The Case for Rapid Interhemispheric Switching. PLoS Biology 6: 2089 – 2093 [PLoS Primer (2008).pdf]

Ashmore R. C., J. A. Renk and M. F. Schmidt (2008) Bottom-up Activation of Forebrain Vocal Motor Structures by the Respiratory Brainstem. J. Neuroscience 28: 2613 – 2623. [Ashmore, Renk and Schmidt (JN 2008).pdf]

Schmidt, M. F. and R. C. Ashmore (2008) Integrating breathing and singing: Forebrain and brainstem mechanisms in Neuroscience of Birdsong (ed. Zeigler, H. P. and P. Marler) Cambridge University Press. [Schmidt and Ashmore (Book Chapter 2008).pdf]

Ashmore R. C., M. Bourjaily and M. F. Schmidt (2008) Hemispheric coordination is necessary for song production in adult birds: Implications for a dual role for forebrain nuclei in vocal motor control. J. Neurophysiology 99: 373–385. [Ashmore, Bourjaily and Schmidt (JNP 2008).pdf]

Nealen P. M. and M. F. Schmidt (2006) Distributed and selective auditory representation of song repertoires in the avian song system. J. Neurophysiology 96: 3433-3447 [Nealen and Schmidt (JNP 2006).pdf]

Ashmore R. C., J. M. Wild and M. F. Schmidt (2005) Brainstem and forebrain contributions to the generation of learned motor behaviors for song J. Neuroscience 25: 8543-8554. [Ashmore, Wild and Schmidt (JN 2005).pdf]

Cardin J.A., Raksin J. N. and M.F. Schmidt (2005) The sensorimotor nucleus NIf is necessary for auditory processing but not vocal motor output in the avian song system. J. Neurophysiology 93: 2157-2166. [Cardin, Raksin and Schmidt (JNP 2005).pdf]

Cardin J.A. and M.F. Schmidt (2004) Noradrenergic inputs mediate state dependence of auditory responses in the avian song system. J. Neuroscience 24: 7745-7753. [Cardin_and_Schmidt (JN 2004).pdf]

Cardin, J.A. and M. F. Schmidt (2003) Song system auditory responses are stable and highly tuned during sedation, rapidly modulated and unselective during wakefulness, and suppressed by arousal. J. Neurophysiology 90: 2884-2899. [Cardin_and_Schmidt (JNP 2004).pdf]

Schmidt M. F. (2003) Pattern of interhemispheric synchronous premotor activity in HVc correlates with key transitions in the song pattern. J. Neurophysiology 90: 3931-3949. [Schmidt (JNP 2003).pdf]

Schmidt M. F. and M. Konishi (1998) Gating of auditory responses in the song control system of awake songbirds. Nature Neuroscience 1: 513-518. [Schmidt and Konishi (Nat. Neurosci. 1998).pdf]

 

Courses Taught: 

 

BIOL251/BBB251: Cellular and Molecular Neurobiology (Fall)

BIOL451/BBB476: Neural Systems and Behavior (Spring)

NGG598: Advanced Systems Neuroscience (Alternate years)

Other Affiliations: 
  • Society for Neuroscience
  • American Physiological Society