Michael Smotherman
Assistant Professor

3258 TAMU
College Station, TX 77843-3258

Office:
Biological Sciences Building West
Room 110
979-845-6504

Lab:
Biological Sciences Building West
Room 107
979-845-3454

Fax: 979-845-2891
Email: msmotherman@mail.bio.tamu.edu

Our primary line of research investigates the neurophysiology of those parts of the mammalian brain that regulate the structure and timing of syllable production in mammals. We use echolocating bats because these mammals exploit an array of auditory and somatosensory feedback cues to precisely regulate the sound of their voice. Part of our lab focuses on the organization of a brainstem vocal pattern generator that is responsible for the production of single sounds. More recently we have developed an experimental protocol for exploring the role of the mammalian striatum in the regulation of complex temporal patterns of vocal emissions. Bats often use specialized “pulse groupings” when echolocating in noisy or crowded situations. Preliminary evidence suggests that these pulse groups are created by an extrapyramidal motor loop consisting of the motor cortex, the dorso-lateral striatum and sensory-motor thalamic nuclei, to coordinate the production of these vocal sequences. This makes echolocating bats an especially useful animal model for exploring the evolution and architecture of the neural circuits that underlie human speech and language production. Analagous circuits have not been identified in rodents or non-human primates. These results have important implications for the treatment of human speech disorders, because important questions about how potentially therapeutic drugs such as striatal dopamine receptor antagonists might affect the speech motor pathways can now be tested in echolocating bats before being tested on humans.

Singing by bats
We maintain a colony of Mexican free-tailed bats (Tadarida brasiliensis), which we use to study echolocation, vocal communication and social behaviors in bats. In the spring, male free-tailed bats sing a complex, highly stereotyped courtship song intended to attract females to their private roosting sites, and males aggressively defend these sites from other intruding males. The song is of particular interest because of its remarkable similarity to the courtship songs of some birds, and because it implies that the bats possess the neural architecture necessary for coordinating long multi-syllabic vocal sequences. A plethora of current graduate and undergraduate student projects are addressing questions of how the song production is regulated (daily, seasonally, and hormonally), what parts of the brain are uniquely involved in singing, and when and if the song is a learned vocalization.

Smotherman, M.and A. Guillen-Servent (2008) Doppler-shift compensation behavior by Wagner’s mustached bat, Pteronotus personatus. Journal of the Acoustical Society of America, (in press)

Schwartz, C., Tressler, J., Keller, H., Vanzant, M., Ezell, S. and M. Smotherman (2007) The tiny difference between foraging and communication buzzes uttered by the Mexican free-tailed bat, Tadarida brasiliensis. Journal of Comparative Physiology A 2007 Vol. 193(8): 853-63

Smotherman, M. (2007). Sensory feedback control of mammalian vocalizations. Behavioral Brain Research , Vol. 182(2): 315-26

Smotherman, M., K. Kobayasi, J. Ma, S. Zhang, and W. Metzner (2006) A mechanism for vocal-respiratory coupling in the mammalian parabrachial nucleus. The Journal of Neuroscience, Vol. 26(18):4860-9.

Smotherman, M. and W. Metzner (2005) Auditory-feedback control of temporal call patterns in echolocating horseshoe bats. J. Neurophysiology 93: 295-303.

Smotherman, M . and W. Metzner (2003) Fine control of call frequency by horseshoe bats. Journal of Comparative Physiology A, 189:435-446.

Smotheman, M ., Zhang, S.Y., and W. Metzner (2003) A neural basis for auditory feedback control of vocal pitch. Journal of Neuroscience , 23:1464-1477.

Smotherman, M . and W. Metzner (2003) Effects of echo intensity on Doppler-shift compensation behavior in horseshoe bats. Journal of Neurophysiology , 89: 814-821.

Smotherman, M.S . (2002) Acetylcholine mediates excitatory inputs to chromatophore motoneurons in the squid, Loligo paeleii . Biological Bulletin, 203:231-232.