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Neuroscience PhD at Wake Forest University at Wake Forest University


Wake Forest University Graduate School » Neuroscience PhD at Wake Forest University

Miriam Ashley-Ross

Miriam Ashley-Ross
My lab is interested in the mechanistic basis of animal behavior. A diverse set of groups serve as models. Currently, my lab has three main research tracks. First, we investigate the evolution of tetrapod (four-footed land animals: mammals, birds, reptiles, amphibians) locomotion by quantifying underwater locomotion using the limbs in salamanders. Fossil evidence indicates that the appearance of the tetrapod limb and foot pre-dated the move to land. Thus, one wants a model that approximates the posture of early tetrapods, and salamanders are our best available match. Second, we study the biomechanics of prey capture in tarantulas. These large, hairy, ground-dwelling spiders can capture small arthropods (such as crickets) in less than one-tenth of a second. How they detect and capture their prey is our current interest. Third, we are examining terrestrial “jumping” by small species of fish that appear to lack any morphological modifications for moving on land. Techniques that we use are high-speed video, electromyography (recording patterns of muscle activity), and in vitro measures of muscle work and power output.

 

Salamanders as a model for understanding the evolution of tetrapod locomotion. If the tetrapod foot, complete with digits, pre-dated the move to land, the obvious question is, "Why?" If you're still going to be a fully aquatic animal, why evolve feet? Why not just stick with fins? We are working to understand how limbs are used for underwater movements in salamanders - how kinematics and motor patterns differ during walking in water versus on land. We are also testing hypotheses regarding the utility of limbs over fins. Prey capture in tarantulas. One of the most interesting things about spiders, from a biomechanical and neural control point of view, is that they have a partially hydraulic skeleton - they lack extensor muscles at two of the major joints in each leg. In order to extend the legs, they have to pump fluid into them by compressing the cephalothorax. With such a seemingly crude mechanism, how do they exert fine control over which legs are extended, and exactly where they go? We are currently examining kinematics to understand the behavior. Terrestrial jumping in fishes. The phrase "like a fish out of water" is used precisely because most fish flounder utterly ineffectively when stranded on land. Yet, many species of small teleost fishes that inhabit near-to-shore (littoral) environments will voluntarily strand themselves on land to evade predators or escape poor water conditions. If they remain on land, non-amphibious fishes (those that do not spend part of their life history out of water) will die from asphyxiation or desiccation. Although most littoral teleosts possess no obvious anatomical specializations to facilitate terrestrial movement, some species can produce an effective terrestrial jump via a “tail-flip” behavior that superficially resembles an aquatic fast-start escape response (C start) that is performed on land. Is it just a C start, or a new motor pattern? We have evidence suggesting the latter, and are investigating the motor pattern and its interaction with mechanical properties of the fish's body to produce the jump.

 

Young, B.A. and M.A. Ashley. 1989. A mathematical model for predicting relative muscle force with a perturbation analysis of selected muscle parameters. Journal of Theoretical Biology, 138: 213-233.   Ashley, M. A., Reilly, S. M., and G.V. Lauder. 1991. Ontogenetic scaling of hindlimb muscles across metamorphosis in the tiger salamander, Ambystoma tigrinum. Copeia, 1991(3): 767-776.   Ashley-Ross, M.A. 1992. The comparative myology of the thigh and crus in the salamanders Ambystoma tigrinum and Dicamptodon tenebrosus. Journal of Morphology, 211: 147-163.   Ashley-Ross, M.A. 1994. Hind limb kinematics during terrestrial locomotion in a salamander (Dicamptodon tenebrosus). Journal of Experimental Biology, 193: 255-283.   Ashley-Ross, M.A. 1994. Metamorphic and speed effects on hind limb kinematics during terrestrial locomotion in the salamander Dicamptodon tenebrosus. Journal of Experimental Biology, 193: 285-305.   Ashley-Ross, M.A. 1995. Patterns of hind limb motor output during walking in the salamander Dicamptodon tenebrosus, with comparisons to other tetrapods. Journal of Comparative Physiology A, 177: 273-285.   Ashley-Ross, M.A. and G.V. Lauder. 1997. Motor patterns and kinematics during backward walking in the Pacific Giant Salamander: evidence for novel motor output. Journal of Neurophysiology, 78: 3047-3060.   Rome, L.C., Cook, C., Syme, D.A., Connaughton, M., Ashley-Ross, M.A., Klimov, A., Tikunov, B., and Y.E. Goldman. 1999. Trading force for speed: why superfast cross-bridge kinetics lead to super low forces. Proceedings of the National Academy of Science, USA, 96: 5826-5831.   Butcher, M.T. and M.A. Ashley-Ross. 2002. Fetlock joint kinematics differ with age in Thoroughbred racehorses. Journal of Biomechanics, 35: 563-571.   Ashley-Ross, M.A. and G.B. Gillis. 2002. A brief history of vertebrate functional morphology. Integrative and Comparative Biology (formerly American Zoologist), 42(2): 183-189.   Ashley-Ross, M.A. and J.U. Barker. 2002. The effect of fiber type heterogeneity on optimized work and power output of hindlimb muscles of the salamander Ambystoma tigrinum. Journal of Comparative Physiology A, 188: 611-620.   Ashley-Ross, M.A. 2002. Mechanical properties of the dorsal fin muscle of seahorse (Hippocampus) and pipefish (Syngnathus). Journal of Experimental Zoology, 293: 561-577.   Morgan, S.M., Ashley-Ross, M.A., and D.J. Anderson. 2003. Foot-mediated incubation: Nazca booby (Sula granti) feet as surrogate brood patches. Physiological and Biochemical Zoology, 76(3): 360-366.   Ashley-Ross, M.A. and B.F. Bechtel. 2004. Kinematics of the transition between aquatic and terrestrial locomotion in the newt Taricha torosa. Journal of Experimental Biology, 207: 461-474.   Morgan, S.M., Clifford, L.D., Ashley-Ross, M.A. and D.J. Anderson. 2004. Parental responses to unexpectedly cool eggs in Nazca boobies Sula granti. Journal of Avian Biology, 35: 416-424.   Walthall, J.C. and M.A. Ashley-Ross. 2006. Postcranial myology of the California newt, Taricha torosa. Anatomical Record, 228A:46-57.   Ashley-Ross, M.A., Lundin, R., and K.L. Johnson. 2009. Kinematics of level terrestrial and underwater walking in the California newt, Taricha torosa. Journal of Experimental Zoology A, 311(4): 240-257.