Angela L. Hewitt

E-mail: hewit051@umn.edu

Year Entered: 2005

Degrees Received:
B.S., Biomedical Engineering, University of Wisconsin, 2002
M.S., Biomedical Engineering, University of Wisconsin, 2005

Honors and Awards:
President-elect, University of Minnesota Students Interested in General Neurology (SIGN)
Finalist, National Collegiate Inventors Competition, 2002
University of Wisconsin Hilldale Undergraduate Research Fellowship, 2002
4^th place Schoof's Prize for Creativity Innovation Competition, 2002

Thesis Advisor: Timothy Ebner, M.D., Ph.D., Neuroscience Graduate Program

Thesis Research: 

My experiments in Dr. Ebner's lab will examine the role of the cerebellum in controlling limb motor movements.  My work will build upon methods developed for recording the electrical signals from single Purkinje cells in the pars intermedia and hemisphere of the cerebellar cortex of monkeys trained in a manual tracking task.  A predominant contemporary motor control hypothesis is that the cerebellum functions as an inverse dynamics model.  Previous work by the Ebner laboratory has shown that Purkinje cells do not carry signals regarding limb kinetics; this observation is inconsistent with the cerebellum being the site of an inverse dynamics model.  However, these results were based upon experiments where monkeys tracked a visually moving target.  It could be argued that the lack of force modulation was due to the kinematic nature of the task.  This raises the question of whether Purkinje cells would respond to force modulation and signal limb dynamics if the task involved explicitly controlling force and used force feedback.  My future work will look at the role of the cerebellum in force modulation during a haptic tracking task.  This will utilize aspects of a computer program that I helped develop during my lab rotation to simulate a force-controlled environment with a robotic arm.  Force feedback (i.e. haptic feedback) guides a trained primate along different movement patterns (such as a circle) based solely upon viscous and elastic force output without confounding visual stimuli.  The animal must track this force target using haptic feedback from the robotic arm.  The final simulated environment could probably best be compared to a moving corner; a person who was blindfolded but had one hand each on two adjoining walls that moved conjointly in different patterns could use the moving corner to guide him or herself along the path.  Although this tracking task is much more difficult than the previously used moving visual target, preliminary testing showed promise that the task could be performed with training and practice.  Recordings of cellular firing collected during the task will then be analyzed for relationships to anatomical position within the cortex, direction, velocity, and force.  Correlations or non-correlations with changing force conditions will help determine the role of cerebellar Purkinje cells, if any, in controlling the limb force in a force control and force feedback task.

Previous Research Experience:
Angela's  research emphasis prior to entering the University of Minnesota was neuromusculoskeletal movement.  Her research interests include brain control interfaces, sensory prosthetics, functional neural imaging, neural control of movement.  She participated in several academic design projects at the University of Wisconsin, one of which resulted in a patent and another with a patent pending:.

• U.S. Patent No 6,702,765: Apparatus for Measuring Tongue/Hard Palate Contact Pressure.
  Inventors: Robbins, JoAnne; Bomsztyk, Elan D.; Heppner (Hewitt), Angela L.; Koranda, Christine L.; Kroner, Aaron R.; Kuchenreuther, Jon M.; Meister, David M.; Staerkel, Bryan S.
  
• U.S. Patent No 7,238,145: Oral-lever Resistance Exercise Device  Inventors: Robbins, JoAnne; Hind, Jacqueline A; Hewitt, Angela L.

Publications: (prior to entering MD/PhD Program)

Hewitt A, Hind J, Kays S, Nicosia M, Doyle J, Tompkins W, Gangnon R, Robbins J. Standardized instrument for lingual pressure measurement. Dysphagia. 2008; 23(1): 16-25.

Robbins J, Kays SA, Gangnon RE, Hind JA, Hewitt AL, Gentry LR, Taylor AJ. The effects of lingual exercise in stroke patients with dysphagia. Arch Phys Med Rehabil. 2007;88:150-158.

Robbins J, Gangnon R, Theis S, Kays S, Hewitt AL, Hind J.  The effects of lingual exercise on swallowing in older adults. J Am Geriatr Soc. 2005;53:1483-1489.