An avid fan and player of soccer, Mario Iobbi believes that life should be stimulating to both the mind and body. “Most every Friday you’ll find me playing indoor soccer at the Rec Center.” When not participating in the physically active side of life, Mario works toward a career in the field of biomedical engineering. According to Mario, the driving force behind his work is “the final product, which is by far the most rewarding part of research. There is a genuine satisfaction to be attained from having a tangible representation of all the hard work.”

Motor areas of the cortex have been hypothesized to control arm movement using population vector coding. In this scheme, each neuron’s activity is mathematically represented as a movement direction vector. By taking the vector sum over a large distribution of cells, a population vector is generated which has been found to point in the hand’s movement direction. We attempt to explain the reaching impairments stroke victims commonly experience by adapting this population vector model to include simulated cell death as well as an inherent firing rate variability. Assuming strokes destroy neurons without preference, cell death is modeled by randomly eliminating vectors. The resulting vector sum begins to skew away from the desired movement direction. Comparisons to data from stroke subjects performing center-out reaching tasks reveal similar trends in initial movement direction error as a function of stroke severity. Furthermore, the simulation suggests a quantitative relationship between a common arm assessment scale used in clinical evaluations and the fraction of neural loss.

David Reinkensmeyer Henry Samueli School of Engineering

Participating in faculty-mentored undergraduate research is a great way to exercise your creativity and invent a new device, technique, or idea. For example, Mario’s paper provides support for the new idea that movement deficits after stroke can be modeled by damaging an experimentally identified neural code. This idea is important because it provides insight into why it may be difficult to move the arm after stroke, and thus what neuroregeneration or neuroengineering techniques might do to restore dexterity. My advice is to follow Mario’s example: develop useful skills by working hard in your classes, find an area that excites you, hook-up with a professor, and exercise your creativity through undergraduate research.