Date of Award

Fall 2008

Document Type

Thesis - Restricted

Degree Name

Master of Science (MS)


Biomedical Engineering

First Advisor

Schindler-Ivens, Sheila

Second Advisor

Schmit, Brian

Third Advisor

Ropella, Kristina


The role of the primary motor cortex and other supraspinal structures in controlling human locomotion remains unclear. Recent advances in neural imaging technologies, such as functional magnetic resonance imaging (fMRI), have made it possible to obtain images of human brain activity during motor tasks. We developed a custom-designed, fMRI-safe pedaling device and recorded human brain activity during sustained, rhythmic, alternating flexion and extension of the lower extremities. Ten healthy volunteers pedaled at a slow (30 RPM), fast (60 RPM), and variable (30-60 RPM) rate while recording fMRl signals in a GE 3T short bore MR-scanner. There was also a passive condition where subjects relaxed and allowed the experimenter to pedal their legs at a rate of 30 RPM. We utilized a block design consisting of 3 runs of each condition. In a single run, subjects pedaled for 30 sec, and then rested for 30 sec. This sequence was repeated 4 times. The magnitude of activation in each voxel was calculated in Analysis of Functional NeuroImages (AFNI) by fitting the falling portion of the BOLD signal immediately after movement had stopped with a standard model (boxcar convolved with gamma function). Because of the delayed nature of the BOLD response, we reasoned that this portion of the signal would contain BOLD signal but not movement-related artifact. Regardless of the pedaling condition, significant activation was observed in the primary and secondary sensorimotor cortices and the cerebellum. Passive pedaling produced similar magnitude and spatial extent of activation in the sensorimotor cortex compared to slow, active pedaling, these brain structures might be involved in integrating sensory signals during locomotion. Fast and Variable speed pedaling produced a significantly higher mean level of activity in the primary and secondary sensorimotor cortices with no difference in volume of activation. This implies that speed of pedaling might be coded in these areas.



Restricted Access Item

Having trouble?