Proposal

1. Title of Project:

The Excitability of the Motor Cortex for Planning Dexterous Manipulation

2. Statement of Purpose:

The use of transcranial magnetic stimulation (TMS) is a relatively new technology that allows access to the brain without the removal of skull fragments. Currently, there is a lab in ASU that examines the relationship between muscle behavior and the nervous system using the TMS. Through my internship in this lab, I will answer the question: does the motor cortex excitability change depending on whether human subjects plan a task that involves positioning the digits on an object versus positioning the digits on an object and exert forces to manipulate it?

3. Background:

I chose this project because I would learn more about the motor abilities of my hands, which would be helpful to know for my desired career path--working and improving prosthetics, especially for amputee veterans.

Men and women commit their lives for their nation, and some return after sacrificing a limb. The relationship between a person participating in military service and its nation is personal in a way that’s subjective to this person, yet  impersonal because this person fights for all the individuals of that nation. Inspired, I committed myself to creating the same relationship with these men and women. I looked up what major prosthetics would be under and I came across biomedical engineering. I was so intrigued at what I found that I committed myself to becoming a biomedical engineer, hopefully specializing in prosthetics. This project will be will teach me the relationship between the brain and the fingers.

4. Prior Research:

The use of transcranial magnetic stimulation (TMS) is a relatively new field but has become a helpful “therapeutic tool,” now being used to treat mood disorders (George et al., 1999). Previous studies have used TMS to identify the brain areas involved in planning and control of manipulation. It has mainly been used to treat people with primary mood disorders and people who have had strokes (Medical News Today, 2004). The TMS is used to treat cases of depression (Mayo Clinic staff).  In this project, instead of as a therapeutic tool, the TMS will be used to stimulate axons in the corticospinal system, which is “the principal motor system for controlling movements that require the greatest skill and flexibility” and it is physically a pathway of axons from the motor cortex to the spinal cord (Martin, 2005).

Previous studies on corticospinal excitability has focused mainly on the visualization and anticipation of hand movement, which is similar to this project I propose which involves the planning of the task of grabbing and object. In one of the previous studies, it was assumed that people assume the weight of an object before lifting it, and based on this assumption, two experiments based on two hypotheses were performed on how that weight is predicted--”information acquired during previous lift” and “arbitrary color cues associated with a particular weight” (Chouinard et al., 2005). Another study has been done that examines the preparation period of “appropriate hand shapes” (Prabhu et al., 2007). By assuming the weight of an object and positioning the fingers, a subject can proceed with lifting an object at optimal position with the right amount of force.

5. Significance:

The Senior Project Committee should allow me to conduct this research because I would really love to take this opportunity and move a step forward to becoming a great biomedical engineer. And I hope to learn how the brain works to provide mobility to the hand.

The knowledge gained by this research can provide insight into fundamental control mechanisms used by the brain and it will pave the way for further studies aiming at identifying brain areas involved in planning and control of skilled hand movements. This knowledge can also help with efforts aiming at rehabilitation of sensorimotor function following neurodegenerative disorders (stroke, Parkinson’s disease, etc.).

Once my project is complete, I would love to be able to publish my findings to the science community or even the college I end up going to.

6. Description:

I will be conducting my research in the inner depths of ASU’s Physical Education Building East in the labs of kinesiology. My project will involve assisting with experiments, participating to laboratory meetings where we discuss the data, and searching the literature. My findings will result in a research paper as my final product.

VII. Methodology:

Before becoming a part of protocol for the project, I will take an exam about ethics (IRB). Once I pass, I will be able to examine data and assist when collecting data. Subjects will be stimulated using TMS on the motor cortex after they are given a cue (either “position your digits on the object” or “position your digits then lift an object”). After one second after the cue, the TMS will emit a pulse that acts as an action potential that gives enough energy for the muscles in the hand to twitch. This pulse will signal the subject to move his or her hand according to the cue. The TMS will be positioned near the head around the area of the brain that controls the hand. By adjusting the strength of the TMS pulse, we can limit the amount of digits that twitch to two: the index finger and the thumb.

The strength of the twitch depends on the excitability of the two intrinsic hand muscles. The excitability of the motor cortex will be measured using the electromyographic (EMG) activity of the hand muscles. Electrodes will be attached to the index finger and thumb muscles, and an EMG system will measure the motor evoked potential (MEP) which represents the excitability. The EMG amplitude will be statistically compared offline between the two tasks.

In between testing, I will examine data and read articles describing how the TMS machine works. I will also participate in discussions about what the data means and how it relates to the main research question.

VIII. Problems:

Between the cue and the TMS signal, the subject has one second to plan the movement of his or her arm towards the object being acted upon. When the TMS emits the pulse, it has a loud popping sound. Subjects tend to anticipate this loud noise during testing, resulting in an unwanted spike in the data where the TMS pulse should be, so this error would cause cloudiness in data. To fix this problem, the trial is simply removed from the data.

IX. Bibliography:

1. Chouinard, P.A.; Leonard, G.; Paus, T. Role of the primary motor and dorsal premotor cortices in the
   anticipation of forces during object lifting. US National Library of Medicine. [Online] 2005
   2277-84 http://www.ncbi.nlm.nih.gov/pubmed/15745953 (accessed Dec 10, 2012).
2. Fadiga, L.; Buccino, G.; Craighero, L.; Fogassi, L.; Gallese, V.; Pavesi, G. Corticospinal excitability is
   specifically modulated by motor imagery: a magnetic stimulation study. US National Library
   of Medicine. [Online] 2007 147-58 http://www.ncbi.nlm.nih.gov/pubmed/10080372

   (accessed Dec 10, 2012).
3. George, M.S.; Lisanby, S.H.; Sackeim, H.A. Transcranial Magnetic Stimulation: Applications in
   Neuropsychiatry. Archives of General Psychiatry. [Online] 1999. 300-311
   http://archpsyc.jamanetwork.com/article.aspx?articleid=204878. (accessed Nov 10, 2012).
4. Jung, N.H., et al. Transcranial magnetic stimulation with a half-sine wave pulse elicits
   direction-specific effects in human motor cortex. BMC Neuroscience. 2012. 1471-2202.
5. Kirkcaldie, M.; Pridmore, S. A bright spot on the horizon: Transcranial magnetic
   stimulation in psychiatry. Open Mind.
6. Lee, L. Imaging the effects of 1 Hz Repetitive Transcranial Magnetic Stimulation during motor
   behaviour.  Ph.D. Dissertation, University College London, London, 2004.
7. Li, S. Effects of motor imagery on finger force responses to transcranial magnetic stimulation.
   [Online] 2004. 273-80.
8. Loh, M.N.; Kirsch L.; Rothwell, J.C.; Lemon, R.C.; Davare, M. Information about the weight of
   grasped objects from vision and internal models interacts within the primary motor cortex. US
   National Library of Medicine. [Online] 2010 6984-90
   http://www.ncbi.nlm.nih.gov/pubmed/20484640 (accessed Dec10, 2012).
9. Martin, J.H. The Corticospinal System: From Development to Motor Control. Sage Journals.
   [Online] 2005, 11, 161-173 http://nro.sagepub.com/content/11/2/161.short (accessed Dec
   10, 2012)
10. Mayo Clinic. Transcranial Magnetic Stimulation.
    http://www.mayoclinic.com/health/transcranial-magnetic-stimulation/MY00185
    (accessed Nov 10, 2012).
11. Meehan, S. K.; Linsdell, M. A.; Handy, T. C.; Boyd, L. A. Interhemispheric enhancement of
    somatosensory cortical excitability through contralateral repetitive transcranial magnetic
    stimulation. Clinical neurophysiology : official journal of the International Federation of
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12. Mozeg, D.; Flak, E. An Introduction to Transcranial Magnetic Stimulation and Its Use in the
    Investigation and Treatment of Depression. University of Toronto Medical Journal, pp
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13. Prabhu G.; Voss M.; Brochier T.; Cattaneo L.; Haggard P.; Lemon R. Excitability of human motor
    cortex inputs prior to grasp. US National Library of Medicine. [Online] 2007 189-201

    http://www.ncbi.nlm.nih.gov/pubmed/17332001 (accessed Dec10, 2012).
14. Stroke Patients Benefit from Transcranial Magnetic Stimulation. Medical News Today. 7 Nov 2004.
15. Wassermann, Eric M. Risk and safety of repetitive transcranial magnetic stimulation: report and suggested guidelines from the International Workshop on the Safety or Repetitive Transcranial Magnetic Stimulation. May 1997. pp. 1-16.