Let’s (Briefly) Break the Brain
Introduction to TMS and an Overview of Current Projects
Arman Abrahamyan
Skype Chat
… are there TMS studies?
Of course. There are a lot. Someone say now is TMS world
[unedited]
Break It … to Understand
[1]
Accidental Brain Breakdown
[2] [3]
What is TMS?
[4]
Talk Structure
Introduction
to TMS
Current
Projects
Introduction to TMS
How does TMS work?
TMS apparatus, major coil types, and modes of stimulation
“Virtual lesion” paradigm
MRI guided coil positioning
Is it safe?
How Does
TMS Work?
Electromagnetic Induction
1831 [5]
[6]
Early Attempts: d’Arsonval
1896
Reported seeing
phosphenes
[7], [8]
Early Attempts: Thompson
1910
Replicated d’Arsonval’s
results
[9], [10]
Early Attempts: Magnussen & Stevens
1914
Electromagnetic field is still not
large and rapidly-changing enough
[11], [12]
Thyristor
Allows starting and
stopping large
electrical currents
within microseconds
[13]
First TMS apparatus
1985
[14, 31]
EM Induction and TMS
[15, 31]
Microscopic Level
TMS causes depolarisation of neuronal membranes
Depolarisation can result in action potential
[16]
Macroscopic Level
Stimulated Area: 1-4 cm3
Affected Neurons: 1-5 billion
[17], [18]
TMS Apparatus, Coil Types, and
Stimulation Modes
TMS Apparatus
[4]
[14]
Circular Coil
Secondary Current Induced by Round Coil
Large Area of Stimulation
[19]
Secondary Current Induced by Double Coil
Focal Area of Stimulation
Induced Electric Field
[33, 19]
Stimulation Modes
sTMS
Single pulse
Less than 1 Hz
Applied online
rTMS
Repetitive pulse
Above 1 Hz
Can be applied online
or offline
[32, 21]
“Virtual Lesion” Paradigm
Use of TMS
Diagnosis & Treatment
Cognitive Neuroscience
• Movement disorders
• Epilepsy
• Depression
• Anxiety disorders
• Stuttering
• Schizophrenia
• Dementia
• Perception
• Attention
• Memory
• Learning
• Emotions
“Virtual Lesion” or Breaking the Brain
[11, 20, 21]
Mechanisms of Interference
No TMS
[25]
Neural Activity: No TMS vs TMS condition
No TMS TMS
[26] [26]
Noise Injection or Signal Suppression?
Noise
Injection
Signal
Suppression
[22] [23]
MRI Guided Stereotaxic
Navigation of the Coil
Brain is Difficult to See Through the Skull
[26]
MRI Guided Neuronavigation
[27] [28]
[29]
Safety
[27]
Risks of TMS
There are no known side effects associated with single-pulse TMS, when used properly
rTMS is known to cause seizure when stimulation parameters are well beyond accepted safety guidelines
[8, 11, 32]
Safety of Participants
Currently established safety guidelines for using TMS in rMTS mode are far below the risk margin for inducing a seizure
Participants undergo a screening check
[8, 11, 32]
Safety of Participants
Participants will be excluded if:◦ Personal or family history of epilepsy
◦ Brain-related abnormal conditions
◦ Head or brain injuries
◦ Migraines or headaches
◦ Medications for a neurological or psychiatric condition
◦ Implanted devices
◦ Heart condition
◦ Pregnancy
[8, 11, 32]
Conclusions
Conclusions
TMS operates on the principle of electromagnetic induction
TMS is relatively easy to operate and apply
TMS can create a “virtual lesion” in a stimulated area of the brain by interfering with a neural activity in that area
The “virtual lesion” paradigm is useful approach for mapping the temporal and functional characteristics of an area of the brain
Following currently established safety guidelines for TMS, it is possible to significantly reduce, if not eliminate, risks associated with TMS
Acknowledgements
Justin Harris Colin Clifford Ehsan Arabzadeh Irina Harris Alexandra Murray
Participants: Evan Livesey Hannah Pincham
Thank you[4]
References
1. http://news.bbc.co.uk/1/hi/health/2293179.stm
2. http://www.nature.com/nrn/journal/v5/n10/full/nrn1521.html
3. Damasio, H., et al., The return of Phineas Gage: clues about the brain from the skull of a famous patient. Science, 1994. 264(5162): p. 1102-5.
4. http://www.magstim.com/downloads/imagegallery.html
5. http://www.tamu-commerce.edu/physics/links/faraday.jpg
6. http://micro.magnet.fsu.edu/electromag/electricity/inductance.html
7. d'Arsonval, A. Dispositifs pour la mesure des courants alternatifs de toutes fréquences. C.R.Soc.Biol.(Paris) 3:450-457, 1896.
8. http://www.csbmb.princeton.edu/tms_orientation.ppt
9. Thompson, S.P. A physiological effect of an alternating magnetic field. Proc R Soc Lond [Biol] B82:396-399, 1910.
10. http://www.scholarpedia.org/article/Transcranial_magnetic_stimulation
11. Walsh, V. and A. Cowey, Magnetic stimulation studies of visual cognition. Trends in Cognitive Sciences, 1998. 2(3): p. 103-110.
12. Magnusson, C.E. and Stevens, H.C. Visual sensations created by a magnetic field. Am J Physiol 29:124-136, 1911.
13. http://www.global-b2b-network.com/direct/dbimage/50298013/ Thyristor_Modules.jpg
14. http://www.scholarpedia.org/article/Transcranial_magnetic_stimulation
References
15. http://brainstimulant.blogspot.com/2008/05/tms-video.html
16. http://en.wikipedia.org/wiki/Action_potential
17. http://berkeley.edu/news/media/releases/2007/09/27_TMS.shtml
18. Kammer, T., M. Vorwerg, and B. Herrnberger, Anisotropy in the visual cortex investigated by neuronavigated transcranial magnetic stimulation. Neuroimage, 2007. 36(2): p. 313-21.
19. Bailey, C.J., J. Karhu, and R.J. Ilmoniemi, Transcranial magnetic stimulation as a tool for cognitive studies. Scand J Psychol, 2001. 42(3): p. 297-305.
20. http://www.joelertola.com/tutorials/brain/index.html
21. Amassian, V.E., et al., Suppression of visual perception by magnetic coil stimulation of human occipital cortex. Electroencephalogr ClinNeurophysiol, 1989. 74(6): p. 458-62.
22. Walsh, V. and A. Cowey, Transcranial magnetic stimulation and cognitive neuroscience. Nat Rev Neurosci, 2000. 1(1): p. 73-9.
23. Harris, J.A., C.W. Clifford, and C. Miniussi, The functional effect of transcranial magnetic stimulation: signal suppression or neural noise generation? J Cogn Neurosci, 2008. 20(4): p. 734-40.
References
24. http://www.wpclipart.com
25. http://www.physics.lsa.umich.edu/zochowski/images/Neurons.jpg
26. http://www.boneclones.com/BC-092-Set.htm
27. http://www.medcat.nl/Research/softaxic.htm
28. http://www.ant-neuro.com/products/visor
29. http://www.youtube.com/watch?v=NQG-ml4aZ_s
30. http://medicine.mercer.edu/Research/safety
31. Barker, A.T., Jalinous, R., and Freeston, I. Non-invasive magnetic stimulation of the human motor cortex. Lancet 1:1106-1107, 1985.
32. Wassermann, E.M., Risk and safety of repetitive transcranial magnetic stimulation: report and suggested guidelines from the International Workshop on the Safety of Repetitive Transcranial Magnetic Stimulation, June 5-7, 1996. Electroencephalogr Clin Neurophysiol, 1998. 108(1): p. 1-16.
33. Ueno, S., Tashiro, T. & Harada, K. Localised stimulation of neural tissue in the brain by means of a paired configuration of time-varying magnetic fields. J. Appl. Phys. 64, 5862–5864 (1988).
Questions