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