6 Structures, Materials, and Processes at the Electrode-to-Tissue Interface |
133 |
for safe current decreased logarithmically with increasing stimulus duration. There was severe damage in the inner layers when the applied current exceeded this threshold. Colodetti et al. [11] found that the retina is sensitive to pressure exerted by the electrode. They studied the type of damage due to pressure exerted by the electrode with and without accompanying high charge stimulation in the rodent retina. Although the type of damage exhibited in both cases were roughly similar, the extent of damaged area was significantly larger in the case of accompanying high charge stimulation. These studies although informative do not in any way give a complete picture of how the retina would respond to continuous stimulation. Also, as increasing efforts are being made to make these implants more sophisticated, the added requirement of a large number of closely spaced electrodes makes it imperative to study the possible consequences of high level stimulation on both the retina and associated cortical structures. Recent work in these areas is presented in Chaps. 7 (Loudin, Butterwick, Huie and Palanker) and 12 (Fried and Jensen).
References
1.Ahuja AK, Behrend MR, Whalen JJ, et al. (2008), The dependence of spectral impedance on disc microelectrode radius. IEEE Trans Biomed Eng, 55(4): p. 1457–60.
2.Baig-Silva MS, Hathcock CD, Hetling JR (2005), A preparation for studying electrical stimulation of the retina in vivo in rat. J Neural Eng, 2(1): p. S29–38.
3.Bard AJ, Faulkner LR (2004), Electrocehmical Methods: Fundamentals and Applications. Second ed, New York: Wiley.
4.Beebe X, Rose TL (1988), Charge injection limits of activated iridium oxide electrodes with 0.2 ms pulses in bicarbonate buffered saline. IEEE Trans Biomed Eng, 35(6): p. 494–5.
5.Brug GJ, Van Den Eeden ALG, Sluythers-Rehbach M, Suythers JH (1984), The analysis of electrode impedances complicated by the presence of a constant phase element. J Electroanal Chem, 176: p. 275–95.
6.Brummer SB, Turner MJ (1975), Electrical stimulation of the nervous system: the principle of safe charge injection with noble metal electrodes. Bioelectrochem Bioenerg, 2: p. 13–25.
7.Brummer SB, Turner MJ (1977), Electrical stimulation with Pt electrodes: I-a method for determination of “real” electrode areas. IEEE Trans Biomed Eng, 24(5): p. 436–9.
8.Brummer SB, Turner MJ (1977), Electrical stimulation with Pt electrodes: II-estimation of maximum surface redox (theoretical non-gassing) limits. IEEE Trans Biomed Eng, 24(5): p. 440–3.
9.Cogan SF, Ehrlich J, Plante TD, et al. (2009), Sputtered iridium oxide films for neural stimulation electrodes. J Biomed Mater Res B Appl Biomater, 89(2): p. 353–61.
10. Cogan SF, Guzelian AA, Agnew WF, et al. (2004), Over-pulsing degrades activated iridium oxide films used for intracortical neural stimulation. J Neurosci Methods, 137(2): p. 141–50.
11. Colodetti L, Weiland JD, Colodetti S, et al. (2007), Pathology of damaging electrical stimulation in the retina. Exp Eye Res, 85(1): p. 23–33.
12. Cui XY, Hetke J, F, Wiler JA, et al. (2001), Electrochemical deposition and characterization of conducting ploymer polypyrrole/pss on multichannel neural probes. Sens Actuators A Phys, 93: p. 8–18.
13. Cui X, Lee VA, Raphael Y, et al. (2001), Surface modification of neural recording electrodes with conducting polymer/biomolecule blends. J Biomed Mater Res, 56(2): p. 261–72.
14. Cui XY, Martin DC (2003), Electrochemical deposition and characterization of poly (3,4-ethylenedioxythiophene) on neural microelectrode arrays. Sens Actuators B Chem,
89: p. 92–102.
134 |
A. Ray and J.D. Weiland |
15. Cui X, Wiler J, Dzaman M, et al. (2003), In vivo studies of polypyrrole/peptide coated neural probes. Biomaterials, 24(5): p. 777–87.
16. Cui XT, Zhou DD (2007), Poly (3,4-ethylenedioxythiophene) for chronic neural stimulation. IEEE Trans Neural Syst Rehabil Eng, 15(4): p. 502–8.
17. Eisenfeld AJ, Bunt-Milam AH, Sarthy PV (1984), Muller cell expression of glial fibrillary acidic protein after genetic and experimental photoreceptor degeneration in the rat retina. Invest Ophthalmol Vis Sci, 25(11): p. 1321–8.
18. Evans DH (1991), Review of voltammetric methods for the study of electrode reactions, in Microelectrodes: Theory and Applications, Montenegro I, Queiros MA, Daschbach JL, eds., Dordrecht: Kluwer Academic.
19. Franks W, Schenker I, Hierlmann A (2005), Impedance characterization and modeling of electrodes for biomedical applications. IEEE Trans Biomed Eng, 52(7): p. 1295–302.
20. Fujikado T, Morimoto T, Kanda H, et al. (2007), Evaluation of phosphenes elicited by extraocular stimulation in normals and by suprachoroidal-transretinal stimulation in patients with retinitis pigmentosa. Graefes Arch Clin Exp Ophthalmol, 245(10): p. 1411–9.
21. Geddes LA (1997), Historical evolution of circuit models for the electrode–electrolyte interface. Ann Biomed Eng, 25(1): p. 1–14.
22. Geddes LA (1999), Chronaxie. Australas Phys Eng Sci Med, 22(1): p. 13–17.
23. Geddes LA (2004), Accuracy limitations of chronaxie values. IEEE Trans Biomed Eng, 51(1): p. 176–81.
24. Geddes LA, Bourland JD (1985), The strength-duration curve. IEEE Trans Biomed Eng, 32(6): p. 458–9.
25. Germain PS, Pell WG, Conway BE (2004), Evaluation and origins of the differences between double-layer capacitance behaviour at Au-metal and oxidized Au surfaces. Electrochim Acta,
49: p. 1775–88.
26. Greenbaum E, Sanders C, Zhou D (2006), Dynamic interactions at retinal prosthesis electrode interface. Invest Ophthalmol Visual Sci 47, ARVO E-abstr#3200.
27. Guven D, Weiland JD, Fujii G, et al. (2005), Long-term stimulation by active epiretinal implants in normal and RCD1 dogs. J Neural Eng, 2(1): p. S65–73.
28. Hamann CH, Hamnett A, Vielstich W (1998), Methods for the study of electrode/electrolyte interface, Chapter 5 in Electrochemistry, Weinheim, Germany: Wiley-VCH, p. 251–338.
29. Jensen RJ, Ziv OR, Rizzo JF, III (2005), Thresholds for activation of rabbit retinal ganglion cells with relatively large, extracellular microelectrodes. Invest Ophthalmol Vis Sci, 46(4): p. 1486–96.
30. Kandel ER, Schwartz JH, Jessell TM (2000), Principles of Neural Science. Fourth ed, New York: McGraw-Hill.
31. Kim DH, Abidian M, Martin DC (2004), Conducting polymers grown in hydrogel scaffolds coated on neural prosthetic devices. J Biomed Mater Res A, 71(4): p. 577–85.
32. Lapicque L (1909), Definition experimentale de l’excitabilite. C R Acad Sci, 67(2): p. 280–3. 33. Lasia A (2002), Electrochemical impedance spectroscopy and its application, in Modern Aspects of Electrochemistry, Conway BE, Bockris JOM, White RE, eds., New York: Kluwer
Academic.
34. Lilly JC (1961), Injury and excitation by electric currents: the balanced pulse-pair waveform, in Electrical Stimulation of the Brain, Sheer DE, ed., Austin, TX: Hogg Foundation for Mental Health.
35. McCreery DB (2004), Tissue reaction to electrodes: the problem of safe and effective stimulation of neural tissue, in Neuroprosthetics: Theory and Practice, Horch KW, Dhillon GS, eds., Singapore: World Scientific Publishing Co. Pte. Ltd.
36. McCreery DB, Agnew WF, Bullara LA (2002), The effects of prolonged intracortical microstimulation on the excitability of pyramidal tract neurons in the cat. Ann Biomed Eng, 30(1): p. 107–19.
37. McCreery DB, Agnew WF, Yuen TG, Bullara L (1990), Charge density and charge per phase as cofactors in neural injury induced by electrical stimulation. IEEE Trans Biomed Eng,
37(10): p. 996–1001.
6 Structures, Materials, and Processes at the Electrode-to-Tissue Interface |
135 |
38. McCreery DB, Agnew WF, Yuen TG, Bullara LA (1995), Relationship between stimulus amplitude, stimulus frequency and neural damage during electrical stimulation of sciatic nerve of cat. Med Biol Eng Comput, 33(3 Spec No): p. 426–9.
39. Merrill DR, Bikson M, Jefferys JG (2005), Electrical stimulation of excitable tissue: design of efficacious and safe protocols. J Neurosci Methods, 141(2): p. 171–98.
40. Nakauchi K, Fujikado T, Kanda H, et al. (2007), Threshold suprachoroidal-transretinal stimulation current resulting in retinal damage in rabbits. J Neural Eng, 4(1): p. S50–7.
41. Plonsey R, Barr RC (1991), Functional neuromuscular stimulation, Chapter 12 in Bioelectricity: A Quantitative Approach, New York: Plenum, p. 271–299.
42. Prokhorov E, Llamas F, Morales-Sanchez E, et al. (2002), In vivo impedance measurements on nerves and surrounding skeletal muscles in rats and human body. Med Biol Eng Comput,
40(3): p. 323–6.
43. Rattay F (1989), Analysis of models for extracellular fiber stimulation. IEEE Trans Biomed Eng, 36(7): p. 676–82.
44. Rattay F (1999), The basic mechanism for the electrical stimulation of the nervous system. Neuroscience, 89(2): p. 335–46.
45. Richardson-Burns SM, Hendricks JL, Foster B, et al. (2007), Polymerization of the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) around living neural cells. Biomaterials,
28(8): p. 1539–52.
46. Richardson-Burns SM, Hendricks JL, Martin DC (2007), Electrochemical polymerization of conducting polymers in living neural tissue. J Neural Eng, 4(2): p. L6–13.
47. Robblee LS, Rose TL (1990), Electrochemical guidelines for selection of protocols and electrode materials for neural stimulation, in Neural Prostheses: Fundamental Studies, Agnew WF, McCreery DB, eds., Englewood Cliffs, NJ: Prentice Hall.
48. Rose TL, Robblee LS (1990), Electrical stimulation with Pt electrodes. VIII. Electrochemically safe charge injection limits with 0.2 ms pulses. IEEE Trans Biomed Eng, 37(11): p. 1118–20 49. Sachs HG, Gekeler F, Schwahn H, et al. (2005), Implantation of stimulation electrodes in the subretinal space to demonstrate cortical responses in Yucatan minipig in the course of visual
prosthesis development. Eur J Ophthalmol, 15(4): p. 493–9.
50. Sekirnjak C, Hottowy P, Sher A, et al. (2006), Electrical stimulation of mammalian retinal ganglion cells with multielectrode arrays. J Neurophysiol, 95(6): p. 3311–27.
51. Shannon RV (1992), A model of safe levels for electrical stimulation. IEEE Trans Biomed Eng, 39(4): p. 424–6.
52. Stieglitz T (2004), Electrode materials for recording and stimulation, in Neuroprosthetics: Theory and Practice, Horch KW, Dhillon GS, eds., Vol. 2, Singapore: World Scientific.
53. Wang K, Fishman HA, Dai H, Harris JS (2006), Neural stimulation with a carbon nanotube microelectrode array. Nano Lett, 6(9): p. 2043–8.
54. Weiland JD, Anderson DJ (2000), Chronic neural stimulation with thin-film, iridium oxide electrodes. IEEE Trans Biomed Eng, 47(7): p. 911–8.
55. Weiland JD, Anderson DJ, Humayun MS (2002), In vitro electrical properties for iridium oxide versus titanium nitride stimulating electrodes. IEEE Trans Biomed Eng, 49(12 Pt 2): p. 1574–9.
56. Weiland JD, Liu W, Humayun MS (2005), Retinal prosthesis. Annu Rev Biomed Eng, 7:
p. 361–401.
57.Whalen JJ, Weiland JW, Searson P (2005), Electrochemical deposition of platinum from aqueous ammonium hexachloroplatinate solution. J Electrochem Soc, 152(11): p. C738–43.
58. Yang JY, Martin DC (2004), Microporous conducting polymers on neural microelectrode arrays II. Physical characterization. Sens Actuators A Phys, 113A: p. 204–11.
59. Zrenner E (2002), The subretinal implant: can microphotodiode arrays replace degenerated retinal photoreceptors to restore vision? Ophthalmologica, 216(Suppl 1): p. 8–20; discussion 52–3.
Chapter 7
Delivery of Information and Power
to the Implant, Integration of the Electrode Array with the Retina, and Safety of Chronic Stimulation
James Loudin, Alexander Butterwick, Philip Huie, and Daniel Palanker
Abstract The fundamental function of a visual prosthesis is to deliver information about a patient’s surroundings to his/her neurons, usually via patterned electronic stimulation. In addition to transmitting visual information from the outside world to the implanted stimulating array, visual prostheses must also pass the electrical power necessary for such stimulation from the external world to the intraocular electrode array. The first section of this chapter reviews three common methods for achieving this data and power transfer: direct wireline connections (suitable for research studies), inductively coupled coils, and photodiode-based optical systems which utilize the natural optics of the eye.
Once the data and power has been received, retinal prostheses must effectively deliver stimulation currents to surviving retinal neurons. This necessitates an understanding of the electrode/retina interface. The second section of this chapter is a histological description of this interface for the case of subretinal implants, investigating the tissue response to flat implants coated with different materials. Several three-dimensional geometries are also described and evaluated to decrease the implant–neuron distance.
Finally, stimulation currents must not damage the stimulated neurons. The third section of this chapter describes measurements and scaling laws associated with tissue damage from electric currents. Damage thresholds are found to be approximately 50–100 times stimulation thresholds.
Abbreviations
AC |
Alternating current |
ASR |
Artificial silicon retina, a retinal prosthesis fabricated by Optobionics |
CMOS |
Combined metal on silicon |
CMP |
Computational molecular phenotyping |
J. Loudin (*)
Department of Applied Physics, Stanford University, 450 Serra Mall, Stanford, CA 94305, USA
e-mail: loudin@stanford.edu
G. Dagnelie (ed.), Visual Prosthetics: Physiology, Bioengineering, Rehabilitation, |
137 |
DOI 10.1007/978-1-4419-0754-7_7, © Springer Science+Business Media, LLC 2011 |
|