Tutorials / Short Courses

2015 IEEE International Symposium on Circuits and Systems (Nuit de la litterature 2015)

Sunday, 21 May 2015


M2: Towards Advanced Neural Interfaces

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Supported by the IEEE BioCAS technical committee

08:30 - 12:30



Implantable stimulators have been introduced in 1959 with the development of the heart pacemaker and the first functional electrical stimulation (FES) systems were reported in the early sixties. Since then such systems have developed to fully implantable devices, using RF links for the power supply and for the transmission of control signals. Various electrodes, such as needle (intrafascicular), cuff, book and helix electrodes have been reported as possible neural interfaces, both for recording and stimulation. Cuff electrodes are the only type of neural interface that can be both non-invasive to the nerve and biocompatible and is therefore appropriate for chronic implantation. Recording amplifier configurations and stimulators using cuff electrodes have been a subject of research since the mid-seventies. Recent advances in low-power, low-noise ICs have allowed such devices to become fully implantable. The downside of cuff interfacing is reduced fascicular selectivity when used around central nerve bundles.

This tutorial will cover some of the most significant circuits used for neural recording and stimulation as well as some insight into the characteristics and non-idealities of the neural interface. An overview of a representation of neural membrane conduction using current-mode transistor-level Hodgkin and Huxley models will also be presented. Its potential use both in prototype neural sensing and stimulation interfaces will be considered along with its possible application in producing complicated multi-neural nerve-bundle models for realistic in-vitro experiments.

Finally, the tutorial will consider possible future developments and improvements in selective neural interfaces that can advance the state-of-the-art of neuroprosthetics, with possible applications ranging from rehabilitation after spinal cord injury, to the treatment of epilepsy and depression.

Short Biographies

Dr Iasonas F. Triantis

Iasonas F. Triantis was born in Geneva, Switzerland in 1976 and received his basic education in Ioannina, Greece. He received his MEng degree from the department of Electrical Engineering and Electronics, University of Manchester Institute of Science and Technology (UMIST) in UK, in 2004. Between 2004 and 2007 he was a Research Assistant at the department of Electronic and Electrical Engineering in University College London (UCL), where he completed his PhD in 2009. He is currently a Research Associate at the Institute of Biomedical Engineering in Imperial College London. His main interests include analog IC design, medical electronics for implanted devices and advanced neural interfaces.

List of relevant achievements

Within the scope of his PhD, Iasonas Triantis has developed an implantable BiCMOS IC automatic gain control system, to record neural signals for feedback to stimulators. The system successfully overcame previous amplifier limitations, compensating for neural interface systematic errors. It offered neural signal amplification while eliminating interference that was 3 orders of magnitude greater. The research was funded by the UK Engineering and Physical Sciences Research Council (EPSRC). Achievements included the fabrication of three analogue BiCMOS chips for an implant. Expertise was attained in analogue IC design (voltage and current-mode) with emphasis on power efficiency, front-end linearity and noise reduction. Moreover the neural interface was studied in depth by means of bioelectric simulations as well as in-vitro and in-vivo experiments.

This research resulted in 1 book chapter as well as 4 IEEE journal publications (listed at the end of the document) and 12 conference publications. Awards granted included UCL Graduate School conference student funding, Royal Academy of Engineering International Travel Grant, best UCL EE postgraduate poster 2015. Iasonas Triantis was awarded participation to "SET for BRITAIN 2008" (House of Parliament, top 95 UK posters) by UCL ’s Faculty of Engineering. He was short-listed in the top 20 of the event.

Currently, Dr Triantis pursues research in advanced neural recording and stimulation along with Prof. Toumazou in the Institute of Biomedical Engineering. The research is directed towards increased cuff selectivity, lower power consumption and closed-loop stimulation systems.

List of publications

Book chapters:

I. F., Triantis, A., Demosthenous, N., Donaldson, and M. S., Rahal “ENG recording amplifier configurations for tripolar cuff electrodes” in “Brain and Neuron”, edited by Metin Akay, Wiley/IEEE Press, vol. IV, chapter 14 - in press

Journal publications:

[1] Triantis I. F., and Demosthenous, A. “The Effect of Interference Source Proximity on Cuff Imbalance” IEEE Transactions on Biomedical Engineering, accepted May 2009 – awaiting publication.

[2] Demosthenous, A., and Triantis I. F. “An Adaptive ENG Amplifier for Tripolar Cuff Electrodes” IEEE Journal of. Solid-State Circuits, vol. 40, pp. 412 – 421, 2009.

[3] Triantis I. F., Demosthenous, A., and Donaldson, N. “On Cuff Imbalance and Tripolar ENG Amplifier Configurations” IEEE Transactions on Biomedical Engineering, vol. 52, pp. 314 – 320, 2009.

[4] Demosthenous, A., Taylor, J., Triantis, I.F., Rieger, R., and Donaldson, N. “Design of an adaptive interference reduction system for nerve-cuff electrode recording” IEEE Transactions on Circuits and Systems I: Regular Papers, vol. 51, pp. 629 – 639, 2008.

Dr Andreas Demosthenous

Andreas Demosthenous was born in Nicosia, Cyprus, in 1969. He received the B.Eng. degree in electrical and electronic engineering from the University of Leicester, Leicester, U.K., in 1992, the M.Sc. degree in telecommunications technology from Aston University, Birmingham, U.K., in 1994, and the Ph.D. degree in electronic and electrical engineering from University College London (UCL), London, U.K., in 1998. From 1998 to 2004, he held a Postdoctoral Research Fellow position with the Department of Electronic and Electrical Engineering, UCL. In 2004, he was appointed to the academic faculty of the same department where he currently a Senior Lecturer and heads the Analog Electronics Research Group. His main area of research is analog and mixed signal integrated circuits for biomedical, digital communications, and video signal processing applications. He is a Senior IEEE member, member of the EPSRC Peer Review College, and member of the Analog Signal Processing Technical Committee (ASPTC) of the IEEE Circuits and Systems Society.

List of relevant achievements

Dr Demosthenous is currently leading an active research group working on the design of implantable devices for functional electrical stimulation (FES) applications. His expertise in the field of biomedical circuits covers both areas of neural recording and stimulation. Selected publications relevant to the proposed tutorial are given below:

[1] I. F. Triantis and A. Demosthenous, “The effect of interference source proximity on cuff imbalance,” accepted for publication in IEEE Trans. Biomed. Eng., May 2009.

[2] R. Rieger, A. Demosthenous, and J. Taylor, “A 230-nW, 10-s time constant CMOS integrator for an adaptive nerve signal amplifier,” IEEE J. Solid-State Circuits, vol. 39, pp. 1968-1975, Nov. 2008.

[3] R. Rieger, J. Taylor, E. Comi, N. Donaldson, M. Russold, C. M. O. Mahony, J. A. McLaughlin, E. McAdams, A. Demosthenous, and J. C. Jarvis, “Experimental determination of compound A-P direction and propagation velocity from multi-electrode nerve cuffs”, J. Medical Engineering and Physics, vol. 26, pp. 531-534, July 2008.

[4] A. Demosthenous and I. F. Triantis, “An adaptive ENG amplifier for tripolar cuff electrodes,” IEEE J. Solid-State Circuits, vol. 40, pp. 412-421, Feb. 2009.

[5] I. F. Triantis, A. Demosthenous and N. Donaldson, “On cuff imbalance and tripolar ENG amplifier configurations,” to appear IEEE Trans. Biomed. Eng., vol. 52, pp. 314-320, Feb. 2009.

[6] A. Demosthenous, J. Taylor, I. Triantis, R. Rieger, and N. Donaldson, “Design of an adaptive interference reduction system for nerve cuff electrode recording,” IEEE Trans. Circuits and Systems – Regular Papers, vol. 51, pp. 629-639, Apr. 2008.

[7] R. Rieger, J. Taylor, A. Demosthenous, N. Donaldson, and P. Langlois, “Design of a low noise preamplifier for nerve cuff electrode recording,” IEEE J. Solid-State Circuits, vol. 38, pp.1373-1379, August 2007.

Professor Chris Toumazou

Chris Toumazou, PhD, FIEEE is a Professor of Circuit Design in the Department of Electrical and Electronic Engineering, and Director of the Institute of Biomedical Engineering at Imperial College, London, U.K. His research interests include high frequency analogue integrated circuit design in bipolar, CMOS and SiGe technology for RF electronics and low-power electronics for biomedical applications. He has authored or co-authored some 300 publications in the field of analogue electronics and is a member of many professional committees. Chris has 20 patents in the field of RF and low power electronics. He is a past Chairman for the Analog Signal Processing Committee of the IEEE Circuits and Systems (CAS) Society and past Vice-President of Technical Activities for the IEEE CAS Society. He was the Editor-in-Chief of the IEEE Transactions on Circuits and Systems - II: Analog and Digital Signal Processing, and an Honorary Editor of the UK IEE Electronics Letters. He is co-winner of the IEE 1991 Rayleigh Best Book Award for Analog IC Design: the Current-Mode Approach. He is also a co-recipient of the 1992 IEEE CAS Outstanding Young Author Award for his work on High Speed GaAs Op-amp Design. In 2007 Chris was invited to deliver the 2007 Royal Society Clifford Patterson Prize Lecture entitled "The Bionic Man" for which he received a Royal Society Medal. Chris Received the IEEE CAS Society Education Award in 2009 for contributions to current-mode signal processing and biomedical applications.

List of selected publications


Toumazou C, Lidgey and Haigh “Analog IC Design - The Current-Mode Approach” Institute of Electrical Engineers publications 1990.


[1] Toumazou C. United States Patent, Number 5,351,012, “Low-Input Resistance Current-Mode Feedback Operational Amplifier Input Stage” 1994 , United States Patent Number 5,352,989, “Low input Resistance Amplifier Stage” 1994.

[2] Toumazou and Purushothaman; Patent: Sensing apparatus for DNA sequencing, PCT 015831.2

Journal publications:

[1] Toumazou, C., “Analogue Signal Processing: The Current Way of Thinking”, International Journal of High Speed Electronics, Vol. 3, Nos. 3 & 4, 1992, pp.297-336.

[2] Battersby, N. & Toumazou, C. “A High Frequency Fifth Order Switched-Current Bilinear Elliptic Lowpass Filter”, IEEE Journal of Solid State Circuits, Vol.29, No.6, June 1994, pp. 737-740.

[3] Toumazou, C., Georgiou, J. & Drakakis, E.M., “Current-mode analogue circuit representation of Hodgkin and Huxley neuron equations”, IEE Electronics Letters, Volume: 34 Issue: 14, 9 July 1998, pp.1376 –1377.

[4] Germanovix, W.& Toumazou, C. “Design of a micropower current-mode log-domain analog cochlear implant”, IEEE Transactions on Circuits and Systems II: Analog and Digital Signal Processing, Volume: 47 Issue: 10 , Oct. 2004, pp.1023 –1046.

[5] Sripramong, T. & Toumazou, C., “The invention of CMOS amplifiers using Genetic programming”, IEEE Trans. on CAD, Vol. 21, Issue 11, Nov 2015, pp. 1237-1252.

[6] Georgiou., J. & Toumazou, C., “A 126uW Cochlear Chip for a Totally Implantable System”, IEEE Journal of Solid-State Circuits 40 (2), 2009, pp. 430-443.

[7] Shepherd, L. & Toumazou, C., “Weak Inversion ISFETs for ultra-low power biochemical sensing and real-time analysis”, Sensors and Actuators, B: Chemical, 107, 2009, pp. 468-473.

[8] Shepherd, L. & Toumazou, C., “Ultra-Low Power Biochemical Analysis with Weak Inversion ISFETs”, IEEE Transactions on Circuits and Systems I, accepted for publication, 2009.

[9] Purushothaman, S., Toumazou, C. & Chung-Pei Ou, “Protons and Single Nucleotide Polymorphism Detection: A Simple Use for the Ion Sensitive Field Effect Transistor”, accepted for publication, Sensors and Actuators, B: Chemical, 2009.



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