Imperial College London

DrKonstantinNikolic

Faculty of EngineeringDepartment of Electrical and Electronic Engineering

Visiting Professor
 
 
 
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Contact

 

+44 (0)20 7594 1594k.nikolic

 
 
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Location

 

Bessemer 420CBessemer BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

117 results found

Gaspar N, Sondhi A, Evans B, Nikolic Ket al., 2015, Live demonstration: A low-power neuromorphic system for retinal implants and sensory substitution, BioCAS 2015, Publisher: IEEE

This demonstration shows a new type of front end for a Retinal Prosthesis/Vision Augmentation (RP/VA) System, as well as a Visual to Auditory Sensory Substitution Device (SSD). Each system serves to process visual scenes then present them in a simplified form (augmented with auditory signals) to assist visually impaired people. Both systems consist of three components: a sensory block to capture the visual scene, a processing block to manage the collected data and generate stimulus patterns, and an output block. Here we are presenting two possible setups. In both setups we use a “silicon retina” in the form of a Dynamic Vision Sensor (DVS) for the sensory block. In the hardware implementation, the processing block consists of a microcontroller, with an additional circuit for visual to audio conversion. The result of the visual processing is presented on an LED-matrix, while the SSD (audio) output can be heard on stereo headphones. In the second setup the processing block is an Android device, running an application called SounDVS. This solution also outputs both audio and video signals. The systems represent wearable, low-power, real-time solutions for receiving and processing video input and creating simplified outputs containing the most salient information about the visual scene.

Conference paper

Rapeaux A, Nikolic K, Williams I, Eftekhar A, Constandinou TGet al., 2015, Fiber size-selective stimulation using action potential filtering for a peripheral nerve interface: A simulation study, 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, Pages: 3411-3414

Functional electrical stimulation is a powerfultool for restoration of function after nerve injury. Howeverselectivity of stimulation remains an issue. This paper presentsan alternative stimulation technique to obtain fiber size-selectivestimulation of nerves using FDA-approved electrode implants.The technique was simulated for the ventral roots ofXenopus Laevis, motivated by an application in bladder control. Thetechnique relies on applying a high frequency alternatingcurrent to filter out action potentials in larger fibers, resultingin selective stimulation of the smaller fibers. Results predict thatthe technique can distinguish fibers with only a 2 µm differencein diameter (for nerves not exceeding 2 mm in diameter). Thestudy investigates the behaviour of electrically blocked nervesin detail. Model imperfections and simplifications yielded someartefacts in the results, as well as unexpected nerve behaviourwhich is tentatively explained.

Conference paper

Leow L, Nikolic K, 2015, Machine vision using combined frame-based and event-based vision sensor, Circuits and Systems (ISCAS), 2015 IEEE International Symposium on

Conference paper

Wadehn F, Schieban K, Nikolic K, 2015, Motion Sensitivity Analysis of Retinal Ganglion Cells in Mouse Retina using Natural Visual Stimuli, 2015 37TH ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC), Pages: 1658-1662, ISSN: 1557-170X

Journal article

Luan S, Williams I, Constandinou TG, Nikolic Ket al., 2014, Neuromodulation: present and emerging methods, Frontiers of Neuroengineering, Vol: 7, ISSN: 1662-6443

Neuromodulation has wide ranging potential applications in replacing impaired neural function (prosthetics), as a novel form of medical treatment (therapy), and as a tool for investigating neurons and neural function (research). Voltage and current controlled electrical neural stimulation (ENS) are methods that have already been widely applied in both neuroscience and clinical practice for neuroprosthetics. However, there are numerous alternative methods of stimulating or inhibiting neurons. This paper reviews the state-of-the-art in ENS as well as alternative neuromodulation techniques - presenting the operational concepts, technical implementation and limitations - in order to inform system design choices.

Journal article

Reverter F, Prodromakis T, Liu Y, Georgiou P, Nikolic K, Constandinou TGet al., 2014, Design Considerations for a CMOS Lab-on-Chip Microheater Array to Facilitate the in vitro Thermal Stimulation of Neurons, IEEE International Symposium on Circuits and Systems (ISCAS), Publisher: IEEE, Pages: 630-633

Conference paper

Jarvis SJ, Nikolic K, Schultz SR, 2014, Optical coactivation in cortical cells: reprogramming the excitation-inhibition balancing act to control neuronal gain in abstract and detailed models, BMC Neuroscience, Vol: 15, Pages: F1-F1, ISSN: 1471-2202

Journal article

Nikolic K, Jarvis S, Schultz S, Grossman Net al., 2013, Controlling the neuronal balancing act: optical coactivation of excitation and inhibition in neuronal subdomains, Publisher: BioMed Central, ISSN: 1471-2202

Conference paper

Grossman N, Simiaki V, Martinet C, Toumazou C, Schultz SR, Nikolic Ket al., 2013, The spatial pattern of light determines the kinetics and modulates backpropagation of optogenetic action potentials, JOURNAL OF COMPUTATIONAL NEUROSCIENCE, Vol: 34, Pages: 477-488, ISSN: 0929-5313

Journal article

Nikolic K, Loizu J, 2013, Drosophila Photo-transduction Simulator, Journal of Open Research Software, Vol: 1, Pages: 1-7

Journal article

Nikolic K, Jarvis S, Grossman N, Schultz Set al., 2013, Computational Models of Optogenetic Tools for Controlling Neural Circuits with Light, 35th Annual International Conference of the IEEE-Engineering-in-Medicine-and-Biology-Society (EMBC), Publisher: IEEE, Pages: 5934-5937, ISSN: 1557-170X

Conference paper

Mou Z, Triantis IF, Woods VM, Toumazou C, Nikolic Ket al., 2012, A Simulation Study of the Combined Thermoelectric Extracellular Stimulation of the Sciatic Nerve of the Xenopus Laevis: The Localized Transient Heat Block, IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, Vol: 59, Pages: 1758-1769, ISSN: 0018-9294

Journal article

Katz ML, Nikolic K, Delbruck T, 2012, Behavioural Emulation of Event-Based Vision Sensors, IEEE International Symposium on Circuits and Systems, Publisher: IEEE, Pages: 737-740, ISSN: 0271-4302

Conference paper

Katz ML, Nikolic K, Delbruck T, 2012, Live Demonstration: Behavioural Emulation of Event-Based Vision Sensorsh, IEEE International Symposium on Circuits and Systems, Publisher: IEEE, Pages: 736-736, ISSN: 0271-4302

Conference paper

Katz ML, Lutterbeck C, Nikolic K, 2012, An Implementation of Magnocellular Pathways in Event-Based Retinomorphic Systems, IEEE Biomedical Circuits and Systems Conference (BioCAS), Publisher: IEEE, Pages: 17-20, ISSN: 2163-4025

Conference paper

Nikolic K, Grossman N, 2011, Multicompartmental Model of Neurons Expressing Channelrhodopsin, 4th INCF Congress of Neuroinformatics, Frontiers in Neuroscience

Conference paper

Nikolic K, Serb A, Constandinou TG, 2011, An Optical Modulator in Unmodified, Commercially-Available CMOS Technology, IEEE Photonics Technology Letters, Vol: 23, Pages: 1115-1117, ISSN: 1041-1135

Here we present a method and structures for mid-infrared, free-space optical communication using unmodified, commercially available complementary metal-oxide semiconductor integrated circuits. The modulator is based onthe free carrier absorption in parasitic PN junction structures under reverse bias. Measured results demonstrate the proof-of-concept with speeds of 100bps (1.55um wavelength), but at least two orders of magnitude improvement can be achieved. This technology will enable non-galvanic chip-to-chip and chip-to-package communication as an alternative to wirebonding in applications that benefit from a planar top chip surface, such as chemical sensing lab-on-chip systems as well as general sensorsand mid-infrared communication.

Journal article

Nikolic K, Constandinou TG, Toumazou C, 2011, Method and Apparatus for Optically Outputting Information from a Semiconductor Device

A method of optically outputting information (e.g. digital data) from a semiconductor device, the method comprising: providing a semiconductor device having a semiconducting p-n junction, the p-n junction having a region of reduced free charge carrier density; applying an electrical signal to modulate the extent of the said region, the electrical signal being representative of the information to be outputted; arranging incident light to pass through at least part of the said region, such that the light is at least partially absorbed in dependence upon the modulated extent of the said region, thereby producing intensity-modulated output light; and detecting the intensity of the output light and thereby determining the outputted information. Also provided is an electro-optical assembly, a package module for mounting a semiconductor device on a printed circuit board, and an integrated circuit chip.

Patent

Grossman N, Nikolic K, Grubb M, Burrone J, Toumazou C, Degenaar Pet al., 2011, High-frequency limit of neural stimulation with ChR2, Conf Proc IEEE Eng Med Biol Soc, Pages: 4167-4170, ISSN: 1557-170X

Optogenetic technology based on light activation of genetically targeted single component opsins such as Channelrhodopsin-2 (ChR2) has been changing the way neuroscience research is conducted. This technology is becoming increasingly important for neural engineering as well. The efficiency of neural stimulation with ChR2 drops at high frequencies, often before the natural limit of the neuron is reached. This study aims to investigate the underlying mechanisms that limit the efficiency of the stimulation at high frequencies. The study analyzes the dynamics of the spikes induced by ChR2 in comparison to control stimulations using patch clamp current injection. It shows that the stimulation dynamics is limited by two mechanisms: 1) a frequency independent reduction in the conductance-to-irradiance yield due to the ChR2 light adaptation process and 2) a frequency dependent reduction in the conductance-to-current yield due to a decrease in membrane re-polarization level between spikes that weakens the ionic driving force. The effect of the first mechanism can be minimized by using ChR2 mutants with lower irradiance threshold. In contrast the effect of the second mechanism is fundamentally limited by the rate the native ion channels re-polarize the membrane potential.

Conference paper

Nikolic K, San Segundo Bello D, Delbruck T, Shih-Chii L, Roska Bet al., 2011, High-sensitivity silicon retina for robotics and prosthetics, SPIE Newsroom

Journal article

Grossman N, Nikolic K, Toumazou C, Degenaar Pet al., 2011, Modeling Study of the Light Stimulation of a Neuron Cell With Channelrhodopsin-2 Mutants, IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, Vol: 58, Pages: 1742-1751, ISSN: 0018-9294

Journal article

Serb A, Nikolic K, Constandinou TG, 2011, A CMOS-based light modulator for contactless data transfer: theory and concept, Silicon Photonics VI, Publisher: SPIE, Pages: 794317-794325

A new technique pertaining to the optical contactless chip-to-board communication using a commercially available CMOS technology is under development. The main concept is to use mid-IR light from a small LED which will enter an IC from the underside, impinge upon one or more pn-junctions and be reflected by a metallic sheet so that it falls on an external, discrete photodetector. After propagation through the doped semiconductor, the light undergoes attenuation due to free carrier absorption. By varying the reverse bias across the pn-junction(s), the depletion region widths are changed and therefore modulation of light intensity can be achieved. Through this scheme, data readout can be realized optically, thus alleviating the need for galvanic contacts (most notably wirebonds).

Conference paper

Serb A, Nikolic K, Constandinou TG, 2011, Feasibility of an Electro-Optic Link for Bondpad-less CMOS Lab-on-Chips, IEEE Biomedical Circuits and Systems (BioCAS) conference, Publisher: IEEE, Pages: 353-356

This paper explores the feasibility of developing CMOS-based lab-on-chips to analyse the properties of a fluid, without the need for bond wires. Both inductive and electro-optical schemes are suggested as possible solutions. Specifically, this paper details a novel approach in achieving electro-optical modulation in unmodified, commercially-available CMOS technology. By exploiting the plasma dispersion effect, it is shown how mid-infrared light can be modulated using parasitic structures designed in a CMOS integrated circuit. Both the fundamental theory and practical realisation are supported with measured data from an experimental setup.

Conference paper

Grossman N, Degenaar P, Nikolic K, 2011, Spike engineering with Channelrhodopsin-2, Neuroscience Letters

Conference paper

Nikolic K, Loizu J, 2010, Drosophila Phototransduction Simulator

This code contains detailed modelling of the single photon response, the quantum bump, of fly photoreceptors. All known components participating in the primary phototransduction process are taken into account, and estimates are given for the both the physical and the chemical parameters. The same model can be used for multiphoton response, i.e. in the case of higher light intensity stimuli. The model successfully reproduces the experimental results for the statistical features of quantum bumps (average shape, peak current average value and variance, the latency distribution, etc), arrestin mutant behaviour, low extracellular Ca cases, etc. The TRP channel activity is modelled using the Monod-Wyman-Changeux (MWC) theory for allosteric interaction. The model can combine deterministic and stochastic approaches and allows for a detailed noise analysis. The computational model was coded in Matlab using the Parallel Computing Toolbox, which allows computations on multicore computers and computer clusters. An appropriate graphic user interface was developed which gives very convenient and instructive presentation of the parameters used in the modelling and could easily be expanded to other G-protein coupled cascade processes.Code covered by the BSD License (Matlab Central, File exchange), please see BSD_License.txt file or visit: http://www.mathworks.com/matlabcentral/fileexchange/view_license?file_info_id=22942 If you use this code please cite the papers [1] and [2].The main file "Drosophila_Phototransduction.m" opens the GUI. The GUI contains the preloaded values for parameters and should be mostly self-explanatory in combination with the paper [1]. It is possible to run stochastic and deterministic models for single and multiple runs. The output consists of a table for some average values and three graphs (for the average quantum bump, latency times distribution and peak current distribution). It is possible to produce some other plots currently commented out

Software

Grossman N, Poher V, Grubb MS, Kennedy GT, Nikolic K, McGovern B, Palmini RB, Gong Z, Drakakis EM, Neil MAA, Dawson MD, Burrone J, Degenaar Pet al., 2010, Multisite optical excitation using ChR2 and micro-LED array, Journal of Neural Engineering, Vol: 7, ISSN: 1741-2560

Journal article

Nikolic K, Toumazou C, 2010, A bio-inspired ultrasensitive imaging chip — Phase one: Design paradigm, Proceedings of the IEEE International Symposium on Circuits and Systems (ISCAS), 2010, Pages: 345-348

Conference paper

Degenaar P, Grossman N, Berlinguer-Palmini R, McGovern B, Pohrer V, Dawson M, Toumazou C, Burrone J, Nikolic K, Neil Met al., 2010, Optoelectronic microarrays for retinal prosthesis, IEEE Biomedical Circuits and Systems Conference, BioCAS 2009, Pages: 183-186

Conference paper

Nikolic K, Loizou J, Degenaar P, 2010, Computational Modelling of the Drosophila Phototransduction Cascade, Biophysical Journal 98

Conference paper

Nikolic K, Loizu J, Degenaar P, Toumazou Cet al., 2010, A stochastic model of the single photon response in Drosophila photoreceptors, Integrative Biology, Vol: 2, Pages: 354-370

We present a quantitative model for the phototransduction cascade in Drosophila photoreceptors. The process consists of four stages: (1) light absorption by Rhodopsin, (2) signal amplification phase mediated by a G-protein coupled cascade, (3) close/open state kinetics of the transient receptor potential (TRP) ion channels which regulate the ionic current in/out of the cell and (4) Ca regulated positive and negative feedbacks.The model successfully reproduces the experimental results for: single photon absorption "quantum bump" (QB), statistical features for QB (average shape, peak current average value and variance, the latency distribution, etc), arrestin mutant behaviour, low extracellular Ca2+ cases, etc. The TRP channel activity is modeled by a Monod-Wyman-Changeux (MWC) model for allosteric interaction, instead of using the usual ad hoc Hill equation. This approach allows for a plausible physical explanation how Ca/calmodulin regulate the protein activity. The cooperative nature of the TRP channel activation leads to "dark current" suppression at the output allowing for reliable detection of a single photon. Stochastic simulations were produced by using the standard rate equations combined with the Poisson distribution for generating random events from the forward and the reverse reaction rates. Noise is inherent to the system but appears to be crucial for producing such reliable responses in this complex, highly nonlinear system. The approach presented here may serve as a useful example how to treat complex cellular mechanisms underlying sensory processes.

Journal article

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