Retinal Prosthesis Dissertation - Student Home Pages

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The main advantage of AER in the context of aiding artificial vision for humans is that events occurring in the scene input to the receiver chip are represented and propagated as impulses or spikes which is the method used by the fibres of the optic nerve. The maximum spike rate represents maximum hue intensity when referring to the RGB true colour format. Note that propagation of signals in the optic nerve is very energy efficient and it can be expected that the neuromorphic AER communication protocol will be similar. iii of ix
Contents An Address Event Representation (AER) Multicast Router for Colour Vision .................................. i Acknowledgements ................................................................................................................................ i Dedication ............................................................................................................................................... i Abstract\Foreword ................................................................................................................................. ii Chapter 1 Introduction/research aim ................................................................................................. 10 1.1 Introductory Literature Review ............................................................................................... 10 1.1.1 Sub retinal ..................................................................................................................... 11 1.1.2 Epi retinal ............................................................................................................................. 14 1.2 Conceptual overview ............................................................................................................. 18 1.3 Sub retinal versus Epi-retinal ................................................................................................. 21 1.4 Introduction to stimulators ........................................................................................................... 21 1.5 Thesis structure ..................................................................................................................... 22 Chapter 2 Early directions .................................................................................................................. 24 2.1 Introduction to initially envisaged project ..................................................................................... 24 2.2 Neural network representation .................................................................................................... 25 2.2.1 The first artificial neuron ........................................................................................................... 26 2.2.2 Hebb’s rule ........................................................................................................................... 28 2.2.3 Adaline and the adaptive linear combiner: a bipolar case of above ..................................... 28 2.2.4 Neural Networks –perceptron training .................................................................................. 30 2.2.5 Linear separability ................................................................................................................ 32 2.2.6 The Delta Rule (used to determine separability) .................................................................. 35 2.3 Address Event Representation (AER) ......................................................................................... 37 2.3.1 The message packet ............................................................................................................ 37 2.4 Comparison to Frame Based Representation (FBR) ................................................................... 38 2.4.1 Comparison Criteria ............................................................................................................. 40 2.4.2 Address Event Representation ............................................................................................ 41 2.5 MATLAB sub-retinal simulation ................................................................................................... 42 2.5.1 MATLAB representation ....................................................................................................... 42 2.5.2 Program operation ............................................................................................................... 43 2.5.1 Files in Appendix A ................................................................................................................... 44 2.5.2 Use of the program ................................................................................................................... 44 2.6 Epi-retinal; method of choice ....................................................................................................... 45 2.6.1 MATLAB representation of epi_retinal approach.................................................................. 47 2.6.2 FPGA representation of epi_retinal approach .......................................................................... 48 2.7 Background to stimulators ........................................................................................................... 49 2.7.1 Charge considerations ......................................................................................................... 49 2.7.2 Achromatic current requirements ......................................................................................... 49 Chapter 3 Concepts ............................................................................................................................. 50 3.1 Neural concepts .......................................................................................................................... 52 3.2 Biological Neuron operation ........................................................................................................ 53 3.3 Natural limit for pulse duration ..................................................................................................... 54 3.4 Retinal colour perception ............................................................................................................. 55 3.5 Human visual processing ............................................................................................................ 57 3.6 Current Retinal Implants .............................................................................................................. 61 3.6.1 Retinal structure ................................................................................................................... 61 3.6.2 Retinal operations ................................................................................................................ 62 3.6.3 Commonality of sub retinal and epi retinal approaches ........................................................ 65 iv of ix
Page 1 and 2: An Address Event Representation (AE
Page 3: Abstract\Foreword This document pro
Page 7 and 8: --Appendix E FPGA Outputs .........
Page 9 and 10: Figure 48 receiver rtl_16 .........
Page 11 and 12: Chapter 1 Introduction/research aim
Page 13 and 14: foveola (fovea pit) there is a one
Page 15 and 16: NB that the photoreceptors of the f
Page 17 and 18: electrodes to be driven implies sti
Page 19 and 20: Typically AER is used as a multi se
Page 21 and 22: Real time - innerpulse relationship
Page 23 and 24: the post processing stage of this w
Page 25 and 26: Appendix C: FPGA Sender chip Append
Page 27 and 28: Red (660nm) R / G Red ( 620750nm )
Page 29 and 30: 1 0 1 1 0 0 1 1 0 1 1 1 Table 3 `xo
Page 31 and 32: Adaptive linear combiner w 0 1 Let
Page 33 and 34: is correct (one class) and -1 (the
Page 35 and 36: x2 Linear separation 1.00 0.90 0.80
Page 37 and 38: This is also the Cartesian co-ordin
Page 39 and 40: 2.4 Comparison to Frame Based Repre
Page 41 and 42: Typical GOP structure (Typically an
Page 43 and 44: point is an event occurs for spike
Page 45 and 46: 2.5.1 Files in Appendix A “ycut.m
Page 47 and 48: MPEG-2 setup AER setup Camera Camer
Page 49 and 50: 2.6.2 FPGA representation of epi_re
Page 51 and 52: Chapter 3 Concepts An epiretinal im
Page 53 and 54: AER Transmission lines INPUT image
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electrical pulse generated is calle
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Figure 25 Retinal colour processing
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cells to modulate this luminance pa
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L+ M- + - R-G G-R B-Y Y-B Note: L(r
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3.6.2 Retinal operations Light reac
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quantified by number of cycles pres
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(Where * is the convolution operato
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T frame C * R * M p Tpacket i.e. Tp
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e relaxed and from (2) the temporal
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one tw o three four five six seven
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3.8.1 Other test images For other b
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Tspike (4ms) Ispike (16ms: interspi
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INDIGO ORANGE YELLOW MAGENTA CYAN B
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4.1 Sender concepts From chapter on
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pixel must equate to 0.02/1024 i.e.
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Clocking hierarchy (32 by 32 image)
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the number of address bits will alt
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Translation report, (3) Map report,
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90 of 200 CLKIN_IN RST_IN pixelcloc
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incorporate colour planes for each
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Chapter 5 Receiver chip The followi
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5.2 Power Analysis Xilinx FPGAs hav
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98 of 200 produce_wire _outputs Ins
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5.5.1 Incoming (short) AER stream T
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Receiver Red plane r1 DAC (4-bit) T
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5.8.2 Electrode size and positionin
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sequence of wiring from the receive
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does this is to inject an equivalen
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6.2.2 Envisaged retinal array This
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a monochrome camera in this space i
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632mW) thus extending battery life
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For the implemented/structural case
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The sender and receiver circuitry p
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Bibliography 1. Woodburn R. Murray
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38. Banks, D.J., P. Degenaar, and C
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74. Freeman, J.A., Skapura, D. M.,
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109. Weiland, J.D., et al. Progress
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141. Indiveri G. Chicca E. Douglas
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172. Singh, P.R., et al. A matched
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206. Stieglitz, T., et al. Developm
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xmixedsource; numberOfFrames = 8; f
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%check {k} =imread (['D:\abc\subima
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%Two for loops the first (outer loo
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%Row break rr6c1=000; rr6c2=000; rr
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--Appendix B FPGA Test setup librar
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stream_blue_pulse_count: out std_lo
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DVI_XCLK_P clock_25MHz, spike_cloc
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use IEEE.STD_LOGIC_UNSIGNED.ALL; --
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--Appendix C FPGA Sender chip libra
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-- else -- resit '1', CLKDV_OUT =>
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FPGA Receiver (structural) chip --A
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FPGA Receiver (structural) chip --E
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FPGA Receiver (structural) chip --r
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FPGA Receiver (structural) chip blu
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FPGA Receiver (structural) chip con
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FPGA Receiver (structural) chip --s
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FPGA Receiver (structural) chip --
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FPGA Receiver (structural) chip --
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FPGA Receiver (structural) chip IO_
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Number with an unused LUT 18 219 8%
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IO Utilization: Number of IOs: 26 N
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The Slice Logic Distribution report
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Router effort level (-rl): Standard
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oming_clock | HOLD | 0.519ns| | 0|
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Part | xc5vlx50tff1136-3 | Process
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Selected Device: 5vlx50tff1136-3 Sl
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used in combination with MAP -timin
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Data Sheet report: ----------------
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“For these implantable devices to
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microstimulator with a 1:4 demultip
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“Medical experiments have estimat
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A Retinomorphic Vision System “In
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“The common language of neuromorp
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