1. ELECTRONICS MEET ANIMAL BRAIN
CHAPTER 1: INTRODUCTION
Introduction:
By enabling better study of animal behaviour‟s neural basis, implantable computers may
revolutionize field biology and eventually lead to neuralprosthetics, hardware-based human-
computer interfaces, and artificial systems that incorporate biological intelligence
principles.Recent advances in microelectromechanical systems (MEMS), CMOS electronics, and
embeddedcomputersystems will finally let us link computercircuitryto neural cells in live
animals and, in particular,to reidentifiable cells with specific, knownneuralfunctions. The key
components of such abrain-computersystem include neural probes, analogelectronics, and a
miniature microcomputer.Researchersdeveloping neural probes such as submicronMEMS
probes, micro clamps, microprobearrays,and similar structures can now penetrateandmake
electrical contact with nerve cells withoutcausing significant or long-term damage toprobesor
cells.Researchers developing analog electronics suchas low-power amplifiers and analog-to-
digital converterscan now integrate these devices with microcontrollerson a single low-power
CMOS die.Further,researchers developing embedded computersystems can now incorporate all
the core cir-cuitry of a modern computer on a single silicon chipthat can run on miniscule power
from a tiny watch battery. In short, engineers have all the pieces they need to build truly
autonomous implantable computersystems.Untilnow,high signal-to-noise recording as wellas
digital processing of real-time neuronal signalshavebeen possible only in constrained
laboratoryexperiments.By combining MEMS probes withanalog electronics and modern CMOS
computingintoself-contained, implantable microsystems,implantablecomputers will free
neuroscientistsfromthe lab bench.With advances in integrated circuit processingwill come ever
more capable andpower-efficientembedded computers. Thesimple neurochips of today will
become the complexembedded systems of tomorrow,when embedding in this ultimate sense will
mean computerelectronics embedded in nerve tissue.
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CHAPTER 2: OVERVIEW OF THE PROJECT
2.1 Brain machine interfaces (BMIs):
BMI‟Soffer a direct path for brain to communicate with outside world, mainly use central neural
activities to control artificial external devices. These techniques to collect the brain signals could
be distinguished as non-invasive or invasive BMIs according to the position of recoding
electrodes. Compared with non-invasive BMIs, invasive BMIs have wide potential in assisting,
augmenting or repairing more complex motor functions of human, especially in patients with
severe body paralysis. This paper will review our lab's research work on invasive BMIs with
subjects on rat and monkey. We built a synchronous recording and analyzing system for rat's
neural activities and motor behavior. Rat could use its intention to control external one
dimensional robotic lever in real time. Also, a remote control training system was designed to
realize rat navigating through 3D obstacle route, as well as switching between “motion” and
“motionlessness” at any point during the route. We further extended our work to develop the
invasive BMI system on non-human primate. While the monkey was trained to perform a 2-D
center-out task, plenty of neural activities in motor cortex were invasively recorded. We showed
the preliminary decoding results of the 2D trajectory, and plan to utilize the decoded prediction
to control an external device, such as robot hand.
2.2Integrating silicon and neurobiology:
Neurons and neuronal networks decide, remember,modulate, and control an animal‟severy
sensation,thought, movement, and act. The intimatedetailsof this network, including the dynamic
propertiesof individual neurons and neuron populations,give a nervous system the power to
control awidearray of behavioral functions.Thegoal of understanding these details
motivatesmanyworkers in modern neurobiology.Tomakesignificantprogress, these
neurobiologists needmethodsfor recording the activity of single neuronsorneuron assemblies, for
long timescales, at highfidelity,in animals that can interact freely with theirsensoryworld and
express normal behavioural responses.
2.3Conventional techniques:
Neurobiologists examine the activities of braincells tied to sensory inputs, integrative
processes,and motor outputs to understand the neural basisof animal behavior and intelligence.
They alsoprobe the components of neuronal control circuitryto understand the plasticity and
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dynamics of control.They want to know more about neuronaldynamicsand networks, about
synaptic interactionsbetween neurons, and about the inextricablelinksbetween environmental
stimuli and neuronalsignaling,behavior,and control.To explore the details of this biological
circuitry,neurobiologists use two classes of electrodes torecord and stimulate electrical signals in
tissueintracellular micropipettes to impale or patch-clamp single cells for interrogation of the
cell‟sinternal workings, andextracellular wires or micromachined probesfor interrogating
multisite patterns of extracellularneural signaling or electrical activityinmuscles.Neurobiologists
use amplifiers and signal generatorsto stimulate and record to and from neurons throughthese
electrodes, and signal-processing systems toanalyze the results. They have used these
techniquesfor decades to accumulate a wealth of understandingabout the nervous system.
Unfortunately, todate, most of these experiments have been performedon slices of brain tissue or
on restrained and immobilizedanimals, primarily because the electronicinstrumentsrequired to
run the experiments occupythebetter part of a lab bench.This situation leaves neurobiologists
with a naggingquestion: Are they measuring the animal‟snormalbrain signals or something far
different?Further,neurobiologists want to understand howanimalbrains respond and react to
environmentalstimuli.The only way to truly answer these questionsis to measure a brain‟sneural
signaling while the animal roams freely in its natural environment.
2.4Salient objectives:
The solution to these problems lies in making thetest equipment so small that a scientist can
implantit into or onto the animal, using materials andimplantation techniques that hurt neither
computernor animal. Recent developments in MEMS, semiconductorelectronics, embedded
systems, biocompatiblematerials, and electronic packagingfinallyallow neuroscientists and
engineers to beginpackagingentire neurobiology experiments intohardwareand firmware that
occupy less space thanahuman fingernail.Researchers call these bioembedded systems
neurochips. Scientists from the University of Washing-ton,Caltech, and Case Western Reserve
Universityhave teamed to build these miniaturized implantableexperimental setups to explore the
neural basis ofbehavior.This research effort has developed or is inthe process of developing the
following:
• miniaturized silicon MEMS probes for recordingfrom the insides of nerve cells;
•biocompatible coatings that protect theseprobes from protein fouling;
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• a stand-alone implantable microcomputer thatrecords from and stimulates neurons,
sensorypathways, or motor control pathways in anintact animal, using intracellular probes, extra-
cellular probes, or wire electrodes;
• Neurophysiological preparations and techniquesfor implanting microchips and wireelectrodesor
MEMS probes into or onto animalsin a way that does not damage the probesortissue;
•Firmware that performs real-time biologyexperiments with implanted computers,
usinganalytical models of the underlying biology;
• software to study and interpret the experimentalresults, eventually leading to
reverseengineeredstudies of animal behavior.As the “Neuroscience Application
Examples”sidebar shows, the first neurochip experiments usesea slugs and moths in artificial
environments, butbroad interest has already arisen for using implantable computers in many
other animals.a computer was melded with a human brain to create a part-man-part-machine
cyborg. Now scientists in New York have created a real-life RoboRat. A rat has had computer
chips integrated into its brain, allowingthe machine-mouse to perform seemingly miraculous
tasks. For example it can push a lever to get a drink without moving a paw or even a muscle.
RoboRat uses its computer implants to manipulate the lever by thought power alone. The
scientists have now created several more RoboRats and they‟ve taken the technology much
further. They can send signals to the rats‟ computer implants using a wireless control, and can
steer the rodent as if it were a remote controlled car. When they stimulate its brain one way and
the rodent turns right; when its stimulated another way it turns left. Merging a living mind with a
machine may sound like a horrendously cruel creation, but the researchers insist this isn‟t the
case. Indeed they say they have some of the happiest lab rats around - because of the way they
train them. The rats are not being forced to do anything they don‟t want to do. They turn left or
right when the scientists push the buttons on the remote control because they‟ve learnt obeying
this command results in the pleasure centre of their brains being stimulated by the computer chip
implant. It‟s a bizarre twist on the concept of free will. The researchers haven‟t created RoboRat
just in the pursuit of pure knowledge. Like RoboCop, RoboRat will eventually have important
public duties to perform…they could be sent on a rescue mission into the rubble after an
Earthquake or building collapse.
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5. ELECTRONICS MEET ANIMAL BRAIN
CHAPTER: 3 BLOCK DIAGRAM
3.1 Block Diagram:
Fig.3.1 block diagram of neuro chip
3.2 A stimulating world:
Passive neurochips that do nothing more than record will provide neurobiologists with a wealth
of data. But even now, with the first neurochips barely in production, neurobiologists are already
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calling for designs that stimulate nerve tissue as well as record from it. Active neurochips
will allow stimulus-response experiments that test models of how nervous systems control
behavior, such as how sensory inputs inform motor-circuit loops and the logic or model behind
the response. Indeed, the neurochip project‟s long-term goal is to develop a hardware and
software environment in which a neurobiologist conceives a stimulus-response experiment,
encodes that experiment in software, downloads the experiment to an implanted neurochip, and
recovers the data when the experiment concludes. Model of integrative biology in which
neurochips play a key part.
Fig.3.2 Flight simulation of moth
A Programmable System-on-a-Chip fromCypress MicroSystems integrates a
microprocessor,variable-gain amplifiers, an ADC, a memory controller,
and a DAC into a single integrated circuit.First-generationneurochips integrate one ormoreICs,
passive elements such as capacitors, batteries,and I/O pads on small micro-PCBs. The
prototypeneurochip used packagedICsand button cells, and occupied a 1 cm ×3 cmprinted-circuit
board. The “production” version,due out of processing in early 2003, uses die-
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onboardtechnology and thin-film batteries, and issmaller than 1 square centimeter. Future-
generation neurochips will integrate all the electronicsontoa single silicon chip, and will likely be
smallerthan10 mm on a side.
3.3 Probes:
Building the probes that let a neurochip eavesdropon the electrical signaling in a nerve
bundle,groupof neurons, or single neuron presents adaunting task. Benchtop experiments on
constrainedanimals typically use metallic needles oftenmade of stainless steel or tungsten
tocommunicatewith nerve bundles, micromachinedsilicon probes to record from groups of
neurons,or glass capillaries filled with a conductive ionicsolution to penetrate and record from
the inside ofindividual neurons. In unconstrained animals, flexiblemetallic needles, attached to
the animal withsurgicalsuperglue, and micromachined siliconprobesstill work.
However,replicating the performanceof glass capillaries in flying, swimming, wigglinganimals is
adifferent story entirely.
Fig.3.3 .Micromachined silicon probes
Several centimeters long and quite fragile, the glasscapillaries that neurobiologists use to probe
theinsides of nerve cells typically have tip diameterssmaller than 0.3 microns. They impale
neurons evenmore fragile than the probes themselves. Neurobiologists
use micromanipulators to painstakinglyandprecisely drive single probes into single
neurons.Fortunately,MEMS technology offers a possiblealternativeto these glass capillaries.
University of Washingtonresearchers aredevelopingsilicon MEMS probes and flexible
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interconnectstructures to mimic the performance of glasscapillariesin an implanted
preparation.Researchers
have already recorded intracellular signals with earlyprototypes, and development is ongoing.3.4
Glyme:
Researchers seek to implant both probes andneurochips inside an animal‟s brain. Unfortunately,
an animal‟s immune system rapidly and indiscriminatelyencapsulates all foreign bodies with
proteins,without regard for the research value ofimplantedprobes and neurochips. The adsorbed
proteinsnot only attenuate the recorded electricalsignals,but can also jeopardize the
animal‟ssurvivalby causing abnormal tissue growth. Researchers at the University of
Washington‟sCenter for Engineered Biomaterials have developedplasma-deposited ether-
terminated oligoethyleneglycol coatings that inhibit protein fouling, asPreliminary research
indicates that
these glyme coatings can reduce the protein fouling of probes and neurochips to levels
acceptable for week-long experiments.
3.5 The power struggle:
Neurochips can derive power from onboard batteries,external radiofrequency sources, a
wiretether, or the nerve tissue itself. The ultimate decision on the power source depends on the
nature oftheexperiments and the animal‟senvironment.Batteriesare attractive because they avoid
the antennasand charge pumps required to capture RFenergy,operate in all environments, do not
restricttheanimal‟smovement the way a tether does, andprovidemuch more power than tapping
nerve cellsforenergy.Batteries have a weight disadvantage, but thinfilmtechnologies using
LiCoO2/LiPON/Li andNi/KOH/Znpromise flexible rechargeable batterieswith peak current
densities greater than 12 mApersquare centimeter for short-duration experiments,and lifetimes
measured in days or longer atlow-currentdensities.
7,8Batteries are ideal for the two sample preparationsshown in the “Neuroscience Application
Examples”sidebar.The typical hawkmoth flighttimeis less than 60 seconds. The 12 mA
providedbya 200 mg, one-square-centimeter battery easilypowersa neurochip for this
experiment‟sduration.Thesea slug trolling methodically along theseafloorlies at the opposite end
of the spectrum,needingonly a few milliamps of current to poweraneurochip for a week. The slug
can easily accom-modate a large battery in its visceral cavity, allow-ing extended untethered
experiments.
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3.6 Memory:
Once implanted, an embedded neurochip mustread its experimental procedure from memory,
runthe experiment, acquire the neural spike trains, thenstore the results in memory. As with all
computersystems, memory size is an issue for neurochips.Fortunately, the electrical spike trains
generated bynerve tissue have a stereotyped shape as shown, suggesting that neurochips should
compressthe neural waveforms before storing them inmemory.Compressingthe signals has two
advantages.
Fig.3.4 flash memory on pcb
First,it effectively increases the onboard storagecapacity. Second, it decreases the frequency
ofmemory writes, reducing power consumption.Even simple compression algorithms such as
runlengthencoding can achieve better than 10 to 1compressionratios on neural signals.
Customalgorithms that apply vector quantization,run-length encoding, and Huffman
encodingtodifferent parts of the neural waveform canachieveup to 1,000 to 1 compression
ratios.Given
the limited computing power of an implantablemicrocomputer, simpler is better when it comes
tocompression, but even simple RLE offers huge.
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CHAPTER 4: DESIGNER CHIPS
4.1 Designer Neurochips:
Like their bench top experimental counterparts,neurochips use amplifiers to boost low-
voltagebiological signals, analog-to-digital converters(ADCs) to digitize these signals,
microcomputersto process the signals, onboard memory to storethe signals, digital-to-analog
converters (DACs)to stimulate nerves, and software to control theoverall experiment.The key
requirements are that the neurochip be smalland lightweight enough to fit inside or onto the
animal, have adequate signal fidelity for interactingwiththe millivolt-level signals characteristic
ofnerve tissue, and have sufficient processing powertoperform experiments of real scientific
value.The basic components of a neurochip are commerciallyavailable today. They include
instrumentation amplifiers, ADCs/DACs, reconfigurablemicrocomputers, and high-density
memory.
4.2MSP430 Microcontrollers (MCUs):
From Texas Instruments (TI) are 16-bit, RISC-based, mixed-signal processors designed
specifically for ultra-low-power. MSP430 MCUs have the right mix of intelligent peripherals,
ease-of-use, low cost and lowest power consumption for thousands of applications – including
yours. TI offers robust design support for the MSP430 MCU platform along with technical
documents, training, tools and software to help designers develop products and release them to
market faster.
Ultra-Low Power
The MSP430 MCU is designed specifically for ultra-low-power applications. Its flexible
clocking system, multiple low-power modes, instant wakeup and intelligent autonomous
peripherals enable true ultra-low-power optimization, dramatically extending battery life.
Flexible Clocking System
The MSP430 MCU clock system has the ability to enable and disable various clocks and
oscillators which allow the device to enter various low-power modes (LPMs). The flexible
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clocking system optimizes overall current consumption by only enabling the required clocks
when appropriate.
Fig.4.1 cyborg beetle
Easy to Get Started
MSP430 MCUs are easy-to-use because of a modern 16-bit RISC architecture and a simple
development ecosystem.
16-Bit Orthogonal Architecture
The MSP430 MCU‟s 16-bit architecture provides the flexibility of 16 fully-addressable, single-
cycle, 16-bit CPU registers with the power of a RISC. The modern design of the CPU offers
versatility using only 27 easy-to-understand instructions and seven consistent addressing modes.
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Fig.4.2 block diagram of MSP430 MC
CHAPTER 5: APPLICATIONS
Wiring a sea slug:
Beneath a research vessel anchored in thePuget Sound, two scientists clad in scuba gear hover
over the bright orange sea slug. From the outside, this slug lookslike any other. But this
particular slug has abattery-powered microcomputer implantedin its brain and minuscule silicon
needles communicatingwith its neurons. The microcomputerfaithfully performs a biology
experimentas the animal goes about its normalbehavior.Meanwhile, the scientists videotape the
slug‟s feeding, fleeing, and social behaviorswhile measuring water currents and
geomagneticfields. Later,these scientists will studytheenvironmental measurements and
electronicrecordings in an attempt to decode howtheslug‟sbrain patterns correlate with
behavior.The anticipated outcome: groundbreakingfindings in behavioral neurobiology.
Monitoring a moth’s flight controls
In a small, dark zoology lab, a giant mothperforms an aerial ballet as it feeds from arobotically
controlled artificial flower, unawarethat the flower‟smovements are programmedto test the
moth‟sflight dynamics.Theultra-high-speed infrared video recordertapesthe moth‟severy
movement.But the special part of this experiment isneither the flower nor the videotaping. It
isthe tiny battery-powered microcomputerattached to the moth‟s thorax that recordselectrical
signals from the flight muscles andsense organs and stores this data in onboardmemory.
Robo-Rats Hunt Landmines
Rats with brain implants that turn them into remote controlled drones could soon be unleashed
on the countryside of Colombia as a secret weapon to combat deadly landmines planted by rebels
and drug lords.
The „robo-rats‟ were created by top American brain scientist doctor John Chapin shortly after
9/11 when it became clear rescue dogs were inadequate to search the rubble of the World Trade
Centre. Unfortunately, technical challenges kept the robo-rats from being finished in time to look
for survivors.
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CHAPTER 6: FUTURE SCOPE
Even as the first miniature neurochips record neuronal action potentials,researchers at the
University of Washingtonare testing stimulus paradigmsto evoke controlled muscular extension
and contraction.Rather than driving the muscles directly using high-resolution voltagestimulus
waveforms generated by digital synthesis and a digital-to-analogconverter, they tried stimulating
nerve bundles instead, using simple digitalwaveforms directly.They derived pulse-width
modulated signalsdirectlyfrom logic gates, and drove these waveforms into the nerve bundlesthat
enervate the muscles.Early results show great promise, not only because the technique
actuallyworked, but because a microcontroller can easily generate digitalpulses, and the drive
currents needed for nerve stimulation are up to 100timessmaller than those needed to drive
muscle tissue directly.This powersavingswill allow functional stimulation by miniature
neurochips.
Next on the research agenda: statistical machine learning. Researchersalready plan to use
smart algorithms, smart software, and smart chips tointeract dynamically with nerve tissue. They
suspect that machine learning can help them study the cause-and-effect relationships involved in
thebehavior of sensory motor circuits. Beyond that, they won‟t speculate,but the applications of
this neurochip research to robotics, medical prosthetics,and a host of other applications seem
obvious.
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CHAPTER7: REFERENCES
 M.R. Enstrom et al., “Abdominal Ruddering and the Control of Flight in the Hawkmoth,” to be
published, 2003; www.sicb.org/meetings/2003/schedule/ abstractdetails.php3?id=758.
 http://www.meritummedia.com/world/robo-rats-hunt-landmines
 http://www.instrumentationtoday.com/mems-accelerometer/2011/08/
 http://homes.cs.washington.edu/~diorio/Publications/InvitedPubs/01160058_IEEEComp.pdf
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