deep brain stimulation ( dbs ) has demonstrated significant therapeutic benefits   in ( i ) treating symptoms relating to neurological motor disorders including parkinson 's disease , essential tremor , and dystonia , ( ii ) controlling epilepsy , and ( iii ) providing relief from chronic pain .
dbs has been also employed for treatment refractory neuropsychiatric indications including tourette 's syndrome , obsessive compulsive disorder , and for treatment resistant depression .
more recently , dbs has been has been proposed as a potential treatment of severe drug and alcohol addiction .
considerable research involving laboratory animals has been conducted in recent years to study the underlying principles of dbs and the mechanisms through which its therapeutic effects are mediated . however ,
a bottleneck in establishing the therapeutic mechanisms and benefits of dbs has been the lack of portable dbs systems that enable long term brain stimulation in freely moving laboratory animals . as a consequence of this , there remains a gap in the existing experimental data investigating mechanisms of chronic dbs action in preclinical animal studies .
most of the existing dbs devices employ complex circuitry and are , as a consequence , quite bulky .
these devices are connected to the implanted electrode through long insulated wires that run from the device to the animal 's head .
the stimulator often needs to be disconnected from the electrode over the course of the study ( i.e. , overnight as the animal is returned to its home cage ) .
thus , in order to better reflect the longer duration stimulation applied to the brain in clinical trials , the laboratory animal would ideally receive this brain stimulation continuously without interruption for days or even weeks . in order to improve the quality of preclinical work , the animal needs to be able to freely move , eat , sleep , swim in water , and carry out several other activities . when connected to the dbs device through long wires , behavioral tests and normal behaviors
the progress of understanding the therapeutic mechanisms and benefits of dbs will benefit from the reduction of the size of power requirement of dbs devices .
this paper presents a novel design for a low power micro deep brain stimulation device for laboratory animals .
three different configurations of the device are presented : single piece head mountable , single piece back mountable , and two piece back mountable .
an investigation of the literature reveals that thus far only a few dbs devices have been reported that are suitable for long term brain stimulation of laboratory animals .
millard and shepherd   developed an implantable , single channel stimulator that generates charge balanced biphasic current pulses delivered to a bipolar electrode array for chronic stimulation of neural tissue ( see fig . 
the subject is placed in a small chamber surrounded by three orthogonal coils of wire which are driven to generate a magnetic field .
currents are induced in wire coils in the implanted stimulator then regulated to produce biphasic current pulses with fixed amplitude of up to 500 \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ \mu{\rm a}$\end{document}. phase duration is adjustable from 25 to 250 \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ \mu{\rm s}$\end{document } per phase .
stimulus rate can be continuously varied , and the temporal precision of the stimulus means that the stimulator can be used in behavioral experiments or for generating electrically evoked potentials .
the application of the stimulator on chronic electrical stimulation of the auditory nerve was described .
developed a lightweight implantable micro stimulator device for mice that delivers biphasic pulses to two individual electrode pairs ( see fig . 
it consists of an implantable stimulator , two stimulation electrodes , an infrared camera system including a monitor and a programming and test fixture to program the stimulus current .
the stimulator housing contained a polycarbonate cylinder with a screw top , and was 30 mm in length with a diameter of 8 mm .
the total length of the lead system from the stimulator to the connector pins was 45 mm .
the microcontroller then had the highest power consumption of all the components of the circuit . to maximize battery life ,
the microcontroller was put in standby mode in between two consecutive biphasic pulse patterns . the bench top validation and in - vivo implementation of the device was presented .
the results indicate that the wireless implantable stimulator in mice delivered continuous bilateral stimulation without restricting the animal mobility and hygiene . in - vivo testing
showed that stimulation of the mice ventral striatum yields similar results as previously shown by others in rats where conventional deep brain stimulation techniques were used .
1.micro dbs devices developed for laboratory animals by ( a ) millard and shepherd , ( b ) haas et al . , ( c ) liu et al . , ( d ) kouzani et al . , and ( e ) forni et al . . 
 
micro dbs devices developed for laboratory animals by ( a ) millard and shepherd , ( b ) haas et al . , ( c ) liu et al . , ( d ) kouzani et al . , and ( e ) forni et al . .
liu et al .   reported a head mountable apparatus and implant method suitable for chronic dbs in rats ( see fig . 
they evaluated the effect of chronic dbs of the rat nucleus accumbens on morphine reinforcement using their dbs apparatus .
an electrode was stereotaxically implanted into the core of unilateral nucleus accumbens and connected to the dbs apparatus fixed to the rat skull .
a 900-second conditioned place preference paradigm was used for determining the effect of electrical stimulation on morphine reinforcement .
kouzani et al .   developed a head mountable dbs device for laboratory animals ( see fig . 
it produces continuous monophonic current pulses of 90 \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ \mu{\rm s}$\end{document } width , with frequency of 130 hz , and amplitude of 200 \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ \mu{\rm a}$\end{document}. to produce timing pulses , a general purpose timer chip was used in its astable mode . to deliver electric current pulses ,
the device was able to produce non - stop stimulating current pulses for about nine days using a 280 mah coin battery .
they did not carry out experiments with laboratory animals , but used a 1 \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ { \rm k}\omega$\end{document } resistor to model the animal 's brain tissue .
ewing and grace   reported a dbs device for the continuous delivery of brain stimulation in rats .
their device was configured to stimulate with square , monophasic , anodic , constant current 100 ms pulses at frequency of 130 hz and amplitude of 100 ma .
the device was carried by the animals via rodent jackets and connected to the electrodes via an external cable .
they used the device to examine how five days of stimulation affected rhythmic brain activity in freely moving rats .
synchronized video and local field potential data was collected from animals in their home cages before , during and after stimulation .
they reported that the initial changes in power observed with short term stimulation were replaced by altered coherence , which may reflect the functional action of dbs .
this easy removal property enables removing or switching the microstimulator during the experiments without having to anaesthetize or operate on the animal , thereby minimizing stress , and maximising the quality of the behavioural and biological data .
the dbs system consists of three components : a stimulating electrode , a stimulator support and an electrical portable microstimulator .
the microstimulator is made up of two main blocks : one adjustable pulse generator and one voltage to current converter .
the pulse generator block is based on a series of four cmos invertors ' chains with a feedback loop allowing to regulate the frequency and a buffer stage on the two last ones , both being coupled through a variable network allowing to vary the duty cycle .
the voltage to current converter is based on a classical bipolar transistor wilson current mirror directly supplied by the buffer output to minimize consumption during off phases of the pulse .
its weight is around 5.6 g with the resin protective coat , and 7.4 g with the two watch batteries .
the initial setting of the current parameters is done before mounting the microstimulator on the head of the rat using an oscilloscope and a 15 \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ { \rm k}\omega$\end{document } output reference resistance . to validate the device
, they performed continuous dbs of the subthalamic nucleus in a classical rat model of pd .
they showed that the long duration stimulation reduces significantly pd - induced akinesia without inducing animal discomfort and tissue damage .
the millard and shepherd 's device   requires a magnetic field that is generated by applying a high voltage to the excitation coil which may have undesirable impact on biological cells .
's device   requires new data to be uploaded to the microcontroller and some fixed resistors be changed for changing the characteristics of the stimulation current .
the size of the device is large , and the device can only stimulate for several hours .
considering the characteristics of the current devices , there is still a need to reduce their power consumption , size , weight , cost , and simplify their maintenance and mounting procedures .
a low power , lightweight portable micro dbs device that can be carried by the animal during the course of a clinical trial is presented in this section .
based on our preclinical research requirements , the duration of the cathodic pulse is set to 90 \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ \mu{\rm s}$\end{document } , the frequency of stimulation is set to 130 hz , and the amplitude of current pulses is set to 200 \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ \mu{\rm a}$\end{document}. however , the stimulation parameters of the device are adjustable as described in the programming subsection .
the device employs the passive charge balancing method to minimize undesirable effects including tissue damage .
the passive charge balancing method is based on an ac - coupling capacitor reducing the demanding electronic circuit .
the device consists of the following components : microcontroller , current source , stimulation electrode , power source , and printed circuit board . 

three different configurations of the micro dbs device are constructed : single piece head mountable , single piece back mountable , and two piece back mountable .
attiny 24a is a low power 8-bit microcontroller based on the avr enhanced reduced instruction set computing architecture .
it provides 2 kb of flash , 128 bytes of eeprom and sram , 12 i / o lines , 32 registers , an 8-bit timer / counter , a 16-bit timer / counter , internal and external interrupts , 8-channel 10-bit adc , a programmable watchdog timer , and internal calibrated oscillator .
it offers four selectable power saving modes : ( i ) in idle mode , the cpu is stopped while allowing the sram , timer / counter , adc , analog comparator , and interrupt system to continue functioning , ( ii ) in adc noise reduction mode , switching noise during adc conversions is minimized by stopping the cpu and all i / o modules except the adc , ( iii ) in power down mode , registers keep their contents and all chip functions are disabled until the next interrupt or hardware reset , ( iv ) in standby mode , the crystal / resonator oscillator is running while the rest of the device is sleeping , allowing very fast start up combined with low power consumption .
the pseudo code for the program that implements the deep brain stimulation operation is given in fig . 
pseudo code for the program that implements the deep brain stimulation operation . in the first step ,
this is done by initializing the two data direction registers of the microcontrollers , ddra and ddrb .
the other i / o pins are configured as input pins . in the second step ,
this is achieved by initializing the power reduction register , prr . in the third step , the led is flashed to show the user that the device has started and is operating correctly , and that the battery is in good condition . in the fourth step , the 16-bit timer / counter 1 unit is programmed to generate the stimulation waveform .
the unit facilitates precise event management , wave generation , as well as signal timing measurement .
it has a number of control registers that can be programmed to determine the desired operation of the unit . in this work
the timer can be programmed to operate in 15 different waveform generation modes . in this work
, the timer is operated in fast pulse width modulation ( pwm ) mode 14 .
it counts from a bottom value to a top value then restarts from the bottom value . for generating a stimulation waveform of width 90 \documentclass[12pt]{minimal } 

\usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ \mu{\rm s}$\end{document } , and frequency 130 hz , the icr1 and ocr1a registers are set to 7692 and 90 , respectively .
however , by varying the content of the timer control registers , the characteristics of the generated waveform can be changed , resulting in the adjustment of the stimulation parameters .
finally , in the fifth step , for power efficiency and to maximize the battery lifetime , the microcontroller is made to enter the idle mode . in this mode ,
accordingly , the cpu and the execution of the program is halted and no further instruction is run , but timer 1 continues operating to provide the desired waveform on its output pin without the intervention of the cpu . the produced waveform is used to switch on / off the transistor pdtc143te that controls the operation of a current source . to deliver electric current pulses ,
lm334 is an adjustable current source with good current regulation from 1 \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ \mu{\rm a}$\end{document } to 10 ma under a voltage range of 1 v to 40 v. the device has three terminals and offers true floating current feature .
the current amplitude \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ { \rm i}_{\rm set}$\end{document } is determined by an external resistor \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ { \rm r}_{\rm set}$\end{document } as follows : \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ { \rm i}_{\rm set}=(1.059\times{\rm v}_{\rm r})/r_{\rm set}$\end{document } , where \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ { \rm v}_{\rm r}$\end{document } is the voltage across \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ { \rm r}_{\rm set}$\end{document}. the average \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ { \rm v}_{\rm r}$\end{document } for the desired operating temperature range is about 62 to 66 mv . for the current amplitude of 200 \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ \mu{\rm a}$\end{document } , we therefore used \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ { \rm r}_{\rm set}=330 \omega$\end{document}. to achieve charge injection , the stimulation electrode is implanted into the target tissue .
we used an electrode by plasticsone that has a stainless steel twisted wire electrode extend below a threaded plastic pedestal .
to supply energy to the micro dbs device for the duration of a clinical trial , a battery is used . for the single piece head mountable configuration , two cell button silver oxide 1.55 v batteries
the diameter and the height of each battery are 11.6 mm and 5.4 mm , respectively .
the weight of the battery is 2.3 g. the capacity of each battery is 190 mah which is well adequate for operating the device for about ten days .
the two batteries are stacked together using conductive glue to form a 3.1 v source . for the single piece back mountable and the two piece back mountable configurations ,
one cell button lithium manganese dioxide 3 v battery is used to power the device .
the diameter and the height of the battery are 20 mm and 3.2 mm , respectively .
the total weight of the battery is 2.8 g. the capacity of the battery is 235 mah which is also well adequate for operating the device for over eleven days . to accommodate the components of the micro dbs device , and connect them according to the circuit schematic shown in fig .  2 ,
two printed circuit boards are developed , one for the single piece head mountable as well as the two piece back mountable configurations , and another for the single piece back mountable configuration .
after fabrication of the printed circuit board , the electronic components of the micro dbs device are assembled onto the boards .
( a ) the board for the single piece head mountable as well as the two piece back mountable configurations .
( b ) the board for the single piece back mountable configuration . 
  fabricated boards .
( a ) the board for the single piece head mountable as well as the two piece back mountable configurations .
this configuration incorporates both the stimulation board and the battery pack as a single piece device that can be attached directly into the stimulation electrode implanted into the target tissue .
the board includes a two pin terminal for connection to the positive and negative sides of the battery pack , and another two pin terminal for connection to the electrode .
a thin brass sheet is cut into small pieces and attached to the positive and negative sides of the battery pack using conductive glue .
then , the power terminals are soldered onto the brass pieces on the positive and negative sides of the battery pack . a sample of the single piece head mountable micro dbs device is shown in fig .  5 . 

the weight of different components of different components of the single piece head mountable micro dbs device is measured using a laboratory scale .
the weight of the stimulation board is 0.71 g , the weight the battery is 2.56 g , and the weight of the entire device is 3.27 g. during the implant procedure , the threaded plastic pedestal of the electrode is fixed into the skull .
next , the stimulation device including the battery is mounted into the electrode via the two pin electrode terminal on the device .
then , the device is sealed with dental cement on top of the animal 's head .
this configuration incorporates the stimulation board , a 20 mm cell button battery holder , and the cell button lithium manganese dioxide 3 v battery in a single piece device .
the board includes a two pin 2.54 mm terminal for connection to the electrode . a two way 2.54 mm receptacle is used to plug a pair of thin wires into the electrode terminal of the stimulation device .
the other end of the wires is connected to a two pin plug that is mounted into the electrode fixed into the skull .
the cell button lithium manganese dioxide 3 v battery is placed inside the battery holder .
the jacket is closed by using a velcro fastener , and a hook gives a secure fit .
the advantage of this configuration is the fact that the battery can be easily replaced extending the operation time of the device unlimitedly .
6 shows samples of the single piece back mountable micro dbs device . 
 fig . 
the weight of different components of different components of the single piece back mountable micro dbs device is measured using a laboratory scale .
the weight of the stimulation board is 1.25 g , the weight of the battery is 2.83 g , the total weight the battery and the battery holder is 3.83 g , and the overall weight of the entire device is 5.08 g. this configuration is similar to the single piece back mountable formation .
the difference is that in this configuration the stimulation board and the battery - holder / battery are separate .
the stimulation board is connected to the battery holder using a pair of thin wires instead of being secured underneath the battery holder .
the stimulation device can be sealed using hot glue and then placed under the animal skin .
alternatively , it can be placed inside the rat jacket near the battery holder . a sample of the two piece back mountable device is shown in fig . 
the overall weight of the device is similar to that of the single piece back mountable device which is around 5.1 g. 
 fig . 
after construction of the micro dbs devices , their performance was evaluated in terms of the lifetime of the battery and also the operation of the device .
three tests were conducted : bench test , in - vitro test , and in - vivo test .
the performance of the micro dbs was tested using a 1 \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ { \rm k}\omega$\end{document } resistor that modeled the animal 's brain tissue .
the bench testing of the micro dbs device with a 1 \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ { \rm k}\omega$\end{document } resistor .
the steady state current consumption of the device after 10 , 20 , and 30 hours of continuous operation was measured using a keithley 2401 sourcemeter .
the sourcemeter has precision current measurement capability within the range 10 pa-1 a. the average steady state current consumption of the device was found to be around 870 \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ \mu{\rm a}$\end{document}. next , to practically determine the number of days the device can be operated by using the 235 mah cell button battery , the sourcemeter was programmed to read the battery voltage and store it every five minutes .
the variation of the battery voltage for the continuous operation of the micro dbs device using a 235 mah cell button battery is shown in fig . 
as can be seen from the figure , the battery voltage remained steady over the course of the first eleven days .
theoretically , the operating voltage of the attiny 24a microcontroller is within the range 1.85.5 v. however , the system continued producing stimulating current pulses below 1.8 v in day 12 .
once the battery voltage fell below 1.5 v , the microcontroller stopped working , and thus the device stopped producing the stimulation pulses . the red arrow in fig . 
8 shows when the device ceased operation due to the low battery voltage after over twelve days of continuous operation .
8.variation of the battery voltage under continuous operation of the micro dbs device using a 235 mah cell button battery . 
 
variation of the battery voltage under continuous operation of the micro dbs device using a 235 mah cell button battery .
a comparison of the head - mountable configuration against similar current devices is presented in table  i. in comparison of the lifetime of each device , the strength of the stimulation current as well as the use of an external source should be taken into account .
the head - mountable configuration offers a much smaller size , and yet longer term higher strength stimulation current pulses . 

table icomparison of micro dbs devicesref.sizesourceweighttermparameters14mm \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ \times$\end{document } 12mmmagnetic coupling2.5gun-
limited10050o \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ \mu a$\end{document } 2525o \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ \mu { \rm s}$\end{document } 505000hz8 mm \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ \times$\end{document } 30mmbattery ( 4.65v)2.1g10 hours201 oc \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ \mu { \rm a}$\end{document } 6i \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ 0\mu { \rm s}$\end{document } 131hz20 mm diameterbattery ( 3v/ 200mah)--0.20.5ma 0.031.4ms 1200hz25 mm diameterbattery ( 3v/ 280mah)7.8g9 days200 \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ \mu { \rm a}$\end{document } 9o
\documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ \mu{\rm s}$\end{document } 130hz15 mm \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ \times$\end{document } 28mmbattery ( 6v1 36mah)7.4g7 days50121 - \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ 0\mu { \rm a}$\end{document } 08o \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ \mu { \rm s}$\end{document } 0130hzproposed12 mm diameterbattery ( 3.1v/ 190mah)3.2g10 days200 \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ \mu { \rm a}$\end{document } 9o \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ \mu { \rm s}$\end{document } 130hz 
  comparison of micro dbs devices the micro dbs device was tested in - vitro at mayo clinic by dr abulseoud 's team .
the test was conducted by placing the stainless steel twisted wire part of the stimulation into a tank of physiologic saline solution .
the cathodic pulses of 90 \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ \mu{\rm s}$\end{document } duration , 130 hz frequency , and 200 \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ \mu{\rm a}$\end{document } amplitude were delivered to the electrode by the device which was powered by the 235 mah cell button battery .
an oscilloscope was used to confirm the continuous delivery of current to the stimulating electrode .
after the successful bench test and in - vitro test , a number of two piece back mountable micro dbs devices ( see fig .  7 ) were tested in - vivo at mayo clinic by dr abulseoud 's group .
the devices were used in a study to examine the role of dbs in reducing ethanol preference in alcohol preferring rats .
eleven adult male wistar rats ( charles rivers ) 1216 weeks at time of experiment were used .
a pair of thin wires connected the stimulation board to the electrode . a second pair of wires connected the stimulation board to the battery holder .
each device created pulses of 90 \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ \mu{\rm s}$\end{document } duration , 130 hz frequency , and 200 \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ \mu{\rm a}$\end{document } amplitude whilst being powered by a 235 mah cell button battery .
the stimulation board , the battery holder and the battery were all placed in a rat jacket ( harvard apparatus ) and secured on the back of the animal . the pair of wires connecting the stimulation board to the stimulating electrode was tunneled under the skin at the back of the neck and externalized for a short distance above the stimulating electrode where it was connected ( see fig . 
the animals did not appear to be bothered by the device , the jacket , or the wires . 

animals were implanted with bipolar twisted electrode ( plasticsone ) into the right nucleus accumbens shell under isoflurane inhalation anesthesia ( 3.0% during induction and 1.5% during maintenance ) ( see fig . 
coordinates from bregma ( flat skull ) are : \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ { \rm ap}=2.04$\end{document } , \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ { \rm m}\hbox{-}{\rm l}=1.2$\end{document } , \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ { \rm d}\hbox{-}{\rm v}=8.0$\end{document } ( from skull ) tilt : 10 degrees .
animals were allowed to recover for three days post - surgery then were divided into two groups : continuous stimulation for 7 days using the head mounted device in a jacket \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ ( { \rm n}=5)$\end{document } and sham group did not receive stimulation \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ ( { \rm n}=6)$\end{document}. data on body weight and water consumption as well as locomotor activity counts was collected during the week before stimulation and during the week of stimulation ( for the continuous group ) . the weight and water consumption of animals
are shown in fig .  10 . as can be seen from the figure , the sham group had less weight at start of experiment , but no significant effect for stimulation on weight as well as total water consumption
10.body weight and water consumption of the animals before stimulation week and during stimulation week . 
 
body weight and water consumption of the animals before stimulation week and during stimulation week . animals \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ ( { \rm n}=5)$\end{document } were housed under 12:12 hour dark : light cycle ( lights on at 6.00 am ) circadian locomotor activity counts in home cage were recorded using an infrared motion detector interfaced with a computerized data acquisition system ( clocklab ) and later analyzed using matlab software .
no significant difference in total locomotor activity counts pre , during , or after stimulation was observed ( one way repeated measure anova \documentclass[12pt]{minimal } 
 \usepackage{amsmath } 
 \usepackage{wasysym } 
 \usepackage{amsfonts } 
 \usepackage{amssymb } 
 \usepackage{amsbsy } 
 \usepackage{upgreek } 
 \usepackage{mathrsfs } 
 \setlength{\oddsidemargin}{-69pt } 
 \begin{document } 
 } { } $ { \rm p}=0.2$\end{document } ) ( see fig . 
the stimulating device was well tolerated and the stimulation at the nac did not alter weight , water consumption or locomotor activity , however it resulted in changes in alcohol consumption and preference in alcohol preferring rats ( data not shown here , and will be published by dr .
the paper presented the development and testing of a low power lightweight micro deep brain stimulation device for laboratory animals .
it can be easily carried by the animal during the course of a clinical trial .
after construction , the performance of the device was evaluated through three tests : bench test , in - vitro test , and in - vivo test . during the tests ,
the device was able to produce non - stop stimulating current pulses for over twelve days using a 235 mah cell button battery .
the evaluation of the device in a study to examine the role of dbs in reducing ethanol preference in alcohol preferring rats was successful .
whilst it did not alter weight , water consumption or locomotor activity of the animals , it resulted in changes in alcohol consumption and preference in alcohol preferring rats . in order to minimize the power consumption , size , and weight of the device ,
however , such feature can be implemented by incorporating a recording electrode and a signal conditioning interface circuit .
the microcontroller used in the device has 10-bit analog - to - digital converter channels that can be used to convert the conditioned output of the recording electrode to a high resolution digital signal .
in addition , similar to the current stimulation devices involving any stimulation electrode , wire , and/or electronic component , performing mri / fmri with this device can also cause tissue damage from component heating particularly around the electrode .
the advantages offered by the device include : ( i ) ultra - low cost when mass produced .
it is expected that the entire device will cost less than$5 ; ( ii ) ultra - low maintenance and ease of use ; ( iii ) quick and easy battery replacement enabling ultra - long term stimulation .
 deep brain stimulation has emerged as an effective medical procedure that has therapeutic efficacy in a number of neuropsychiatric disorders . 
 preclinical research involving laboratory animals is being conducted to study the principles , mechanisms , and therapeutic effects of deep brain stimulation . 
 a bottleneck is , however , the lack of deep brain stimulation devices that enable long term brain stimulation in freely moving laboratory animals . 
 most of the existing devices employ complex circuitry , and are thus bulky . 
 these devices are usually connected to the electrode that is implanted into the animal brain using long fixed wires . in long term behavioral trials , 
 however , laboratory animals often need to continuously receive brain stimulation for days without interruption , which is difficult with existing technology . 
 this paper presents a low power and lightweight portable microdeep brain stimulation device for laboratory animals . 
 three different configurations of the device are presented as follows : 1 ) single piece head mountable ; 2 ) single piece back mountable ; and 3 ) two piece back mountable 
 . the device can be easily carried by the animal during the course of a clinical trial , and that it can produce non - stop stimulation current pulses of desired characteristics for over 12 days on a single battery . 
 it employs passive charge balancing to minimize undesirable effects on the target tissue . 
 the results of bench , in - vitro , and in - vivo tests to evaluate the performance of the device are presented . 
Introduction
Existing Micro Brain Stimulation Devices for Laboratory Animals
Proposed Micro Brain Stimulation Device
Evaluation
Conclusion