a wearable channel selection-based brain computer interface for

7/26/2019 A Wearable Channel Selection-based Brain Computer Interface For

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A Wearable channel selectio

based Brain computer Interfafor Motor Imagery Detectio

Authors: Chi-Chun Lo, sung-!i Chien

"ublished in #ensors,$ %ebruary &'($


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Abstract

Motor imagery-based brain computer interface)BCI* is a communication interfaan e ternal machine and the brain

Many .inds of spatial filters are used to enhance electroencephalography)//0*related to motor imagery

he approach of channel selection is important techni1ue In e isting //0 ma//0 electrodes +ith conducti2e gel to ac1uire multi channel //0 signals an

transferring to bac.end computer to perform channel selectionA no2el +earable channel selection based brain computer interface is proposed


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Content

Introduction

Methods #ystem hard+are design and Implementation #ystem soft+are design

3esults

Discussion

Conclusion

3eferences


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Introduction

he Motor 4Imagery based brain computer interface is the direct communicatioan e ternal machine and the brain

MI-based BCI is a type of acti2e BCI +hich does not re1uire e ternal stimuli

/2en related synchroni5ation

#patial filters: )i* Common spatial pattern

)ii* Independent component analysis )iii* Laplacian deri2ation

)i2* Common a2erage reference

Channel selection: %eature selection is used for selecting related feature channels


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"roposed method

A no2el +earable channel selection based brain computer interface is proposedimagery detection

"roposed system consists of follo+ing:

)i* %ront end +earable //0 de2ice

)ii* Bac. end host system

Method: 3etractable comb shaped acti2e dry electrodes are used in the +earable //0 de2ic

An analog circuit of CA3 spatial filter is also designed to perform a spatial filter Channel selection function is used


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&-Description of Methods used

& ( #ystem hard+are design and Implementation: "roposed system contains front end +earable //0 de2ice and bac. end host system

3etractable comb shaped dry acti2e electrodes- o measure //0 signals /asy to use and +ear

//0 signal

Wireless //0 6ia

)%ront end* Bluetooth

Amplification7

%ilter

ChannelChannelselectionselection

Bac. endBac. end


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%ront-end +earable //0 de2icehis system consists: 8 retractable comb shaped dry acti2e electrodes, Wireless

module and +earable mechanical design

Wearable mechanical design: (* %le ible plastic

&* #tructure: Circle structure Cla+ shaped structure

3etractable comb shaped dry acti2e electrodes are embedded in these cla+ shaped s "lacement of acti2e electrodes

"roposed retractable comb shaped dry acti2e electrodes and basic scheme:


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Bloc. diagram

)a*

)b*

)c*

Figure- )a*,)b*"hotograph of proposed +ireless //0

ac1uisition module9 )c*Basic schematic of analog CA3spatial filter circuit


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Wireless //0 ac1uisition module


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Wireless //0 ac1uisition module

ADC

//0 amplifiercircuit

Microprocessor

Channel selectionChannel selection

Bac. end hostBac. end hostsystemsystem

Wireless transmissioncircuit

Bluetooth 2& '


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Bac.-/nd ost systemSystem software design:

and motion or hand motor imagery results in the change of //0 po+er in sensocorte and reflects on mu rhythm and beta rhythm his change of //0 po+errelated desynchroni5ation )/3D* and e2ent related synchroni5ation )/3#*

he channel selection algorithm +ould choose the t+o channels that contain momotor imagery features for the left hand motor imagery and right hand motor im

Channel selection algorithm:

Figure - Illustration of the procedure of channel selection algor


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Channel selection algorithm

%irst ;s%irst ;s


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Motor Imagery detection algorithm


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3esults"erformance of 3etractable Comb-#haped Dry Acti2e /lectrode:

raditionally Ag=AgCl electrode +ith conducti2e gel is considered as a standard electrodmeasure //0

)i* Alpha rhythm e periment is performed

Figure . )a* //0 signals ) bthe e periment of alpha rhythm)c* heir coherence corresponfre1uencies


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"erformance of 3etractable Comb-#haped Dry Acti2e /lec

#teady state 2isually e2o.ed potential)##6/"*

Motor Imagery test

)a*

)b*

)c*

Figure . //0 signals and //0 spectra for ##6/" e periment +ith)a * 8 59 )b * (' 59 and ) c* (& 5 flashing light sources

Figure- Comparison of /3D 1uantificatiusing retractable comb-s

acti2e electrodes and +et electrodes fimagery


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"erformance of Channel #election %unc

)a*

)b*

)c*

Figure . / perimental results for ) a* locations and ) b* /3D 1uantifications of schannels9 ) c* a2eraged /3D 1uantifications of each //0 channel for the right and th

motor imagery


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"erformance of Motor Imagery Detection

)a*-All motor imagery )b*-right hand motor imagery )c*-right h


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DiscussionIn e isting method, pin length of metal electrode part +as constant #o it ms.in incompletely in particular under motion

In this proposed method, retractable comb-shaped dry acti2e electrode is dmeasure //0 signals on hairy sites +ithout conducti2e gel

"roposed electrode could pro2ide an ultra high input impedance and ultra lo+ inpto reduce the influence of high s.in electrode interface impedance

%rom e periment results: //0 signals obtained from proposed electrode and +et electrode results i

coherence Compared +ith +et electrodes, the phase distortion of the proposed

corresponding to different fre1uencies is 2ery slight "roposed electrode successfully measure the //0 signals in hairy site +ithout con

gel and could pro2ide a good signal 1uality it effecti2ely impro2es the con2eniein daily life


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Discussion

/ perimental channel results: It sho+s locations of selected channels corresponding to the right and left hand motor imagery ar

at C; and C> #tudy on Motor Imagery based BCIs: "furtscheller et al , proposed 0ra5 BCI and the approaches of linear discrimination analy

net+or.s +ere used for //0 feature classification Lan et al , "roposed a method for ran.ing of all channels Ar2aneh et al ,proposed sparse common spatial pattern )#C#"* algorithm to remo2e noisy

channels ?us et al , proposed a multi class motor imagery based BCI based on multinomial logi

classifier @bermaier et al , proposed fi2e class brain computer interface +ith the techni1ue of //0 patte

& mental tas.s Most of abo2e BCI systems +ere not +earable systems


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Comparison bet+een other BCI systems a proposed BCI


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ConclusionA no2el +earable channel selection based brain computer interface for motodetection +as proposed

sage of retractable comb-shaped dry acti2e electrodes is con2enient in daily lif

In the front-end +earable //0 de2ice, an analog CA3 spatial filter circuit +as desi perform the function of spatial filter +ithout any calculation

%rom e perimental results,/3D feature corresponding to the right=left hand mocould easily be e tracted

/ffecti2ely reduce the data transmission

Integrating this design +ith other electronic de2ices such as tablets, mobilereduce the limitation of BCI applications


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3eferences

a wearable channel selection-based brain computer interface for

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