a wearable channel selection-based brain computer interface for
TRANSCRIPT
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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