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EEG electrode placement for motor imagery, Y01-M12-D19

Do, 19.08.2014
Year 1, Month 12, Day 19
(11 bulan dan 19 hari telah berlalu)

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EEG electrode placement for motor imagery.

Emotiv EPOC:
– left:  AF3, F3, F7, FC5, P3 (CMS), P7, T7, O1
– right: AF4, F4, F8, FC6, P4 (DRL), P8, T8, O2
reference: CMS, DRL

Easy Cap, in lab.
– left:  F3, C3, P3, O1, TP9
– right: F4, C4, P4, O2, TP10
– middle: FPz, AFz, Fz, FCz, Cz, Pz
The configuration of 16 electrodes is from Markus Kroesen’s Bachelor Thesis, 2013, University of Oldenburg
“Vergleich verschiedener EEG-Verstärker zur Steuerung von Brain-Computer Interfaces”

Question: Why they are different?
Answer: They are different because the Emotiv is modified into Easymotiv and Markus Kroesen was developing P300-based BCI speller.
Read below.

Question: Are there different effect in motor imagery using Emotiv system? Do experiment!
Answer: I am considering other hardware than Emotiv, i.e. mBrainTrain, because since August 2014, the prices are not so different.

Easymotiv = Easy Cap and modified Emotiv


Well, it is time consider mBrainTrain, instead of Easymotiv


Similarity between both caps:
– left:  F3, P3, O1
– right: F4, P4, O2

Question: Are the references still P3 and P4?
Answer: Not necessarily. The ground and reference can be put anywhere with Easymotiv (Easy Cap + Emotiv)

– AF3, AFz, AF4 are aligned
– F7, F3, Fz, F4, F8 are aligned
– FC5, FC1, FCz, FC2, FC6 are aligned
– T7, Cz, T8 are aligned
– P7, P3, Pz, P4, P8 are aligned
– from previous experience, AFz was ground (GND) and Cz was reference

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Diana Valbuena 2010 motor imagery cap:
left:  FC3, C5, C3, C1, CP3
right: Fc4, C6, C4, C2, CP4
middle: AFz, Cz
reference: right ear lobe / or left?
ground (GND): AFz
Laplacian spatial filter, with C3 and C4 are central, others are surrounding

Question: Right ear or left? Diana Valbuena paper is not consistent.
Answer: inconsistency is solved by Laplacian spatial filter. This filter make the signals reference-independent.

Question: Is Cz is also ground (GND)?
Answer: Cz can associate with motoric movement. It is unlikely to set Cz as reference or ground.

Similarity between Diana and Easy Cap:
– left:  C3
– right: C4
– middle: AFz, Cz

1. Diana Valbuena, 2010, “Selection of Reactive Frequency Bands during Motor Imagery”. BRAINROBOT, Ch. 9, pp 109. Shaker Verlag.
– inconsistent reference placement but Laplacian spatial filter solve it.
– good idea of signal processing of ERD/ERS classification
– read other papers from citation to get idea of motor imagery, signal processing and electrode placement

2. G. Pfurtscheller, C. Brunner, A. Schlögl, F.L. da Silva, 2006, “Mu rhythm (de)synchronization and EEG sigle-trial classification of different motor imagery tasks”. NeuroImage, vol. 31, pp. 153-159.
– Diana Valbuena got idea of EEG electrode placement from this paper

3. B. Hjorth, 1975, “An online transformation of EEG scalp potentials into orthogonal source derivations”. Electroencephalography and Clinical Neurophysiology, vol. 39, pp. 526-530.
– Diana Valbuena got idea of Laplacian spatial filter from this paper

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Irina Schierholz 2013 motor imagery cap:
– left:        FC1, C3, CP1, CP3, CP5, P3
– right:       FC2, C4, CP2, CP4, CP6, P4
– middle: AFz, FCz, Cz,                Pz
reference: FCz
ground (GND): AFz
Laplacian spatial filter, with C3 and C4 are central, others are surrounding

Similarity between Diana’s and Irina’s cap:
– left:        C3, CP3
– right:       C4, CP4
– middle: AFz, Cz,
– ground (GND): AFz

1. Irina Schierholz, 2013, “Feasibility of humanoid robot feedback for motor imagery training”. Master Thesis, University of Oldenburg

2. Catharina Zich, 2013, “Wireless EEG with individual electrode positions facilitates motor imagery learning”. Master Thesis, University of Oldenburg

3. S. Debener, F. Minow, R. Emkes, K. Gandras, M. de Vos, 2012, “How about taking a low-cost, small, and wireless EEG for a walk?”. Psychophysiology, 49(11), 1449-1453
– about Easymotiv (Easy Cap + modified Emotiv)

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standard EEG 10-20 system:

My previous experiment on steady-state evoked potential (SSVEP):
Condro, 2010, “Improvement of Response Times in SSVEP-based Brain-Computer Interface”. Master Thesis. University of Bremen.

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EEG electrode placement for motor imagery.
without picture:
With picture:

See previous post about electrode position for mu wave

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My other thought about electrode position for P300

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Seperti pada posting sebelumnya tentang mu wave, kalau aku telah membaca master thesis Irina Schierholz. Ada hal yang perlu dipikirkan tentang posisi elektroda untuk motor imagery. Selain itu, aku berencana menggunakan mBrainTrain dan tidak lagi Emotiv. Oleh karena itu, tulisan tentang motor imagery kurevisi di sini.

Bremen, 19 Agustus 2014


Darah Juang Doktoral http://drhdrdro.blogspot.com/2014/08/eeg-electrode-placement-for-motor.html


About iscab.saptocondro

Ignatius Sapto Condro Atmawan Bisawarna (iscab.saptocondro) Blogger, Engineer. I was born in Bandung, Indonesia, and has spent 25 years of my life there. I worked in Semarang, Indonesia, and then continued to study in Bremen, Germany. I work in Germany until I find myself. Well, now, I am a PhD student in Oldenburg, Lower Saxony or Niedersachsen, Germany.

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