Thursday, September 12, 2013

EEG electrode placement for motor imagery, Y01-M01-D12

Do, 12.09.2013 in Oldenburg
Year 1, Month 1, Day 12
(12 hari telah berlalu)

======= = =======

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

Question 1: Why they are different?
Question 2: Are there different effect in motor imagery using Emotiv system? Do experiment!

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

Question 3: Are the references still P3 and P4?

- 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

======= = =======

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 4: Right ear or left? Diana Valbuena paper is not consistent.
Answer to Q4: inconsistency is solved by Laplacian spatial filter. This filter make the signals reference-independent.

Question 5: Is Cz is also ground (GND)?

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

1. 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

======= = =======

standard EEG 10-20 system:

My previous experiment:
Condro, 2010, "Improvement of Response Times in SSVEP-based Brain-Computer Interface". Master Thesis. University of Bremen.

======= = =======

EEG electrode placement for motor imagery.

======= = =======

Semakin banyak tanda tanya dalam kepalaku. Tapi aku yakin dengan mencoba Easy Cap, aku bisa tahu gambaran permasalahan apa yang dihadapi di sini.

Banyak baca, banyak lupa.
Sedikit baca, sedikit lupa.
Tidak baca, tiada lupa.

Oldenburg, 12 September 2013


No comments:

Post a Comment