Get specific electrodes and use aliases

We need to import some functions

from pprint import pprint

from eeg_positions import (
    get_alias_mapping,
    get_available_elec_names,
    get_elec_coords,
    plot_coords,
)

Let’s assume we need only a small subset of electrodes for our work. We can print all available electrode names in eeg_positions.

elec_names = get_available_elec_names()
pprint(elec_names[::-1])

['M2',
 'M1',
 'A2',
 'A1',
 'NAS',
 'RPA',
 'LPA',
 'POO8h',
 'POO6',
 'POO6h',
 'POO4',
 'POO4h',
 'POO2',
 'POO2h',
 'POO1h',
 'POO1',
 'POO3h',
 'POO3',
 'POO5h',
 'POO5',
 'POO7h',
 'PO8h',
 'PO6',
 'PO6h',
 'PO4',
 'PO4h',
 'PO2',
 'PO2h',
 'PO1h',
 'PO1',
 'PO3h',
 'PO3',
 'PO5h',
 'PO5',
 'PO7h',
 'PPO8h',
 'PPO6',
 'PPO6h',
 'PPO4',
 'PPO4h',
 'PPO2',
 'PPO2h',
 'PPO1h',
 'PPO1',
 'PPO3h',
 'PPO3',
 'PPO5h',
 'PPO5',
 'PPO7h',
 'P8h',
 'P6',
 'P6h',
 'P4',
 'P4h',
 'P2',
 'P2h',
 'P1h',
 'P1',
 'P3h',
 'P3',
 'P5h',
 'P5',
 'P7h',
 'TPP8h',
 'CPP6',
 'CPP6h',
 'CPP4',
 'CPP4h',
 'CPP2',
 'CPP2h',
 'CPP1h',
 'CPP1',
 'CPP3h',
 'CPP3',
 'CPP5h',
 'CPP5',
 'TPP7h',
 'TP8h',
 'CP6',
 'CP6h',
 'CP4',
 'CP4h',
 'CP2',
 'CP2h',
 'CP1h',
 'CP1',
 'CP3h',
 'CP3',
 'CP5h',
 'CP5',
 'TP7h',
 'TTP8h',
 'CCP6',
 'CCP6h',
 'CCP4',
 'CCP4h',
 'CCP2',
 'CCP2h',
 'CCP1h',
 'CCP1',
 'CCP3h',
 'CCP3',
 'CCP5h',
 'CCP5',
 'TTP7h',
 'FTT8h',
 'FCC6',
 'FCC6h',
 'FCC4',
 'FCC4h',
 'FCC2',
 'FCC2h',
 'FCC1h',
 'FCC1',
 'FCC3h',
 'FCC3',
 'FCC5h',
 'FCC5',
 'FTT7h',
 'FT8h',
 'FC6',
 'FC6h',
 'FC4',
 'FC4h',
 'FC2',
 'FC2h',
 'FC1h',
 'FC1',
 'FC3h',
 'FC3',
 'FC5h',
 'FC5',
 'FT7h',
 'FFT8h',
 'FFC6',
 'FFC6h',
 'FFC4',
 'FFC4h',
 'FFC2',
 'FFC2h',
 'FFC1h',
 'FFC1',
 'FFC3h',
 'FFC3',
 'FFC5h',
 'FFC5',
 'FFT7h',
 'F8h',
 'F6',
 'F6h',
 'F4',
 'F4h',
 'F2',
 'F2h',
 'F1h',
 'F1',
 'F3h',
 'F3',
 'F5h',
 'F5',
 'F7h',
 'AFF8h',
 'AFF6',
 'AFF6h',
 'AFF4',
 'AFF4h',
 'AFF2',
 'AFF2h',
 'AFF1h',
 'AFF1',
 'AFF3h',
 'AFF3',
 'AFF5h',
 'AFF5',
 'AFF7h',
 'AF8h',
 'AF6',
 'AF6h',
 'AF4',
 'AF4h',
 'AF2',
 'AF2h',
 'AF1h',
 'AF1',
 'AF3h',
 'AF3',
 'AF5h',
 'AF5',
 'AF7h',
 'AFp8h',
 'AFp6',
 'AFp6h',
 'AFp4',
 'AFp4h',
 'AFp2',
 'AFp2h',
 'AFp1h',
 'AFp1',
 'AFp3h',
 'AFp3',
 'AFp5h',
 'AFp5',
 'AFp7h',
 'O1h',
 'O1',
 'POO7',
 'PO7',
 'PPO7',
 'P7',
 'TPP7',
 'TP7',
 'TTP7',
 'FTT7',
 'FT7',
 'FFT7',
 'F7',
 'AFF7',
 'AF7',
 'AFp7',
 'Fp1',
 'Fp1h',
 'O2h',
 'O2',
 'POO8',
 'PO8',
 'PPO8',
 'P8',
 'TPP8',
 'TP8',
 'TTP8',
 'FTT8',
 'FT8',
 'FFT8',
 'F8',
 'AFF8',
 'AF8',
 'AFp8',
 'Fp2',
 'Fp2h',
 'OI1h',
 'OI1',
 'POO9h',
 'PO9h',
 'PPO9h',
 'P9h',
 'TPP9h',
 'TP9h',
 'TTP9h',
 'FTT9h',
 'FT9h',
 'FFT9h',
 'F9h',
 'AFF9h',
 'AF9h',
 'AFp9h',
 'NFp1',
 'NFp1h',
 'OI2h',
 'OI2',
 'POO10h',
 'PO10h',
 'PPO10h',
 'P10h',
 'TPP10h',
 'TP10h',
 'TTP10h',
 'FTT10h',
 'FT10h',
 'FFT10h',
 'F10h',
 'AFF10h',
 'AF10h',
 'AFp10h',
 'NFp2',
 'NFp2h',
 'T10h',
 'T8',
 'T8h',
 'C6',
 'C6h',
 'C4',
 'C4h',
 'C2',
 'C2h',
 'C1h',
 'C1',
 'C3h',
 'C3',
 'C5h',
 'C5',
 'T7h',
 'T7',
 'T9h',
 'I1h',
 'I1',
 'POO9',
 'PO9',
 'PPO9',
 'P9',
 'TPP9',
 'TP9',
 'TTP9',
 'T9',
 'FTT9',
 'FT9',
 'FFT9',
 'F9',
 'AFF9',
 'AF9',
 'AFp9',
 'N1',
 'N1h',
 'I2h',
 'I2',
 'POO10',
 'PO10',
 'PPO10',
 'P10',
 'TPP10',
 'TP10',
 'TTP10',
 'T10',
 'FTT10',
 'FT10',
 'FFT10',
 'F10',
 'AFF10',
 'AF10',
 'AFp10',
 'N2',
 'N2h',
 'Iz',
 'OIz',
 'Oz',
 'POOz',
 'POz',
 'PPOz',
 'Pz',
 'CPPz',
 'CPz',
 'CCPz',
 'Cz',
 'FCCz',
 'FCz',
 'FFCz',
 'Fz',
 'AFFz',
 'AFz',
 'AFpz',
 'Fpz',
 'NFpz',
 'Nz']

A keen eye may have identified some “odd” electrodes, that are not really part of the 10-20, 10-10, or 10-05 systems: 'A1', 'A2', 'M1', 'M2'

These are supplied with eeg_positions for convenience as so-called “alias” positions. See below:

alias_mapping = get_alias_mapping()
for key, val in alias_mapping.items():
    print(f"{key}: {val}")

A1: LPA+(-0.1, -0.01, -0.01)
A2: RPA+(0.1, -0.01, -0.01)
M1: TP9
M2: TP10

We see that for example A1 is mapped to a position near the left preauricular point (LPA). This position is meant to reflect that the A1 electrode is typically a clip-on electrode applied to the earlobe.

Similarly, the M1 electrode is typically applied to the left mastoid on the head of a study participant. Its position approximately coincides with the TP9 position.

But now back to the topic: We want to get coordinates for a small subset of electrodes!

# Just use `elec_names`
coords = get_elec_coords(
    elec_names=["A1", "A2", "FC3", "CP4", "M1", "LPA", "RPA", "T10"],
    drop_landmarks=False,
    dim="3d",
)

coords.head()

	label	x	y	z
0	FC3	-0.5547	0.3048	0.7742
1	CP4	0.5547	-0.3048	0.7742
2	M1	-0.9511	-0.3090	0.0000
3	LPA	-1.0000	0.0000	0.0000
4	RPA	1.0000	0.0000	0.0000

Plot it, and see how close LPA and A1 (and RPA and A2) are in space.

fig, ax = plot_coords(coords, text_kwargs=dict(fontsize=10))

ax.axis("off")
fig

<Figure size 640x480 with 1 Axes>