About the unit of raw EEG data

935963004 commented 3 months ago

Hi, authors. Thanks for your exellent dataset! I am wondering about the unit of raw EEG data. I am loading the data from Matlab files:

from scipy import io
matdata = io.loadmat('task1-SR/Matlab files/resultsZAB_SR.mat', squeeze_me=True, struct_as_record=False)['sentenceData']
for sent in matdata:
        print(sent.rawData)
        break

and I got the output:

[ 0.8102897   0.4924412   0.44047612 ...  0.30642092  0.20077913
   0.32715505]
 [ 0.1091525  -0.05207972 -0.28782055 ...  0.26032427 -0.04572273
   0.02665068]
 [ 0.70459163  0.5766893   1.1255366  ... -0.6907126  -1.1149031
  -0.67108846]
 ...
 [ 1.1299472   0.49951333  0.40294212 ...  0.8088422  -0.11194292
   0.3848682 ]
 [ 2.194058    1.2687929   1.1725545  ...  0.4536394  -1.0771086
   0.00784904]
 [ 0.          0.          0.         ...  0.          0.
   0.        ]]

I want to know the unit of these raw data. Are they based on uV (10e-6 Volt)? Or other units? Thanks for your help!

samuki commented 3 months ago

Hi @935963004. Yes, the unit is microvolt.

935963004 commented 3 months ago

Thanks! I have another question. When I calculate the time length using sent.rawData.shape[1] (divided by 500 Hz), I find that most time lengths are only 1~3 seconds. I feel a bit confused about how can the subjects read so many words (usually 20+ words) in such a short time. Are these data accurate? Here are some of the counts:

num_words time_length (s)
21 1.808
32 3.1
18 2.142
25 2.302
18 2.158
10 1.552
8 1.12
15 1.162
12 2.55
24 2.94
13 1.318
16 1.486
9 1.616

samuki commented 1 month ago

Hi @935963004, sorry for the extended wait! Could you provide more details on the source of those reading times? Most of the should be higher than 1–3 seconds.

norahollenstein / zuco-benchmark

About the unit of raw EEG data #5