(Muse 2014) Regarding Raw_fft0, 1, 2, 3 and Absolute Power of each band


#1

Hello everybody :slight_smile:
I am Jungryul Seo who is researching on context-aware computing in graduate school, South Korea.
I have a little bit stupid question.
I collected EEG data using Muse 2014 version for researching and used calcuated value such as Alpha Absolute Power which were calcuated by Muse until this time.

Ah… today my supervisor advised me to calculate some features which Muse didn’t calculate.

In order to do that, I need to handle raw_fft0, 1, 2, 3 data for calculating.
In my best understanding, raw_fft0, 1, 2, 3 data are seems to be a result of FFT.
The above attached figure is a screenshot of captured data.

As we know, Delta frequency range is 1Hz ~ 4Hz. And, Muse 2014 frequency resolution is 0.86Hz.
Following to Muse Available data document, they said “The absolute band power for a given frequency range (for instance, alpha, i.e. 9-13Hz) is the logarithm of the sum of the Power Spectral Density of the EEG data over that frequency range.”

Following to document content, I treid to calculate Delta band absolute power, but I could not get same result of Muse calculate value.

I am confusing whether I did a mistake, misunderstanding or missing something.
Would you please anyone advise me about my problem?

Thanks aforehand :slight_smile:
Jungryul Seo


#2

@Jack can you provide the correct formula please?


#3

Ah… First of all, thanks for replying on my question quite fastly. (Honestly, I am surprised!) :slight_smile:

My English ability is not good, please understand.
Of course, my research ability is also bad too.

I could not understand the meaning of correct formula in your text, perfectly. In my best understand of your text, do you mean which formula what I used?

Following to my screenshot, I assumed that raw_fft0,1,2,3 are FFT results of TP9, FP1, FP2, and TP10 respectively. As you know, each data has 192 float values, and each value represents power specturm density from 0 Hz to 110 Hz by 0.86 Hz unit.

In order to calculate Delta band absolute power, I refered document (http://developer.choosemuse.com/tools/available-data).

In the document, I read “The absolute band power for a given frequency range (for instance, alpha, i.e. 9-13Hz) is the logarithm of the sum of the Power Spectral Density of the EEG data over that frequency range.”, and I tried to follow it.

However, I could not understand sentence of “the logarithm of the sum of the Power Spectral Density” perfectly, especially, whether I need to use Log_10 or natural log. Thus I tested several ways with MS Excel.

Please refer my figure.
Case 1. (e.g., Excel formula = “Log10(SUM(C2:G2))”)
1 - Summing 0.86 Hz, 1.72 Hz, 2.58 Hz, and 4.3Hz of raw_fft values.
2 - Applying summed value into log_10

Case 2. (e.g., Excel formula = “LN(SUM(C2:G2))”)
1 - Summing 0.86 Hz, 1.72 Hz, 2.58 Hz, and 4.3Hz of raw_fft values.
2 - Applying summed value into natural log

Case 3. (e.g., Excel formula = “SUM(C2:G2)”)
1 - Just Summing 0.86 Hz, 1.72 Hz, 2.58 Hz, and 4.3Hz of raw_fft values.

Ah… is this enough information?

Cheers
Jungryul Seo


#4

I was tagging @Jack from Interaxon to ask him to respond.