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Questions tagged [eeg]

The recording of voltages along the scalp for the purpose of monitoring brain wave activity and localizing sources of ionic currents

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0answers
26 views

How to account for number of electrodes in EEG data while converting to frequency domain?

I have raw data from 64 electrode EEG in CSV format where there are multiple rows and 64 columns. I am using the following Python code to separate the data into frequency bands: ...
0
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2answers
65 views

May I know how to find Time frequency power spectrogram of a signal?

I am analyzing EEG signal and I am unable to understand the term Time-Frequency Power Spectrogram. Please Can anyone help me? Thank you in advance.
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3answers
45 views

Can an EEG be re-sampled to fix a poor voltage resolution?

I’ve made quite a bad mistake in ca. 14 EEG recordings – I recorded at 10uV resolution @ 5000 Hz instead of 0.1 uV @ 500 Hz. I’m conducting an ERP experiment, and the signals of interest are on the ...
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1answer
89 views

Manual filter or digital filter first for EEG?

I am getting conflicting advise regarding how to clean my EEG data: 1) Manually remove artefacts first and then apply digital filters OR 2) Apply digital filters first and then manually remove ...
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0answers
127 views

Filter Bank Common Spatial Pattern (FBCSP) Algorithm

I know that for Common Spatial Pattern (CSP) algorithm i need two covariance matrices, for Filter Bank CSP algorithm i have filtered one trial of EEG signal into 9 frequency bands. My question is ...
0
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1answer
181 views

Wavelet transform and FFT using to extract feature power bands with EEG signals

I am using 5 channels [ fz , cz , c3 , c4 , pz] to detect drowsiness of driver My First Question is, what is the right input to get feature power band ( Theta , alpha , gamma , beta ) to wavelet ...
1
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1answer
177 views

Common Spatial Pattern for EEG Signals

I am having difficulty in understanding the use of CSP for EEG signal feature extraction and subsequently. Since I am using two classes, this query will be restricted to it. In essence CSP requires 2 ...
1
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1answer
96 views

Spatial spectrum of EEG data: non-uniform DFT?

I want to compute the spatial spectrum of EEG data collected using a non-uniformly sampled grid of sensors (as in the figure below). One way to do this would be to interpolate the data on a ...
0
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0answers
175 views

output shape of STFT

I cant figure out why our output image is 257 * 32 , 32 I know why , but 257 I cant understand ? this is the exact word of this paper wich applied STFT on 3 channel of eeg signal : Short time Fourier ...
1
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1answer
433 views

How to apply Hamming Window and compute FFT?

I'm borrowing an EEG device whose accompanying software also computes the FFT of the data it collects. The software provides the user with a file of EEG values and a file of FFT values computed from ...
0
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1answer
65 views

EEG, PSI interpretation

My colleague and I started exploring EEG processing and, especially, functional connectivity. We decided to try the Phase Slope Index (PSI) and conducted a simple experiment as follows: it consists of ...
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2answers
91 views

How do I know if my EEG signal need denoising?

I recently started working on sleep study. For my research I download sleep EEG data from physionet. The EEG data has 100 Hz sampling rate and was recorded from 2 bipolar EEG site. When I start the ...
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3answers
4k views

How to correctly compute the EEG Frequency Bands with Python?

so I am trying to compute the EEG(25 channels, 512 sampling rate, 248832/channel) bands (alpha, beta, gamma, etc.) with Python. I managed to do so by: firstly filtering the signal with a butterworth ...
2
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1answer
2k views

How to compute the power bands of an eeg signal using python?

so I have an eeg signal (edf format) that has 25 channels and 248832 entries, sampling frequency of 512Hz. I have to compute the frequency bands: – Delta: 0.1-4Hz – Theta: 4-8Hz – Alpha: 8-12Hz – ...
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1answer
285 views

DWT versus band-pass filter

Which technique gives better result in extracting a band from a signal, let's say the alpha band (8-13 Hz): using a band-pass-filter or a DWT (Discrete Wavelet Transformation)? P.S.: I am working in ...
3
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1answer
35 views

What is the meaning of negative second for a Morlet wavelet?

I kind of familiar with wavelet transform (I just used it in code but do not have a deep understanding about it). I've been reading an article and came across this sentence: where 4Fs is the ...
1
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1answer
1k views

why butterworth bandpass filter changes signal in the passband?

I want to apply a butterworth bandpass filter to EEG signals and it's not working so I tried with a simple signal: t=[0:0.01:10]; s3= 9*sin(2*pi*4*t); Still ...
0
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2answers
272 views

Compute absolute power spectrum in MATLAB

I have EEG signals. Is there a way to compute the absolute power spectrum in MATLAB within a frequency band? I know I have to use the fft function but I can't find any details about the absolute power ...
0
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1answer
1k views

Compute phase coherence between two eeg signals

I have two EEG signals/channels and I would like to compute phase coherence in MATLAB. I have this paper: https://www.nature.com/npp/journal/v39/n5/full/npp2013330a.html but it does not say what Sij ...
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2answers
7k views

What does epoch mean in EEG?

I need to understand the meaning of an epoch in EEG signal. I have an EEG signal. Then how can I get the epoch?
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0answers
298 views

How to choose notch frequencies for filtering line noise?

I'm using the function to filter out line noise at 60 Hz (and 120, 180 Hz) caused by electrical noise: ecogNotch In the case below I can effectively filter out the line noise with a notch filter at ...
0
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0answers
312 views

What's the suitable specifications for the FIR filter?

i have EEG signal,the sampling frequency is 256 HZ .The wavelet decomposition that i will use does not allow the extraction of specific frequency bands without additional filtering. Thus, in order to ...
0
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1answer
682 views

Low pass FIR filter for EEG signal

I'm trying to do Analysis of EEG Signal for the Detection of epileptic seizure so in the pre-processing of the EEG signal I use a low pass FIR filter ...
0
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0answers
34 views

Reduce impact of outliners for frequency analysis by increasing signal length?

I am working on a project to detect drivers drowsiness with EEG signals. I am using the frequency values retrieved by FFT. I have some outliners (artifacts) in my signals, which I don't want to remove ...
3
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1answer
127 views

What do certain terms mean in EEG processing describing frequency bands?

I've recently started a project about detecting driver drowsiness with an EEG and came across some terms I didn't quite understood: ...increase in theta activity occur... - ...low voltage theta ...
2
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1answer
765 views

Bandpass filter to get EEG frequency bands?

I'm doing a project with an EEG to detect driver drowsiness and learned about EEG frequency bands (alpha, beta, gamma...). As the frequency bands are simple frequency ranges, I wonder if I can use ...
1
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1answer
76 views

What is QEEG technically, and how is it computed?

I've been working with EEG signals for a while. I wonder how to compute QEEG (or Brain Map) representation. I feel it is extracted from raw EEG and I want to know what is technical method for QEEg ...
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0answers
117 views

EOG artifacts turn up in several ICA source signals

I try to remove EOG artifacts from my EEG signals (I am using a EPOC+ for recording and MNE Python for processing). Therefore I've recorded test data with blinks every 5 seconds. The blinks can be ...
5
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2answers
2k views

Which order to perform downsampling and filtering?

I have EEG data recorded with 128Hz sampling rate. As my goal is to reduce the amount of data (and maybe noise), I want to downsample the data to 64Hz (I am only interested in range 0.5 - 30Hz). I ...
1
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1answer
4k views

Cross correlate a 2D array

I have a 2D array of eeg data with shape (64,512) - 64 electrodes, 512 timepoints I want to calculate the maximum cross correlation (irrespective of lag/time shift) between every single electrode, so ...
0
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1answer
2k views

How to segment frequency bands after FFT and calculate power?

I have been working with EEG signal. I have raw EEG data for a 2-second (i.e. $t=2$) duration. My objectives are: Transforming these raw data from time domain to frequency domain. Segmentation into ...
1
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1answer
1k views

How is the topo / scalp map from an EEG Signal with ICA created?

I am lately experimenting with an EEG and found this Library: MNE Python. I am using an ICA to find and correct artifacts - this is working fine. It's now possible to plot a topo / scalp map for the ...
0
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1answer
2k views

How do we use signal::filter and signal::butter in R for EEG data?

I am trying to design an experiment to determine the peak amplitude of an EEG signal in response to a stimulus. Till now, our team has been using MATLAB and since we wish to go open source, we are ...
0
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1answer
308 views

Origin of artifacts 12 Hz away from electrical line noise (50 Hz)?

I made electroencephalographic measurements from people while they were sleeping. When plotting the frequencies, I see that I do not only have an expected 50 Hz (and 150 Hz and 250 Hz...) artifact (...
0
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1answer
80 views

What could be causing these humps every 10 Hz on my PSD estimate data?

I am working with EEG recordings about 1,000,000 data pts long, recorded at 4,000 Hz. I'm generating PSD estimates for these recordings using the matlab "periodogram" function like so: ...
0
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2answers
3k views

How to identify and differentiate frequency and time in EEG data using python?

I have an EEG data of 200 Hz and sampled at 4097. I have few doubts and questions related to this data: What does it mean by sampling in EEG data? I am getting the sample rate and the frequency when ...
0
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1answer
304 views

AR model order selection for half second EEG fragments

I am using MATLAB to evaluate power spectral density estimates of half second EEG signals, using modified covariance method. Can anyone suggest me how to select the AR model order for this process? Is ...
0
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1answer
976 views

Python MNE - reading EEG data from array

I have EEG data that comes in the form of a 3D numpy array (epoch * channel * timepoint). timepoint is a 256 element array containing each sampled timepoint (1s total, at 256Hz). epoch is an ...
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3answers
2k views

Phase locking value / phase synchronization

I have pairs of EEG signals filtered to give me just alpha bands. For a machine learning problem I have found that calculating the phase locking value between the alpha signals of these 2 channels ...
0
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2answers
254 views

EEG Power at specific time points

I'm in the process of building features for an EEG machine learning problem and have been doing some reading about what features may be useful. Turns out, that alpha band (8-12Hz) power can make a ...
1
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2answers
562 views

Signal power without FFT

I have an EEG signal thats about 1second long, sampling frequency of 256Hz, measured in microvolts, and I want to calculate the power of a specific frequency band (8-12Hz) I believe the correct way ...
0
votes
1answer
7k views

Python - time frequency spectrogram

I have some 64 channel EEG data sampled at 256Hz and I'm trying to conduct a time frequency analysis for each channel and plot a spectrogram. The data is stored in a numpy 3d array, where one of the ...
0
votes
1answer
657 views

Python bandpass filter - singular matrix error

I've been trying to design a bandpass filter using scipy but I keep getting a LinAlg Singular Matrix error. I read that a singular matrix is one that is not invertable, but I'm not sure how that error ...
1
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3answers
3k views

Pre-processing EEG signals

Good Afternoon Everybody. I am developing filters for EEG signals in these days. During the Develop I find some problems: The filter is FIR (band-pass using a convolution of low-pass filter and ...
3
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1answer
422 views

Classifying sleep stages from only EEG

I'm currently working on a project that requires me to classify sleep stages (Awake W, N1, N2, N3 and REM) based on only an EEG. Various algorithms and classifying standards (such as Rechtschaffen &...
0
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2answers
751 views

segmenting an EEG data

I have an EEG labeled data, which is the data that used for training, And I want to segment those data based on the time of EEG signal (Time-based Epoching) as a preprocessing step, based on the ...
1
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1answer
268 views

FASTICA algoritm produce independent components does not equal to the dimensionality of EEG signals

From my knowledge about independent component analysis the number of channel or variables will not be affected by this algorithm and the number of independent components will be equal to number of ...
0
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1answer
606 views

What is bispectrum?

I am working on a project that uses EEG signals of the brain to identify emotional states. While surveying the literature, I came across several references where "derived features of bispectrum" are ...
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2answers
502 views

What is a 'time-variant' signal?

I have found in the literature a "time-variant signal" term , but I could not understand what that's mean. I know that there is "time-variant systems", but this is the first time, which I see a time-...
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2answers
4k views

Why is this MATLAB butterworth filter giving me wrong results

Given a 128 Hz signal, in MATLAB I entered the following command ...