8
votes
Accepted
What are proper EEG frequency bands and electrode placements for imagined speech?
A study by D’Zmura et al. (2009) in which two syllables were spoken in imagination showed that imagined speech information was present in EEG alpha, beta and theta bands. The beta band (13-18 Hz) ...
- 20.4k
4
votes
What is the meaning of the peak polarity in EEG data?
Short answer
The peak polarity of an EEG is arbitrary.
Background
Positive and negative in an EEG measure is arbitrary. If you measure the EEG between two electrodes and you flip the wires, the ...
- 20.4k
4
votes
Why are biosignals from the body said to be continuous?
Biological signals are analogues and hence continuous. Early EEG systems simply recorded the analogue signals and displayed it as a continuous signal graphically as wiggly lines written by little pens ...
- 20.4k
3
votes
Accepted
What happens at sampling rates lower or higher that the Nyquist rate?
Short practical answer
for a signal to be properly sampled, it has to be done [at] the Nyquist sampling rate
Up front: sampling at the Nyquist frequency is the bare minimum rate to reproduce the ...
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2
votes
What happens at sampling rates lower or higher that the Nyquist rate?
Here is the 10 KHz signal (the maximum frequency of the signal is 10 KHz):
Now, if we sample the signal at 5 KHz and 10 KHz, the signal will look like
as shown below (the brown points):
It is clear ...
- 21
2
votes
Method/Unit for measuring activity in specific frequency band for EEG
How you analyse your data depends a bit on how you did your time-frequency decomposition.
If you're using a fast Fourier transform, you will likely cut out the temporal window of interest prior to ...
- 2,553
2
votes
How is the biological error signal in predictive coding computed?
TL;DR: We don't know whether the brain really uses predictive coding or not. But neurally computing an error signal on a small scale is possible (see below).
Predictive coding is an hypothesis for a ...
2
votes
How is the biological error signal in predictive coding computed?
I provided an answer to a similar question here that limitedly deals with the role of biological prediction errors.
Here's an excerpt of that answer:
...to answer this properly, we must first make it ...
- 503
2
votes
Accepted
What are the methods to reject ocular artifacts in the EEG?
According to a review by Croft & Barry (2000), a number of possible methods exist to prevent, or reject ocular artifacts in the EEG;
Prevention/reduction of artifact instances
Recording with ...
- 20.4k
2
votes
What does fMRI data look like after pre-processing?
The MRI signal is a small electrical current induced in the receiver coil by the precession of magnetization during resonance, i.e., a manifestation of Faraday's Law of Induction, wherein a changing ...
- 20.4k
2
votes
Features for blink detection in real-time single channel EEG
The EEG signature of eye blinks is typically visible for about 200ms of data. When you want to move a window of 50 to 200 samples, I assume that your sampling frequency is 1000Hz (you should specify ...
- 310
2
votes
EEG segmentation and denoising which one should done first?
Depending on whom you ask, you get both answers. That's mostly dependent on the denoising algorithm. If you're using an adaption of GST, you are segmenting first with an n-1 overlap.
If you're using ...
- 71
2
votes
Reference signal when measuring EEG
For the unipolar configuration, why can't we just use Earth ground as
our reference instead of having a reference electrode or performing an
average of measurements on all the electrodes?
The ...
- 20.4k
1
vote
Why is Electric Artefact still present in my recording?
There are many many reasons why interference can occur so it's almost impossible to give a direct answer with the details provided. You should at least give details like a spectrogram and experimental ...
- 11
1
vote
How to handle single trial ERP (P300)
I remember trying using single-epoch measurements with electroretinogram (ERG) recordings. Basically, ERG responses are electrical potential recordings from the neural activity in the retina. ERGs are ...
- 20.4k
1
vote
Why are biosignals from the body said to be continuous?
To add to the answer provided by @AliceD, pure digital waveforms are square waveforms as they represent steps between 1s and 0s and are therefore not continuous.
Analogue waveforms are not. They are ...
- 12k
1
vote
Accepted
The number of things we can focus on at once
You already seem to be making the difference between a point of focus, versus "things in the back of ones mind". I think that's quite apt.
Different authors have come up with different theories about ...
- 20.4k
1
vote
Accepted
Can a bipolar EEG signal be converted to a monopolar (unipolar) one?
Short answer
As far as I can see - no you can't.
Background
In EEG systems, unipolar signals are measurements against a distant reference electrode, for example Fpz (Fig. 1). So suppose I have ...
- 20.4k
1
vote
How to map EEG time-series and visualize meditative states frequencies?
Thank you for your interesting question!
Generally, there are three types of methods to process your EEG time-series data:
Time domain methods (e.g., regression, statistical analysis on your EEG ...
- 115
1
vote
Accepted
High Density Signal Meaning
"High-density EEG" refers to the number of electrodes in the array. Typically, any EEG rig with more than 64 electrodes is considered to be high-density electroencephalography.
- 1,493
1
vote
How to analyze auditory steady state responses?
ASSR analysis is based on the fact that the electrophysiological responses are time locked with the stimulus repetition rate.
There is not one possible method of analysis. Generally spoken, ASSR ...
- 20.4k
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