14
votes
Accepted
Why is Fast Fourier Transform applied to raw EEG data?
Fast-Fourier Transform (FFT) transforms a signal from the time domain into the frequency domain. Basically, any time-dependent signal can be broken down in a collection of sinusoids. In this way, ...
- 52.2k
5
votes
Why is Fast Fourier Transform applied to raw EEG data?
Any periodic waveform can be produced by adding up a series of sin waves of the appropriate frequency and amplitude. The FFT looks at a complex waveform and calculates those frequencies and ...
- 193
4
votes
Accepted
What physical or mental actions can be picked up by EEGs?
Many EEG responses are swamped in random brain activity, artifacts and background noise. A single movement typically doesn't evoke measurable activity, because its amplitude is so small with respect ...
- 52.2k
4
votes
Accepted
Why don't we hear ultrasonic sounds as aliased versions of the original signals?
Short answer
The cochlea is a tonotopic map with certain physically determined boundaries that determine the range of frequencies perceived. Ultrasonic soundwaves simply do not have a correlate on ...
- 52.2k
4
votes
Neurons: how does the brain reduce electromagnetic interference?
There is an extensive Q&A about the difference between brain waves and EM waves over on our sister site Psychology & Neuroscience: https://psychology.stackexchange.com/q/15222/14382 (though ...
- 41.3k
3
votes
What signal processors comprise an Event-Related Potential system for EEG?
Event-related potentials are an issue in many aspects of physiology, not just in EEG analysis, so this answer is more general.
The main problem is that electrical or other signals that are associated ...
- 710
3
votes
Accepted
Do repetitive movements on EEGs show up as discernible patterns?
Specific events, e.g. finger flexions, generate synchronized neuronal responses in the brain that can be measured on the scalp with EEG. However, a voltage response to a single event typically ...
- 52.2k
3
votes
Accepted
What are wave frequencies in the EEG?
EEGs are often analyzed in the frequency domain, where signals are subjected
to spectral analysis, typically by Fast Fourier Transformation, or FFT.
What an FFT basically does is decomposing a ...
- 52.2k
2
votes
Accepted
Why are local field potentials generally band-pass filtered?
There is no physical limitation whatsoever on the frequency band you wish to record, other than the hardware limitations on the sampling rate.
Often electrophysiological recordings suffer from noise (...
- 52.2k
2
votes
Why don't we hear ultrasonic sounds as aliased versions of the original signals?
I think that you are misquoting Aliasing.
Digital acoustics is explained in a mathematical sense, Aliasing is a maths concept. Real life acoustics is explained in a physical sense, which talks about ...
- 9,622
2
votes
Accepted
Understanding the configuration of channels in the 10-20 EEG montage
EEG 10-20 system. source: Wikipedia
How many actual channels are there?
21 in the figure, i.e., the number of active electrodes.
What's the difference between reference and active ...
- 52.2k
2
votes
What signal processors comprise an Event-Related Potential system for EEG?
ERPs are typically analyzed in terms of amplitude and latency. FFT is not really an option; it doesn't make sense. There may be some applications where it may be useful, but these are quite specific. ...
- 52.2k
2
votes
Accepted
Criteria for compound action potential thresholds
Action potentials of single neurons (APs) are the building blocks of compound action potentials (CAPs). While each of the individual APs is a yes-or-no response with a clear-cut defined threshold, ...
- 52.2k
2
votes
Accepted
Are neurons capable of buffering a signal to sync up with other data?
For this answer, I'll use a very broad definition of "buffer" as a mechanism to integrate information at different delays. I have no interest in getting into specific computer science ...
- 41.3k
1
vote
Neurons: how does the brain reduce electromagnetic interference?
There are two aspects to this question. The first, dealing with EMR associated with AC generated in the usual range is already properly answered. However, in the case of mobile phone radio and wifi ...
- 179
1
vote
Accepted
The role of PCA (Principal Component Analysis) in recording neurons
Like vkehayas mentions in a comment, they're using it for spike sorting, as you've guessed. This involves both identifying signals from putative neurons (vs noise) and separating different source ...
- 41.3k
1
vote
Issues obtaining Fo in DIY Imaging Fluorometer
This paper1 gives a definition of all the various parameters. F0 (that's Fzero, not F letter "o" I think) is defined as the dark state fluorescence. There is a second parameter F0' that is ...
- 9,508
1
vote
Accepted
Analysing the ERP (Event-Related Potential from EEG recordings) in terms of the P-300 wave
So, are repetitions wanted in this kind of experiment?
Yes: repetitions reduce random noise and increase the chance to tell artifact from response. Adaptation is a serious issue, typically becoming ...
- 52.2k
1
vote
Electrocardiogram: Difference between Atrial Fibrillation and Atrial Flutter
A-Flutter will have discernible waves that can be counted, usually. The R-R interval will be regular or maybe slightly irregular if there's a variable conduction block in the AV Node. A-Fib will ...
- 31
1
vote
Accepted
Electrocardiogram: Missed beats in presence of Ectopic beats or Premature Atrial/Ventricular Contraction beats
After developing and checking the algorithm with simulated ECG data, i found out that premature beats (as the name suggests) itself arrive prematurely i.e. their R-R peak interval is less then the R-R ...
- 129
1
vote
Accepted
Possible to remove accumulated haze on fluorescence interference filters?
In fact, filters can be damaged by heat. However, newer filter coatings are less prone to heat damage [details].
For the barrier filter, it's less likely to be heat damage. The older/less expensive ...
- 221
1
vote
Possible to remove accumulated haze on fluorescence interference filters?
Its probably not from heat. Filters are basically a glass substrate with some ionic compound deposited in thin layers. These won't oxidize at reasonable temperatures, and furthermore since you have ...
- 952
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