[Eeglablist] Approximate Entropy values very low

[Cedric Cannard]

Hi Lizzy,

Did you use default parameters (e.g. embedding dimension m and tolerance r)? 
In get_entropy(), the EEG signal is z-scored, and r is estimated on the standard deviation of the signal, following some recommendations.
https://urldefense.com/v3/__https://github.com/amisepa/get_entropy/blob/98488048e6aa54af570aaf2d82377f5af0684a58/get_entropy.m*L221__;Iw!!Mih3wA!GiseWTo2tQTr3IvYtQFZQAd-zJlMUriv9NVKg9N-_3cgGY9gS83kFKAQmda_cbP_xIjqjwS8Vl4z8fpYNfJh0Ewcng$ 
This may explain the differences with "typical" ranges in the literature. 
However, there is no real official guidelines for estimating entropy measures, and these methods are supposed to be better for noisy biosginals. 

You could try to remove the scoring on that line and see if you get values closer to what you are used to see. Let me know!

Fuzzy entropy is actually recommended, but it takes longer to compute. 

See: 
https://urldefense.com/v3/__https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5644759/__;!!Mih3wA!GiseWTo2tQTr3IvYtQFZQAd-zJlMUriv9NVKg9N-_3cgGY9gS83kFKAQmda_cbP_xIjqjwS8Vl4z8fpYNfI2-PIfYQ$ 
https://urldefense.com/v3/__https://hal.science/hal-02267711/document__;!!Mih3wA!GiseWTo2tQTr3IvYtQFZQAd-zJlMUriv9NVKg9N-_3cgGY9gS83kFKAQmda_cbP_xIjqjwS8Vl4z8fpYNfLR8wlO7Q$ 

Hope this helps

Cedric Cannard, PhD



On Friday, March 22nd, 2024 at 10:40 AM, Lizzy Blundon via eeglablist <eeglablist at sccn.ucsd.edu> wrote:

> Hi there,
> 
> I just tried out get_entropy.m on 345 s of resting state data, 19
> electrodes, filtered between 3 and 45 Hz. My ApEn values are very low
> (~0.1). Any idea why that might be?
> 
> Thank you!
> 
> Lizzy
> 
> --
> Elizabeth G. Blundon, Ph.D.
> Research Fellow
> Nova Scotia Health Authority
> Dalhousie University
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