Figure - PMC

Skip to main content

An official website of the United States government

Here's how you know

Here's how you know

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

View full-text article in PMC

. 2019 Sep 2;2:327. doi: 10.1038/s42003-019-0575-3

Search in PMC
Search in PubMed
View in NLM Catalog
Add to search

© The Author(s) 2019

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

PMC Copyright notice

Fig. 4 — Alpha-Suppression (αS) detection procedure. a Unsegmented EEG signal. b Frontal electrodes. c Detection of IES based on Fp1 and Fp2. Box 1: signal average (Fp1 + Fp2)/2. Box2: threshold detection for regions inside ±8 μV band, lasting at least 1 s. d (Upper) EEG signal S(t) wavelet decomposition filtered in the band 8–16 Hz resulting in S_α (light blue). d (Middle) Extraction of oscillatory features of S_α(t): the minimums x_i, the maximums y_i, the distance d_i = |x_i − y_i|. The average Amp(t) of the distance d_i is computed in the widow interval [t − w/2;t + w/2], where w = 1s. d (Middle low) Nonlinear filtering enhancing transient oscillatory periods. X_i (orange) and Y_i (blue) are Amp(t) (gray) minimums and maximums respectively. The multiplicative function Φ(t) is the sum of weight function ϕ(t) (green), multiplied by a Heaviside function H at time t_i of maximal amplitude Y_i = Amp(t_i). The resulting function with enhanced oscillatory regions is S_ϕ(t) = S_α(t)Φ(t) (red). d (Lower) Signal below a T = 0.25 threshold (orange) applied on normalized |S_ϕ(t)| (blue) and present at least on two electrodes is considered as an α-S. e Segmented EEG signal with detected IES (red) using method (c) and α-S (yellow) using (d)