Values of the areas under the receiver operating characteristic curve (AUC) of all subjects under the two algorithms, and the time windows is 50 ms.

<p>Values of the areas under the receiver operating characteristic curve (AUC) of all subjects under the two algorithms, and the time windows is 50 ms.</p

Effect of IC on ERP signal.

<p>ERPs stimulated by the (A) high-complexity target image, (B) high-complexity nontarget image, (C) medium-complexity target image, (D) medium-complexity nontarget image, (E) low-complexity target image, and (F) low-complexity nontarget image. (G) Trial averaged target ERP wave forms calculated from (A), (C) and (E), where the red, blue, and green lines indicate the ERP components inspired by high-, medium- and low-complexity image. Similarly, images in (H) are indicative of nontarget image.</p

All subjects AUC under different classifiers.

<p>All subjects AUC under different classifiers.</p

Target and non-target class waveforms.

<p>(A) All single-trial event-related potentials (ERPs) to target images at electrode Pz. (B) All single-trial ERPs to nontarget images at electrode Pz. (C) Grand averages across all trials of the target EEG signals at electrode Pz. (D) Grand averages across all trials of the nontarget EEG signals at electrode Pz.</p

The brain activity varied between 400 ms to 600 ms in different image complexity (HIC, MIC, and LIC).

<p>The brain activity varied between 400 ms to 600 ms in different image complexity (HIC, MIC, and LIC).</p

Rapid serial visual presentation (RSVP) paradigm.

<p>The RSVP sequence consisted of 25 blocks (a total of 2400 images, i.e., 25 target categories with 300 images and 175 nontarget categories with 2100 images), and each block comprised one target category (12 images) and seven nontarget categories (84 images). The images are presented in 25 blocks, with a distinct target category in each block. The target categories of each block are shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0184713#pone.0184713.t001" target="_blank">Table 1</a>. Each image is presented for 200 ms (The image is similar but not identical to the original image, and is therefore for illustrative purposes only).</p

Target categories for the 25 blocks.

<p>Target categories for the 25 blocks.</p

Values of the areas under the receiver operating characteristic curve (AUC) of all subjects under the two algorithms, and the time windows is 25 ms.

<p>Values of the areas under the receiver operating characteristic curve (AUC) of all subjects under the two algorithms, and the time windows is 25 ms.</p

Three group images are sorted from high to low IC (The image is similar but not identical to the original image, and is therefore for illustrative purposes only).

<p>Three group images are sorted from high to low IC (The image is similar but not identical to the original image, and is therefore for illustrative purposes only).</p

The amplitude and latency changes at different complexities.

<p>The amplitude and latency changes at different complexities.</p