**5. Conclusions**

EEG signals are reliable information that cannot be simulated or faked. To decode EEG and relate these signals to specific emotion is a complex problem. A ffective states do not have a simple mapping with specific brain structures because di fferent emotions activate the same brain locations, or conversely, a single emotion can activate several structures.

In recent years, EEG-based BCI emotion recognition has been a field a ffecting computing that has generated much interest. Significant advances in the development of low-cost BCI devices with increasingly better usability have encouraged numerous research studies.

In this article, we reviewed the di fferent algorithms and processes that can be part of EEG-based BCI emotion recognition systems: (1) Emotion elicitation, (2) signal acquisition, (3) feature extraction and selection, (4) classification techniques, and (5) performance evaluation. For our survey of this topic, we mined di fferent databases and selected 60 studies carried out under a computer science perspective to gain insight into state of the art and sugges<sup>t</sup> possible future research e fforts.

As seen in this review, computational methods still do not have standards for various applications. Researchers continuing to look for new solutions in an ongoing e ffort. The study of the relationship between brain signals and emotions is a complex problem, and novel methods and new implementations are continuously presented. We expect that many of the existing challenges will soon be solved and will pave the way for a vast area of possible applications using EEG-based emotion recognition.

**Author Contributions:** Conceptualization and Investigation as part of his Ph.D. research, E.P.T.; E.A.T., M.H.- Á., and S.G.Y. contributed with overall supervision, review editing. All authors have read and agreed to the published version of the manuscript.

**Funding:** Escuela Politécnica Nacional funded the publication of this article.

**Conflicts of Interest:** The authors declare no conflict of interest.
