Atiyeh Yaghoubiy - M.Sc. student in Bioengineering, Department of Biomedical Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran.
Keivan Maghooli - Assistant Professor in Bioengineering, Department of Biomedical Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran.

Expressing emotions plays an important role in interpersonal relationships and human interactions. Emotions affect a lot of processes such as cognition, decision, creativity, learning, etc. Recent studies on the relationship between computer and human helps the emotion recognition field to develop the meaningful interactions between the operator and the machine in training, medicine and many other related fields. Because of the human s ability to understand may different emotions and also because human is unable to hide, emotions can be detected using different methods. In the recent years emotion extraction using bio signals has occupied an important place among the research fields. Different systems and devices have been proposed which the most goal nowadays is to improve their accuracy, resolution and speed as well as their degree of being user friendly. This paper explores the different emotion models, applications, different extraction methods as well as problems and challenges ahead

Emotion models, bio-signals, emotion dimensions, human-machine interactions