**6. Conclusion**

We have discussed the basic architecture of BCI system using EEG as brain signals to control external devices in rehabilitation and communication. Exogenous and endogenous signals elicited by external stimuli and motor imagery respectively can enhance neuroplasticity and improve motor function. However, research on other modalities such as sensory and cognition are still at its primitive stage. Applications in the biomedical field are blooming but challenges in creating the best system that fits in all conditions still remain.
