## 4 Discussion of Results  
### General Discussion about Speech Imagery with Mental Tasks  
Based on the method used by deaf people, this study introduces 3D and 2D lip methods for speech imagery as a potential communication approach in the future. The 3D lip is considered an easy method for general communication. Another method can be used to enable communication in different areas. In another study, audio-visual images used only five sounds, but it was impossible to create another sound. Another article reported the use of a mental task with speech imagery, but it was difficult for the subject to imagine for a long time. It is difficult to visualize the writing of strokes and rotation with audio characters. This idea is only applicable to Chinese characters. Our proposed model uses two models that are combined for the basic sound of languages. It is easier to use mental tasks instead of imagination. Each model uses two tasks with different complexities for mental work. In contrast to 2D, 3D can support all of the characters. This indicates that 3D imagery is better than 2D imagery given the same model. However, further research is required to improve its accuracy. Additionally, 3D lip imagery can be used to learn in everyday life. It is easy to imagine this for all age groups. Questionnaires also show that most people can easily become distracted when performing mental tasks. Before the study, the activities of the sensorimotor cortex, [PERSON]'s region, and [PERSON]'s region were particularly significant [25; 26]. Our research used an identical model to other mental research to focus on the primary and pre-movement cortexes, temporal cortex, and complementary motor area (SMA). Our study was driven by a second motivation, which is to offer this method to patients with spinal cord injuries. In addition, this type of amputation, unlike physical amputation, makes it possible to retain motion pictures for a long time. According to ERSPs, the effect of the EEG energy signal is determined only in a determinated frequency range. Therefore, the frequency range was verified before the ERS maps were drawn. Each topic had a different frequency range. The stability calculation based on the EEG band was not considered (e.g., theta, alpha, and beta groups). Our study offers a specific range for most channels. The stability of the ERD/ERS values was tested using Cronbach's alpha coefficients. They achieved the highest compatibility [26] for word outcomes in subjective subtraction and spatial navigation tasks. As with [PERSON]'s results, task \"A\" showed a higher stability in both phases. Therefore, based on the specific activity, the temporal stability of ERD/ERS also varied in three time intervals. The ERD and ERS coefficients were the most stable. This depends on the attention paid to the subject at the beginning of the imagination. It Is difficult to distinguish between EEG signals in the same channel using two different tasks. However, in each dimension, imagination in a channel is different for two activities. However, using ERD/ERS diagrams of the two works in the same figure can indicate the difference. This difference is shown by increasing the EEG energy amplitude. The range of \"A\" is more like \"M\" and like any other task (characters). By testing several brain regions of the left frontal lobe and the posterior temporal lobes, the semantic processing relationship is revealed by the semantic execution system of