## 4 Discussion  
This review has analyzed studies using BMIs to determine if an increase in the number of sensory modalities is associated with increased SoE and improved BMI performance. Most studies employed motor imagery-based BMIs through EEG recordings and included only one type of feedback, either visual or visual immersive. This type of feedback was consistently associated with increased SoE, but only 55.56% of the cases were associated with an improvement in BMI performance. Studies that combined two different types of sensory feedback either used visual (or visual immersive) and auditory feedback or, alternatively, visual (or visual immersive) and haptic feedback in the forms of vibration or electrical stimulation. While most studies utilized one or two types of sensorial feedback in an EEG motor imagery-based BMI, a small number explored different approaches such as SSVEPs, intracortical recordings, or incorporated more than two types of sensory feedback. Additionally, a relatively limited number of studies were conducted in patients. Lastly, a noticeable bias towards male participants was observed. The studies analyzed in this review do not support the notion that an increased number of sensory modalities enhances SoE and BMI performance. However, they also highlight the fact that, to date, no study has systematically explored the influence of different sensorial modalities in SoE and BMI performance. SoE, particularly the sense of ownership (SoO) over external objects, has been investigated using the rubber hand paradigm [42]. In this paradigm, users have one of their hands hidden but exposed to tactile stimuli while simultaneously observing a substitute rubber hand. During the experiment, the rubber hand receives the same stimulus at the same time as the participant's hidden hand, leading the participants to attribute the proprioceptive sensation to the observed stimulus rather than the one delivered to their own skin. Some researchers have proposed that the SoO experienced towards the rubber hand contributes to the SoA. In other words, participants who feel a strong SoO over the rubber hand also report a high perceived SoA, believing they could control the movements of the rubber hand if they desired [42; 68]. Several studies included in this review reported a suggested connection between SoO and SoA [17; 20; 53; 54]. However, previous research has shown that a strong SoO over a rubber hand can occur without feeling agency over its movements [69]. Also, visual representations resembling a human body or body part have been found to enhance the SoE compared to more abstract representations with subjects reporting feeling less embodied by a virtual block [20] or a robotic tweezer [53] than by a human-like hand. Several research groups have made efforts to develop BMI tasks with more realistic actors such as robots or avatars. Many studies have focused on exploring the effects of congruent and incongruent sensory feedback on actions and their influence on SoE. This has been examined in relation to visual [12; 16; 19; 37; 52], auditory [18], or haptic [37; 56] congruency/incongruency of feedback. These studies support the idea that the sense of agency is a fundamental component of embodiment processes and is influenced by sensorimotor congruence in the executed action, with sensory input playing a crucial role [19]. It appears that, as long as some congruent sensorial feedback is provided, the SoO [68] and SoA [70] can be induced in participants. In other words, these participants believe they are controlling a task through a BMI when, in fact, they are not. Therefore, it is possible to induce some SoO in an additional bodily part, such as a third hand, without losing the SoO in their real hands [68]. These studies suggest that the intention to control a BMI may recruit both SoO and SoA. In general, congruent visual stimuli have been found to elicit higher levels of SoO [12; 16; 52] and SoA [19; 37].