## 4 Discussion
### Currently Available Commercial Products and Computational Methods Used in BCI  
While the field of BCI and VR is rapidly evolving, commercially available solutions that fully integrate both technologies are still limited. Most products focus on either BCI or VR separately. However, here are some commercially available solutions and companies that are making strides in combining BCI and VR. Neurorehabilitation and therapy include, e.g., the following solutions:  
1. MindMaze--offers VR-based neurorehabilitation games controlled by EEG signals, targeting cognitive and motor skills;
2. Neofect--develops VR games and rehabilitation programs for stroke patients, incorporating sensors for movement tracking and feedback;
3. SynChlink--provides VR-based assessments and training programs for visual and vestibular function, utilizing eye-tracking technology. Gaming and entertainment include, e.g., the following solutions:  
1. Emotiv--offers EEG headsets and software development kits for integrating brain-wave data into games and applications;
2. NextMind--developed a non-invasive neural interface that allows users to control digital experiences with their thoughts, but the company has shut down;
3. Neurosky--manufactures EEG-enabled headsets for consumer and research applications, including gaming and entertainment. Research and development include, e.g., the following solutions:  
1. OpenBCI--provides open-source hardware and software platforms for BCI research and development, enabling researchers to create custom BCI-VR applications;
2. g.tec--offers a range of BCI systems and software for research and clinical applications, including VR integration options;  
VR hardware with potential for BCI integration are the following:  
1. Varjo--develops high-end VR headsets with advanced eye-tracking capabilities, which could be leveraged for BCI applications;
2. HP Reverb G2 Omnicept Edition--features integrated eye-tracking, heart rate, and facial expression sensors, offering the potential for developing more immersive and responsive BCI-VR experiences. The field of brain-computer interface and virtual reality integration has immense potential, but current commercial applications remain relatively limited, reflecting the early developmental stage of this technology. Leading companies like MindMaze and Emotiv have pioneered commercially available BCI headsets, primarily targeting gaming and entertainment applications. The Technology Readiness Level scale, a widely used metric to assess technological maturity, ranges from basic principles to fully operational systems. MindMaze's technology, for instance, has reached TRL 7, with its use in clinical rehabilitation settings. Conversely, Emotiv's headsets, which focus on consumer-grade neurofeedback and accessibility, fall under TRL 6. Several other companies are also emerging in this space, each with its own distinct focus and target applications. These include Neofect, which develops rehabilitation devices that integrate with VR; SynChlink, which focuses on eye-tracking and VR for neurological assessments; NextMind, which explores BCI control for digital experiences; Neurosky, which offers affordable EEG headsets for meditation and attention training; OpenBCI, which provides open-source hardware and software for BCI research and development; g.tec, which specializes in high-performance BCI systems for research and clinical use; Varjo, which develops high-end VR headsets with integrated eye-tracking; and HP, which offers the Reverb G2 Omnicept Edition, a VR headset with built-in eye-tracking and facial expression recognition. However, these solutions often face limitations in terms of signal quality, user training requirements, and the range of applications they support. Consequently, the majority of BCI-VR solutions remain confined to research labs and clinical settings, indicating the need for further technological advancements, particularly in areas like miniaturization, cost reduction, and user-friendliness, to drive broader market adoption.