Brain Computer Interface (BCI) decoding performance refers to the accuracy and reliability with which a BCI system can interpret and decode brain signals obtained through EEG (Electroencephalography) recordings, specifically focusing on error-related potentials (ErrPs). BCIs are innovative systems that allow direct communication and control between the human brain and external devices, such as computers or prosthetic limbs. EEG is a non-invasive technique that measures the electrical activity of the brain using electrodes placed on the scalp. It captures neural signals that represent various cognitive and motor processes. Error-related potentials (ErrPs) are specific brainwave patterns generated in response to the occurrence or anticipation of errors during cognitive tasks or feedback. They can be detected and extracted from EEG recordings and used as informative markers in BCI systems. ErrPs provide valuable insights into the user's cognitive processes, including error detection, error monitoring, and response correction. The decoding performance of a BCI system using EEG ErrPs is a crucial aspect of its effectiveness and usability. It involves the development and application of signal processing techniques, machine learning algorithms, and classification methods to accurately interpret the neural activity captured by EEG electrodes. To achieve high decoding performance, various steps are involved. These include signal preprocessing, artifact rejection, feature extraction, and selection, as well as spatial and temporal filtering techniques. Additionally, machine learning algorithms are employed to train the system to classify and interpret the extracted features. The choice of appropriate classification algorithms plays a significant role in determining the system's accuracy and real-time performance. Improving BCI decoding performance using EEG ErrPs has wide-ranging applications. It can facilitate advancements in neurofeedback, allowing individuals to enhance their cognitive control and self-regulation. BCIs using ErrPs have potential therapeutic applications in neurorehabilitation for individuals with neurological disorders or motor impairments. They can also enable assistive technology for individuals with limited motor control, providing alternative means of communication and control. Overall, the study and enhancement of BCI decoding performance using EEG ErrPs contribute to the development of more robust and reliable brain-machine interfaces, paving the way for improved human-computer interaction and the integration of neural interfaces into various fields of research and everyday life. Brain-Computer Interface (BCI) technology is poised to have a profound impact on people with severe communication and control disabilities due to locked-in syndrome (LIS). The patients suffering from LIS are paralyzed with no voluntary control over their motor movement and speech, despite intact cognition . The LIS can result from a variety of clinical conditions, including stroke, Spinal Cord Injury (SCI), motor neuron disease, most notably Amyotrophic Lateral Sclerosis (ALS), etc. BCI systems bypass the natural communication pathway between the brain and peripheral nervous system and provide an alternative pathway for communication and control. Thus, the BCI system decodes the neuronal signatures from the acquired brain signals and then translates the decoded output to control an external device.