Decoding P300 evoked potentials for Brain Computer Interfaces (BCI) aimed at assisting potential end-users at home

Abstract

A Brain Computer Interface (BCI) is a communication system that provides an alternative channel to natural communication and control processes since it bypasses the body's normal efferent pathways, which are the neuromuscular output channels. Hence, a BCI system monitors brain activity and translates specific signal features, which reflect the user's intent, into commands that operate a device. BCIs are especially interesting for severely impaired individuals that cannot perform physical movements. Conventional augmentative and alternative communication technologies require some form of muscle control and thus may not be useful for those with the most severe motor disabilities, such as late-stage amyotrophic lateral sclerosis (ALS), brainstem stroke or severe cerebral palsy. This Thesis proposes the use of P300 evoked potentials as signal control in BCI systems for end-users, i.e. severely impaired people. Selective attention to a specific and infrequent flashing symbol evokes a brain pattern called P300, which appears around the central and parietal brain cortex, about 300 ms after the stimulus presentation. A novel assistive BCI tool for environment control at home is researched. The proposed application is based on P300 evoked responses to infrequent stimuli, known as the 'oddball' paradigm. P300-based BCIs could be the most proper type of BCIs for severely disabled populations since it does not require training period. Furthermore, its typical paradigm allows to select in a fast manner the desired symbol among a large number of choices only by focusing on it. The methodology proposed in this work is focused on the real end-users. Thus, the design, the experiments and the assessment are centred on the potential end-users' needs. A population of 30 potential BCI end-users, people with severe impairments due to different pathologies and degree of both motor and cognitive disabilities, took part in the study. Participants were recruited through the Spanish National Reference Centre on Disability and Dependence (León, Spain). The main needs identified for the population under study were related to three main categories: comfort, communication and security. Hence, the proposed assistive BCI tool was designed to cover them. Specifically, it enables to manage 8 devices, usually present at home, by means of 115