The effects of letter matrix and inter stimulus interval on P300 Event Related Potential

Abstract

According to the General Statistics Office (Ministry of Planning and investment) collaborated with the United Nations Children’s Fund in Viet Nam, from 2016 to 2017, there were nearly 5 million households which had disabilities in the country. The proportion of people with disabilities who were over 2 years old accounted for 7% of the population. Another statistic is based on the Christopher & Dana Reeve Foundation report in 2013, about 5.4 million Americans suffer from disability [2]. Many research works, therefore, have been built with the aim of improving the ability of movement and communication, based on biomedical signals, especially the Brain-Computer Interface (BCI) system. BCI is a technology that enables the use of the brain’s neural activity to communicate with others or to control machines, artificial limbs, or robots without direct physical movements. BCI based on electroencephalogram (EEG) can be applied to the disabled individual system. In recent years, there are many people suffering from the loss of all voluntary muscle control in Viet Nam. Therefore, they really need alternative interaction methods to control their behaviors with external environment. Thanks to the development of Brain-Computer interfaces and the EEG headset have been helping people who are incapable of any motion for function can communicate with the external world, due to the P300 signal. As the important consideration to discover which factors affect the accuracy of BCI system to improve communication quality for the ability of disabled people, we decide to discover the impact of character matrix size and inter stimulus interval on event related potential. The duration of the inter stimulus interval (ISI) between targets is set at 187,5 ms and 125 ms for two different matrix sizes 3x3 and 6x6. The results provide that the largest amplitudes of P300 waveforms occur remarkably at the occipital and frontal channels and are higher than in 6x6 letter matrix compared with 3x3 matrix. The different matrix size and ISI does not affect on the appearance time of the P300 signal, and it is in the range 235-244 ms after stimulation. These good results promise to help other researches to build a perfect experimental procedure in real assistance application for using BCI – P300 systems.