A Spelling Paradigm With an Added Red Dot Improved the P300 Speller System Performance.

Yan Wu,Zhaohua Lu,Qi Li,Weiwei Zhou

doi:10.3389/fninf.2020.589169

Yan Wu, Zhaohua Lu + Show 2 more

Open Access

https://doi.org/10.3389/fninf.2020.589169

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Abstract

The traditional P300 speller system uses the flashing row or column spelling paradigm. However, the classification accuracy and information transfer rate of the P300 speller are not adequate for real-world application. To improve the performance of the P300 speller, we devised a new spelling paradigm in which the flashing row or column of a virtual character matrix is covered by a translucent green circle with a red dot in either the upper or lower half (GC-RD spelling paradigm). We compared the event-related potential (ERP) waveforms with a control paradigm (GC spelling paradigm), in which the flashing row or column of a virtual character matrix was covered by a translucent green circle only. Our experimental results showed that the amplitude of P3a at the parietal area and P3b at the frontal–central–parietal areas evoked by the GC-RD paradigm were significantly greater than those induced by the GC paradigm. Higher classification accuracy and information transmission rates were also obtained in the GC-RD system. Our results indicated that the added red dots increased attention and visuospatial information, resulting in an amplitude increase in both P3a and P3b, thereby improving the performance of the P300 speller system.

Highlights

Brain–computer interface (BCI) systems allow people to communicate without using their muscles, which provides a direct communication pathway for patients with severe amyotrophic lateral sclerosis (ALS) and other locked-in syndromes (LIS) (Sellers and Donchin, 2006; Kubler and Birbaumer, 2008)
We proposed a new spelling paradigm to attract more attention from subjects and increase visuospatial information, in which the flashing row or column of a virtual character matrix was overlaid with a translucent green circle in which a red dot was positioned in either the upper or lower half (GC-RD spelling paradigm)
Positive deflections were clearly observed at the central area (C3, CZ, and C4), parietal area (P7, P3, PZ, P4, and P8), and occipital area (O1, OZ, and O2) in both paradigms, indicating the P300 potential event-related potential (ERP) component (Polich, 2007)

Summary

Introduction

Brain–computer interface (BCI) systems allow people to communicate without using their muscles, which provides a direct communication pathway for patients with severe amyotrophic lateral sclerosis (ALS) and other locked-in syndromes (LIS) (Sellers and Donchin, 2006; Kubler and Birbaumer, 2008). An ERP is a response of the brain to an external stimulus, which is generally used to implement a BCI system. The P300 is an ERP component generated from the observation of a rare or odd event and manifests as a positive waveform appearing around 300 ms after presentation of the stimulus (Bernat et al, 2001). In 1988, Farwell and Donchin described a BCI system, known as the P300 speller, which allows the patient to spell characters by detecting the P300 potential (Farwell and Donchin, 1988). When the row or column containing the target character is intensified, which has a one-sixth probability and constitutes a rare event, a P300 potential is elicited. The target character is determined by the row and the column that elicited a P300 potential.

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