Abstract
Most existing brain-computer interfaces (BCIs) detect specific mental activity in a so-called synchronous paradigm. Unlike synchronous systems which are operational at specific system-defined periods, self-paced (asynchronous) interfaces have the advantage of being operational at all times. The low-frequency asynchronous switch design (LF-ASD) is a 2-state self-paced BCI that detects the presence of a specific finger movement in the ongoing EEG. Recent evaluations of the 2-state LF-ASD show an average true positive rate of 41% at the fixed false positive rate of 1%. This paper proposes two designs for a 3-state self-paced BCI that is capable of handling idle brain state. The two proposed designs aim at detecting right- and left-hand extensions from the ongoing EEG. They are formed of two consecutive detectors. The first detects the presence of a right- or a left-hand movement and the second classifies the detected movement as a right or a left one. In an offline analysis of the EEG data collected from four able-bodied individuals, the 3-state brain-computer interface shows a comparable performance with a 2-state system and significant performance improvement if used as a 2-state BCI, that is, in detecting the presence of a right- or a left-hand movement (regardless of the type of movement). It has an average true positive rate of 37.5% and 42.8% (at false positives rate of 1%) in detecting right- and left-hand extensions, respectively, in the context of a 3-state self-paced BCI and average detection rate of 58.1% (at false positive rate of 1%) in the context of a 2-state self-paced BCI.
Highlights
Brain-computer interface (BCI) systems form a possible alternative communication and control solutions for individuals with severe disabilities
As we are interested in low false positive rates, we do not report the performance of the system for higher false positive rates
For subject 2, the mean true positive rate of DET1-power spectral density (PSD)-linear discriminant analysis (LDA) is more than 15% higher than that of DET1-PSD-1NN with significance level of P < .03 using “paired t-test”
Summary
Brain-computer interface (BCI) systems form a possible alternative communication and control solutions for individuals with severe disabilities. In BCI systems, the user’s cortical activity associated with an intentional control of a device (such as attempted finger movements) is directly mapped to an applicationspecific control signal. This allows the user to control various devices such as a neural prosthetic by cognitive processes only, that is, by bypassing traditional interface pathways (which cannot be used by individuals with severe disabilities). Between periods of intentional control (IC), users are said to be in a no-control (NC) state; they may be idle, daydreaming, thinking about a problem or lunch, or performing any other action other than trying to control the BCI transducer. NC support is necessary for most types of machine or device interactions where
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