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Towards development of a 3-state self-paced brain-computer interface.

Bashashati A, Ward RK, Birch GE - Comput Intell Neurosci (2007)

Bottom Line: They are formed of two consecutive detectors.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.

View Article: PubMed Central - PubMed

Affiliation: Electrical and Computer Engineering Department, University of British Columbia, Vancouver, BC, Canada V6T 1Z4. alibs@ece.ubc.ca

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.

No MeSH data available.


Screen contents for each of the right-hand (a) and left-hand 				(b) extension movement trials,  is the time of movement execution.
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fig2: Screen contents for each of the right-hand (a) and left-hand (b) extension movement trials, is the time of movement execution.

Mentions: Four able-bodied subjects participated in this study. All subjects were male (except subject 4), right-handed (except subject 4), 25–30 years old, and only subject 2 had prior BCI experience. Subjects were seated 150 cm in front of a computer monitor. The data were collected while the subjects were performing a cue-based (synchronized) task. At random intervals of 5.6–7 seconds (mean of 6.7 seconds), a target window was displayed on the subject's monitor. As shown in Figure 2, a box moved from the left side to the right side of the screen. When the box reached the target window, the subject attempted to activate the custom-made switch by extending his/her right- or left-hand. An arrow in the moving box, pointing to the left or the right showed the subject whether to move the right- or the left-hand. For each subject, an average of 150 trials for each movement was collected in two sessions carried in the same day.


Towards development of a 3-state self-paced brain-computer interface.

Bashashati A, Ward RK, Birch GE - Comput Intell Neurosci (2007)

Screen contents for each of the right-hand (a) and left-hand 				(b) extension movement trials,  is the time of movement execution.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2234253&req=5

fig2: Screen contents for each of the right-hand (a) and left-hand (b) extension movement trials, is the time of movement execution.
Mentions: Four able-bodied subjects participated in this study. All subjects were male (except subject 4), right-handed (except subject 4), 25–30 years old, and only subject 2 had prior BCI experience. Subjects were seated 150 cm in front of a computer monitor. The data were collected while the subjects were performing a cue-based (synchronized) task. At random intervals of 5.6–7 seconds (mean of 6.7 seconds), a target window was displayed on the subject's monitor. As shown in Figure 2, a box moved from the left side to the right side of the screen. When the box reached the target window, the subject attempted to activate the custom-made switch by extending his/her right- or left-hand. An arrow in the moving box, pointing to the left or the right showed the subject whether to move the right- or the left-hand. For each subject, an average of 150 trials for each movement was collected in two sessions carried in the same day.

Bottom Line: They are formed of two consecutive detectors.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.

View Article: PubMed Central - PubMed

Affiliation: Electrical and Computer Engineering Department, University of British Columbia, Vancouver, BC, Canada V6T 1Z4. alibs@ece.ubc.ca

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.

No MeSH data available.