title: Estimating the intended sound direction of the user: toward an auditory brain-computer interface using out-of-head sound localization.
abstract: The auditory Brain-Computer Interface (BCI) using electroencephalograms (EEG) is a subject of intensive study. As a cue, auditory BCIs can deal with many of the characteristics of stimuli such as tone, pitch, and voices. Spatial information on auditory stimuli also provides useful information for a BCI. However, in a portable system, virtual auditory stimuli have to be presented spatially through earphones or headphones, instead of loudspeakers. We investigated the possibility of an auditory BCI using the out-of-head sound localization technique, which enables us to present virtual auditory stimuli to users from any direction, through earphones. The feasibility of a BCI using this technique was evaluated in an EEG oddball experiment and offline analysis. A virtual auditory stimulus was presented to the subject from one of six directions. Using a support vector machine, we were able to classify whether the subject attended the direction of a presented stimulus from EEG signals. The mean accuracy across subjects was 70.0% in the single-trial classification. When we used trial-averaged EEG signals as inputs to the classifier, the mean accuracy across seven subjects reached 89.5% (for 10-trial averaging). Further analysis showed that the P300 event-related potential responses from 200 to 500 ms in central and posterior regions of the brain contributed to the classification. In comparison with the results obtained from a loudspeaker experiment, we confirmed that stimulus presentation by out-of-head sound localization achieved similar event-related potential responses and classification performances. These results suggest that out-of-head sound localization enables us to provide a high-performance and loudspeaker-less portable BCI system.
authors: Nagaoka University of Technology, Nagaoka, Niigata, Japan.
authors: Isao
authors: I
authors: Nambu
authors: Masashi
authors: M
authors: Ebisawa
authors: Masumi
authors: M
authors: Kogure
authors: Shohei
authors: S
authors: Yano
authors: Haruhide
authors: H
authors: Hokari
authors: Yasuhiro
authors: Y
authors: Wada
mesh_terms: D000161:Acoustic Stimulation; D001921:Brain / Q000502:physiology*; D062207:Brain-Computer Interfaces; D003463:Cues; D004569:Electroencephalography; D018913:Event-Related Potentials, P300 / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D013017:Sound Localization / Q000502:physiology*; D060388:Support Vector Machine; D055815:Young Adult