Abstract
Background and ObjectiveRecently, a promising Brain-Computer Interface based on Steady-State Visual Evoked Potential (SSVEP-BCI) was proposed, which composed of two stimuli presented together in the center of the subject’s field of view, but at different depth planes (Depth-of-Field setup). Thus, users were easily able to select one of them by shifting their eye focus. However, in that work, EEG signals were collected through electrodes placed on occipital and parietal regions (hair-covered areas), which demanded a long preparation time. Also, that work used low-frequency stimuli, which can produce visual fatigue and increase the risk of photosensitive epileptic seizures. In order to improve the practicality and visual comfort, this work proposes a BCI based on Depth-of-Field using the high-frequency SSVEP response measured from below-the-hairline areas (behind-the-ears). MethodsTwo high-frequency stimuli (31 Hz and 32 Hz) were used in a Depth-of-Field setup to study the SSVEP response from behind-the-ears (TP9 and TP10). Multivariate Spectral F-test (MSFT) method was used to verify the elicited response. Afterwards, a BCI was proposed to command a mobile robot in a virtual reality environment. The commands were recognized through Temporally Local Multivariate Synchronization Index (TMSI) method. ResultsThe data analysis reveal that the focused stimuli elicit distinguishable SSVEP response when measured from hairless areas, in spite of the fact that the non-focused stimulus is also present in the field of view. Also, our BCI shows a satisfactory result, reaching average accuracy of 91.6% and Information Transfer Rate (ITR) of 5.3 bits/min. ConclusionThese findings contribute to the development of more safe and practical BCI.
Highlights
Biological signals are a key factor in development of nonconventional channels of communication between humans and machines
One of the most common Brain-Computer Interfaces (BCIs) paradigms is based on SteadyState Visual Evoked Potential (SSVEP), which is a brain response from visual cortex elicited by a periodic visual stimulation [5,6]
This study aims to answer three main questions: (1) Can high-frequency SSVEP measured from below-the-hairline areas be modulated by shifting eye focus? (2) Can the SSVEP measured from these hairless areas be suitable for BCI usage? (3) What is the system performance for online mode? The article follows with an explanation of the materials and methods used in this evaluation
Summary
Biological signals are a key factor in development of nonconventional channels of communication between humans and machines. In Electroencephalogram (EEG), this potential represents oscillatory components with the same stimulus frequency (and/or its harmonics) [7]. This response can be divided into three bands: low- (up to 12 Hz), medium- (12–30 Hz) and high-frequency ( ≥ 30 Hz) [7]. A promising Brain-Computer Interface based on Steady-State Visual Evoked Potential (SSVEP-BCI) was proposed, which composed of two stimuli presented together in the center of the subject’s field of view, but at different depth planes (Depth-of-Field setup). In order to improve the practicality and visual comfort, this work proposes a BCI based on Depth-of-Field using the high-frequency SSVEP response measured from below-the-hairline areas (behind-the-ears)
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