Use of high-frequency visual stimuli above the critical flicker frequency in a SSVEP-based BMI

Sakurada, Takeshi; Kawase, Toshihiro; Komatsu, Tomoaki; Kansaku, Kenji

doi:10.1016/j.clinph.2014.12.010

Cited by 77 publications

(82 citation statements)

References 42 publications

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“…To reduce mental workload, the spelling rate can be adjusted by increasing the stimulation duration and the gaze switching time. In addition, more comfortable stimulation parameters [e.g., high-frequency stimulation above 40 Hz (20)] can be used to reduce visual fatigue. Fig.…”

Section: Discussionmentioning

confidence: 99%

High-speed spelling with a noninvasive brain–computer interface

Chen

Wang

Nakanishi

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

729

663

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The past 20 years have witnessed unprecedented progress in braincomputer interfaces (BCIs). However, low communication rates remain key obstacles to BCI-based communication in humans. This study presents an electroencephalogram-based BCI speller that can achieve information transfer rates (ITRs) up to 5.32 bits per second, the highest ITRs reported in BCI spellers using either noninvasive or invasive methods. Based on extremely high consistency of frequency and phase observed between visual flickering signals and the elicited single-trial steady-state visual evoked potentials, this study developed a synchronous modulation and demodulation paradigm to implement the speller. Specifically, this study proposed a new joint frequency-phase modulation method to tag 40 characters with 0.5-s-long flickering signals and developed a user-specific target identification algorithm using individual calibration data. The speller achieved high ITRs in online spelling tasks. This study demonstrates that BCIs can provide a truly naturalistic high-speed communication channel using noninvasively recorded brain activities.brain-computer interface | electroencephalogram | steady-state visual evoked potentials | joint frequency-phase modulation B rain-computer interfaces (BCIs), which can provide a new communication channel to humans, have received increasing attention in recent years (1, 2). Among various applications, BCI spellers (3-9) are especially valuable because they can help patients with severe motor disabilities (e.g., amyotrophic lateral sclerosis, stroke, and spinal cord injury) communicate with other people. Currently, electroencephalogram (EEG) is the most popular method of implementing BCI spellers due to its noninvasiveness, simple operation, and relatively low cost. However, low signal-to-noise ratio (SNR) of the scalp-recorded EEG signals and lack of computationally efficient solutions in EEG modeling limit the information transfer rates (ITRs) of EEGbased BCI spellers to ∼1.0 bits per second (bps) (1, 4). For example, the well-known P300 speller proposed by Farwell and Donchin (5) can spell up to five letters per minute (∼0.5 bps). Until recently few studies using visual evoked potentials (VEPs) demonstrated higher ITRs of 1.7-2.4 bps (6, 7). In contrast, the invasive BCI spellers in humans and monkeys show higher performance. For example, the P300 speller with electrocorticogram recordings obtained a peak ITR of 1.9 bps in a human subject (8). A recent monkey study on keyboard neural prosthesis using multineuron recordings reported an ITR up to 3.5 bps (9). Although communication speed of the EEG-based spellers has been significantly improved in the past decade (4), it still remains a key obstacle to real-life applications in humans.Recently, the BCI speller using steady-state VEPs (SSVEPs) has attracted increasing attention due to its high communication rate and little user training (4, 10, 11). An SSVEP speller typically uses SSVEPs to detect the user's gaze direction to a target character (10). Although the SSVE...

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Section: Discussionmentioning

confidence: 99%

High-speed spelling with a noninvasive brain–computer interface

Chen

Wang

Nakanishi

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

729

663

View full text Add to dashboard Cite

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“…This constitutes a severe limitation of the long-term application of SSVEP-BCIs. To alleviate visual strain, substantial efforts have been devoted towards the development of covert attention-based BCIs [5,10–12], high-frequency SSVEP BCIs [13,14,7,10,15], and hybrid SSVEP BCIs integrating other visual BCIs paradigms [16,17]. Nevertheless, the reported systems were either associated with a limited number of BCI commands or showed relatively low information transfer rates.…”

Section: Introductionmentioning

confidence: 99%

Application of a single-flicker online SSVEP BCI for spatial navigation

et al. 2017

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A promising approach for brain-computer interfaces (BCIs) employs the steady-state visual evoked potential (SSVEP) for extracting control information. Main advantages of these SSVEP BCIs are a simple and low-cost setup, little effort to adjust the system parameters to the user and comparatively high information transfer rates (ITR). However, traditional frequency-coded SSVEP BCIs require the user to gaze directly at the selected flicker stimulus, which is liable to cause fatigue or even photic epileptic seizures. The spatially coded SSVEP BCI we present in this article addresses this issue. It uses a single flicker stimulus that appears always in the extrafoveal field of view, yet it allows the user to control four control channels. We demonstrate the embedding of this novel SSVEP stimulation paradigm in the user interface of an online BCI for navigating a 2-dimensional computer game. Offline analysis of the training data reveals an average classification accuracy of 96.9±1.64%, corresponding to an information transfer rate of 30.1±1.8 bits/min. In online mode, the average classification accuracy reached 87.9±11.4%, which resulted in an ITR of 23.8±6.75 bits/min. We did not observe a strong relation between a subject’s offline and online performance. Analysis of the online performance over time shows that users can reliably control the new BCI paradigm with stable performance over at least 30 minutes of continuous operation.

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“…Additionally, it has been shown that low frequency flicker is more perceptible and more irritating for the user (Lin et al, 2012). Stimulation with higher frequencies reduces discomfort (Sakurada et al, 2015) but decreases BCI performance and increases the rate of BCI illiteracy (Volosyak et al, 2011). These studies indicate that, in order to enhance the usability of SSVEP-based BCIs the traditionally used stimuli should be improved.…”

Section: Introductionmentioning

confidence: 99%

Tradeoff between User Experience and BCI Classification Accuracy with Frequency Modulated Steady-State Visual Evoked Potentials

Dreyer

Herrmann

Rieger

2017

Front. Hum. Neurosci.

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Steady-state visual evoked potentials (SSVEPs) have been widely employed for the control of brain-computer interfaces (BCIs) because they are very robust, lead to high performance, and allow for a high number of commands. However, such flickering stimuli often also cause user discomfort and fatigue, especially when several light sources are used simultaneously. Different variations of SSVEP driving signals have been proposed to increase user comfort. Here, we investigate the suitability of frequency modulation of a high frequency carrier for SSVEP-BCIs. We compared BCI performance and user experience between frequency modulated (FM) and traditional sinusoidal (SIN) SSVEPs in an offline classification paradigm with four independently flickering light-emitting diodes which were overtly attended (fixated). While classification performance was slightly reduced with the FM stimuli, the user comfort was significantly increased. Comparing the SSVEPs for covert attention to the stimuli (without fixation) was not possible, as no reliable SSVEPs were evoked. Our results reveal that several, simultaneously flickering, light emitting diodes can be used to generate FM-SSVEPs with different frequencies and the resulting occipital electroencephalography (EEG) signals can be classified with high accuracy. While the performance we report could be further improved with adjusted stimuli and algorithms, we argue that the increased comfort is an important result and suggest the use of FM stimuli for future SSVEP-BCI applications.

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Use of high-frequency visual stimuli above the critical flicker frequency in a SSVEP-based BMI

Cited by 77 publications

References 42 publications

High-speed spelling with a noninvasive brain–computer interface

High-speed spelling with a noninvasive brain–computer interface

Application of a single-flicker online SSVEP BCI for spatial navigation

Tradeoff between User Experience and BCI Classification Accuracy with Frequency Modulated Steady-State Visual Evoked Potentials

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