Portable Drowsiness Detection through Use of a Prefrontal Single-Channel Electroencephalogram.

Mikito Ogino,Yasue Mitsukura

doi:10.3390/s18124477

Abstract

Drowsiness detection has been studied in the context of evaluating products, assessing driver alertness, and managing office environments. Drowsiness level can be readily detected through measurement of human brain activity. The electroencephalogram (EEG), a device whose application relies on adhering electrodes to the scalp, is the primary method used to monitor brain activity. The many electrodes and wires required to perform an EEG place considerable constraints on the movement of users, and the cost of the device limits its availability. For these reasons, conventional EEG devices are not used in practical studies and businesses. Many potential practical applications could benefit from the development of a wire-free, low-priced device; however, it remains to be elucidated whether portable EEG devices can be used to estimate human drowsiness levels and applied within practical research settings and businesses. In this study, we outline the development of a drowsiness detection system that makes use of a low-priced, prefrontal single-channel EEG device and evaluate its performance in an offline analysis and a practical experiment. Firstly, for the development of the system, we compared three feature extraction methods: power spectral density (PSD), autoregressive (AR) modeling, and multiscale entropy (MSE) for detecting characteristics of an EEG. In order to efficiently select a meaningful PSD, we utilized step-wise linear discriminant analysis (SWLDA). Time-averaging and robust-scaling were used to fit the data for pattern recognition. Pattern recognition was performed by a support vector machine (SVM) with a radial basis function (RBF) kernel. The optimal hyperparameters for the SVM were selected by the grind search method so as to increase drowsiness detection accuracy. To evaluate the performance of the detections, we calculated classification accuracy using the SVM through 10-fold cross-validation. Our model achieved a classification accuracy of 72.7% using the PSD with SWLDA and the SVM. Secondly, we conducted a practical study using the system and evaluated its performance in a practical situation. There was a significant difference (* p < 0.05) between the drowsiness-evoked task and concentration-needed task. Our results demonstrate the efficacy of our low-priced portable drowsiness detection system in quantifying drowsy states. We anticipate that our system will be useful to practical studies with aims as diverse as measurement of classroom mental engagement, evaluation of movies, and office environment evaluation.

Highlights

Researchers have tried to identify human mental states, such as drowsiness, stress, and concentration, by electroencephalogram (EEG) [1,2]
power spectral density (PSD) (Theta, Alpha) resulted in an area under the curve (AUC) of 0.643. They were greater than those produced by AR, which resulted in an AUC of 0.593, as well as multiscale entropy (MSE), which had an AUC of 0.600
In order to score each package of recorded data, we averaged the 30 drowsiness level samples and transformed them into a drowsiness probability, which was 1.00 when all outputs of the four samples were one and 0.00 when all outputs were zero

Summary

Introduction

Researchers have tried to identify human mental states, such as drowsiness, stress, and concentration, by electroencephalogram (EEG) [1,2]. By using multichannel EEG devices, information-rich high-quality data can be obtained and a high accuracy of drowsiness detection can be attained. Such devices are difficult to attach to the scalp of users, and application of the gel required for usage of the electrodes is time-consuming. The EEG signal detected from the limited locations can be further used for the detection of prefrontal brain activity related to human experiences such as emotion [9,10,11] Despite these advantages, the restrictions imposed by our method make drowsiness detection more difficult in comparison with other studies that use single-channel

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