Review on identity feature extraction methods based on electroencephalogram signals / 生物医学工程学杂志

Biometrics plays an important role in information society. As a new type of biometrics, electroencephalogram (EEG) signals have special advantages in terms of versatility, durability, and safety. At present, the researches on individual identification approaches based on EEG signals draw lots of attention. Identity feature extraction is an important step to achieve good identification performance. How to combine the characteristics of EEG data to better extract the difference information in EEG signals is a research hotspots in the field of identity identification based on EEG in recent years. This article reviewed the commonly used identity feature extraction methods based on EEG signals, including single-channel features, inter-channel features, deep learning methods and spatial filter-based feature extraction methods, etc. and explained the basic principles application methods and related achievements of various feature extraction methods. Finally, we summarized the current problems and forecast the development trend.

A sLORETA study for gaze-independent BCI speller.

EEG-based BCI (brain-computer-interface) speller, especially gaze-independent BCI speller, has become a hot topic in recent years. It provides direct spelling device by non-muscular method for people with severe motor impairments and with limited gaze movement. Brain needs to conduct both stimuli-driven and stimuli-related attention in fast presented BCI paradigms for such BCI speller applications. Few researchers studied the mechanism of brain response to such fast presented BCI applications. In this study, we compared the distribution of brain activation in visual, auditory, and audio-visual combined stimuli paradigms using sLORETA (standardized low-resolution brain electromagnetic tomography). Between groups comparisons showed the importance of visual and auditory stimuli in audio-visual combined paradigm. They both contribute to the activation of brain regions, with visual stimuli being the predominate stimuli. Visual stimuli related brain region was mainly located at parietal and occipital lobe, whereas response in frontal-temporal lobes might be caused by auditory stimuli. These regions played an important role in audio-visual bimodal paradigms. These new findings are important for future study of ERP speller as well as the mechanism of fast presented stimuli.

The effect of semantic congruence for visual-auditory bimodal stimuli.

It is commonly believed that brain has faster reaction speed and higher reaction accuracy on visual-auditory bimodal stimuli than single modal stimuli in current neuropsychological researches, while visual-auditory bimodal stimuli (VABS) do not show corresponding superiority in BCI system. This paper aims at investigating whether semantically congruent stimuli could also get better performance than semantically incongruent stimuli in Brain Computer Interface (BCI) system. Two VABS based paradigms (semantically congruent or incongruent) were conducted in this study. 10 healthy subjects participated in the experiment in order to compare the two paradigms. The results indicated that the higher Event-related potential (ERP) amplitude of semantic incongruent paradigm were observed both in target and non-target stimuli. Nevertheless, we didn't observe significant difference of classification accuracy between congruent and incongruent conditions. Most participants showed their preference on semantically congruent condition for less workload needed. This finding demonstrated that semantic congruency has positive effect on behavioral results (less workload) and insignificant effect on system efficiency.

The timing of theta phase synchronization accords with vigilant attention.

Vigilant attention plays an important role in some industries and everyday life. However, its mechanism relating to phase synchronization of cortical oscillations is still unknown, which hinders the development of predicting and preventing vigilant attentional deficit. This study utilized psychomotor vigilance test (PVT) to elicit vigilance decrement. High and low levels of vigilant attention were represented by short and long reaction time, respectively. Electroencephalogram (EEG) was collected and phase synchronization between prefrontal and parietal cortices was analyzed by using debiased weighted phase lag index (dWPLI). The result suggests that vigilant attention of high level has earlier timing of theta (4-8Hz) phase synchronization, compared with that of low level. We concluded that phase synchronization may relate closely with the variation of vigilant attention.

Research on EEG features of attended & unattended vigilance.

Vigilance refers to the brain alertness to objective things, including the concentration of attention and the capability to response emergencies. It is of great importance to study vigilance monitoring to avoid accidents caused by decrease of vigilance. In this study, traditional Mackworth Clock Test (MCT) was modified to induce decline of attended and unattended vigilance. We analyzed EEG features in different levels of attended vigilance and assessed unattended vigilance by amplitude of mismatch negative (MMN) which can be evoked by audio odd ball stimulations. The results show that with attended vigilance going down, power of theta and alpha bands of electroencephalogram (EEG) increases and Lempel-Ziv Complexities (LZC) show an undulated decline tendency. And with unattended vigilance going down, amplitude of MMN reduces significantly. This research has great reference value for the further vigilance study.

Bi-modal enhancement effect from combination of visual and auditory stimulus / 国际生物医学工程杂志

Objective To investigate the cognitive difference between uni-modal (V,A) and bi-modal (VA)target stimuli from both vision and audition,and then to study the neural mechanisms of bi-modal enhancement.Methods This experiment adopted a speeded target stimuli detection task, both behavioral and electroencephalographic responses to uni-modal and bi-modal target stimuli which were combined from visual and auditory target stimuli,were recorded from 14 normal subjects using a 64-channel EEG NeuroScan system.The differences of cognitive between uni-modal and bi-modal stimulus were tested from both behavioral (reaction time (RT) and error rate (ER)) and event-related potentials (ERPs) (P2 latency and amplitude,P3 latency and amplitude)data,and the correlation between behavioral and ERPs results were analyzed.Results As a result,the RT,ER and P3 latency has significant difference between uni-modal and bi-modal target stimuli.In addition,there were significant correlation between behavioral data and P3 latency,especially from the RT and P3 latency.Conclusion By comparing the difference between uni-modal and bi-modal from both behavioral and ERPs results,we could reached the conclusion that the neural mechanism of bi-modal target detection was predominant over that of vision and audition uni-modal target detection,the enhancement take place not only involved in early ERP components (such as P1 and N1),but engaged at the late ERP components (such as P2 and P3).