Research progress of asynchronous brain-computer interfaces based on alpha control technology / 国际生物医学工程杂志

Brain-computerinterface(BCI) is a kind of direct channel for information communication and control established between the human brain and computer or other electronic equipment.BCI is a novel information communication system which does not depend on the conventional brain information pathways.The asynchronous brain-computer interface technology is based on alpha wave control,and can automatically switch system mode between working and idle and select the larger EEG signal associated with motion imagination.In this paper,the basic knowledge of BCI and alpha wave-based asynchronous BCI technology were introduced.The key technology and application prospect of the novel alpha wave-based asynchronous BCI technology were summarized,and the status and existing problems were analyzed.

The Meaning of P50 Suppression: Interaction of Gamma and Alpha Waves

OBJECTIVES: Sensory gating dysfunctions in patients with schizophrenia and bipolar disorder have been investigated through two similar methods ; P50 suppression and prepulse inhibition paradigms. However, recent studies have demonstrated that the two measures are not correlated but rather constitute as distinct neural processes. Recent studies adopting spectral frequency analysis suggest that P50 suppression reflects the interaction between gamma and other frequency bands. The aim of the present study is to investigate which frequency component shows more significant interaction with gamma band. METHODS: A total of 108 mood disorder patients and 36 normal subjects were included in the study. The P50 responses to conditioning and test stimuli with an intra-pair interval of 500 msec were measured in the study population. According to P50 ratio (amplitude to the test stimulus/amplitude to the conditioning stimulus), the subjects with P50 ratio less than 0.2 were defined as suppressed group (SG) ; non-suppressed group (NSG) consisted of P50 ratio more than 0.8. Thirty-five and 25 subjects were included in SG and NSG, respectively. Point-to-point correlation coefficients (PPCCs) of both groups were calculated between two time-windows : the first window (S1) was defined as the time-window of one hundred millisecond after the conditioning auditory stimulus and the second window (S2) was defined as the time-window of 100 msec after the test auditory stimulus. Spectral frequency analysis was performed to investigate which frequency band results in the difference of PPCC between SG and NSG. RESULTS: Significant reduction of PPCC between S1 and S2 was observed in the SG (Pearson's r = 0.24), compared to PPCC of the NSG (r = 0.58, p < 0.05). In spectral frequency analysis, gamma band showed "phase-reset" and similar responses after the two auditory stimuli in suppressed and non-suppressed group. However in the case of alpha band, comparison showed significantly low PPCC in SG (r = -0.14) compared to NSG (r = 0.36, p < 0.05). This may be reflecting "phase-out" of alpha band against gamma band at approximately 50 msecs after the test stimulus in the SG. CONCLUSIONS: Our study suggests that normal P50 suppression is caused by phase-out of alpha band against gamma band after the second auditory stimulus. Thus it is demonstrated that normal sensory gating process is constituted with attenuated alpha power, superimposed on consistent gamma response. Implications of preserved gamma and decreased alpha band in sensory gating function are discussed.

Effects of Theanine on the Release of Brain Alpha Wave in Adult Males

L-theanine Is an amino acid in green tea and has been known to decrease serotonin and increase norepinephrine in rat brains, and also reported to produce mental relaxation, lower blood pressure and improve learning ability in human beings. But, few studies on these effects for human beings have been conducted so far. This study was conducted to evaluate the effect of L-theanine on the release of brain alpha waves known to be related with mental relaxation and concentration. Twenty healthy male volunteers aged 18 to 30 years without any Physical and Psychological diseases were recruited through written advertisement. Alpha power values of EEG as a surrogate marker of mental relaxation and concentration were measured in frontal and occipital regions for 40 minutes after administration of four placebo or test tablets and 20 minute resting period. The same procedure crossed over at 7-day intervals. We analyzed average alpha power values in frontal and occipital regions at 10 minute intervals. Repeated ANOVA revealed that there were significant differences of occipital alpha power values between placebo and test groups with high anxiety (p0.05) . The results of this study suggest that L-theanine containing tablets promote the release of alpha waves related to mental relaxation and concentration in young adult males.

The Effects of L-theanine Containing Functional Beverage on Mental Relaxation and Fatigue Perception

BACKGROUND: L-theanine is one of the most popular amino acids in green tea and has been known to produce mental relaxation, lower blood pressure and improve learning ability in human beings. But, few studies on these effects for human beings have been conducted so far. This study was conducted to evaluate the effect of L-theanine containing functional beverage on mental relaxation and fatigue perception. METHODS: Twenty healthy volunteers aged 30 to 55 years those who has had persistent fatigue for more than 1 month without any specific disease were recruited through written advertisement. All the subjects gave their informed consent, and the study was approved by Institutional Review Board of St. Mary's Hospital. This study was performed in a randomized placebo controlled double blind cross over fashion. Pathologic fatigue due to disease state was screened through medical history, physical examination, laboratory tests and questionnaires. alpha to beta power value of EEG as a surrogate marker of mental relaxation was measured in frontal and occipital regions for an hour after administration of placebo or test (200 mg L-theanine) solutions and crossed over at 7-day intervals. We analyzed average alpha to beta power value of EEG in frontal and occipital regions at 10 minute intervals for each 5 minutes. The baseline and 7-day follow-up scores of fatigue severity scale (FSS) were also evaluated. RESULTS: Repeated ANOVA revealed that there were significant differences of frontal alpha to beta power value between placebo and test in high anxiety group (P0.05). Fatigue score was significantly decreased in test (P0.05) after 7-day administration of placebo or test solutions. The mean differences from baseline in placebo and test were 0.42, and 0.80, respectively. CONCLUSIONS:The results of this study suggest that L-theanine containing functional beverage should promote alpha to beta power value in relation to mental relaxation, and also have the effect of reducing the fatigue perception.

Research on control system of brain-computer interface based on the alpha waves in EEG / 医疗卫生装备

A system design of brain-computer interface based on the alpha waves in human electroencephalography(EEG) is presented in this paper.With the effects on the alpha wave amplitudes of human eye's open and close involved in,the selection control of four direction targets can be performed on a computer screen.The system speed and accuracy rate are investigated through the experiments involving 5 subjects.It is shown that the system is easy to operate and needs no complex learning and biofeedback training.The studying results provide a good technical foundation for the development of BCI control panel and the realization of the system integration.It has the potential application for clinical engineering and is valuable for further research.