TY - JOUR T1 - Power spectrum analysis on the multiparameter electroencephalogram features of physiological mental fatigue. JF - Sheng Wu Yi Xue Gong Cheng Xue Za Zhi Y1 - 2009 A1 - Zhang, Ai-hua A1 - Zheng, Shi Dong A1 - Pei, Xiao-Mei A1 - Ouyang, Yi KW - Adult KW - Electroencephalography KW - Entropy KW - Humans KW - Male KW - Mental Fatigue KW - Signal Processing, Computer-Assisted KW - Young Adult AB -

The aim of this experiment is to find a feasible impersonal index for analyzing the physiological mental fatigue level. Three characteristic parameters, relative power in different rhythm, barycenter frequency and power spectral entropy, are extracted from two channels' electroencephalogram (EEG) under two physiological mental fatigue states. Then relationships between such three parameters and physiological mental fatigue are analyzed to explore whether they can be of use for detecting (or monitoring) the mental fatigue level. The experiment results show that the relative power, barycenter frequency and power spectral entropy of EEG exhibit strong correlation with physiological mental fatigue level. While physiological mental fatigue level increases, the relative power in theta, alpha and beta rhythms, barycenter frequency and power spectral entropy of EEG decrease, but the relative power in delta rhythm of EEG increases. The relative power in four rhythms, barycenter frequency and power spectral entropy of EEG reflect the change of physiological mental fatigue level sensitively, and may hopefully be used as indexes for detecting physiological mental fatigue level.

VL - 26 UR - http://www.ncbi.nlm.nih.gov/pubmed/19334577 IS - 1 ER - TY - JOUR T1 - Towards an independent brain-computer interface using steady state visual evoked potentials. JF - Clin Neurophysiol Y1 - 2008 A1 - Brendan Z. Allison A1 - Dennis J. McFarland A1 - Gerwin Schalk A1 - Zheng, Shi Dong A1 - Moore-Jackson, Melody A1 - Jonathan Wolpaw KW - Adolescent KW - Adult KW - Attention KW - Brain KW - Brain Mapping KW - Dose-Response Relationship, Radiation KW - Electroencephalography KW - Evoked Potentials, Visual KW - Female KW - Humans KW - Male KW - Pattern Recognition, Visual KW - Photic Stimulation KW - Spectrum Analysis KW - User-Computer Interface AB -

OBJECTIVE: 

Brain-computer interface (BCI) systems using steady state visual evoked potentials (SSVEPs) have allowed healthy subjects to communicate. However, these systems may not work in severely disabled users because they may depend on gaze shifting. This study evaluates the hypothesis that overlapping stimuli can evoke changes in SSVEP activity sufficient to control a BCI. This would provide evidence that SSVEP BCIs could be used without shifting gaze.

METHODS: 

Subjects viewed a display containing two images that each oscillated at a different frequency. Different conditions used overlapping or non-overlapping images to explore dependence on gaze function. Subjects were asked to direct attention to one or the other of these images during each of 12 one-minute runs.

RESULTS: 

Half of the subjects produced differences in SSVEP activity elicited by overlapping stimuli that could support BCI control. In all remaining users, differences did exist at corresponding frequencies but were not strong enough to allow effective control.

CONCLUSIONS: 

The data demonstrate that SSVEP differences sufficient for BCI control may be elicited by selective attention to one of two overlapping stimuli. Thus, some SSVEP-based BCI approaches may not depend on gaze control. The nature and extent of any BCI's dependence on muscle activity is a function of many factors, including the display, task, environment, and user.

SIGNIFICANCE: 

SSVEP BCIs might function in severely disabled users unable to reliably control gaze. Further research with these users is necessary to explore the optimal parameters of such a system and validate online performance in a home environment.

VL - 119 UR - http://www.ncbi.nlm.nih.gov/pubmed/18077208 IS - 2 ER -