Regulation And Control Of Brain Alertness Via Flash Stimulation Of The Visual Channel

Visual channels represent one of the main process through which the brain perceives its external environment.As such,flash stimulus offers a unique and powerful method with which the brain and cognitive function can be explored.With ongoing developments in neural engineering,recent years have brought about new technologies such as the regulation of brain state which are promising avenues for minimizing the dangerous effects of mental fatigue,i.e.the decrease in alertness upon performing extended and demanding mental tasks.The work described herein explores the effect of brain resonance on physical factors,with the primary goal being the regulation and control of brain vigilance through the use of flash stimulus.The regulation of SSVEP that responded to the flash stimulus with one target and two targets with different phases were explored,which provided the theoretical guide to the selection of the best flash stimulus parameter.At the same time,The effects of flash stimulus on the brain vigilance,on the basis of the establishment of mental fatigue load model and the application of flash stimulus of continuous beta frequency,were researched.The brain rhythms changed following with flash stimulus according to frequency following response.And the whole set of experiment parameters which included the subjective evaluation,the experiment task operation,EEG and ECG characteristics,were detected and analyzed to prove the feasibility of the control of the brain vigilance.The main content of this thesis contained the following aspects:1)Four kinds of flash stimulus modes that were two eyes gazing at same target and two eyes gazing at two targets with different phases were performed.The time domain amplitude and SSVEP response were contrasted and analyzed.The regulation of SSVEP that responded to different stimulus frequencies and phase differences were explored.The experimental results showed that the beta band frequency owned better SSVEP response,which could be a method applying in improving alertness,and the highest SSVEP amplitude appeared when the eyes gazed the same target.2)We designed the flash stimulus as a method of a visual physical stimulus.Compared to flash stimulus in a single beta frequency,continuous beta-band frequency could induce better brain resonance effect.Beta frequency flash stimulus was applied to subjects when brain vigilance has been reduced by N-back task.The analysis results of EEG and ECG signals relating to alertness showed that beta band energy increased in most of the electrodes after the flash stimulus and the Lempel-Ziv complexity increased in many electrodes,however,the value of these parameters after N-back task were just the opposite.After flash stimulus,the RR interval decreased,meanwhile the ratio of the low frequency and high frequency of the heart rate variability and Lyapunov index increased.Further,the use of a continuous beta-band frequency for the stimulus was found to effectively regulate and enhance the EEG fast wave rhythm,activate the cerebral cortex,and promote brain arousal levels.These findings therefore act as a proof of principle for controlling brain vigilance with visual stimulus and will continue to be explored in greater detail.