Elementary Development Of An Optical-electric System For Detection Of Functional Brain Activities

As multimodal neuroimaging has been a hotspot in the modern cognitive neuroscience, more valuable information becomes available with the combination of different imaging techniques together. The electric signal of the neuroactivity can be measured by Electroencephalogram (EEG),and record the event-related potential (ERP) correlating with some special event. Near-infrared spectroscopy(NIRS)has been developed rapidly in recent years,whose temporal resolution can be up to several milliseconds for the detection of hemodynamic changes occurred on cerebral cortex. There will be a wide application combining the two technologis.In this paper,the basic principle of EEG and NIRS was introduced and also an optical-electric system for detection of functional brain activities has been designed elementarily,base on the former NIR system in our laboratory. To the hardware,the amplification and filter circuit of the weak EEG signal,the NIRS light source and its drive circuit,and the detector were application specific integrated circuits (ASIC) products. The electrode was in the center of the probe,which was so flexible that was easy to belt on and made good attachment to skin. A type of DAQ (PCI6259) was in charge of time sequence arrangement of light sources and triple-channel signals collection,which sampling rate was 400 Hz. There was some improvement to the former NIR system software. The whole structure used multithreaded method,rejecting the timer controlling of the former system. It made the threads of sampling,calculating and plotting execute at the same time so that the signal collection and the real time display of the change of EEG wave,HbO2,Hb and Blood volume could be realized.By means of performance test and model experiment,the system property and accuracy of measurement was validated. The in-vivo experiment was in virtue of collection of EEG signal under calm condition and Cuff experiment. Through the observation and analysis the change of the curve,we could demonstrate the feasibility of in-vivo measurement.