On Stroop Effect In Prefrontal Cortex With FNIRS/ERP Multimode Imaging

The research of cognition soared with the advent of modern functional brain imaging techniques. At the present time, most of the researchers use single mode imaging techniques to obtain information of changes in metabolism (hemoglobin) or neuronal activities. However, as the understanding of the brain function progresses, the multimode imaging techniques which combine the advantages of single mode imaging techniques are becoming focus of this field. With the multimode method, researchers get access to the information of changes in metabolism (hemoglobin) and neuronal activities simultaneously, which makes the research of neuron-vascular coupling feasible. In this paper, fNIRS/ERP(Near-infrared Spectroscopy, NIRS; Event-Related Potential, ERP)multimode imaging technique was employed to study the Stroop effect in the prefrontal cortex. And with the synchronal information of hemoglobin and neuron, the mechanism of neuron-vascular coupling was discussed.The home-made fNIRS circuit was combined with the commercial EEG recording system to form the fNIRS/ERP multimode imaging system. And the fNIRS measurement and the ERP recording were synchronized by software control.Due to the different characteristics of the two imaging techniques, an improved experiment paradigm of Stroop was designed, which not only conform with the fNIRS technique which measures slow signals but also the EEG/ERP recording technique which measures relatively quick signals. The VisualC++6.0 and Presentation were adopted to program the experiment procedure for fNIRS measurement and EEG/ERP recording respectively. The program presents the task according to the paradigm, meanwhile records the behavior data of the experiment.Two beforehand experiments which used a home-developed fNIRS imager and the commercial EEG/ERP recording system the same as the one in the multimode imaging system were conducted. According to the behavior and measurement results of 11 subjects in the experiments, the paradigm designed in this paper activated prominent Stroop effect in the prefrontal cortex, and the optimal area for the multimode imaging system to measure is in the left of the midline of prefrontal head.After the correctness of the paradigm and the optimal detecting area were confirmed, the fNIRS/ERP multimode imaging experiment was operated. The synchronal result of changes of hemoglobin and neuronal potential shows that the changes in the quantity of oxyhemoglobin and deoxyhemoglobin relate to the changes of potential on the scalp in time. And the former is 100~200ms lagged of the later.