Near infrared spectroscopy(NIRS)is generally accepted as a functional brain imaging technology for brain activation study.With multichannel highly sensitive NIRS instruments,it has become possible to assess functional connectivity of different brain negions by NIRS.However,the feasibility needs to be validated in complex cognitive activities.In this study,we recorded the hemodynamic activity of the bilateral prefrontal cortex(PFC)during a color-word matching Stroop task.Wavelet transform coberence(WTC)analysis was applied to ascss the functional conectivity of all homologous channel pairs within the left/right PFC.Both the behavioral and brain activ ation results showed signifcant Stroop effects.The results of WTC analysis revealed that,bilateral functional connectivity was significantly stronger during both the incongruent stimuli and neutral stimuli compared to that of the rest period.It also showed significant Stroop effect.Our findings demonstrate that,NIRS bcomes a valuable tool to elucidate the functional conectivity of brain cortex in complex cognitive activities.
Combining photoacoustic（PA） imaging with laser speckle（LS） imaging（LSI） can simultaneously determine total hemoglobin concentration（HbT）,hemoglobin oxygen saturation（SO2）,and blood flow rates.Thus,the co-registration of PA and LS images is important in physiological studies and pathological diagnosis.This letter presents a co-registration algorithm combining mutual information with the maximum betweenclass variance segmentation method（Otsu method）.The mutual information and Otsu method are used to provide the registration measure criterion and image feature recognition,respectively.The evaluation results show that the registration function possesses a single maximum peak and high smoothness across the global co-registration district,indicating a robust behavior.Moreover,this method has good registration accuracy,and the fusion result simultaneously visualizes the separate functional information of two kinds of images.
