The Study Of Evaluation Method Of Brain Development And Degeneration Based On FNIRS Signal

Functional near infrared infrared spectroscopy(fNIRS)has developed rapidly as a noninvasive brain functional imaging tool in the field of brain science research.Studies have shown that the hemodynamic response of the brain changes with age.At present,there have been many research achievements of newborn brain development and brain function network connection based on fNIRS.However,there are few studies on the evaluation of the lifespan development from infants to the elderly.This paper based fNIRS technology to assess brain development and degradation from six important stages of brain development,including preterm infants,term infants,three-month infants,children,adults,and the elderly.Firstly,the fNIRS system is used to collect resting state data for six age groups.The near-infrared light intensity data was converted into oxy-hemoglobin(HbO)and deoxyhemoglobin(Hb)data using modified Lambert-Beer law.Select quality channels based on their waveform and spectrogram.For motion artifacts,the peak wavelet filter algorithm is proposed,which can effectively remove motion noise in the hemoglobin time series.Bandwidth filtering is used to extract low-frequency hemoglobin signals and remove physiological noise from the signals.The HbO and Hb signals in the three frequency bands of 0.01-0.05 Hz,0.05-0.1Hz,and 0.01-0.1Hz are got.Secondly,a phase sequence analysis method for HbO and Hb based on hemodynamic is proposed.Including two algorithms such as phase synchronization index and timevarying phase difference.After comparison,the Hilbert transform was selected to calculate the time-varying phase difference and phase coupling index of each channel in the three frequency bands.The calculation results are statistics by Watson-williams multi-sample test.The phase patterns in the three frequency bands appear to be biased to the in-phase in the neonatal stage,and gradually approach anti-phase with aging,but in the elderly stage,biased to in-phase.The phase coupling index increases with age in the three frequency bands,and reaches the maximum value in the childhood and adult stages,then decreases after entering the elderly stage.Divide the brain into the front cortex,left temporal cortex and right temporal cortex to study brain spatial differences.Using Spass two-way analysis of variance on the time-varying phase difference and phase coupling index,The results show that the two indicators are not different among different brain regions within the same age group.But in different brain regions,they show differences with the development of age.Finally,the time-delay entropy and the normalized characteristic entropy based on oxygen hemoglobin signal are proposed to analyze the near-infrared signal brain space complexity.According to the different brain regions covered by the near-infrared channel,the results are counted at the stage of brain development and the stage of brain degeneration respectively.Studies have shown that the brain space complexity of three-month infants is significantly higher than that of newborns.In the degenerative stage,the brain space complexity of the elderly is significantly lower than that of children and adults.This indicates that the complexity of near-infrared signals in brain space can be used as a biological marker to evaluate brain development and degenerationThe brain development assessment method based on fNIRS proposed in this article can be used to evaluate the development of preterm infants and the brain degeneration of the elderly.It is of great value for assessing the state of brain development in the lifespan.