Utilizing Functional near-infrared spectroscopy (fNIRS) to investigate spontaneous hemodynamic activity in the motor cortex The figure below shows the results from a finger-tapping experiment that is performed in order to activate the motor cortex. Hemodynamic activity is increased in the motor cortex region during the finger tapping and the activity gradually decreases as it moves away from the motor cortex.
Optical Imaging for Diagnosis of Autism Spectrum Disorder
Functional near-infrared spectroscopy (fNIRS) was used to investigate spontaneous hemodynamic activity in the temporal cortex for typically developing (TD) children and children with autism spectrum disorder (ASD). Forty-seven children participated in the experiments including twenty-five with ASD.
Compared with TD children, children with ASD showed weaker bilateral resting-state functional connectivity (RSFC), but much stronger fluctuation magnitude in terms of oxy-hemoglobin (HbO2) and deoxy-hemoglobin (Hb). Differentiating between ASD and TD based on a support vector machine (SVM) model including bilateral RSFC and the fluctuation power of HbO2 and Hb as variables could achieve high accurate classification with sensitivity of 81.6% and specificity of 94.6%. This study demonstrates optical brain imaging has the potential for screening children with risk of ASD.
Fig (Above): Schematic representation of the brain showing the location of each measurement channel.
Fig (Above): Correlation maps of HbO2 and Hb for TD and ASD children. Three seeds locating at the left superior (Ch4), middle (Ch6) and inferior (Ch8) gyrus were selected for generating correlation maps. The seed region can be visually recognized by the maximal color value in each map. The mapping area in each hemisphere was about 6 cm×6 cm.
Near-infrared diffuse correlation spectroscopy is used to record spontaneous cerebral blood flow fluctuations in the frontal cortex. Nine adult subjects participated in the experiments, in which 8-min spontaneous fluctuations were simultaneously recorded from the left and right dorsolateral and inferior frontal regions.
Resting-state functional connectivity was measured by the temporal correlation of the low frequency fluctuations. Our data shows the resting-state functional connectivity within the dorsolateral region is significantly stronger than that between the inferior and dorsolateral regions, in line with previous observations with functional near-infrared spectroscopy. This indicates that diffuse correlation spectroscopy is capable of investigating brain functional connectivity in terms of cerebral blood flow.
Fig (Above): (a) Locations of sources (red) and detectors (blue) in reference to the international EEG 10-20 system. The source-detector distance was 2.75 cm for S-DDLFC,1, S-DDLFC,2, S-DIFC and 1.0 cm for S-Ds. (b) An example of the placement of the probe on the subject. (c) The placement of each optode on the probe in (b).
Fig (Left): (a) Group average for inter-regional (0.32±0.32), (0.34±0.27) and intra-regional RSFC (0.64±0.25) on the left cortex. (b) Inter-regional (0.34±0.29), (0.34±0.26) and intra-regional RSFC (0.62±0.23) on the right cortex. The error bar is the standard deviation across all subjects. The z-test shows the difference between the intra- and inter-regional RSFC on both cortex is significant with P<0.0002, while there was no significant difference between the left and right cortex (z-test: P>0.8).