High-density multidistance fNIRS enhances detection of brain activity during a word-color Stroop task.

Significance: Functional near-infrared spectroscopy (fNIRS) enables neuroimaging in scenarios where other modalities are less suitable, such as during motion tasks or in low-resource environments. Sparse fNIRS arrays with 30 mm channel spacing are widely used but have limited spatial resolution. High-density (HD) arrays with overlapping, multidistance channels improve sensitivity and localization but increase costs and setup times.

Quantifying the impact of hair and skin characteristics on fNIRS signal quality for enhanced inclusivity.

Functional near-infrared spectroscopy (fNIRS) is a promising neuroimaging method owing to its non-invasive nature and adaptability to real-world settings. However, fNIRS signal quality is sensitive to individual differences in biophysical factors such as hair and skin characteristics, which can considerably impact the absorption and scattering of near-infrared light. If not properly addressed, these factors risk biasing fNIRS research by disproportionately affecting signal quality across diverse populations.

Imaging myelin degradation in ex vivo prefrontal cortex tissue blocks in Alzheimer's disease and chronic traumatic encephalopathy.

Introduction: Alzheimer's disease (AD) and chronic traumatic encephalopathy (CTE) are tauopathies with gray matter (GM) myelin changes that are challenging to assess with standard imaging. New methods are needed to quantify myelin integrity in autopsy brain tissues.

Methods: We used polarization-sensitive optical coherence tomography (PS-OCT) to measure bulk tissue relative retardance and birefringence microscopy for high-resolution imaging of myelin degradation.

Validation of the Linearity in Image Reconstruction Methods for Speckle Contrast Optical Tomography.

Speckle contrast optical spectroscopy (SCOS) is an optical technique capable of measuring human cerebral blood flow and brain function non-invasively. Its tomographic extension, speckle contrast optical tomography (SCOT), can provide blood flow variation maps with measurements using overlapping source-detector channel pairs. Linearity is often assumed in most image reconstruction methods, but non-linearity could exist in the relations between measured signals and blood flow variations.

Speckle contrast optical spectroscopy for cuffless blood pressure estimation based on microvascular blood flow and volume oscillations.

This work introduces high-speed (390 Hz) speckle contrast optical spectroscopy (SCOS) to enable simultaneous measurements of multi-anatomic site microvascular blood volume and flow oscillations. Simultaneous blood flow and volume waveforms were extracted at two wavelengths on the wrist and finger, in reflectance and transmission mode, respectively. Blood volume changes (also known as photoplethysmography, or PPG) were determined based on intensity oscillations.