David Boas

• PhD
• Professor (Full) at Boston University

Significance Neuroscience of the everyday world requires continuous mobile brain imaging in real time and in ecologically valid environments, which aids in directly translating research for human benefit. Combined functional near-infrared spectroscopy (fNIRS) and electroencephalography (EEG) studies have increased in demand, as the combined systems...

Capillary stalling has emerged as an important mechanistic and potential therapeutic target in mouse models of several neurological disorders. Time-series optical coherence tomography angiography (OCTA) has been used to rapidly detect capillary stalling over hundreds of capillaries in 3D and can be used to study this phenomenon in a research settin...

INTRODUCTION Disturbances in microvascular flow dynamics are hypothesized to precede the symptomatic phase of Alzheimer's disease (AD). However, evidence in presymptomatic AD remains elusive, underscoring the need for therapies targeting these early vascular changes. METHODS We employed a multimodal approach, combining in vivo optical imaging, mol...

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 30mm channel spacing are widely used but have limited spatial resolution. High-density (HD) arrays with overlapping, multi-distan...

Cerebral blood flow (CBF) dysregulation is correlated with pathologies including ischemic stroke and Alzheimer's disease. Portable real-time CBF monitoring, with spatial specificity, would aid neuroscience research and clinical decision-making. Recently, speckle contrast optical spectroscopy (SCOS) enabled non-invasive human CBF measurement, demons...

Previous research suggests that book reading and screen time have contrasting effects on language and brain development. However, few studies have explicitly investigated whether children's brains function differently during these two activities. The present study used functional near‐infrared spectroscopy (fNIRS) to measure brain response in 28 ty...

Functional near-infrared spectroscopy (fNIRS) is an increasingly popular neuroimaging technique that measures cortical hemodynamic activity in a non-invasive and portable fashion. Although the fNIRS community has been successful in disseminating open-source processing tools and a standard file format (SNIRF), reproducible research and sharing of fN...

A major challenge in neuroscience is visualizing the structure of the human brain at different scales. Traditional histology reveals micro- and meso-scale brain features but suffers from staining variability, tissue damage, and distortion, which impedes accurate 3D reconstructions. The emerging label-free serial sectioning optical coherence tomogra...

Functional Near-Infrared Spectroscopy (fNIRS) holds transformative potential for research and clinical applications in neuroscience due to its non-invasive nature and adaptability to real-world settings. However, despite its promise, fNIRS signal quality is sensitive to individual differences in biophysical factors such as hair and skin characteris...

Stem cell grafting can promote glial repair of adult stroke injuries during the subacute wound healing phase, but graft survival and glial repair outcomes are perturbed by lesion severity and mode of injury. To better understand how stroke lesion environments alter the functions of cell grafts, we employed optical coherence tomography (OCT) to long...

Functional near-infrared spectroscopy (fNIRS) technology has been steadily advancing since the first measurements of human brain activity over 30 years ago. Initially, efforts were focused on increasing the channel count of fNIRS systems and then to moving from sparse to high density arrays of sources and detectors, enhancing spatial resolution thr...

Accurate sensor placement is vital for non-invasive brain imaging, particularly for functional near-infrared spectroscopy (fNIRS) and diffuse optical tomography (DOT), which lack standardized layouts such as those in electroencephalography (EEG). Custom, manually prepared probe layouts on textile caps are often imprecise and labor intensive. We int...

INTRODUCTION Disturbances in microvascular flow dynamics are hypothesized to precede the symptomatic phase of Alzheimer’s disease (AD). However, evidence in presymptomatic AD remains elusive, underscoring the need for therapies targeting these early vascular changes. METHODS We employed a multimodal approach, combining in vivo optical imaging, mol...

Continuous and non-invasive blood pressure (BP) monitoring has the potential to greatly improve hypertension diagnosis and management, along with enabling valuable personal health monitoring in the population at large. Existing methods rely on cuff-based sphygmomanometers, which are cumbersome and disrupt sleep. Despite extensive research utilizing...

Significance Widefield microscopy of the entire dorsal part of mouse cerebral cortex enables large-scale (“mesoscopic”) imaging of different aspects of neuronal activity with spectrally compatible fluorescent indicators as well as hemodynamics via oxy- and deoxyhemoglobin absorption. Versatile and cost-effective imaging systems are needed for large...

Speckle contrast optical spectroscopy (SCOS) is an emerging camera-based technique that can measure human cerebral blood flow (CBF) with high signal-to-noise ratio (SNR). At low photon flux levels typically encountered in human CBF measurements, camera noise and nonidealities could significantly impact SCOS measurement SNR and accuracy. Thus, a gui...

Background: Little is known about how the brains of autistic children process language during real-world “social contexts,” despite the fact that challenges with language, communication, and social interaction are core features of Autism Spectrum Disorder (ASD). Methods: We investigated the neural bases of language processing during social and non-...

Significance: Accurate sensor placement is vital for non-invasive brain imaging, particularly for functional near infrared spectroscopy (fNIRS) and diffuse optical tomography (DOT), which lack standardized layouts like EEG. Custom, manually prepared probe layouts on textile caps are often imprecise and labor-intensive. Aim: We introduce a method fo...

A major challenge in neuroscience is to visualize the structure of the human brain at different scales. Traditional histology reveals micro- and meso-scale brain features, but suffers from staining variability, tissue damage and distortion that impedes accurate 3D reconstructions. Here, we present a new 3D imaging framework that combines serial sec...

Significance The non-invasive measurement of cerebral blood flow based on diffuse optical techniques has seen increased interest as a research tool for cerebral perfusion monitoring in critical care and functional brain imaging. Diffuse correlation spectroscopy (DCS) and speckle contrast optical spectroscopy (SCOS) are two such techniques that meas...

When analyzing complex scenes, humans often focus their attention on an object at a particular spatial location. The ability to decode the attended spatial location would facilitate brain computer interfaces for complex scene analysis (CSA). Here, we investigated capability of functional near-infrared spectroscopy (fNIRS) to decode audio-visual spa...

Dynamic light scattering (DLS) and laser speckle contrast imaging (LSCI) are closely related techniques that exploit the statistics of speckle patterns, which can be utilized to measure cerebral blood flow (CBF). Conventionally, the temporal speckle intensity auto-correlation function $g_2^t(\tau )$ is calculated in DLS, while the spatial speckle c...

We present a microlens array-based laser speckle contrast imaging (mla-LSCI) system with multi-point illumination and wide field detection, which will give us a map of slow tissue dynamics across the mice cortex.

We have developed the fiber-based speckle contrast optical spectroscopy (SCOS) system to measure human cerebral blood flow (CBF) and brain functions, and demonstrated that SCOS outperforms traditional diffuse correlation spectroscopy (DCS) systems.

We show the repeatability of the functional connectivity default mode and dorsal attention networks in 15 human subjects measured with whole head functional near infrared spectroscopy.

By characterizing longitudinal changes in microvascular flow disruptions post-stroke, we investigate the significance of capillary stalling in recoverable peri-infarct tissues in connection to long-term outcome with the potential for therapeutics.

By comparing two prominent imaging modalities to study cerebral microvasculature, we aim to identify the advantages and limitations of each modality to study capillary stalling dynamics.

Background Alzheimer’s disease (AD) shares many risk factors with cardiovascular diseases, and much evidence shows that AD involves a cerebrovascular component. AD patients display disturbances in brain hemodynamics characterized by decreased cerebral blood flow (CBF) during steady‐state conditions. It has been suggested that capillary stalls heavi...

Objective Functional near-infrared spectroscopy (fNIRS) is a non-invasive functional neuroimaging method that takes advantage of the optical properties of hemoglobin to provide an indirect measure of brain activation via task-related relative changes in oxygenated hemoglobin (HbO). Its advantage over fMRI is that fNIRS is portable and can be used w...

Significance: Widefield microscopy of the entire dorsal part of mouse cerebral cortex enables large-scale (mesoscopic) imaging of neuronal activity with fluorescent indicators as well as hemodynamics via oxy- and deoxyhemoglobin absorption. Versatile and cost-effective imaging systems are needed for large-scale, color-multiplexed imaging of multipl...

The study of aging and neurodegenerative processes in the human brain requires a comprehensive understanding of cytoarchitectonic, myeloarchitectonic, and vascular structures. Recent computational advances have enabled volumetric reconstruction of the human brain using thousands of stained slices, however, tissue distortions and loss resulting from...

The combination of polarization-sensitive optical coherence tomography (PS-OCT) and birefringence microscopy (BRM) enables multiscale assessment of myelinated axons in postmortem brain tissue, and these tools are promising for the study of brain connectivity and organization. We demonstrate label-free imaging of myelin structure across the mesoscop...

Laser speckle contrast imaging (LSCI) is a rapidly developing technology broadly applied for the full-field characterization of tissue perfusion. Over the recent years, significant advancements have been made in interpreting LSCI measurements and improving the technique’s accuracy. On the other hand, the method’s precision has yet to be studied in...

Objective Functional near-infrared spectroscopy (fNIRS) is a non-invasive functional neuroimaging method that indirectly measures cortical activation via task-related changes in oxygenated hemoglobin (HbO). We used fNIRS during a working memory task to assess learning effect over time by assessing brain activity (fNIRS signal) and task performance....

We introduce an ultrasound speckle decorrelation-based time-lagged functional ultrasound technique (tl-fUS) for the quantification of the relative changes in cerebral blood flow speed (rCBF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">speed</sub> ), cerebral blood volume (rCBV) and cerebral blood fl...

Significance Brief disruptions in capillary flow, commonly referred to as capillary “stalling,” have gained interest recently for their potential role in disrupting cerebral blood flow and oxygen delivery. Approaches to studying this phenomenon have been hindered by limited volumetric imaging rates and cumbersome manual analysis. The ability to pre...

Laser speckle contrast imaging (LSCI) measures 2D maps of cerebral blood flow (CBF) in small animal brains such as mice. The contrast measured in LSCI also includes the static and slow-varying components that contain information about brain tissue dynamics. But these components are less studied as compared to the fast dynamics of CBF. In traditiona...

Cerebral blood flow (CBF) is crucial for brain health. Speckle contrast optical spectroscopy (SCOS) is a technique that has been recently developed to measure CBF, but the use of SCOS to measure human brain function at large source-detector separations with comparable or greater sensitivity to cerebral rather than extracerebral blood flow has not b...

Previous studies suggest that producing and comprehending semantically related words relies on inhibitory control over competitive lexical selection which results in the recruitment of the left inferior frontal gyrus (IFG). Few studies, however, have examined the involvement of other regions of the frontal cortex, such as the dorsolateral prefronta...

Significance: The accurate large-scale mapping of cerebral microvascular blood flow velocity is crucial for a better understanding of cerebral blood flow (CBF) regulation. Although optical imaging techniques enable both high-resolution microvascular angiography and fast absolute CBF velocity measurements in the mouse cortex, they usually require d...

While two-photon fluorescence microscopy is a powerful platform for the study of functional dynamics in living cells and tissues, the bulk motion inherent to these applications causes distortions. We have designed a motion tracking module based on spectral domain optical coherence tomography which compliments a laser scanning two-photon microscope...

Functional Near-Infrared Spectroscopy (fNIRS) is a non-invasive optical technique that measures cerebral hemodynamics across multiple regions of interest, and thereby characterises brain functional activation. Since its first description in 1993, fNIRS has undergone substantial developments in hardware, analysis techniques, and applications. Thirty...

High-speed laser scanning microscopes are essential for monitoring fast biological phenomena. However, existing strategies that achieve millisecond time resolution with two-photon microscopes (2PMs) are generally technically challenging and suffer from compromises among imaging field of view, excitation efficiency, and depth penetration in thick ti...

Background Normal brain function depends on the ability of the vasculature to increase blood flow to regions with high metabolic demands. Impaired neurovascular coupling, such as the local hyperemic response to neuronal activity, may contribute to poor neurological outcome after stroke despite successful recanalization, that is, futile recanalizati...

In age-related neurodegenerative diseases, pathology often develops slowly across the lifespan. As one example, in diseases such as Alzheimer's, vascular decline is believed to onset decades ahead of symptomology. However, challenges inherent in current microscopic methods make longitudinal tracking of such vascular decline difficult. Here, we desc...

The study of neurodegenerative processes in the human brain requires a comprehensive understanding of cytoarchitectonic, myeloarchitectonic, and vascular structures. Recent computational advances have enabled volumetric reconstruction of the human brain using thousands of stained slices, however, tissue distortions and loss resulting from standard...

Significance: Short-separation (SS) regression and diffuse optical tomography (DOT) image reconstruction, two widely adopted methods in functional near-infrared spectroscopy (fNIRS), were demonstrated to individually facilitate the separation of brain activation and physiological signals, with further improvement using both sequentially. We hypoth...

Cerebral blood flow (CBF) is an important indicator of brain health and function. Diffuse correlation spectroscopy (DCS) is an optical technique that enables non-invasive and continuous bedside monitoring of human CBF. However, traditional DCS consisting of a few channels has relatively low signal-to-noise ratio (SNR), preventing measurements at lo...

Non-invasive continuous blood pressure monitoring remains elusive. There has been extensive research using the photoplethysmographic (PPG) waveform for blood pressure estimation, but improvements in accuracy are still needed before clinical use. Here we explored the use of an emerging technique, speckle contrast optical spectroscopy (SCOS), for blo...

Functional neuroimaging, which measures hemodynamic responses to brain activity, has great potential for monitoring recovery in stroke patients and guiding rehabilitation during recovery. However, hemodynamic responses after stroke are almost always altered relative to responses in healthy subjects and it is still unclear if these alterations refle...

Whole-brain irradiation (WBI, also known as whole-brain radiation therapy) is a mainstay treatment modality for patients with multiple brain metastases. It is also used as a prophylactic treatment for microscopic tumors that cannot be detected by magnetic resonance imaging. WBI induces a progressive cognitive decline in ~ 50% of the patients surviv...

Functional near-infrared spectroscopy (fNIRS) is an increasingly popular neuroimaging technique that measures cortical hemodynamic activity in a non-invasive and portable fashion. Although the fNIRS community has been successful in disseminating several open-source processing tools and a standard file format (SNIRF), the development of reproducible...

We developed interferometric dynamic laser speckle imaging (iDLSI) capable of three-dimensional volumetric measurements of the blood flow. Here, we present the numerical and analytical model for g 2,iDLSI (τ) and perform preliminary measurement in the mouse brain.

Bessel beam two-photon microscopy has revealed shorter stalling events than previously measured. Even these brief disruptions in flow can result in hypoxia.

We have developed a camera characterization protocol to estimate the camera parameters needed for estimation of fundamental speckle contrast in photon-starved speckle contrast optical spectroscopy (SCOS) systems.

We present a short-separation speckle contrast optical spectroscopy (ss-SCOS) system to enhance the static and slow tissue components with the multi-exposure time-based speckle contrast model to extract both the slow tissue and fast blood flow dynamics.

NinjaNIRS seeks to provide an open-source ecosystem to increase adoption of functional near-infrared spectroscopy (fNIRS) with integrated EEG in the real world. Co-location and high module count enables high-density, whole-head coverage of both modalities.

We have developed the fiber-based speckle contrast optical spectroscopy (SCOS) system to measure human cerebral blood flow (CBF) and brain functions, and demonstrated that SCOS outperforms traditional diffuse correlation spectroscopy (DCS) systems.

We have developed the fiber-based speckle contrast optical spectroscopy (SCOS) system to measure human cerebral blood flow (CBF) and brain functions, and demonstrated that SCOS outperforms traditional diffuse correlation spectroscopy (DCS) systems.

Disruptions in capillary flow have the potential to drive pathology across numerous diseases. But our understanding of the temporal and spatial dynamics of these events are hindered by slow volumetric imaging rates and the reliance on laborious manual analysis to process data. To address the challenges of increasing volumetric imaging speed, we use...

Two photon microscopy and optical coherence tomography (OCT) are two standard methods for measuring flow speeds of red blood cells in microvessels, particularly in animal models. However, traditional two photon microscopy lacks the depth of field to adequately capture the full volumetric complexity of the cerebral microvasculature and OCT lacks the...

Significance: Functional near-infrared spectroscopy (fNIRS) is a popular neuroimaging technique with proliferating hardware platforms, analysis approaches, and software tools. There has not been a standardized file format for storing fNIRS data, which has hindered the sharing of data as well as the adoption and development of software tools. Aim:...

We introduce a dynamic speckle model (DSM) to simulate the temporal evolution of fully developed speckle patterns arising from the interference of scattered light reemitted from dynamic tissue. Using this numerical tool, the performance of laser speckle contrast imaging (LSCI) or speckle contrast optical spectroscopy (SCOS) systems which quantify t...

The cerebral cortex is organized in cortical layers that differ in their cellular density, composition, and wiring. Cortical laminar architecture is also readily revealed by staining for cytochrome oxidase—the last enzyme in the respiratory electron transport chain located in the inner mitochondrial membrane. It has been hypothesized that a high-de...

Strategies to image biological phenomena at millisecond time scales are generally technically challenging and suffer from compromises between imaging field-of-view, depth penetration and excitation efficiency in thick tissue. We present a simple and cost-effective solution that enables a conventional video-rate two-photon microscope (2PM) to perfor...

Significance Advances in electronics have allowed the recent development of compact, high channel count time domain functional near-infrared spectroscopy (TD-fNIRS) systems. Temporal moment analysis has been proposed for increased brain sensitivity due to the depth selectivity of higher order temporal moments. We propose a general linear model (GLM...

Short-separation regression (SS) and diffuse optical tomography (DOT) image reconstruction, two widely adopted methods in functional near-infrared spectroscopy (fNIRS), have been demonstrated to individually facilitate the separation of brain activation and physiological signals, with further improvement by using both sequentially. Motivated by the...

Two photon microscopy and optical coherence tomography (OCT) are two standard methods for measuring flow speeds of red blood cells in microvessels, particularly in animal models. However, traditional two photon microscopy lacks the depth of field to adequately capture the full volumetric complexity of the cerebral microvasculature and OCT lacks the...

When analyzing complex scenes, humans often focus their attention on an object at a particular spatial location. The ability to decode the attended spatial location would facilitate brain computer interfaces for complex scene analysis. Here, we investigated functional near-infrared spectroscopy's (fNIRS) capability to decode audio-visual spatial at...

This report is the second part of a comprehensive two-part series aimed at reviewing an extensive and diverse toolkit of novel methods to explore brain health and function. While the first report focused on neurophotonic tools mostly applicable to animal studies, here, we highlight optical spectroscopy and imaging methods relevant to noninvasive hu...

Background. Despite recanalization after ischemic stroke, neurovascular coupling, i.e., the local hyperaemic response to neuronal activity, is impaired in peri-ischemic brain regions. Such reduction in neurovascular coupling may contribute to neurological deterioration over time. The mechanism underlying dysfunctional neurovascular coupling followi...

Significance Functional near-infrared spectroscopy (fNIRS) is a noninvasive technique for measuring hemodynamic changes in the human cortex related to neural function. Due to its potential for miniaturization and relatively low cost, fNIRS has been proposed for applications, such as brain–computer interfaces (BCIs). The relatively large magnitude o...

Background Subcortical white matter lesions are exceedingly common in cerebral small vessel disease and lead to significant cumulative disability without an available treatment. Here, we tested a rho-kinase inhibitor on functional recovery after focal white matter injury. Methods A focal corpus callosum lesion was induced by stereotactic injection...

Objective: Serial sectioning optical coherence tomography (OCT) enables distortion-free volumetric reconstruction of several cubic centimeters of human brain samples. We aimed to identify anatomical features of the ex vivo human brain, such as intraparenchymal blood vessels and axonal fiber bundles, from the OCT data in 3D, using intrinsic optical...