SignificanceKnee osteoarthritis (OA) is a disease that causes chronic pain in the elderly population. Currently, OA is mainly treated pharmacologically with analgesics, although research has shown that neuromodulation via transcranial direct current stimulation (tDCS) may be beneficial in reducing pain in clinical settings. However, no studies have reported the effects of home-based self-administered tDCS on functional brain networks in older adults with knee OA.AimWe used functional near-infrared spectroscopy (fNIRS) to investigate the functional connectivity effects of tDCS on underlying pain processing mechanisms at the central nervous level in older adults with knee OA.ApproachPain-related brain connectivity networks were extracted using fNIRS at baseline and for three consecutive weeks of treatment from 120 subjects randomly assigned to two groups undergoing active tDCS and sham tDCS.ResultsOur results showed that the tDCS intervention significantly modulated pain-related connectivity correlation only in the group receiving active treatment. We also found that only the active treatment group showed a significantly reduced number and strength of functional connections evoked during nociception in the prefrontal cortex, primary motor (M1), and primary somatosensory (S1) cortices. To our knowledge, this is the first study in which the effect of tDCS on pain-related connectivity networks is investigated using fNIRS.ConclusionsfNIRS-based functional connectivity can be effectively used to investigate neural circuits of pain at the cortical level in association with nonpharmacological, self-administered tDCS treatment.
KEYWORDS: Near infrared spectroscopy, Data acquisition, Standards development, Software development, Neuroimaging, Neurophotonics, Design and modelling, MATLAB, Data storage, Compliance
SignificanceFunctional 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.AimWe endeavored to design a file format to facilitate the analysis and sharing of fNIRS data that is flexible enough to meet the community’s needs and sufficiently defined to be implemented consistently across various hardware and software platforms.ApproachThe shared NIRS format (SNIRF) specification was developed in consultation with the academic and commercial fNIRS community and the Society for functional Near Infrared Spectroscopy.ResultsThe SNIRF specification defines a format for fNIRS data acquired using continuous wave, frequency domain, time domain, and diffuse correlation spectroscopy devices.ConclusionsWe present the SNIRF along with validation software and example datasets. Support for reading and writing SNIRF data has been implemented by major hardware and software platforms, and the format has found widespread use in the fNIRS community.
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 human brain studies. We outline current state-of-the-art technologies and software advances, explore the most recent impact of these technologies on neuroscience and clinical applications, identify the areas where innovation is needed, and provide an outlook for the future directions.
Significance: Deficits in sensorimotor function in persons with type II diabetes mellitus (PwDM) have traditionally been considered a result of peripheral nerve damage. Emerging evidence has suggested that factors outside of nerve damage due to type II diabetes mellitus, such as impaired hemodynamic function, contribute significantly to both sensory and motor deficits in PwDM.
Aim: The focus of the current study was to evaluate functional cortical hemodynamic activity during sensory and motor tasks in PwDM.
Approach: Functional near-infrared spectroscopy was used to monitor oxyhemoglobin (HbO) and deoxyhemoglobin (HbR) across the cortex during sensory and motor tasks involving the hands.
Results: Decline in HbO across sensory and motor regions of interest was found in PwDM with simultaneous deficits in manual motor tasks, providing the first evidence of functional cortical hemodynamic activity deficits relating to motor dysfunction in PwDM. Similar deficits were neither specifically noted in HbR nor during evaluation of sensory function. Health state indices, such as A1c, blood pressure, body mass index, and cholesterol, were found to clarify group effects.
Conclusions: Further work is needed to clarify potential sex-based differences in PwDM during motor tasks as well as the root of reduced cortical HbO indices but unchanged HbR indices in PwDM.
Significance: Knee osteoarthritis (OA) is a common joint disease causing chronic pain and functional alterations (stiffness and swelling) in the elderly population. OA is currently treated pharmacologically with analgesics, although neuromodulation via transcranial direct current stimulation (tDCS) has recently generated a growing interest as a safe side-effect free treatment alternative or a complement to medications for chronic pain conditions. Although a number of studies have shown that tDCS has a beneficial effect on behavioral measures of pain, the mechanistic action of neuromodulation on pain sensitivity and coping at the central nervous system is not well understood.
Aim: We aimed at observing longitudinal changes of cortical hemodynamics in older adults with knee OA associated with a two-week-long tDCS self-treatment protocol.
Approach: Hemodynamics was measured bilaterally in the motor and somatosensory cortices with functional near-infrared spectroscopy (fNIRS) in response to thermal pain induced ipsilaterally to the knee primarily affected by OA.
Results: We found that both oxyhemoglobin- and deoxyhemoglobin-related functional activations significantly increased during the course of the tDCS treatment, supporting the notion that tDCS yields an increased cortical excitability. Concurrently, clinical measures of pain decreased with tDCS treatment, hinting at a potential spatial dissociation between cortically mediated pain perception and suppression and the prevalence of neuromodulatory effects over cortical pain processing.
Conclusions: fNIRS is a valid method for objectively tracking pain in an ambulatory setting and it could potentially be used to inform strategies for optimized tDCS treatment and to develop innovative tDCS protocols.
During extra-vehicular activities (EVAs) or space walks astronauts over use their fingertips under pressure inside the
confined spaces of gloves/space-suite. The repetitive hand motion is a probable cause for discomfort and injuries to the
finger-tips. We describe a new wireless fiber-optic probe that can be integrated inside the astronaut glove for non-invasive
blood perfusion measurements in distal finger tips. In this preliminary study, we present blood perfusion
measurements while performing hand-grip exercises simulating the use of space tools.
We have developed a non-invasive diagnostic instrument based on a scanning fluorophotometer integrating autofluorescence and dynamic light scattering techniques. The device makes a scan along the optical axis of the eye. In a DLS measurement, it is extremely important to precisely define the position of the volume-under-test inside the eye and its effective volume. In this work, a specific optical computer aided design tool based on the Navarro's model of the human eye is used to simulate the optical path of the DLS laser beams and to calculate position and size of the volume-under-test.
Pigment dispersion syndrome and pigmentary glaucoma are
investigated by a scanning instrument based on dynamic light
scattering technique. The measurements are oriented to evaluate
the various conjectures about the pathogenesis of pigmentary
glaucoma and to establish a diagnostic tool that may be used for
an early detection of this type of glaucoma.
Dynamic light scattering (DLS) and autofluoresence (AF) are two promising optical diagnostic techniques for use in ophthalmology. In this paper the DLS and AF are integrated in one instrument and applied to study healthy and pathological ocular tissues to detect changes at the molecular level. Measurements performed on 17 patients (age range 20-80 years) are presented. Out of these, 7 patients were healthy normals, 10 had glaucoma and the two oldest patients had both glaucoma and cataracts.
A digital control unit for use with a new integrated instrument for dynamic light scattering and natural fluorescence measurements is presented. This unit, based on a microcontroller (Microchip PIC16F877), process signals from an optical head and controls instrument functions. The microcontroller internal counters are used to perform real- time photon counting measurement by processing the TTL signals obtained from the photodetectors. The new system provides reliable and simultaneous DLS and AF measurements from the same ocular volume located from the cornea to the retina.
Dynamic light scattering (DLS) and autofluorescence (AF) are non-invasive diagnostic techniques that can monitor changes at the molecular level in ocular tissues. In the present study, we demonstrate as simultaneous measurements of autofluorescence and dynamic light scattering on the corneal tissues can be performed using a novel specifically designed instrument. The integrated instrument takes advantage of the singular techniques by improving the measurement quality and the reliability of the diagnosis. Preliminary tests on volunteers show promise in relation to possible use in the clinical practice.
Over the past two decades, great efforts have been made in ophthalmology to use optical techniques based on dynamic light scattering and tissue natural fluorescence for early (at molecular level) diagnosis of ocular pathologies. In our previous studies, the relationship between the corneal AF and DLS decay widths of ocular tissues were established by performing measurements on diabetes mellitus patients. In those studies, corneal AF mean intensities were significantly correlated with DLS decay width measurements for each diabetic retinopathy grade in the vitreous and in the cornea. This suggested that the quality of the diagnosis could be significantly improved by properly combining these two powerful techniques into a single instrument. Our approach is based on modifying a commercial scanning ocular fluorometer (Fluorotron Master, Ocumetrics Inc., CA, USA) to include both techniques in the same scanning unit. This configuration provides both DLS and AF real time measurements from the same ocular volume: they can be located in each section of the optical axis of the eye from the cornea to the retina. In this paper, the optical setup of the new system is described and preliminary in-vitro and in-vivo measurements are presented.
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