visual-evoked-potential-recordings-mice-using-dry-non-invasive-multi

Visual Evoked Potential Recordings in Mice Using a Dry Non-invasive Multi-channel Scalp EEG Sensor

For scalp EEG research environments with laboratory mice, we designed a dry-type 16 channel EEG sensor which is non-invasive, deformable, and re-usable ...

Gwangju Institute of Science and Technology (GIST)

Light scattering in biological tissue significantly limits the accessible depth for localized optical interrogation and deep-tissue optical imaging. This challenge can be overcome by exploiting the time-reversal property of optical phase conjugation (OPC) to reverse multiple scattering events or suppress turbidity. However, in living tissue, scatterers are highly movable and the movement can disrupt time-reversal symmetry when there is a latency in the OPC playback. In this paper, we show that the motion-induced degradation of the OPC turbidity-suppression effect through a dynamic scattering medium shares the same decorrelation time constant as that determined from speckle intensity autocorrelation - a popular conventional measure of scatterer movement. We investigated this decorrelation characteristic time through a 1.5-mm-thick dorsal skin flap of a living mouse and found that it ranges from 50 ms to 2.5 s depending on the level of immobilization. This study provides information on relevant time scales for applying OPC to living tissues.

Relation between speckle decorrelation and optical phase conjugation (OPC)-based turbidity suppression through dynamic scattering media: a study on in vivo mouse skin.

Measurement of bioluminescent or fluorescent optical reporters with an implanted fiber-optic probe is a promising approach to allow real-time monitoring of molecular and cellular processes in conscious behaving animals. Technically, this approach relies on sensitive light detection due to the relatively limited light signal and inherent light attenuation in scattering tissue. In this paper, we show that specific geometries of lensed fiber probes improve photon collection in turbid tissue such as brain. By employing Monte Carlo simulation and experimental measurement, we demonstrate that hemispherical- and axicon-shaped lensed fibers increase collection efficiency by up to 2-fold when compared with conventional bare fiber. Additionally we provide theoretical evidence that axicon lenses with specific angles improve photon collection over a wider axial range while conserving lateral collection when compared to hemispherical lensed fiber. These findings could guide the development of a minimally-invasive highly sensitive fiber optic-based light signal monitoring technique and may have broad implications such as fiber-based detection used in diffuse optical spectroscopy.

Lensed fiber-optic probe design for efficient photon collection in scattering media.

Although computational studies of electrical brain stimulation (EBS) have received attention as a cost-effective tool, few studies have validated the technique, particularly in invasive cortical stimulation.

Validation of Computational Studies for Electrical Brain Stimulation With Phantom Head Experiments.

A new authentication method employing a laser and a scanner is proposed to improve image contrast of the finger vein and to extract blood flow pattern for liveness detection. A micromirror reflects a laser beam and performs a uniform raster scan. Transmissive vein images were obtained, and compared with those of an LED. Blood flow patterns were also obtained based on speckle images in perfusion and occlusion. Curvature ratios of the finger vein and blood flow intensities were found to be nearly constant, regardless of the vein size, which validated the high repeatability of this scheme for identity authentication with anti-spoofing.

Imaging of the Finger Vein and Blood Flow for Anti-Spoofing Authentication Using a Laser and a MEMS Scanner.

Dry eye syndrome is one of the most common ocular diseases, and meibomian gland dysfunction (MGD) is the leading cause of evaporative dry eye syndrome. When the tear film lipid layer becomes thin due to obstructive or hyposecretory meibomian gland dysfunction, the excessive evaporation of the aqueous layer can occur, and this causes evaporative dry eye syndrome. Thus, measuring the lipid layer thickness (LLT) is essential for accurate diagnosis and proper treatment of evaporative dry eye syndrome.

Article	Year
Relation between speckle decorrelation and optical phase conjugation (OPC)-based turbidity suppression through dynamic scattering media: a study on in vivo mouse skin. Biomedical optics express\| PubMed ID: 25657876	2015
Lensed fiber-optic probe design for efficient photon collection in scattering media. Biomedical optics express\| PubMed ID: 25657886	2015
Validation of Computational Studies for Electrical Brain Stimulation With Phantom Head Experiments. Brain stimulation\| PubMed ID: 26209594	2015
Imaging of the Finger Vein and Blood Flow for Anti-Spoofing Authentication Using a Laser and a MEMS Scanner. Sensors (Basel, Switzerland)\| PubMed ID: 28441728	2017
Image-based quantitative analysis of tear film lipid layer thickness for meibomian gland evaluation. Biomedical engineering online\| PubMed ID: 29169367	2017

Euiheon Chung

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