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At least 199 records · Page 11Linked to original sources
PubMedDate not supplied

Optical imaging of the intrinsic signal as a measure of cortical plasticity in the mouse.

The responses of cells in the visual cortex to stimulation of the two eyes changes dramatically following a period of monocular visual deprivation (MD) during a critical period in early life. This phenomenon, referred to as ocular dominance (OD) plasticity, is a widespread model for understanding cortical plasticity. In this study, we designed stimulus patterns and quantification methods to analyze OD in the mouse visual cortex using optical imaging of intrinsic signals. Using periodically drifting bars restricted to the binocular portion of the visual field, we obtained cortical maps for both contralateral (C) and ipsilateral (I) eyes and computed OD maps as (C - I)/(C + I). We defined the OD index (ODI) for individual animals as the mean of the OD map. The ODI obtained from an imaging session of less than 30 min gives reliable measures of OD for both normal and monocularly deprived mice under Nembutal anesthesia. Surprisingly, urethane anesthesia, which yields excellent topographic maps, did not produce consistent OD findings. Normal Nembutal-anesthetized mice have positive ODI (0.22 +/- 0.01), confirming a contralateral bias in the binocular zone. For mice monocularly deprived during the critical period, the ODI of the cortex contralateral to the deprived eye shifted negatively towards the nondeprived, ipsilateral eye (ODI after 2-day MD: 0.12 +/- 0.02, 4-day: 0.03 +/- 0.03, and 6- to 7-day MD: -0.01 +/- 0.04). The ODI shift induced by 4-day MD appeared to be near maximal, consistent with previous findings using single-unit recordings. We have thus established optical imaging of intrinsic signals as a fast and reliable screening method to study OD plasticity in the mouse.

Animals↗
PubMed1994

Fabrication of patterned sensor arrays with aryl azides on a polymer-coated imaging optical fiber bundle.

Arrays of sensing regions are photodeposited on the distal tip of a single imaging optical fiber. First, the distal surface of the fiber is spin-coated with a thin film of poly(hydroxyethyl methacrylate). The fluorophor is then derivatized with a photoreactive group and subsequently immobilized in a finite area of the film by discrete illumination. Dye incorporation occurs only in the illuminated areas, creating distinct regions of analyte-sensitive fluorescent dye at the fiber's distal end. This paper describes both the chemistry and the manipulations required to make an optical microarray and demonstrates the technique with pH sensors. The fabrication of a four-sensor array is described along with performance data.

Azides↗
PubMedDate not supplied

Diffuse optical imaging of the whole head.

Near-Infrared Spectroscopy (NIRS) and diffuse optical imaging (DOI) are increasingly used to detect hemodynamic changes in the cerebral cortex induced by brain activity. Until recently, the small number of optodes in NIRS instruments has hampered measurement of optical signals from diverse brain regions. Our new DOI system has 32 detectors and 32 sources; by arranging them in a specific pattern, we can cover most of the adult head. With the increased number of optodes, we can collect optical data from prefrontal, sensorimotor, and visual cortices in both hemispheres simultaneously. We describe the system and report system characterization measurements on phantoms as well as on human subjects at rest and during visual, motor, and cognitive stimulation. Taking advantage of the system's larger number of sources and detectors, we explored the spatiotemporal patterns of physiological signals during rest. These physiological signals, arising from cardiac, respiratory, and blood-pressure modulations, interfere with measurement of the hemodynamic response to brain stimulation. Whole-head optical measurements, in addition to providing maps of multiple brain regions' responses to brain activation, will enable better understandings of the physiological signals, ultimately leading to better signal processing algorithms to distinguish physiological signal clutter from brain activation signals.

Adult↗
PubMed2000

Dynamics of capillary isoelectric focusing in the absence of fluid flow: high-resolution computer simulation and experimental validation with whole column optical imaging.

A 150-component, dynamic electrophoresis simulator was developed and applied to the description of capillary isoelectric focusing (CIEF) of amphoteric substances in quiescent solution. The simulator is shown to be capable of producing high-resolution pH 3-10 focusing data with 140 individual carrier ampholytes (20/pH unit) and at current densities that are used in CIEF, i.e., under conditions that were hitherto unaccessible by dynamic computer simulation. Having a focusing capillary of 5-cm length, the predicted focusing dynamics for amphoteric dyes obtained at a constant voltage of 1500 V (300 V/cm) are shown to qualitatively agree with data obtained by whole-column optical imaging. The simulation data provide detailed insight into the dynamics of the focusing process for the cases with the focusing column being sandwiched between 40 mM NaOH (catholyte) and 100 mM phosphoric acid (anolyte) or having the column ends only permeable for OH- and H+ at cathode and anode, respectively. Simulation data reveal that the number of sample boundaries migrating from the two ends of the column to the focusing positions is always equal to the number of sample components. The number of detectable migrating sample boundaries, however, can be lower. Whole-column optical imaging is demonstrated to be the method of choice for following the approach to equilibrium. With that detection format, transient sample peaks can be recognized and properly identified. This would also be possible with a scanning detector moving rapidly and repeatedly along the column but cannot be accomplished by a stationary detector placed at a specified location. The data presented demonstrate that the model together with imaging monitoring can be used to optimize the CIEF separation conditions.

Coloring Agents↗
PubMed2001

Temporal spatial differences observed by functional MRI and human intraoperative optical imaging.

Pre-operative functional magnetic resonance imaging (fMRI), cortical evoked potentials (EPs) and intraoperative optical imaging of intrinsic signals (iOIS) were employed to relate the temporal-spatial characteristics of sensorimotor responses in human brain. Peripheral somasthetic stimulation (2 s) was provided either by a 110 Hz finger vibrator or transcutaneous median nerve stimulation in eight patients undergoing neurosurgical procedures. Each technique provided unique spatial patterns and temporal response profiles. EPs and iOIS activities were observed over the surface of pre- and post-central gyri (at the level of the superior genu) with very similar spatial distributions. In contrast, fMRI spatial distributions depended upon the model used for statistical correlation analysis. Using a monophasic response model, fMRI primarily localized within the central sulcus and did not demonstrate large signal changes over the pre- and post-central gyri (areas with iOIS/EP activity). However, as initial negative responses were incorporated into the response model, fMRI progressively localized closer to the iOIS and somatosensory EP maps. Temporally, responses to single stimuli differed between the fMRI and iOIS techniques. Using a monophasic model for fMRI analysis, the total fMRI response was delayed by 2--3 s relative to iOIS. As initial negative responses were incorporated in the analysis, the fMRI time course developed temporal characteristics similar to iOIS. Ultimately, when fMRI time courses were examined over pixels co-localizing with iOIS activation (without using statistical correlation analysis), the fMRI temporal profile included an initial decrease in signal (an initial dip) that closely resembled the time course of iOIS response. This is the first study to experimentally co-localize (temporally and spatially) iOIS and fMRI signals in human subjects. The spatial/temporal differences in this study likely reflect the capillary versus venous contributions of iOIS and fMRI, respectively. The temporal/spatial co-localization of the iOIS signal and the fMRI initial dip suggests the initial fMRI dip and the iOIS signal may result from similar physiologic events.

Algorithms↗
PubMed2004

Visualization of intrathoracically disseminated solid tumors in mice with optical imaging by telomerase-specific amplification of a transferred green fluorescent protein gene.

Currently available methods for detection of tumors in vivo such as X-ray, computed tomography, and ultrasonography are noninvasive and have been well studied; the images, however, are not specific for tumors. Direct optical imaging of tumor cells in vivo that can clearly distinguish them from surrounding normal tissues may be clinically useful. Here, we describe a new approach to visualizing tumors whose fluorescence can be detected using tumor-specific replication-competent adenovirus (OBP-301, Telomelysin) in combination with Ad-GFP, a replication-deficient adenovirus expressing green fluorescent protein (GFP). Human telomerase reverse transcriptase is the catalytic subunit of telomerase, which is highly active in cancer cells but quiescent in most normal somatic cells. We constructed an adenovirus 5 vector in which the human telomerase reverse transcriptase promoter element drives expression of E1A and E1B genes linked with an internal ribosome entry site and showed that OBP-301 replicated efficiently in human cancer cells, but not in normal cells such as human fibroblasts. When the human lung and colon cancer cell lines were infected with Ad-GFP at a low multiplicity of infection, GFP expression could not be detected under a fluorescence microscope; in the presence of OBP-301, however, Ad-GFP replicated in these tumor cells and showed strong green signals. In contrast, coinfection with OBP-301 and Ad-GFP did not show any signals in normal cells such as fibroblasts and vascular endothelial cells. We also found that established subcutaneous tumors could be visualized after intratumoral injection of OBP-301 and Ad-GFP. A549 human lung tumors and SW620 human colon tumors transplanted into BALB/c nu/nu mice were intratumorally injected with 8 x 10(5) plaque-forming units of Ad-GFP in combination with 8 x 10(6) plaque-forming units of OBP-301. Within 3 days of treatment, the fluorescence of the expressed GFP became visible by a three-chip color cooled charged-coupled device camera in these tumors, whereas intratumoral injection of Ad-GFP alone could not induce GFP fluorescence. Moreover, intrathoracic administration of Ad-GFP and OBP-301 could visualize disseminated A549 tumor nodules in mice after intrathoracic implantation. Our results indicate that intratumoral or intrathoracic injection of Ad-GFP in combination with OBP-301 might be a useful diagnostic method that provides a foundation for future clinical application.

Adenoviridae↗
PubMed1986

Optical image quality and the cone mosaic.

Contrary to the orthodox view that optical image quality should "match" the photoreceptor grain, anatomical data from the eyes of various animals suggest that the image quality is significantly superior to the potential resolution of the cone mosaic in most retinal regions. A new theory is presented to explain the existence of this relation and to better appreciate eye design. It predicts that photoreceptors are potentially visible through the natural optics.

Animals↗
PubMed2003

Biased micromechanical cantilever arrays as optical image memory.

We show that an array of optically actuated biased cantilevers can work as an optical data storage, able to encode data stored as arrays of optical pixels (images). Each of these optical pixels can, in addition, have a predetermined pixel depth, expressed as a certain number of gray levels. This new optical memory is able to work at a data rate of approximately 7 GB/s for an image with 128 x 128 pixels.

Journal Article↗
PubMed2001

Developmental changes in trial-to-trial variations in whisker barrel responses studied using intrinsic optical imaging: comparison between normal and de-whiskered rats.

We used an intrinsic optical imaging technique to examine postnatal developmental changes in the rat barrel response to a single whisker movement. We compared the optical response patterns between control and de-whiskered rats, from which whiskers were removed except for the D1 whisker just after birth. Barrel responses were evoked by D1-whisker movement stimulation, and the intrinsic optical signals were detected from the somatosensory cortex through the dura mater. In the control rats, the area of the barrel response decreased gradually as postnatal development proceeded from 2 to 7 wk, until reaching the adult pattern. On the other hand, in the de-whiskered rats, the barrel response area did not change during development and showed a larger size than in the control rats. We also compared the trial-to-trial variations in the barrel responses between the two groups. In the control rats, trial-to-trial variations in the optical responses were observed under the same conditions of whisker stimulation, and the extent of the variations decreased with postnatal development up to 7 wk. In the de-whiskered rats, trial-to-trial variations were also observed, but the extent was larger and unchanged during development. In both groups, the positions of the response area were the same with respect to the bregma. These results suggest that the decrease in the area and variations in the optical responses are caused by interactions of the corresponding whisker barrel with neighboring barrels and that these interactions are necessary for the developmental stabilization of the intracortical horizontal connections, which are widespread and have high plasticity in early postnatal periods.

Animals↗
PubMed2004

Improving the diffuse optical imaging spatial resolution of the cerebral hemodynamic response to brain activation in humans.

We compare two geometries of sources and detectors for optimizing the diffuse optical imaging resolution of brain activation in humans. Because of limitations in the instruments' dynamic range, most diffuse optical brain activation images have used only nonoverlapping measurements. We demonstrate theoretically and with a human experiment that a simple geometry of sources and detectors can provide overlapping measurements within the limitation of instrumentation dynamic range and produce an image resolution and localization accuracy that is twofold better.

Adult↗
PubMedDate not supplied

Near-infrared fluorescent RGD peptides for optical imaging of integrin alphavbeta3 expression in living mice.

Near-infrared fluorescence optical imaging is a powerful technique for studying diseases at the molecular level in preclinical models. We recently reported that monomeric RGD peptide c(RGDyK) conjugated to the NIR fluorescent dye specifically targets integrin receptor both in cell culture and in living subjects. In this report, Cy5.5-conjugated mono-, di-, and tetrameric RGD peptides were evaluated in a subcutaneous U87MG glioblastoma xenograft model in order to investigate the effect of multimerization of RGD peptide on integrin avidity and tumor targeting efficacy. The binding affinities of Cy5.5-conjugated RGD monomer, dimer, and tetramer for alpha(v)beta(3) integrin expressed on U87MG cell surface were determined to be 42.9 +/- 1.2, 27.5 +/- 1.2, and 12.1 +/- 1.3 nmol/L, respectively. All three peptide-dye conjugates had integrin specific uptake both in vitro and in vivo. The subcutaneous U87MG tumor can be clearly visualized with each of these three fluorescent probes. Among them, tetramer displayed highest tumor uptake and tumor-to-normal tissue ratio from 0.5 to 4 h postinjection. Tumor-to-normal tissue ratio for Cy5.5-conjugated RGD monomer, dimer, and tetramer were found to be 3.18 +/- 0.16, 2.98 +/- 0.05, and 3.63 +/- 0.09, respectively, at 4 h postinjection. These results suggest that Cy5.5-conjugated monomeric, dimeric, and tetrameric RGD peptides are all suitable for integrin expression imaging. The multmerization of RGD peptide results in moderate improvement of imaging characteristics of the tetramer, compared to that of the monomer and dimeric counterparts.

Animals↗
PubMedDate not supplied

Optical image processing with liquid-crystal display for image intensifier/television systems.

We have studied the effect of real-time optical image processing (OIP) in an image intensifier/television (II-TV) radiographic imaging system by using a liquid-crystal display (LCD) placed between the II and the TV camera. The LCD compresses the dynamic range of the transmitted image by modulating the spatial distribution of the light intensity of the image from the output phosphor of the II. The degree of dynamic-range compression can be designed so that the dependence of the signal-to-noise ratio (SNR) of the LCD-TV system on x-ray intensity matches that of the quantum noise. We measured the physical properties of an LCD and evaluated its capability for OIP. Our experimental results demonstrate that it is feasible to use an LCD to compress the dynamic range and to improve the SNR of the image. The advantages of implementing OIP with an LCD in image acquisition systems in which a TV camera is used are discussed.

Humans↗
PubMed2005

Anisoplanatic deconvolution of adaptive optics images.

A modified method for maximum-likelihood deconvolution of astronomical adaptive optics images is presented. By parametrizing the anisoplanatic character of the point-spread function (PSF), a simultaneous optimization of the spatially variant PSF and the deconvolved image can be performed. In the ideal case of perfect information, it is shown that the algorithm is able to perfectly cancel the adverse effects of anisoplanatism down to the level of numerical precision. Exploring two different modes of deconvolution (using object bases of pixel values or stellar field parameters), we then quantify the performance of the algorithm in the presence of Poissonian noise for crowded and noncrowded stellar fields.

Journal Article↗
PubMed1993

The layout of iso-orientation domains in area 18 of cat visual cortex: optical imaging reveals a pinwheel-like organization.

In this study we used optical imaging based on activity-dependent intrinsic signals to determine the distribution of cells responding to gratings of various orientations moving in different directions in area 18 of cat visual cortex. To test directional-selective clustering of neurons, we compared cortical activity maps obtained by stimulation with two gratings of identical orientation but moving in opposite directions. We found those maps to be almost identical, suggesting that neurons are not notably clustered into directionality columns. We also compared activity maps obtained with gratings of different orientations. Each of the orientation maps was similar to the 2-deoxyglucose maps previously reported. Having compiled the information obtained from the different orientations into one "orientation preference map," we found, in contrast to earlier reports, that iso-orientation domains are not elongated parallel bands but are small patches organized in "pinwheels" around points that we refer to as "orientation centers." We furthermore show that the only locations at which orientation preference changes rapidly are these orientation centers and not lines or loops. In addition, this report clarifies that our observations on the functional architecture of cat area 18, although at first sight at variance with earlier observations, are actually fully consistent with them. We therefore propose that in cat visual cortex pinwheel-like patterns of orientation preference form an irregular mosaic of modular units with an average density of 1.2 pinwheels per square millimeter.

Animals↗
PubMed2003

Near-field optical imaging of abasic sites on a single DNA molecule.

Scanning near-field optical microscopy (SNOM) imaging was performed to allow for the direct visualization of damaged sites on individual DNA molecules to a scale of a few tens of nanometers. Fluorescence in situ hybridization on extended DNA molecules was modified to detect a single abasic site. Abasic sites were specifically labelled with a biotinlylated aldehyde-reactive probe and fluorochrome-conjugated streptavidin. By optimizing the performance of the SNOM technique, we could obtain high contrast near-field optical images that enabled high-resolution near-field fluorescence imaging using optical fiber probes with small aperture sizes. High-resolution near-field fluorescence imaging demonstrated that two abasic sites within a distance of 120 nm are clearly obtainable, something which is not possible using conventional fluorescence in situ hybridization combined with far-field fluorescence microscopy.

Aldehydes↗
PubMed1993

Dynamic multichannel near-infrared optical imaging of human brain activity.

The present paper demonstrates functional brain mapping with an optical imaging technique by using tissue-transparent near-infrared light. With a maximal five-channel optical monitoring system, we succeeded in detecting region-specific changes in both the hemoglobin oxygenation state and blood volume during various mental tasks, in addition to visual and auditory stimulation. The time course of increases in blood supply varied with each brain region and depended on the type of internal operations occurring during the mental tasks. Changes in the hemoglobin oxygenation state were also different from region to region. This showed that there were regional variations of the oxygen delivery-oxygen utilization relationship during activation of brain activity. The usefulness of multichannel near-infrared functional imaging was well documented.

Acoustic Stimulation↗
PubMed2005

Three-dimensional localization and optical imaging of objects in turbid media with independent component analysis.

A new approach for optical imaging and localization of objects in turbid media that makes use of the independent component analysis (ICA) from information theory is demonstrated. Experimental arrangement realizes a multisource illumination of a turbid medium with embedded objects and a multidetector acquisition of transmitted light on the medium boundary. The resulting spatial diversity and multiple angular observations provide robust data for three-dimensional localization and characterization of absorbing and scattering inhomogeneities embedded in a turbid medium. ICA of the perturbations in the spatial intensity distribution on the medium boundary sorts out the embedded objects, and their locations are obtained from Green's function analysis based on any appropriate light propagation model. Imaging experiments were carried out on two highly scattering samples of thickness approximately 50 times the transport mean-free path of the respective medium. One turbid medium had two embedded absorptive objects, and the other had four scattering objects. An independent component separation of the signal, in conjunction with diffusive photon migration theory, was used to locate the embedded inhomogeneities. In both cases, improved lateral and axial localizations of the objects over the result obtained by use of common photon migration reconstruction algorithms were achieved. The approach is applicable to different medium geometries, can be used with any suitable photon propagation model, and is amenable to near-real-time imaging applications.

Algorithms↗