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Results for “Optical mapping”

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At least 433 records · Page 24Linked to original sources
PubMed1999

[Application of the simplified method of optic recording for mapping focuses of the neuronal activity in the somatosensory cortex of the white rats].

In rats, a differential signal was used for evoking an optical image in the barrel-field zone which represented a difference between cortical images during the control and the stimulation periods. After a subtraction of averaged sequences of frames, an image of spots reflecting a probable location of activated groups of neurones was obtained. Natural low frequency stimulation of vibrissae is supposed to be the most effective. The method of intrinsic optical activity imaging can be applied for preliminary mapping of cortical zones.

Animals↗
PubMed2005

The application of optical recording of intrinsic signals to simultaneously acquire functional, pathological and localizing information and its potential role in neurosurgery.

INTRODUCTION: The accurate intraoperative localization of epileptic foci and surrounding functional architecture is critical to a successful surgical outcome. Current techniques are limited either by their inability to simultaneously sample large areas of cortex with high spatial resolution or account for dynamic alterations in cortical morphology. Optical recording of intrinsic signals can map neuronal activity in a large area of cortex with a spatial resolution in the order of <100 mum. We explored methods of simultaneously representing localizing information, functional architecture and the border of an epileptic focus in vivo with intrinsic signal imaging. METHODS: The functional architecture of V1 was mapped using optical imaging of intrinsic signals in the ferret at 707 nm (n = 9). Interictal and ictal foci were then generated with focal iontophoresis of bicuculline methiodide and 4-aminopyridine into V1 and mapped optically. Blood vessel architecture was mapped using light acquired at 540 nm. RESULTS: Epilepsy maps could be superimposed on maps of the underlying functional architecture and surface blood vessel pattern to produce composite pathological-functional maps. Sufficient data for localization as well as identification of both pathological and functional architecture could be conveyed in a single image. CONCLUSIONS: Cortical maps generated with intrinsic signal imaging can combine topographic and localizing information about normal functional architecture and interictal and ictal onset zones with extremely high spatial resolution. These maps may be useful in guiding surgical resections and multiple subpial transections to minimize unnecessary damage to functional brain surrounding neocortical pathology.

Animals↗
PubMedDate not supplied

Corneal thickness and elevation maps computed from optical rotary scans.

PURPOSE: Recently, the authors presented a technique that allows corneal thickness measurements along any meridian from optical sections obtained using a rotary scanning system. This paper presents three-dimensional mapping of the corneal thickness and topography of both corneal surfaces, obtained with the rotary system. METHOD: Corneal thickness and topography are computed from optical sections obtained by illumination with a collimated beam expanded in a fan by a small cylindrical lens. This lens is provided with motor driven rotation to perform automated rotary scanning of the whole cornea. Two cameras are used to capture the images of the optical sections. RESULTS: With this system, it is possible to obtain measurements of corneal thickness, as well as corneal topography. Corneal thickness and elevation maps are shown. CONCLUSIONS: Although still under development, this new optical system allows measurement of the thickness of the whole cornea as well as topographical mapping of both corneal surfaces.

Corneal Topography↗
PubMed1999

Spontaneous regeneration of severed optic axons restores mapped visual responses to the adult rat superior colliculus.

To test whether a spontaneous and functional regeneration of severed axons could occur within the adult mammalian central nervous system, a long-term recovery of microelectrode-mapped visual response was sought in the superior colliculus (SC) after its total or near-total abolition by a precise guillotine cut of the retinocollicular pathway. Recoveries were found 3 weeks or later in 15 of the 36 animals studied; in 10 of these recoveries, half or more of the width of the SC was involved. The recovered responses were often activated from within a normally small area of the visual field. Appropriate retinotopic maps were restored. Intraocular horseradish peroxidase tracing revealed a variety of novel optic trajectories, passing around lesions even of totally cut pathways, which eventually terminated in normally retinorecipient layers of those recovered SCs. Such detours could not be explained by a mechanical reorientation of brain structures. When exactly comparable lesions were examined within a few days, there were no detours: severed optic axons faced the cuts. In long-term animals where responsiveness remained absent, optic axonal reorientations were observed near lesions but the SC was not innervated. Extensive long-term recoveries were in marked contrast to the occasional rapid ones, found within a few days postlesion, which involved only an outermost silenced border of SC. These were attributed to a rapid reversal of conduction failure in spared, bordering, axons of this topographically organized pathway. The findings support the conclusion that, after they are cut, numbers of optic axons can regenerate to the SC and restore appropriate circuitry therein.

Animals↗
PubMed2003

Brain mapping: new wave optical imaging.

Optical imaging of intrinsic signals is widely used for high-resolution brain mapping in various animal species. A new approach using continuous data acquisition and Fourier decomposition of the signal allows for much faster mapping, opening up the possibility of applying this method to new experimental questions.

Animals↗
PubMed1991

Visual instruction of the neural map of auditory space in the developing optic tectum.

Neural maps of visual and auditory space are aligned in the adult optic tectum. In barn owls, this alignment of sensory maps was found to be controlled during ontogeny by visual instruction of the auditory spatial tuning of neurons. Large adaptive changes in auditory spatial tuning were induced by raising owls with displacing prisms mounted in spectacle frames in front of the eyes; neurons became tuned to sound source locations corresponding to their optically displaced, rather than their normal, visual receptive field locations. The results demonstrate that visual experience during development calibrates the tectal auditory space map in a site-specific manner, dictating its topography and alignment with the visual space map.

Animals↗
PubMed1997

Optical imaging of anatomical maps derived from magnetic resonance images using time-independent optical sources.

We present a model suitable for computing images of absorption cross sections of thick tissue structures illuminated at near infrared (NIR) wavelengths from tomographic projection data. Image reconstruction is accomplished by solving a system of linear equations derived from transport theory. Reconstruction results using different algebraic solvers are shown for anatomical maps of the breast, derived from magnetic resonance imaging data, containing two simulated pathologies, in which case qualitatively good reconstructions were obtained. Evaluation of magnetic resonance (MR) data to optimize NIR optical tomographic imaging methods and to assess the feasibility of a combined MR-optical measurement scheme is discussed.

Adipose Tissue↗
PubMed1998

Wavelength-dependent differences between optically determined functional maps from macaque striate cortex.

This study investigates the role of wavelength in determining the source and dynamic range of activity-driven reflectance changes in macaque striate cortex. By using short (600 nm) and long (720 nm) wavelengths to map ocular dominance, orientation, and position from the same region of cortex on alternate trials, we isolated wavelength-dependent differences in the contributions of different tissue compartments. In agreement with previous reports, 600-nm illumination was found to produce optical signals that were more than twice the size of those obtained with 720-nm illumination. In addition, 600- and 720-nm images were found to correlate everywhere except in regions occluded by blood vessels, where the images obtained at 600 nm correlated with the overlying vasculature. Since the 720-nm images do not correlate with the vasculature, this difference suggests that differential images obtained under 600-nm illumination are disproportionately sensitive to vascular events (e.g., changes in blood flow, volume, etc.). This finding is supported by the absorption spectra of hemoglobin and its derivatives, which absorb 600-nm light 4-1000 times more strongly than 720-nm light. Hence, for the 40% of cortex covered by blood vessels larger than 50 microns, images obtained at 600 nm are dominated by the vascular compartment to the exclusion of signals from the neural compartment below.

Animals↗
PubMed1980

Reflectance of rat brain structures mapped by an optical fiber technique.

A method to detect differences in reflectance as a pair of glass fibers is advanced through various brain structures at a constant speed is described. The system has been used to develop a technique for accurate and easy placement of electrodes or cannulae into a limited brain region. The probe consisted of two thin (50 micrometer in diameter) glass optic fibers. A 5 W lamp was used to transmit light down one of these fibers. The relative intensity of light reflected from brain tissue into the other optic fiber was monitored with a photomultiplier and ink-writing recorder. Different brain structures were shown to vary in the amount of reflectance, with white matter having much higher reflectance than gray matter. It was demonstrated in a total of 239 penetrations that the patterns of successive changes in the reflected light response, as the probe was lowered into the brain, was characteristic for each frontal plane. The probe may additionally be itself used as an electrode if plated with silver.

Animals↗
PubMed2000

The morphogenesis of the zebrafish eye, including a fate map of the optic vesicle.

We have examined the morphogenesis of the zebrafish eye, from the flat optic vesicle at 16 hours post fertilization (hpf) to the functional hemispheric eye at 72 hpf. We have produced three-dimensional reconstructions from semithin sections, measured volumes and areas, and produced a fate map by labeling clusters of cells at 14-15 hpf and finding them in the 24 hpf eye cup. Both volume and area increased sevenfold, with different schedules. Initially (16-33 hpf), area increased but volume remained constant; later (33-72 hpf) both increased. When the volume remained constant, the presumptive pigmented epithelium (PE) shrank and the presumptive neural retina (NR) enlarged. The fate map revealed that during 14-24 hpf cells changed layers, moving from the PE into the NR, probably through involution around the margin of the eye. The transformation of the flat epithelial layers of the vesicle into their cup-shaped counterparts in the eye was also accompanied by cellular rearrangements; most cells in a cluster labeled in the vesicle remained neighbors in the eye cup, but occasionally they were separated widely. This description of normal zebrafish eye development provides explanations for some mutant phenotypes and for the effects of altered retinoic acid.

Animals↗
PubMed2006

Corneal pachymetry mapping with high-speed optical coherence tomography.

OBJECTIVE: To map corneal thickness before and after LASIK with optical coherence tomography (OCT). DESIGN: Cross-sectional observational study. PARTICIPANTS: Forty-two eyes of 21 normal subjects undergoing LASIK. METHODS: A high-speed (2000 axial scans/second) 1.3-microm-wavelength corneal and anterior segment OCT prototype was used for corneal scanning. The scan pattern consisted of 10-mm radial lines on 8 meridians centered on the vertex reflection. The entire scan pattern of 1024 a-scans was acquired in 0.5 seconds. We developed automated computer processing for 3-dimensional corneal reconstruction and measurement. Corneal thickness was measured normal to the anterior surface and presented as color pachymetry maps and zonal statistics. The maps were divided into a central zone (<2 mm) and 3 annular areas (pericentral, 2-5 mm; transitional, 5-7 mm; peripheral, 7-10 mm), which were further divided into quadrantal zones. The average, minimum, and maximum corneal thicknesses were computed for zones within the 7-mm diameter. Optical coherence tomography and ultrasound pachymetry were measured 3 times at the preoperative and 3-month postoperative visits. Reproducibility was assessed by the pooled standard deviations (SDs) of the repeated measurements. MAIN OUTCOME MEASURES: Optical coherence tomography pachymetric map and zonal statistic, and ultrasound pachymetry. RESULTS: Before LASIK, central corneal thicknesses (CCTs) were 546.9+/-29.4 microm (mean +/- SD) for OCT and 553.3+/-33.0 microm for ultrasound. After LASIK, CCTs were 513.7+/-44.5 microm for OCT and 498+/-46.6 microm for ultrasound. Optical coherence tomography and ultrasound CCT were highly correlated (Pearson correlation r = 0.97 before LASIK and 0.98 afterwards). Optical coherence tomography CCT was slightly less than ultrasound CCT before surgery (mean difference, -6.4 microm; 95% limits of agreement, -23.2 to 10.4 microm) but slightly greater after LASIK (15.7 microm; -1.6 to 33 microm). These differences were statistically significant, but no more than the CCT measurement differences between ultrasound pachymeters. The reproducibility of the OCT zonal pachymetry averages was roughly 2 microm. CONCLUSIONS: High-speed OCT provided noncontact, rapid, reproducible pachymetric mapping over a wide area of the cornea. It is equivalent to ultrasound for CCT measurement before and after LASIK. This technology could be valuable for planning keratorefractive procedures and diagnosis of corneal diseases.

Adult↗
PubMed2000

Combined space-variant maps for optical-flow-based navigation.

A robot navigating in an unstructured environment needs to avoid obstacles in its way and determine free spaces through which it can safely pass. We present here a set of optical-flow-based behaviors that allow a robot moving on a ground plane to perform these tasks. The behaviors operate on a purposive representation of the environment called the "virtual corridor" which is computed as follows: the images captured by a forward-facing camera rigidly attached to the robot are first remapped using a space-variant transformation. Then, optical flow is computed from the remapped image stream. Finally, the virtual corridor is extracted from the optical flow by applying simple but robust statistics. The introduction of a space-variant image preprocessing stage is inspired by biological sensory processing, where the projection and remapping of a sensory input field onto higher-level cortical areas represents a central processing mechanism. Such transformations lead to a significant data reduction, making real-time execution possible. Additionally, they serve to "re-present" the sensory data in terms of ecologically relevant features, thereby simplifying the interpretation by subsequent processing stages. In accordance with these biological principles we have designed a space-variant image transformation, called the polar sector map, which is ideally suited to the navigational task. We have validated our design with simulations in synthetic environments and in experiments with real robots.

Animals↗
PubMed2000

A principal components-based method for the detection of neuronal activity maps: application to optical imaging.

We present a novel analysis technique for the extraction of neuronal activity patterns from functional imaging data. We illustrate this technique on data from optical imaging. Optical imaging of the mammalian visual cortex probe the patterns in which the neuronal responses to various aspects of the visual world, such as orientation and color, are spatially organized within the cortex. Recovering these patterns from the image data is a challenging problem as the neuronal response signal is extremely weak in comparison to the background vegetative processes (e.g., circulation and respiration). The proposed technique obtains the neuronal activity pattern using a combination of principal component analysis and statistical significance testing. The performance of this method is compared with the results of existing analysis techniques. The comparison shows the new method to be more sensitive than previous methods.

Animals↗
PubMedDate not supplied

Single molecule mapping of the optical field distribution of probes for near-field microscopy.

The most difficult task in near-field scanning optical microscopy (NSOM) is to make a high quality subwavelength aperture probe. Recently, we have developed high definition NSOM probes by focused ion beam (FIB) milling. These probes have a higher brightness, better polarization characteristics, better aperture definition and a flatter end face than conventional NSOM probes. We have determined the quality of these probes in four independent ways: by FIB imaging and by shear-force microscopy (both providing geometrical information), by far-field optical measurements (yielding throughput and polarization characteristics), and ultimately by single molecule imaging in the near-field. In this paper, we report on a new method using shear-force microscopy to study the size of the aperture and the end face of the probe (with a roughness smaller than 1.5 nm). More importantly, we demonstrate the use of single molecules to measure the full three-dimensional optical near-field distribution of the probe with molecular spatial resolution. The single molecule images exhibit various intensity patterns, varying from circular and elliptical to double arc and ring structures, which depend on the orientation of the molecules with respect to the probe. The optical resolution in the measurements is not determined by the size of the aperture, but by the high optical field gradients at the rims of the aperture. With a 70 nm aperture probe, we obtain fluorescence field patterns with 45 nm FWHM. Clearly, this unprecedented near-field optical resolution constitutes an order of magnitude improvement over far-field methods like confocal microscopy.

Journal Article↗
PubMed2002

Intraobserver reproducibility of a two-dimensional mapping of the optic nerve head perfusion.

PURPOSE: To evaluate the intraobserver reproducibility of a software designed to assess retinal blood flow with the Heidelberg Retina Flowmeter (HRF). METHODS: Ten subjects were consecutively recruited, and one eye of each patient was randomly selected for study. Blood flow measurements were analyzed by using an automatic full field perfusion image analysis (AFFPIA) program, which calculates the Doppler frequency shift and hemodynamic variables (flow, volume, and velocity) for each pixel. The resulting perfusion image is processed with respect to underexposed and overexposed pixels, saccades, and retinal vessel tree. Intraobserver reproducibility was calculated for the AFFPIA program. All the optic nerve heads were horizontally divided into three sections (superior, central, and inferior). The retinal blood flow was calculated in the superior and inferior section, and each section was further divided into three areas (temporal, nasal, and rim). The blood flow was evaluated for each area. RESULTS: When the same observer analyzed the same image five times (intraobserver intraimage reproducibility), the AFFPIA coefficient of variation ranged from 0.5% to 5% in the temporal area, from 0.1% to 5.3% in the nasal area, and from 0.5 to 28% in the rim area. When the same observer analyzed three different images of the same section once (intraobserver interimage reproducibility), the AFFPIA coefficient of variation of flow measurements ranged from 1% to 7.3% in the temporal area, from 1.5% to 10% in the nasal area, and from 2 to 30% in the rim area. CONCLUSION: Retinal blood flow measured by HRF and analyzed by AFFPIA had good intraobserver reproducibility. The reproducibility was significantly better in the temporal and nasal areas than in the rim area.

Aged↗