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PubMed1991

Relationship of retinotopic ordering of axons in the optic pathway to the formation of visual maps in central targets.

We examined in rats the relationship between the ordering of retinal axons in the optic pathway and the formation of a retinotopically organized projection to their primary target, the contralateral superior colliculus (SC). We have previously found that axons labeled by focal injections of 1,1'-dioctadecyl 3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI) made in temporal or nasal retina of perinatal rats commonly mistarget along the medial-lateral and rostral-caudal axes of the SC. By postnatal day (P) 11-12, the retinocollicular projection attains an adult-like topography. Incorrectly targeted axons or axon segments are removed; axons that persist terminate in the topographically appropriate part of the SC (Simon and O'Leary: Dev Biol 137:125, 1990). In the present study, we made similar DiI injections, covering less than 2% of the retinal area, in peripheral temporal, nasal, superior, or inferior retina, in rats of two age groups, embryonic day (E) 21 to P (postnatal day) 2 and P11-P17. Whole mounts of retina, optic nerve and tract, and SC, and cross sections of the optic nerve, were examined. In E21-P2 rats, retinal axons labeled from each retinal site are diffusely distributed in the SC, and poorly ordered in the optic pathway. In retina, labeled axons travel in fascicles directly from the injection site to the optic disc, but neighbor relationships begin to degrade as fascicles split and mix. Retinotopic order is virtually lost in the optic nerve; axons labeled from each injection site disperse throughout its cross-sectional area, but the labeled axons tend to be concentrated toward a specific half of the nerve depending upon their retinal origin. This slight tendency toward retinotopic order increases in the optic tract, but axons are still poorly ordered as they leave the tract and enter the SC. Targeting errors along the medial-lateral axis of the SC, but apparently not along its rostral-caudal axis, are related to the positioning of axons across the width of the optic tract. In P11-P17 rats, axons labeled from each injection site arborize only in a small, topographically correct part of the SC. However, the distributions of labeled retinal axons observed in whole mounts of the retina and optic pathway have a degree of disorder similar to those in E21-P2 rats. Further, the scatter of labeled axons in optic nerve cross sections is comparable in both age groups. Therefore, the emergence of topographic order in the retinocollicular projection is not accompanied by an emergence of a retinotopic ordering of axons in the optic nerve.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Correlation of asymmetry of visual field loss with optic disc topography in normal-tension glaucoma.

OBJECTIVE: To compare the differences in optic disc configuration with different stages of visual field loss in normal-tension glaucoma. DESIGN: Interocular pairwise comparisons. SETTING: Glaucoma clinic of a teaching hospital. PATIENTS: Thirteen patients with normal-tension glaucoma and asymmetric visual field loss of at least 2.5 dB in the mean defect of the visual field indexes. INTERVENTIONS: Areas under the optic disc profiles mapped from values for radial sections of the optic disc measured at intervals of 30 degrees and expressed as percentages of the area of a rectangle were obtained from stereophotographs with a computerized image analysis system. Visual fields were tested with automated perimetry (OCTOPUS), using program G1. MAIN OUTCOME MEASURE: Correlation analyses between the interocular differences in the areas under the optic disc profile and the interocular differences in the visual field indexes. RESULTS: The correlation coefficients between the interocular differences in mean defect and those of the area under the optic disc profile in the superior to temporal sections ranged from -.71 to -.61 (.007 < P < .028). The interocular differences in loss variance correlated with the differences in the area under the optic disc profile in the superior section (r = -.61, P = .0252). CONCLUSION: The differences in visual field loss between the two eyes in normal-tension glaucoma appear mainly to reflect morphometric changes in the superior half of the optic disc.

Aged↗
PubMed1991

Stretched and upside-down maps of auditory space in the optic tectum of blind-reared owls; acoustic basis and behavioral correlates.

Vision during early life plays an important role in calibrating sound localization behavior. This study investigates the effects of visual deprivation on sound localization and on the neural representation of auditory space. Nine barn owls were raised with eyelids sutured closed; one owl was congenitally anophthalmic. Data from these birds were compared with data from owls raised with normal visual experience. Sound localization behavior was significantly less precise in blind-reared owls than in normal owls. The scatter of localization errors was particularly large in elevation, though it was abnormally large in both dimensions. However, there was no systematic bias to the localization errors measured over a range of source locations. This indicates that the representation of auditory space is degraded in some way for blind-reared owls, but on average is properly calibrated. The spatial tuning of auditory neurons in the optic tectum was studied in seven of the blind-reared owls to assess the effects of early visual deprivation on the neural representation of auditory space. In normal owls, units in the optic tectum are sharply tuned for sound source location and are organized systematically according to the locations of their receptive fields to form a map of auditory space. In blind-reared owls, the following auditory properties were abnormal: (1) auditory tuning for source elevation was abnormally broad, (2) the progression of the azimuths and elevations of auditory receptive fields across the tectum was erratic, and (3) in five of the seven owls, the auditory representation of elevation was systematically stretched, and in the two others large portions of the representation of elevation were flipped upside down. The following unit properties were apparently unaffected by blind rearing: (1) the sharpness of tuning for sound source azimuth, (2) the orientation of the auditory representation of azimuth, and (3) the mutual alignment of the auditory and visual receptive fields in the region of the tectum representing the area of space directly in front of the animal. The data demonstrate that the brain is capable of generating an auditory map of space without vision, but that the normal precision and topography of the map depend on visual experience. The space map results from the tuning of tectal units for interaural intensity differences (IIDs) and interaural time differences (ITDs; Olsen et al., 1989).(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Stimulation↗
PubMed1986

A method for reconstructing patterns of somatosensory cerebral cortical activity.

An interactive graphics package was developed in order to acquire, display, and manipulate images of cerebral cortical autoradiographic data. The primary purpose for development of the system was to reconstruct accurate 2-dimensional maps of the functional activity within the somatosensory cerebral cortex. A Datacube Q-bus graphics module (QVG/QAF-123) was interfaced with the Micro PDP-11/23 to accept a standard RS170 video input signal, and autoradiographs of serial sections (each 20 microns thick) of a cerebral cortex were digitized individually to 768 X 512 X 8 bit resolution. Input look-up tables were used to standardize the autoradiographic data. Boundaries of the somatosensory cortex were entered (with a Summagraphics MM 1201 digitizer), and the image data was stored on disk file (a method of data compression was devised). A method for segmenting the image data for many (sequential) sections was developed that provided arrays from which the maps were generated. Thresholding, histogram equalization, edge detection and edge enhancement, and filters in both the spatial and frequency domains were employed to process the images of the maps. Plots of optical density values along any axis of the maps and gray level histograms of any map region could also be generated. Maps made by the described method are much higher in resolution than those produced by traditional (manual) methods, and permit analysis of the reconstructions in both the frequency and spatial domains.

Animals↗
PubMed2004

Mapping water quality and substrate cover in optically complex coastal and reef waters: an integrated approach.

Sustainable management of coastal and coral reef environments requires regular collection of accurate information on recognized ecosystem health indicators. Satellite image data and derived maps of water column and substrate biophysical properties provide an opportunity to develop baseline mapping and monitoring programs for coastal and coral reef ecosystem health indicators. A significant challenge for satellite image data in coastal and coral reef water bodies is the mixture of both clear and turbid waters. A new approach is presented in this paper to enable production of water quality and substrate cover type maps, linked to a field based coastal ecosystem health indicator monitoring program, for use in turbid to clear coastal and coral reef waters. An optimized optical domain method was applied to map selected water quality (Secchi depth, Kd PAR, tripton, CDOM) and substrate cover type (seagrass, algae, sand) parameters. The approach is demonstrated using commercially available Landsat 7 Enhanced Thematic Mapper image data over a coastal embayment exhibiting the range of substrate cover types and water quality conditions commonly found in sub-tropical and tropical coastal environments. Spatially extensive and quantitative maps of selected water quality and substrate cover parameters were produced for the study site. These map products were refined by interactions with management agencies to suit the information requirements of their monitoring and management programs.

Animals↗
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↗
PubMed2002

A new autosomal recessive non-progressive congenital cerebellar ataxia associated with mental retardation, optic atrophy, and skin abnormalities (CAMOS) maps to chromosome 15q24-q26 in a large consanguineous Lebanese Druze Family.

Congenital cerebellar ataxias are a heterogeneous group of non-progressive disorders characterized by hypotonia and developmental delay followed by the appearance of ataxia, and often associated with dysarthria, mental retardation, and atrophy of the cerebellum. We report the mapping of a disease gene in a large inbred Lebanese Druze family, with five cases of a new form of non-progressive autosomal recessive congenital ataxia associated with optic atrophy, severe mental retardation, and structural skin abnormalities, to a 3.6-cM interval on chromosome 15q24-15q26.

Abnormalities, Multiple↗
PubMed2002

Imaging the local density of states of optical corrals.

This paper reports the experimental observation, at optical frequencies, of the electromagnetic local density of states established by nanostructures corresponding to the recently introduced concept of optical corral [G. Colas des Francs et al., Phys. Rev. Lett. 86, 4950 (2001)]. The images obtained by a scanning near-field optical microscope under specific operational conditions are found in agreement with the theoretical maps of the optical local density of states. A clear functionality of detection by the scanning near-field optical microscope is thereby identified since the theoretical maps are computed without including any specific tip model.

Journal Article↗
PubMed2000

Topographic projection from the optic tectum to the auditory space map in the inferior colliculus of the barn owl.

In the barn owl (Tyto alba), the external nucleus of the inferior colliculus (ICX) contains a map of auditory space that is calibrated by visual experience. The source of the visually based instructive signal to the ICX is unknown. Injections of biotinylated dextran amine and Fluoro-Gold in the ICX retrogradely labelled neurons in layers 8-15 of the ipsilateral optic tectum (OT) that could carry this instructive signal. This projection was point-to-point and in register with the feed-forward, auditory projection from the ICX to the OT. Most labelled neurons were in layers 10-11, and most were bipolar. Tripolar, multipolar, and unipolar neurons were also observed. Multipolar neurons had dendrites that were oriented parallel to the tectal laminae. In contrast, most labelled bipolar and tripolar neurons had dendrites oriented perpendicular to the tectal laminae, extending superficially into the retino-recipient laminae and deep into the auditory recipient laminae. Therefore, these neurons were positioned to receive both visual and auditory information from particular locations in space. Biocytin injected into the superficial layers of the OT labelled bouton-laden axons in the ICX. These axons were generally finer than, but had similar bouton densities as, feed-forward auditory fibers in the ICX, labelled by injections of biocytin into the central nucleus of the inferior colliculus (ICC). These data demonstrate a point-to-point projection from the OT to the ICX that could provide a spatial template for calibrating the auditory space map in the ICX.

Animals↗
PubMed2003

Functional architecture of eye position gain fields in visual association cortex of behaving monkey.

In the behaving monkey, inferior parietal lobe cortical neurons combine visual information with eye position signals. However, an organized topographic map of these neurons' properties has never been demonstrated. Intrinsic optical imaging revealed a functional architecture for the effect of eye position on the visual response to radial optic flow. The map was distributed across two subdivisions of the inferior parietal lobule, area 7a and the dorsal prelunate area, DP. Area 7a contains a representation of the lower eye position gain fields while area DP represents the upper eye position gain fields. Horizontal eye position is represented orthogonal to the vertical eye position across the medial lateral extents of the cortices. Similar topographies were found in three hemispheres of two monkeys; the horizontal and vertical gain field representations were not isotropic with a greater modulation found with the vertical. Monte Carlo methods demonstrated the significance of the maps, and they were verified in part using multiunit recordings. The novel topographic organization of this association cortex area provides a substrate for constructing representations of surrounding space for perception and the guidance of motor behaviors.

Animals↗
PubMed1996

Principle, validity, and reliability of scanning laser Doppler flowmetry.

PURPOSE: The objective of this study is to present the reliability and validity of scanning laser Doppler flowmetry (SLDF) performing a high-definition topography of perfused vessels of the retina and the optic nerve head with simultaneous evaluation of blood flow. METHODS: The examination of blood flow by SLDF is based on the optical Doppler effect. The data acquisition and evaluation system is a modified laser scanning device; the wavelength of the laser source is 670 mm, with a power of 100 microW (Heidelberg Engineering, HRF). The reliability of SLDF was estimated by performing five separate measurements in 10 eyes on 5 days. The validity of the method was tested by two experiments. First, in an experimental set-up, the capability of SLDF to measure the velocity of a moving plane in absolute units was estimated. Second, comparative measurements were performed of retinal blood flow in normal eyes and in 33 glaucomatous eyes with SLDF and a commercially available single-point laser Doppler flowmeter (Oculix). RESULTS: We found SLDF to produce a high reliability. The reliability coefficients r1 of flow, volume, and velocity were 0.82, 0.81, and 0.83, respectively. Comparative measurements of the retinal blood flow by SLDF and a single-point laser Doppler flowmeter of corresponding retinal points showed a linear and significant relationship between flow (r = 0.83, p < 0.0001), volume (r = 0.51, p < 0.0001), and velocity (r = 0.59, p < 0.0001). In the experimental set-up, SLDF was able to quantitatively measure velocity in absolute units. CONCLUSIONS: SLDF enables the visualization of perfused vessels of the juxtapapillary retina and the optic nerve head in high resolution by two-dimensional mapping of the optical Doppler shift and a reproducible evaluation of capillary blood flow.

Evaluation Studies as Topic↗
PubMedDate not supplied

Demonstration of dual parallel jet interaction in an in vitro model of multivalvular disease by use of optical visualization and color Doppler flow mapping.

Parallel jets, such as those occurring in the heart in multivalvular diseases like combined mitral stenosis and aortic insufficiency, have created difficulty when color Doppler flow mapping or continuous wave Doppler has been used to localize or to measure the jets because they appear to merge. Dual jet interaction was reproduced in an in vitro transparent model by driving two parallel adjacent jets, one lower velocity, higher mass, through a 19 mm2 orifice, and the other higher peak velocity, smaller mass through two orifices, 0.27 mm2 and 1.5 mm2, by use of a solution of India ink and cornstarch to optically visualize the jet interaction and image the interaction by color Doppler. Consistent deviation of the lower velocity jet towards the higher velocity jet was observed, and the large jet angled more strongly towards the small jet for the 1.5 mm2 small jet orifice than for the 0.27 mm2 orifice for constant large and small jet velocities. There was a better linear correlation of the amount of large jet angulation to the ratio of both jets' Reynolds numbers than to the ratio of both flow rates. The jets interacted as close as 1.3 cm from their point of origin, and the region after the jets merged was a highly turbulent mixing zone where neither jet could be separately imaged or visualized. These observations suggest that relative velocity plays a primary role in determining jet interaction which is a recruitment phenomena but that other hydrodynamic parameters, such as flow rate and Reynolds numbers, determine the degree to which the jets deviate.

Aortic Valve Insufficiency↗
PubMed2003

Optical imaging of epileptiform events in visual cortex in response to patterned photic stimulation.

In a subset of patients with epilepsy, patterned visual stimuli can trigger clinical seizures. The etiology of this phenomenon, and the complex interaction between functional architecture and epilepsy, were investigated in ferret visual cortex. Optical imaging of intrinsic signals was used to visualize maps of orientation, ocular dominance and spatial frequency. Acute interictal spike foci were then induced within V1 using focal iontophoresis of bicuculline methiodide and optically mapped during presentation of patterned visual stimuli. We found that specific orientations and spatial frequencies could preferentially trigger epileptiform events, depending on the location of the epicenter of the epileptic focus within the columnar architecture of visual cortex. These data support a cortical etiology of the clinical phenomenon of pattern-sensitive epilepsy. We were not able to demonstrate a spatial correlation between the functional architecture maps and the topography of the epileptic focus. These findings implicate short-range rather than long-range horizontal excitatory connections in the lateral spread of interictal spikes, which may be specific to the epilepsy model of acute focal disinhibition. Orientation and spatial frequency maps were severely disturbed in the region of the focus but were unaltered in the surrounding cortex. Thus, optical imaging of intrinsic signals can be used to simultaneously map epilepsy and normal functional anatomy with high spatial resolution.

Action Potentials↗
PubMed1987

Corresponding spatial gradients of TOP molecules in the developing retina and optic tectum.

The topographic map of cell position in the avian retina is inverted in its projection to the optic tectum. Dorsal retinal ganglion cell axons project to ventral tectum, and ventral retinal ganglion cells project to dorsal tectum. Topographic gradients of toponymic (TOP) cell surface molecules along the dorsoventral axes of retina and tectum also are inverted. TOP molecules are most abundant in dorsal retina and ventral tectum and least abundant in ventral retina and dorsal tectum during the period of initial retinal-tectal interaction. Thus, TOP molecules may be involved in orienting the retinotectal map.

Animals↗
PubMed2000

Mapping the visual field to the optic disc in normal tension glaucoma eyes.

PURPOSE: To establish the anatomical relationship between visual field test points in the Humphrey 24-2 test pattern and regions of the optic nerve head (ONH) DESIGN: Cross-sectional study. PARTICIPANTS: Glaucoma patients and suspects from the Normal Tension Glaucoma Clinic at Moorfields Eye Hospital. METHODS: Sixty-nine retinal nerve fiber layer (RNFL) photographs with well-defined RNFL defects and/or prominent bundles were digitized. An appropriately scaled Humphrey 24-2 visual field grid and an ONH reference circle, divided into 30 degrees sectors, were generated digitally. These were superimposed onto the RNFL images. The relationship of visual field test points to the circumference of the ONH was estimated by noting the proximity of test points to RNFL defects and/or prominent bundles. The position of the ONH in relation to the fovea was also noted. MAIN OUTCOME MEASURES: The sector at the ONH corresponding to each visual field test point, the position of the ONH in relation to the fovea, and the effect of the latter on the former. RESULTS: A median 22 (range, 4-58), of a possible 69, ONH positions were assigned to each visual field test point. The standard deviation of estimations was 7.2 degrees. The position of the ONH was 15.5 degrees (standard deviation 0.9 degrees ) nasal and 1.9 degrees (standard deviation 1.0 degrees ) above the fovea. The location of the ONH had a significant effect on the corresponding position at the ONH for 28 of 52 visual field test points. CONCLUSIONS: A clinically useful map that relates visual field test points to regions of the ONH has been produced. The map will aid clinical evaluation of glaucoma patients and suspects, as well as form the basis for investigations of the relationship between retinal light sensitivity and ONH structure.

Cross-Sectional Studies↗
PubMed1998

Ultrastructural changes and immunocytochemical localization of microtubule-associated protein 1 in guinea pig optic nerves after acute increase in intraocular pressure.

PURPOSE: To investigate ultrastructural changes and localization of microtubule-associated protein 1 (MAP 1) in optic nerves of guinea pigs in conditions of acute increase in intraocular pressure (IOP). METHODS: Intraocular pressure was increased acutely in 40 guinea pig eyes, and 40 eyes were examined in 20 normal control animals. Analytic methods included quick-freezing and deep-etching (QF-DE) and conventional fixation. Microtubule-associated protein 1 immunocytochemistry was performed. RESULTS: In conventional ultrathin sections, an alteration of the axoplasmic ultrastructure was seen only at the level of the lamina cribrosa sclerae. The number of microtubules was significantly decreased in the axoplasm that exhibited accumulations of membranous organelles. Cross-bridged filaments on microtubules were significantly reduced in number when determined by the QF-DE method. The immunostaining of tubulin or MAP 1 was less positive than in other samples with normal IOP, revealed by light microscopic immunocytochemistry. Immunoelectron microscopy demonstrated that MAP 1 was significantly decreased in the axoplasm that showed accumulations of membranous organelles. CONCLUSIONS: The acute alteration of axoplasmic ultrastructures in some parts of the optic nerves at the level of the lamina cribrosa involves a decrease in the amount of MAP 1 and a decrease in the number of axonal cross-bridges on microtubules in a condition of acutely increased IOP, which could be related to microtubule instability and abnormal organelle transport in the axoplasm.

Acute Disease↗