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PubMed1985

Interhemispheric influences on area 19 of the cat.

Anatomical studies have shown an extensive network of homotopic and heterotopic interhemispheric connections in area 19 of the cat visual cortex (Segraves and Rosenquist 1982a; 1982b). We have investigated their functional organization by recording visual responses in area 19 of cats following a midsagittal section of the optic chiasm. This operation interrupts all crossed optic fibers coming both from the nasal and the temporal retinae; as a result, each hemisphere receives optic fibers only from the lateral hemiretina of the ipsilateral eye which conveys information from the contralateral visual field. Visual information transmitted to the same hemisphere from the contralateral retina and the ipsilateral visual field must be attributed to an indirect, interhemispheric pathway. We found that a rather high proportion of neurons (31.8%) in area 19 of seven split-chiasm cats responded to visual stimuli presented to the contralateral eye. All neurons receiving this interhemispheric activation were also driven by the ipsilateral eye via an intrahemispheric pathway. The property of binocularity was significantly related to the visuotopic map in that both receptive fields of each binocular neuron adjoined or were in the immediate vicinity of the vertical meridian. Due to the small size of receptive fields in area 19, the contribution of the interhemispheric pathway to the representation of the visual field is rather limited and it is certainly less extensive than that predicted by anatomical studies. The representation of the ipsilateral visual field in area 19 of intact cats, as assessed electrophysiologically, was comparable to that found in split-chiasm cats. Recordings in areas 17-18 of split-chiasm cats showed that the visual field represented through the corpus callosum in these visual areas is certainly not less and probably more, extensive than that found in area 19. The results support the conclusion that the relation to the vertical meridian and the receptive field size can explain the organization of the interhemispheric connections in the visual areas studied so far.

Animals↗
PubMed1987

Intraoperative mapping-guided argon laser ablation of malignant ventricular tachycardia.

Intraoperative mapping-guided laser ablation of arrhythmogenic myocardium was performed in 5 patients with refractory sustained ventricular tachycardia (VT). Using a 15-W argon laser coupled to a 300-mu optical fiber, a bloodless laser ventriculotomy was successfully performed in 4 patients with VT. Visually- and mapping-guided endocardial ablation of 7 VT morphologic patterns was performed. Five of the 7 sites of VT origin were unresectable using standard resection techniques. Postoperatively, spontaneous and inducible VT was suppressed in all patients (without antiarrhythmic drugs in 4 patients and with a previously ineffective drug 1 patient). Mean pulmonary capillary wedge pressure, cardiac index and left ventricular ejection fraction were unchanged (p greater than 0.2) from preoperative values. Mean maximal creatinine kinase-MB isoenzyme concentration was 139 +/- 75 IU. All patients were New York Heart Association functional class II at discharge. During follow-up, no spontaneous arrhythmia has recurred in any patient. Thus, intraoperative argon laser ablation is effective for VT ablation alone or in conjunction with standard surgical resection techniques.

Aged↗
PubMed2004

Combined three-dimensional anisotropy contrast imaging and magnetoencephalography guidance to preserve visual function in a patient with an occipital lobe tumor.

OBJECTIVE: Three-dimensional anisotropy contrast (3-DAC) magnetic resonance imaging and magnetoencephalography (MEG) of visually evoked magnetic fields (VEFs) were used to accurately localize the optic radiation and primary visual cortex before surgery for an occipital tumor. PATIENT AND METHODS: A 26-year-old male presented with an occipital lobe tumor located intrinsically underneath the right calcarine fissure. 3-DAC imaging showed that the right optic radiation was located along the superior and lateral surfaces of the lesion. Mapping of the VEFs demonstrated that the primary visual cortex was located superior and lateral to the lesion. The lesion was totally resected via an infero-medial cortical incision using a frameless stereotactic system. Histopathology indicated a pilocytic astrocytoma. No visual deficit was found before or after surgery. CONCLUSION: Combined 3-DAC imaging and MEG can provide essential information about the optic radiation and primary visual cortex for planning the surgical treatment of occipital lobe tumors.

Adult↗
PubMed2006

Proteins of the cauda epididymal fluid associated with fertility of mature dairy bulls.

We evaluated the relationships between proteins in cauda epididymis fluid (CEF) and fertility scores of dairy bulls. Fertility was expressed as the percentage point deviation (PD) of bull nonreturn rate from the average fertility of all bulls at an artificial insemination center. The number of services for each bull ranged from 1074 to 52 820, and PD values ranged from +7.7% to -6.6%. CEF from 20 bulls was obtained from vasa deferentia cannulae and was separated from sperm by centrifugation immediately after collection. Samples were evaluated by 2-dimensional (2-D) sodium dodecyl sulfate polyacrylamide gel electrophoresis gels stained with Coomassie blue, and polypeptide maps were analyzed by PDQuest software. Protein quantities, defined as the total integrated optical density of the spots, were compared between groups of high-fertility sires (n = 12; PD >or= 0) and low-fertility sires (n = 8; PD < 0) and were also used as independent variables in regression analysis. Proteins were identified by capillary liquid chromatography-nanoelectrospray ionization-tandem mass spectrometry. An average of 118 spots was detected in 2-D maps of the CEF, but we were unable to distinguish any protein that was expressed only in high-fertility or in low-fertility bulls. However, the amount of alpha-L-fucosidase 2 and cathepsin D was 2.3- and 2.4-fold greater (P < .05) in high-fertility than in low-fertility bulls, respectively. Conversely, the intensities of 3 isoforms (24-27 kd; pl 6.3-5.8) of prostaglandin D-synthase (PGDS) were from 3.2- to 2.2-fold greater in low-fertility sires (P < .05). An empirical regression model established that a significant proportion (R(2) = 0.72; P < .0001) of the variation in fertility scores (PD values) was explained by the intensities of cathepsin D and 1 isoform of PGDS (24 kd; pl 6.3). Thus, multiple proteins present in the CEF are potential biomarkers of fertility in high-use, mature Holstein bulls.

Animals↗
PubMed2007

Visual system of calliphorid flies: organization of optic glomeruli and their lobula complex efferents.

Reconstructions of silver-stained brains revealed 27 optic glomeruli that occupy a major volume of the lateral protocerebrum. Axons from different morphological types of columnar output neurons from the lobula complex sort out to specific glomeruli. Glomeruli are partially enwrapped by glial processes and are invaded by the dendrites and terminals of local interneurons that connect different glomeruli in a manner analogous to local interneurons in the antennal lobes. Each type of columnar neuron contributes to a palisade-like ensemble that extends across the whole or a circumscribed area of the retinotopic mosaic. A second class of outputs from the lobula comprises wide-field neurons, the dendrites of which interact with planar fields or column-like patches of retinotopic inputs from the medulla. These neurons also send their axons to optic glomeruli. Dye fills demonstrate that lobula complex neurons supplying glomeruli do not generally terminate directly on descending neurons. Local interneurons and projection neurons provide integrative circuitry within and among glomeruli. As exemplified by the anterior optic tubercle, optic glomeruli can also have elaborate internal architectures. The results are discussed with respect to the identification of motion- and orientation-selective neurons at the level of the lobula and lateral protocerebrum and with respect to the evolutionary implications raised by the existence of neural arrangements serving the compound eyes, which are organized like neuropils serving segmental ganglia equipped with appendages.

Animals↗
PubMed2003

Electrophysiological imaging of functional architecture in the cortical middle temporal visual area of Cebus apella monkey.

We studied the spatial organization of directionally selective neurons in the cortical middle temporal visual area (area MT) of the Cebus monkey. We recorded neuronal activity from multielectrode arrays as they were stepped through area MT. The set of recording sites in each array penetration described a plane parallel to the cortical layers. At each recording site, we determined the preferred direction of motion. Responses recorded at successive locations from the same electrode in the array revealed gradual changes in preferred direction, along with occasional directional reversals. Comparisons of responses from adjacent electrodes at successive locations enabled electrophysiological imaging of the two-dimensional pattern of preferred directions across the cortex. Our results demonstrate a systematic organization for directionality in area MT of the New World Cebus monkey, which is similar to that known to exist in the Old World macaque. In addition, our results provide electrophysiological confirmation of map features that have been documented in other cortical areas and primate species by optical imaging. Specifically, the tangential organization of directional selectivity is characterized by slow continuous changes in directional preference, as well as lines (fractures) and points (singularities) that fragment continuous regions into patches. These electrophysiological methods also allowed a direct investigation of neuronal selectivities that give rise to map features. In particular, our results suggest that inhibitory mechanisms may be involved in the generation of fractures and singularities.

Animals↗
PubMed2004

High-resolution functional optical imaging: from the neocortex to the eye.

Much work remains to be done to establish the clinical usefulness of the RFI for early diagnosis and treatment guidance. The discoveries obtained by functional optical imaging of the neocortex in the last 15 years and the recent RFI studies of the eyes of normal subjects and patients with diabetic retinopathy, glaucoma, and age-related macular degeneration suggest that functional optical imaging of the retina is likely to become a multi-modality powerful clinical tool.

Animals↗
PubMedDate not supplied

Chorioretinal topography and histopathology in laser-induced choroidal neovascularization.

OBJECTIVE: To investigate the correspondence between topographic mapping of the vitreoretinal and chorioretinal surfaces in vivo and histopathology findings. MATERIALS AND METHODS: Choroidal neovascularization was induced in the retina of a primate by an argon laser. Serial optical section images of the retina were obtained using an optical imaging system based on the Retinal Thickness Analyzer. Topography of the vitreoretinal and chorioretinal surfaces was mapped. The animal was killed and the eyes enucleated for histopathologic examination. RESULTS: In the normal retina, the topography of the vitreoretinal surface showed a depression at the center of the fovea while the chorioretinal surface was relatively flat, corresponding to normal anatomy. In the retina with choroidal neovascularization, the topography of the vitreoretinal surface indicated a smooth elevation while there were irregular elevations in the topography of the chorioretinal surface. Histological sections displayed focal serous retinal detachment, metaplasia of retinal pigment epithelium, and choroidal neovascularization. CONCLUSION: Topographic mapping of the vitreoretinal and chorioretinal surfaces in vivo corresponds with histological findings and shows promise for quantitative evaluation of pathologic alterations caused by chorioretinal diseases.

Animals↗
PubMed1996

Estimation of self-motion by optic flow processing in single visual interneurons.

Humans, animals and some mobile robots use visual motion cues for object detection and navigation in structured surroundings. Motion is commonly sensed by large arrays of small field movement detectors, each preferring motion in a particular direction. Self-motion generates distinct 'optic flow fields' in the eyes that depend on the type and direction of the momentary locomotion (rotation, translation). To investigate how the optic flow is processed at the neuronal level, we recorded intracellularly from identified interneurons in the third visual neuropile of the blowfly. The distribution of local motion tuning over their huge receptive fields was mapped in detail. The global structure of the resulting 'motion response fields' is remarkably similar to optic flow fields. Thus, the organization of the receptive fields of the so-called VS neurons strongly suggests that each of these neurons specifically extracts the rotatory component of the optic flow around a particular horizontal axis. Other neurons are probably adapted to extract translatory flow components. This study shows how complex visual discrimination can be achieved by task-oriented preprocessing in single neurons.

Animals↗
PubMed2004

Quantification of ternary mixtures of heavy metal cations from metallochromic absorbance spectra using neural network inversion.

A new method based on artificial neural networks (ANN) for the processing of spectrophotometric data is proposed and illustrated on the example of the simultaneous quantification of ternary mixtures of zinc, cadmium, and mercury cations in aqueous solutions. Three types of commercially available metallochromic indicators were used as a simple model setup to create spectral data analogous to those normally received from an optical sensor array. In conventional ANN training methods for chemical sensors based on spectrophotometric data, a calibration is established by mathematically correlating the measured optical signal as network input with the concentration of the calibration sample as network output. In several situations, however, especially when dealing with mixed sample solutions, the relationship between a measured absorption spectrum and the corresponding ion concentrations is ambiguous, resulting in an "ill-posed problem". On the other hand, if the training direction is reversed by correlating known sample concentrations with measured optical signals, the relationship becomes reasonable for the ANN to obtain its structure. The proposed model illustrated in this paper is based on a more reasonable direct mapping and estimation by artificial neural network inversion (ANNI). In the training step, sample mixtures of known concentrations are optically measured to construct networks correlating the input data (ion concentrations) and the output data (absorption spectra). In the estimation step, the ion concentrations of unknown samples are estimated using the constructed ANN. The measured spectra of the unknown samples are fed to the output layer, and the appropriate input concentrations are determined by ANNI. When training the ANN system with 143 ternary mixtures of Zn2+, Cd2+, and Hg2+ in a concentration range from 1 to 100 microM, root-mean-square errors of prediction (RMSEP) of 0.45 (Zn2+), 0.96 (Cd2+), and 0.32 microM (Hg2+) were observed for the estimation of concentrations in 30 test samples, using the ANNI procedure. This newly proposed model, which involves the construction of an ANN based on direct mapping and estimation by ANNI, opens up one way to overcome the limitations of nonselective sensors, allowing the use of more easily accessible semiselective receptors to realize smart chemical sensing systems.

Journal Article↗
PubMed1994

Visual hemispheric dominance induced in split brain cats during development: a model of deficient interhemispheric transfer derived from physiological evidence in single visual cortex cells.

The effects of cancellation of both interhemispheric callosal transfer and interocular interactions, were studied in early monocularly deprived cats. The main purpose of this study was therefore to prove whether unilateral hemispheric dominance would result under these conditions and to what extent each hemisphere will be functionally independent. Secondly, we have attempted to establish such an experimental model physiologically, on the single cell level. Interhemispheric transfer was surgically canceled by sagittal transection of the corpus callosum. In addition, the ocular projections were separated by sagittal transection of the optic chiasm in the transbuccal approach. This condition had practically induced visual split brain condition in these cats. These manipulations were carried out concurrently with monocular deprivation (SBDK group) which was surgically done by eye closure during the critical period of development of the visual system. Thus, the hemisphere ipsilaterally to the visually deprived eye had developed under conditions of deficient visual experience while the hemisphere ipsilaterally to the normal eye had developed under conditions of unaltered visual experience. A group of cats (SBK) similarly operated but equally binocularly exposed during development was served as controls. In addition, adult cats similarly operated during adulthood either chronically or acutely were studied to evaluate the effects of interhemispheric and interocular separation. Other groups of cats were also studied for comparison, and included sham operated and normal adult cats. At adulthood, electrophysiological studies were done on these cats, in which action potentials were extracellularly recorded from single cells in the visual cortex (area 17-18 boundary) following anesthesia and paralysis. Stimulation was carried out manually and by a computer driven optical system, presenting on a tangent screen light bars at various spatial positions, orientations and directions. Receptive fields were thus mapped for all neurons and their dimensions and eccentricities were measured. The responsiveness, ocular dominance and other parameters were also studied for these cells. The results in the early deprived cats and in their controls, had shown a full separation between the two hemispheres, as reflected in the almost absolute ipsilateral eye responsiveness (> 97.0% cells). In comparison, in the sham operated and in the normal control cats only minor proportions of cells (13.0-18.7%) have been found as ipsilaterally and monocularly driven, showing almost full interhemispheric and interocular interaction. The main difference, however, in the results between the early monocularly deprived cats and their controls is that in the first group the two hemispheres were asymmetric concerning the amount of visual activation and in the second one they were very symmetric.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1980

[Reactions of dogfish shark (Squalus acanthias L.) forebrain neurons evoked by visual stimulation].

In unanesthetized immobilized spiny dogfish sharks, functional organization of the forebrain afferent projections was studied with the aid of evoked potentials (EPs) and neuronal responses to adequate stimulation of the eye with light and to electric stimulation of the optic nerve. The forebrain spontaneous unit activity (from 0.1 to 2.8 Hz) changed in response to the optic nerve electric stimulation with latency varying from 58 to 280 msec. Two foci of maximum unit activity were found at the depth of the visual area: at the levels from 850 to 1050 microns and from 1400 to 1600 microns from the forebrain surface. Histogram analysis of the data obtained showed that the main components of EPs reflected postsynaptic processes occurring in the dendrites of the forebrain visual area.

Animals↗
PubMed1997

Optical imaging of cat auditory cortex cochleotopic selectivity evoked by acute electrical stimulation of a multi-channel cochlear implant.

We measured reflectance changes by means of optical imaging of intrinsic signals to study the effects of acute electrical cochlear stimulation on the topography of the cat auditory cortex. After single-pulse electrical stimulation at selected sites of a multichannel implant device, we found topographically restricted response areas representing mainly the high-frequency range in AI. Systematic variation of the stimulation pairs and thus of the cochlear frequency sites revealed a systematic and corresponding shift of the response areas that matched the underlying frequency organization. Intensity functions were usually very steep. Increasingly higher stimulation currents evoked increasingly larger response areas, resulting in decreasing spatial, i.e. cochleotopic, selectivity; however, we observed only slight positional shifts of the focal zones of activity. Electrophysiological recordings of local field potential maps in the same individual animals revealed close correspondence of the locations of the cortical response areas. The results suggest that the method of optical imaging can be used to map response areas evoked by electrical cochlear stimulation, thereby maintaining a profound cochleotopic selectivity. Further experiments in chronically stimulated animals will shed more light on the degree of functional and reorganizational capacities of the primary cortex and could be beneficial for our understanding of the treatment of profound deafness.

Animals↗