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PubMed1996

Discrepancy between brain magnetic fields elicited by pattern and luminance stimulations in the fovea: adequate stimulus positions and a measure of discrepancy.

A conventional equivalent current dipole estimation provides one of the quantitative measures to evaluate the discrepancy between two single-dipole-like magnetic field patterns, though there is one problem; all stimulus positions in the visual field do not necessarily contribute to the generation of a single-dipole-like magnetic field. Another important problem occurs when the field pattern is complex and cannot be approximated by a dipole. This makes it difficult to evaluate the discrepancy between two magnetic field patterns by the dipole parameters. In this paper, we determined the stimulus positions adequate for generating single-dipole-like magnetic field patterns by evaluating the magnetic field's goodness-of-fit to the field generated by a single dipole. We propose to use a similarity (SIM) as a quantitative measure of the discrepancy between two complex magnetic field patterns. The SIM is defined as an angle between two magnetic field vectors. We evaluated the discrepancy between the 100 ms post-stimulus responses to pattern-reversal (Rv) stimulus, pattern-onset (Pat) stimulus, and luminance-onset (Lumi) stimulus. The following results were obtained: (1) Stimulation of some of the octants in the fovea, far from the vertical meridian, elicited a single-dipole-like magnetic field pattern at a latency of 100 ms, though stimulation of the central part of the fovea, and stimulation of the octants along the vertical meridian, did not elicit a single-dipole-like magnetic field pattern; (2) The discrepancy between responses was quantitatively evaluated by the SIM even if the field patterns were complex; (3) The SIM analysis showed that the discrepancy between the responses to the Rv and the Lumi stimuli, as well as that between the responses to the Pat and the Lumi stimuli, were greater than that between the responses to the Rv and the Pat stimuli.

Adult↗

PubMed1988

The Schilling test cannot be replaced by an absorption test with unlabeled vitamin B12.

It was the purpose of this study to evaluate the diagnostic usefulness of an oral absorption test using nonlabeled Vit B12 suggested by a commercial distributor as an alternative for the more expensive Schilling test (ST). Plasma levels of Vit B12 were measured with a commercial kit before and 4 h after oral administration of 1 mg Vit B12 in 32 normals, in 16 patients with normal ST, and in 14 patients with abnormal ST for determination of sensitivity and specificity with the ST as golden standard. In normals, a mean of 767 +/- 404 pg/ml before and 1096 +/- 776 pg/ml after oral Vit B12 with a mean increase of 331 +/- 453 pg/ml was measured. Because of the obvious large variation, no meaningful range for normal absorption could be established. In the two patient subsets, there was no Gaussian distribution of the results, with a meridian of Vit B12 increase after absorption of 142 pg/ml, range 27-2668 pg/ml, in the group with normal ST and a meridian of 244 pg/ml ranging from 40 to 2453 pg/ml in the group with abnormal ST. Statistical nonparametric analysis did not reveal any difference between the two groups. Assuming a minimum required increase of 100 pg/ml, as suggested by the kit distributor, a sensitivity of only 27% and a specificity of 75% was obtained.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1977

Surgical induction of corneal astigmatism. An experimental study.

The aim of all ocular surgery is to preserve or restore optimal visual function. Reduction of excessive postoperative astigmatism after keratoplasty, cataract extraction, or other anterior segment operations has been obtained in clinical surgery by corneal wedge resection. The purpose of this experimental investigation was to quantify and evaluate the results of different microsurgical techniques in crescentic resection of a corneal wedge. Twenty-five rabbits were operated and the induced changes of corneal curvature measured by keratometry. The immediate and long-term results are presented. The effect of wedge resection was a steepening of the meridian perpendicular to the resection and a flattening of the meridian parallel to the resection. The astigmatism induced was less pronounced than the changes obtained in human surgery. There were no postoperative ocular complications and all corneas remained clear. It is suggested that the operation be performed in all cases of severe corneal astigmatism uncorrected by lenses.

Animals↗

PubMed1989

A multimedia medical communication link between a radiology department and an emergency department.

The most critical aspect of a radiologist's work is communicating his findings to the attending physician responsible for the patient's care. This is also the part of the process that is least well organized and the most subject to failure. At the University of Ottawa Medical Communications Research Centre we are investigating technical means to improving communications between radiologists and attending physicians. We first introduce the radiology communication service problem and show why it is essentially a multimedia communication problem. We then briefly describe a multimedia communication system designed and implemented by our research team. The multimedia system consists of several work stations linked by the Hospital's local area network (LAN). Each physician work station comprises a Compaq 386/20-Mhz microcomputer with 16 Mbytes of RAM, a 500-Mbyte image disk, and an image memory that drives a 1,000-line monochrome monitor. The images are digitized using a Konica laser-based film digitizer (2430 by 2000 10-bit pixels for a standard chest radiograph). The multimedia file server manager station is built around a PC-AT compatible with a Northern Telecom Meridian SL-1ST digital PBX and a Meridian Mail digital voice messaging system. This last device is used to store voice data and is linked via the PBX to the workstations' digital telephones. A Sytek 6,000 LAN links all work stations to the file server. All data, image, and graphic information is transmitted via this network, while the twisted pair connections linking the digital PBX to the telephone sets are used for transmitting voice data.(ABSTRACT TRUNCATED AT 250 WORDS)

Computer Communication Networks↗

PubMed1997

Manual interception of moving targets. I. Performance and movement initiation.

We investigated the capacities of human subjects to intercept moving targets in a two-dimensional (2D) space. Subjects were instructed to intercept moving targets on a computer screen using a cursor controlled by an articulated 2D manipulandum. A target was presented in 1 of 18 combinations of three acceleration types (constant acceleration, constant deceleration, and constant velocity) and six target motion times, from 0.5 to 2.0 s. First, subjects held the cursor in a start zone located at the bottom of the screen along the vertical meridian. After a pseudorandom hold period, the target appeared in the lower left or right corner of the screen and traveled at 45 degrees toward an interception zone located on the vertical meridian 12.5 cm above the start zone. For a trial to be considered successful, the subject's cursor had to enter the interception zone within 100 ms of the target's arrival at the center of the interception zone and stay inside a slightly larger hold zone. Trials in which the cursor arrived more than 100 ms before the target were classified as "early errors," whereas trials in which the cursor arrived more than 100 ms after the target were classified as "late errors." Given the criteria above, the task proved to be difficult for the subjects. Only 41.3% (1080 out of 2614) of the movements were successful, whereas the remaining 58.7% were temporal (i.e., early or late) errors. A large majority of the early errors occurred in trials with decelerating targets, and their percentage tended to increase with longer target motion times. In contrast, late errors occurred in relation to all three target acceleration types, and their percentage tended to decrease with longer target motion times. Three models of movement initiation were investigated. First, the threshold-distance model, originally proposed for optokinetic eye movements to constant-velocity visual stimuli, maintains that response time is composed of two parts, a constant processing time and the time required for the stimulus to travel a threshold distance. This model only partially fit our data. Second, the threshold-tau model, originally proposed as a strategy for movement initiation, assumes that the subject uses the first-order estimate of time-to-contact (tau) to determine when to initiate the interception movement. Similar to the threshold distance model, the threshold-tau model only partially fit the data. Finally, a dual-strategy model was developed which allowed for the adoption of either of the two strategies for movement initiation; namely, a strategy based on the threshold-distance model ("reactive" strategy) and another based on the threshold-tau model ("predictive" strategy). This model provided a good fit to the data. In fact, individual subjects preferred to use one or the other strategy. This preference was allowed to be manifested at long target motion times, whereas shorter target motion times (i.e., 0.5 s and 0.8 s) forced the subjects to use only the reactive strategy.

Adult↗

PubMed2000

"Third tier" ventral extrastriate cortex in the New World monkey, Cebus apella.

The ventral extrastriate cortex adjacent to the second visual area was studied in the New World monkey Cebus apella, using anaesthetised preparations. The visuotopic organisation and myeloarchitecture of this region demonstrate the existence of a distinct strip of cortex, 3-4 mm wide, with an ordered representation of the contralateral upper visual quadrant, up to 60 degrees eccentricity. This upper-quadrant representation is probably homologous to the ventral subdivision of the third visual complex (V3v) of Old World monkeys, also known as the ventral posterior area. The representation of the horizontal meridian in V3v forms its posterior and medial border with V2, while the upper vertical meridian is represented anterior and laterally, forming a congruent border with the fourth visual area (V4). Central visual fields are represented in posterior and lateral portions of V3v, in the inferior occipital sulcus, while the periphery of the visual field is represented anteriorly, on the tentorial surface. Cortex anterior to V3v, at the ventral occipitotemporal transition, had neurones that had poor visual responses. No representation of the lower quadrant was found adjacent to V3v in ventral cortex. However, we observed cells with perifoveal receptive fields centred in the lower quadrant immediately dorsal to V3v, around the junction of the inferior occipital and lunate sulci. These observations argue against the idea that V3v is an area restricted to the ventral cortex in New World monkeys and support the conclusions of previous anatomical studies in Cebus that showed a continuity of myeloarchitecture and connectional patterns between ventral and lateral extrastriate cortices. Together, these data suggest that V3v may be part of a larger area that extends into dorsolateral extrastriate cortex, overlapping to some extent with the caudal subdivision of the dorsolateral area described in other New World monkeys.

Animals↗

PubMed2001

Spatial deployment of attention within and across hemifields in an auditory task.

Research on visual attention has demonstrated that covert attention can be focused on particular locations within one hemifield, but that a specific "meridian" cost may also be found for shifting attention between hemifields. These issues have received less consideration for audition, even though reliable behavioral measures for the effects of spatial attention on hearing are now available. We examined the spatial distribution of covert attention in an auditory task following spatially non-predictive peripheral auditory cues (which should induce exogenous attention shifts), or following symbolic central cues that predicted the likely location for the auditory target (to induce endogenous attention shifts). In both cases, we found that attention can be focused not only on one hemifield versus another, but also within one hemifield in an auditory task. However, there was no unequivocal evidence for a meridian effect in audition.

Adult↗

PubMed2005

Fixation topography in normal test persons.

BACKGROUND: The eye is moved so that the object of interest falls on the central fovea, where the spatial resolution is highest. In the present study we quantified eye movements of normal test persons during steady fixation and characterized the fixation using a 3D fixation plot (X horizontal eye position, Y vertical eye position, Z time in each eye position). METHOD: Fixation eye movements were quantified binocularly in ten normal test persons during a 40-s fixation task using an infrared recording technique. RESULTS: The fixation plot was characterized by a single preferred fixation locus in 17 eyes. One eye had two distinctly separated preferred fixation locations and in two eyes the configuration of fixation plot was flat with no single identifiable locus of fixation. The fixation plots were elliptical along the horizontal meridian in 9 eyes, elliptical along the vertical meridian in 8 eyes, and round in 3 eyes. The fixation area (RAF95) ranged between 1418 and 14182 arcmin(2), and a significant positive correlation was found between RAF95 and the mean microsaccadic amplitude (p<0.001). CONCLUSION: The fixation plots are often characterized by a single preferred fixation locus but may also be almost flat with no identifiable location of fixation. The individual fixations patterns resembles the cone density contour plots as found in histological studies, and it may be speculated, that the shape of the fixation plot is determined by the cone density topography.

Adult↗

PubMed2000

Measurement of a novel optic disc topographic parameter, "spikiness", in glaucoma.

BACKGROUND: Structural changes in the lamina cribrosa have been implicated in the pathogenesis of glaucomatous optic atrophy, but not observed. This paper presents a novel parameter of topographic variability within the optic disc, termed "spikiness", which may reflect glaucoma-related changes in the lamina. METHODS: Four age-matched groups of normal patients (n=12, mean age 64.8 years) and patients with ocular hypertension (n=14, mean age 63.1), primary open-angle glaucoma (n=11, mean age 70) and low-tension glaucoma (n=15, mean age 66.3) were recruited. Images of normal and glaucomatous eyes from the Heidelberg Retina Tomograph were imported into ERDAS image processing software where the spikiness data (30 consecutive mean surface height values across the base of the optic cup in both the vertical and horizontal meridians) were extracted in a format that facilitated further statistical analysis. RESULTS: Significant differences in topographic variability (spikiness) existed in the vertical (F=3.64, P=0.01) but not the horizontal meridian (F=1.25, P=0.3) through the optic disc. Spikiness was inversely related to Humphrey mean deviation (P<0.05), and cup-disc ratio (P<0.004) and was directly related to nerve fibre layer thickness (P<0.005). Of particular interest was the finding that the spikiness measure was the only optic disc parameter to significantly discriminate low tension glaucoma from primary open angle glaucoma. CONCLUSION: A new measure of surface variability (topography) at the floor of the optic cup has been described. The new index of spikiness may represent a measurement of lamina cribrosa fragility which has been implicated, but not previously estimated, in glaucomatous eyes.

Aged↗

PubMed1999

Information from false statements concerning visual acuity and visual field in cases of psychogenic visual impairment.

BACKGROUND: If visual acuity (VA) and/or visual field (VF) is claimed to be worse than in reality, it can be difficult to estimate the actual VA/VF. This paper describes a method of proving malingering and of estimating the actual VA by statistical evaluation of the subjective responses to discrete visual stimuli. METHODS: VA is measured by using a Landolt or Snellen optotype with four possible directions. There are n (> or = 16) questions at each acuity level. Each direction of the optotype occurs with the same frequency. The sequence is not predictable. In testing the VF, the stimulus is presented in an unpredictable sequence but with the same frequency at each of four distinct locations outside the claimed field at the horizontal and the vertical meridian. The field is divided into four quadrants defined by the 45 degrees-225 degrees and 135 degrees-315 degrees meridians. The candidate is requested to search for the light. The target quadrant of the first eye movement is recorded. At each VA level, the distribution function of the binomial formula allows estimation of the probability Pc of < or = kc and > or = kc correct answers to n questions by mere accident. Regarding the VF, the direction of the first saccade at each stimulus presentation can be processed accordingly. RESULTS: If n = 32 and kc = 0,1,2, the chance P that this pattern is merely accidental is about 0.0001, 0.001, 0.007. Values of P < or = 0.01 strongly suggest that the answers were voluntarily wrong. Preference for the opposite direction can also point to psychogenic influence: If ko = 15,16,17,18, P is about 0.006, 0.002, 0.0006, 0.0002. CONCLUSION: Systematically false statements can yield valuable information about the actual visual functions.

Adult↗

PubMed1999

Morphometric study of the displacement of retinal ganglion cells subserving cones within the human fovea.

BACKGROUND: A study was carried out to measure the displacement of retinal ganglion cells subserving the cones within the human fovea. METHODS: Four human retinas were examined along the nasal or vertical hemi-meridians. Total displacement was estimated by adding the displacement due to fibres of Henle and bipolar cells, measured as the lateral extension of the Henle fibres and of the obliquely running fibre bundles within the inner nuclear layer, respectively. RESULTS: At the foveal border (0.5-0.8 mm or 1.8-2.9 deg eccentricity) the mean offset due to fibres of Henle and mean total lateral displacement was at a maximum of 0.32 +/- 0.03 mm and 0.37 +/- 0.03 mm, respectively. A steep decrease of displacement was found outside the foveal border out to an eccentricity of 2.0-2.5 mm. We were able to plot displacement along the vertical meridian in relation to eccentricity with good correlation between three eyes. The data were used to establish different mathematical functions describing the relation between eccentricity and displacement. These functions were applied to previously presented data on densities of retinal ganglion cells and cones. CONCLUSIONS: The present estimates of displacement within the human central fovea offer the possibility of analysis of quantitative relations between cones and retinal ganglion cells. Our data provide predictive guidance by establishing that vitreo-retinal procedures causing damage to retinal ganglion cells up to 1 mm from the foveal centre could have implications for loss of information generated within the fovea.

Adult↗

PubMed1996

Three-dimensional arrangement of enamel prisms and their relation to the formation of Hunter-Schreger bands in dog tooth.

The three-dimensional architecture of enamel prisms and their relationship to Hunter-Schreger bands were examined in the developing enamel of several dog teeth by light and electron microscopy, and computer-assisted reconstruction. Sections were prepared from a single demineralized tooth germ. Longitudinal semithin sections parallel to the meridian of the tooth showed parazones and diazones of the Hunter-Schreger bands in alternate rows at equal intervals. On sections vertical to the tooth crown through the middle region of parazone or diazone, a row of parallel prisms were angulated with the largest tilting angle being 55 degrees to the enamel-dentin junction, running in opposite directions in the respective zones. Tangential sections parallel to the enamel-dentin junction showed numerous belt-like zones arranged perpendicular to the meridian of the tooth. Each belt-like zone consisted of a group of enamel prisms oriented in the same direction, those in the neighboring zones being oriented in an opposite direction. The densely stained boundaries between the adjacent belt-like zones corresponded to the interface between parazone and diazone. Computer-reconstructed enamel prisms in the adjacent two zones were oriented in the opposite sidewards direction with occasional confluence and divergence. Scanning electron-microscopic observation of the developing enamel surface exposed by dissolution of the enamel organ revealed band-like arrangements of groups of pits encasing the Tomes' processes of secretory ameloblasts. The secretory faces of the pits inclined uniformly in the same sidewards direction, with those in the neighboring groups, in the opposite direction.

Animals↗

PubMed2003

Comparison of a commercial reversed passive latex agglutination assay to an enzyme immunoassay for the detection of Shiga toxin-producing Escherichia coli.

A multicenter study was performed to compare the performance of a prototypic reversed passive latex agglutination assay (VTEC Screen "Seiken"; Denka-Seiken, Japan) with the Premier EHEC Enzyme Immunoassay (Meridian Diagnostics, USA) for the detection of Shiga toxin in 554 diarrheal stool samples. Standard culture on sorbitol MacConkey agar and the use of latex agglutination reagents were included to identify the Escherichia coli O157, O26 and O111 serotypes. There was 99% agreement between the VTEC screen and enzyme immunoassay (kappa=0.823). Seventeen samples were positive for toxin by one or both assays. One toxin-positive sample using the enzyme immunoassay and four positive samples using the VTEC Screen could not be confirmed. Serotypes identified included: O157:H7 (n=8), O26 (n=2), O111 (n=1) and O45:H2 (n=1). The VTEC screen is easy to perform and comparable to the Meridian EHEC test for detection of Shiga toxin in clinical samples.

Escherichia coli↗

PubMed2005

Laser acupuncture induced specific cerebral cortical and subcortical activations in humans.

As recent studies demonstrated, acupuncture can elicit activity in specific brain areas. This study aims to explore further the central effect using laser acupuncture. We investigated the cerebral effects of laser acupuncture at both acupoints GB43 with functional magnetic resonance imaging (fMRI). As a control condition the laser was mounted at the same acupoints but without application of laser stimulation. The group results showed significant brain activations within the thalamus, nucleus subthalamicus, nucleus ruber, the brainstem, and the Brodmann areas 40 and 22 for the acupuncture condition. No significant brain activations were observed within the placebo condition. The activations we observed were laser acupuncture-specific and predominantly ipsilateral. This supports the assumption that acupuncture is mediated by meridians, since meridians do not cross to the other side. Furthermore, we could show that laser acupuncture allows one to design a pure placebo condition.

Acupuncture Points↗

PubMed2006

Changes in the structure of neuronal connections in the visual cortex of cats with experimentally induced bilateral strabismus.

The spatial distribution of neuronal connections in cortical field 17 was studied in cats with experimentally induced bilateral convergent strabismus on postnatal days 10-14. Horseradish peroxidase was applied microiontophoretically to individual columns of neurons in fields 17 and 18 and retrograde-labeled cells were identified in both hemispheres. Increases and decreases in the extent of intra-hemisphere connections were seen in the mediolateral direction (projections of the horizontal meridian of the visual field). Most columns showed increases in inter-hemisphere connections in this same direction, which may support the more reliable unification of the two visual hemifields. In addition, some columns showed increases in intra-and inter-hemisphere connections in the rostrocaudal direction (projections of the vertical meridian). Thus, bilateral strabismus induced during the critical period of development leads to changes in the structure of both intra-hemisphere and inter-hemisphere connections of individual cortical columns in fields 17 and 18.

Animals↗

PubMed2026

Transcriptomic Insights into Acupuncture Mechanisms in Protecting Ovarian Function in Mice with Premature Ovarian Insufficiency.

OBJECTIVE: To explore the molecular mechanisms underlying the protective effect of acupuncture on ovarian function in mice with cyclophosphamide-induced premature ovarian insufficiency (POI) via transcriptomic analysis. METHODS: Twenty female C57BL/6 mice were divided into 4 groups: control, model, acupuncture, and non-meridian/non-acupoint (NOMA). POI was induced in the model, acupuncture, and non-meridian/non-acupoint groups via cyclophosphamide injection. The acupuncture group received acupuncture at Guanyuan (CV 4), bilateral Guilai (ST 29), and Sanyinjiao (SP 6) for 3 weeks. After the intervention, ovarian tissue weight and ovarian coefficient were calculated, serum levels of key reproductive hormones including follicle-stimulating hormone (FSH), luteinizing hormone (LH) and anti-Müllerian hormone (AMH) were detected, and ovarian histopathological changes were observed to evaluate ovarian function. Transcriptome sequencing was performed to identify differentially expressed genes (DEGs), followed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses to explore key functional terms and signaling pathways. Western blot was finally applied to validate the expression of core proteins related to mitochondrial function, endoplasmic reticulum stress and inflammatory pathways. RESULTS: The model group showed reduced ovarian weight and elevated FSH levels. The acupuncture group exhibited significantly higher ovarian weight and coefficient, lower FSH levels, and increased E2 and AMH levels compared to the model group (all P<0.01). Transcriptomic analysis revealed 4,021 DEGs between groups. GO and KEGG analyses revealed that these DEGs were mainly involved in oocyte development, steroid hormone synthesis, and pathways related to mitochondrial function, endoplasmic reticulum stress, and inflammatory signaling. Western blot analysis showed that acupuncture partially restored mitochondrial function markers cytochrome c oxidase subunit IV and NADH dehydrogenase 1 beta subcomplex subunit 8 and reduced endoplasmic reticulum stress markers (glucose-regulated protein 78 and Calnexin, P<0.01). It also downregulated pro-inflammatory proteins (IL-17R, IL-17A, NF-κB p65, p-NF-κB p65, ERK1/2, and p-ERK1/2) and upregulated proteins related to metabolic homeostasis (peroxisome proliferator-activated receptor γ, receptor-interacting protein 140, nicotinamide phosphoribosyltransferase, and sirtuin 1, P<0.01). CONCLUSION: Acupuncture effectively alleviates cyclophosphamide-induced POI in mice, improves ovarian function and follicular quality by regulating cellular functions and inflammatory pathways, suggesting a novel therapeutic approach for POI.

acupuncture↗

PubMed1978

Computer analysis of left ventricular dynamic geometry in man.

Analysis of left ventricular performance in 20 normal patients was undertaken using biplane cineangiography and a semiautomatic computer image processing system. The analysis included evaluation of volumes, ejection fraction, regional shortening, patterns of ejection and filling and, when simultaneous left ventricular pressure was recorded stroke work, stroke power, wall stress and internal myocardial work. All of these data were calculated from digitized images stored permanently on digital magnetic tape, and can be reproduced without reanalysis of the cine film. Normal left ventricular function is described by an end-diastolic volume index of 82 +/- 3 ml, an ejection fraction of 60 +/- 2 percent, left ventricular mass index of 97 +/- 6 g/m2, peak first derivative of volume (dV/dt) of 485 +/- 28 ml/sec, anterior shortening of 48 +/- 2.3 percent, inferior shortening of 33 +/- 1.7 percent, lateral shortening of 29 +/- 1.5 percent, anterior mean shortening velocity (Vcf, in percent of end-diastolic length [L]/sec) of 1.5 +/- 0.1 L/sec, inferior Vcf of 1.1 +/- 0.06 L/sec and lateral Vcf of 0.94 +/- 0.2 L/sec, stroke work of 1.33 +/- 0.21 joules, mean stroke power of 3.7 +/- 0.62 joules/sec, integrated left ventricular pressure (tension-time index) of 2,866 +/- 340 mm Hg-sec, and integrated stress (stress-time index) of 7,260 +/- 765 (X 10(3)) dynes sec/cm2. Internal myocardial work was calculated from the strain energy. More internal work was expended in circumferential than logitudinal shortening (circumferential, 0.69 +/- 0.1 joules; longitudinal, 0.41 +/- 0.08, P less than 0.01), because hoop stress was greater than meridian stress (hoop, 201 +/- 20 dynes/cm3 X 10(3); meridian, 126 +/- 13, P less than 0.001). This analysis of left ventricular performance provides a reliable means for identifying abnormal ventricular function and may be more sensitive than any one measurement alone. The use of digital image processing makes this complex functional analysis of left ventricular performance feasible.

Adult↗

PubMed1975

Ocular torsion and the function of the vertical extraocular muscles.

The vertical corneal meridia are not kept perpendicular to the horizon in human and nonhuman primates when the head or body is tilted, i.e., compensatory counter-rolling of the eyes does not occur. The slight torsional displacement of the vertical corneal meridia noted by many observers may be the result of rotation around an axis or to translation of the globe. The neurologic and structural systems that control the actions of the vertical muscles in human and nonhuman primates do not appear to provide a mechanism for wheel-rotation of the eyes around the pupillary axis. Ocular torsion is not a normal function of the vertical extraocular muscles. Their function is probably the reverse, i.e., the inhibition or prevention of ocular torsion and the stabilization of the eyes when the head or body inclines. Torsional displacement of a vertical corneal meridian occurs only when there is an abnormal muscle imbalance. Wheel-like movements (cycloduction) around the pupillary axis or visual line do not occur. Torsional displacement of a vertical corneal meridian occurs only with a simultaneous vertical movement. The vertical rectus and the oblique muscles in man work together to produce vertical ocular movements regardless of head position of body posture while maintaining the vertical corneal meridia parallel to the sagittal plane of the head. The vestibular apparatus may be responsible for distributing innervation among these muscles, enabling them to function in this manner.

Animals↗