Biomedical subjects

M Ohmi

Publications and source records attributed to M Ohmi.

At least 109 records · Page 6Linked to original sources

PubMed1987

Circular vection as a function of foreground-background relationships.

It has previously been reported that illusory self-rotation (circular vection) is most effectively induced by the more distant of two moving displays. Experiments are reported in which the relative effectiveness of two superimposed displays in generating circular vection as a function of (i) the separation in depth between them, (ii) their perceived relative distances, and (iii) which display was in the plane of focus was investigated. Circular vection was governed by the motion of the display that was perceived to be the more distant, even when it was actually nearer. However, actual or perceived distance was found to be not the crucial factor in circular vection because even when the distance between the two displays was virtually zero, vection was controlled by the display perceived to be in the background. When the displays were well separated in depth, vection was not affected by whether the near or the far display was in the plane of focus, nor by which display was fixed or pursued by the eyes.

Depth Perception↗

PubMed1986

Directional preponderance in human optokinetic nystagmus.

In afoveate animals, and in neonatal or cortically deficient foveate animals, monocular optokinetic nystagmus (OKN) is controlled by directly innervated subcortical nuclei and occurs only in response to temporonasal motion. In higher mammals, the subcortical nuclei receive direct inputs predominantly from the nasal hemiretinae and indirect inputs from the visual cortex. These indirect inputs counterbalance the directional asymmetry of the primitive mechanism. These facts lead to the prediction that the velocity of the slow phase of OKN in the normal human adult should be higher for stimuli moving centripetally rather than centrifugally in each monocular and binocular hemified. The predicted patterns of directional preponderance were found in both monocular and binocular hemifields. Directional asymmetries were still present in monocular hemifields when the central retina was occluded and were reduced when the stimulus was confined to a narrow central strip of the visual field. These results are discussed in terms of the contributions of the central and peripheral retina to directional preponderance.

Adult↗

PubMed1986

Optokinetic nystagmus: the effects of stationary edges, alone and in combination with central occlusion.

In Experiment 1 we investigated the independent and combined effects of horizontal OKN of stationary edges and occlusion of the central retina. For a display 60 degrees wide moving at 30 degrees/sec a symmetrically placed pair of vertical nonoccluding bars suppressed OKN when near the center of the display but had no effect when 30 degrees apart. A 7 degrees-high 60 degrees-wide central occluder reduced OKN gain by 37%. However, a central occluder with edges only 30 degrees wide abolished OKN. In Experiment 2 this interaction between central occlusion and stationary edges was confirmed with a wider display over a range of stimulus velocities and configurations. A functional explanation of this interaction is presented.

Adult↗

PubMed1984

Depression of host-defence mechanisms following cardiac surgery.

The purpose of the present study was to determine the effects of open-heart surgery on host-defence mechanisms, by studying serial changes in serum immunoglobulins, circulating lymphocyte function in patients undergoing open-heart surgery. Serum proteins and immunoglobulins were significantly depressed immediately after operation and these depressions were correlated to the degree of the durations of cardiopulmonary bypass and associated hypothermia. White cell counts in peripheral blood increased significantly after operation. In contrast, total circulating lymphocytes were depressed postoperatively. The depression of circulating lymphocytes was mainly due to a marked decrease in the number of T-cells. Mitogen responses of lymphocytes stimulated by phytohemagglutinin were also depressed postoperatively. The quantitative and qualitative depression of cell-mediated immunity following open-heart surgery was observed. However, these depressions returned to preoperative levels in one week and had no clinical significance.

Adult↗

PubMed1984

The efficiency of the central and peripheral retina in driving human optokinetic nystagmus.

Previous experiments to decide whether the gain of optokinetic nystagmus (OKN) is increased or decreased by occlusion of the central retina involved the use of stationary edges on the occluder and unmatched contrasts. With these factors controlled, it was confirmed that OKN gain is severely reduced by occlusion of the central retina but only at stimulus velocities above about 30 degrees/sec. The gain of horizontal OKN was found not to increase with increasing width of the display if the lateral edges are blurred. The high gain of centrally driven OKN may be related to the ability of higher mammals to stabilize the images of objects at a given distance in a complex parallactic visual field.

Humans↗

PubMed1984