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At least 19 recordsLinked to original sources
PubMed1977

Optokinetic motion sickness: continuous head movements attenuate the visual induction of apparent self-rotation and symptoms of motion sickness.

Symptoms of motion sickness are sometimes experienced during exposure to optokinetic stimulation. Two experimetns were performed to compare the symptoms of motion sickness elicited when subjects were exposed to incremental changes in optokinetic stimulation while sitting passively and while continuously executing shoulder-to-shoulder head movements. In the first experiment, a fixed head-movement frequency (20 cpm) was used, wheras in the second the subjects varied the frequency of their head movements in order to maintain suppression of illusory self-rotation. In both experiments, subjects in the head-moving condition had fewer and less severe symptoms of motion sickness and experienced illusory self-rotation after longer exposure times and at higher optokinetic velocities than in the head-stationary condition. Subjects in th- head-movement condition of the second experiment increased the frequency of their head movements as the velocity of optokinetic stimulation increased. The symptoms of motion sickness elicited during optokinetic stimulation tended to be dizziness, headache, eye-strain, and stomach awareness appearing in no fixed order. The pattern and constellation of symptoms are unlike those elicited by vestibular stimulation.

Eye Movements↗
PubMed1977

Visual motion aftereffect induced by simulated rectilinear motion.

Visual motion aftereffect characteristics comparable to those associated with rotary and translatory movement of a test field are demonstrated for simulated rectilinear motion of the observer. The intensity and time duration of the phenomenon are shown to be positively correlated. The implications of this for individual observers are considered. The results of this experiment are correlated with those for adaptation and for recovery from adaptation that were obtained from the same group of observers. The findings are shown to support the hypothesis that visual motion affereffect is a manifestation of the adaptation recovery function of velocity sensitive mechanisms.

Adult↗
PubMed1975

ESR spectral analysis of the molecular motion of spin labels in lipid bilayers and membranes based on a model in terms of two angular motional parameters and rotational correlation times.

Electron spin resonance (ESR) spectral line shapes are calculated for a nitroxide spin-labeled molecule undergoing rapid restricted rotations (twisting) about its long molecular axis while simultaneously tumbling within a cone. Explicit expressions are derived for the hyperfine splittings and g-values, as well as for the secular contributions to the motionally modulated linewidths. The present model is useful for analyzing the restricted twisting and tumbling motions, and rotational correlation times, of spin-labeled molecules in bilayers. Simulated spectra compare well with experimental spectra of lecithin bilayers marked with cholestane spin label, over a wide temperature range.

Cholestanes↗
PubMed1975

Choice reaction time to visual motion during prolonged rotary motion in airline pilots.

Thirteen airline pilots were studied to determine the effect of preceding rotary accelerations on the choice reaction time to the horizontal acceleration of a vertical line on a cathode-ray tube. On each trial, one of three levels of ratary and visual acceleration was presented with the ratary stimulus preceding the visual by one of seven periods. The two accelerations were always equal and were presented in the same or opposite directions. The reaction time was found to increase with increases in the time the rotary acceleration preceded the visual acceleration, and to decrease with increased levels of visual and rotary acceleration. The reaction time was found to be shorter when the accelerations were in the same direction than when they were in opposite directions. These results suggest that these findings are a special case of general effect that the authors have termed "gyrovisual modulation."

Acceleration↗
PubMed1979

Induced motion as a function of the speed of the inducing object, measured by means of two methods.

Induced motion is illustrated by the apparent motion imparted to a stationary disc by the horizontal motion of an enclosing frame. The present study examined the effect of frame speed, with a constant extent of frame motion, on the magnitude of induced motion for average frame speeds varying from 0.17 to 2.85 deg s-1. The induced motion was measured by two methods. (i) The observer adjusted the horizontal distance between comparison posts to indicate the extent of the horizontal induced motion in a physically stationary disc. (ii) The observer adjusted the slant of a comparison rod to indicate the apparent path of motion of the disc physically moving straight up and down in phase with the horizontal motion of the surrounding frame. The latter method requires the observer to integrate two apparent components of motion of the disc, one from its physical vertical motion and the other from its induced horizontal motion. The results from both methods show that substantial amounts of induction occurred at all of the frame speeds. The vector addition of apparent motions from real and from induced motion obtained from the second method, and the substantial amounts of induction found with the high frame speeds are interpreted to indicate that the processes underlying the perception of real and induced motion are essentially the same.

Adult↗
PubMed1977

Ventricular septal motion and left ventriclular dimensions during abnormal ventricular activation.

To determine the effect of abnormal ventricular activation on ventricular septal motion, left ventricular endocardial motion and left ventricular dimensions, 12 patients with normal motion were studied with echocardiography during incremental pacing of the right ventricular apex, outflow and inflow regions. Three types of abnormal ventricular septal motion were seen: The type I pattern was characterized by an early rapid preejection posterior ventricular septal motion followed by another posterior systolic motion that lasted throughout ejection, both of which were associated with septal thickening. In the type II pattern an early rapid preejection posterior ventricular septal motion was followed by an anterior ejection motion; the latter was not accompanied by septal thickening. The type III pattern consisted of an early preejection posterior ventricular septal motion followed by a mid and late systolic posterior motion: the latter motion extended through diastole. During right ventricular apical pacing, 8 of 11 patients showed a type 1 pattern, 1 a type II pattern and 2 a normal septal motion. During right ventricular outflow pacing,seven of nine patients showed a type II pattern, one a type III pattern and one a type I pattern. During right ventricular inflow pacing, eight of nine patients showed a type II pattern and one a type III pattern. At faster pacing rates patterns of types I and III changed to a type II pattern (five patients). End-diastolic dimensions decreased significantly during incremental right ventricular pacing when compared with those during sinus rhythm. End-systolic dimensions decreased significantly only during right ventricular apical and outflow pacing at maximal rates. In the seven patients who had pacing from all three sites, the decrease in left ventricular dimensions did not significantly differ when the three pacing sites were compared. These findings suggest that (1) abnormal ventricular septal motion during right ventricular pacing (induced left bundle branch block patterns) is dependent on the sequence of ventricular activation; (2) ventricular septal motion during right ventricular outflow and inflow pacing is similar to that seen in spontaneous left bundle branch block, whereas the pattern of septal motion during right ventricular apical pacing is different from that of spontaneous left bundle branch block; and (3) changes in left ventricular dimension are dependent on ventricular pacing rate but independent of pacing site.

Adult↗
PubMed1979

Stereoscopic subsystems for position in depth and for motion in depth.

We describe psychophysical evidence that the human visual system contains information-processing channels for motion in depth in addition to those for position in depth. These motion-in-depth channels include some that are selectively sensitive to the relative velocities of the left and right retinal images. We propose that the visual pathway contains stereoscopic (cyclopean) motion filters that respond to only a narrow range of the directions of motion in depth. Turning to the single-neuron level we report that, in addition to neurons turned to position to depth, cat visual cortex contains neurons that emphasize information about the direction of motion at the expense of positional information. We describe psychophysical evidence for the existence of channels that are sensitive to change size, and are separate from the channels both for motion and for flicker. These changing-size channels respond independently of whether the stimulus is a bright square on a dark ground or a dark square on a bright ground. At the physiological level we report single neurons in cat visual cortex that respond selectively to increasing or to decreasing size independently of the sign of stimulus contrast. Adaptation to a changing-size stimulus produces two separable after-effects: an illusion of changing size, and an illusion of motion in depth. These after-effects have different decay time constants. We propose a psychophysical model in which changing-size filters feed a motion-in-depth stage, and suppose that the motion-in-depth after-effect is due to activity at the motion-in-depth stage, while the changing-size after-effect is due to to activity at the changing-size and more peripheral stages. The motion-in-depth after-effect can be cancelled either by a changing-size test stimulus or by relative motion of the left and right retinal images. Opposition of these two cues can also cancel the impression of motion in depth produced by the adapting stimulus. These findings link the stereoscopic (cyclopean) motion filters and the changing-size filters: both feed the same motion-in-depth stage.

Animals↗
PubMed1975

Improvement in left ventricular wall motion following nitroglycerin.

Coronary artery disease patients frequently have left ventricular wall motion abnormalities. Though nitroglycerin is commonly used in ischemic heart disease, its effects on wall motion abnormalities is unknown. In this study we have evaluated the effects of nitroglycerin on wall motion abnormalities and on ejection fraction in 25 patients. Sixteen had coronary artery disease (greater than 70% luminal narrowing). Six had no evidence of heart disease and three had congestive cardiomyopathies with normal coronary arteries. Left ventricular angiography was performed prior to and six minutes after administration of 0.4 mg of sublingual nitroglycerin. Twelve of the 16 coronary artery disease patients had wall motion abnormalities, and in seven of these, segmental wall motion improved after nitroglycerin. In five, all motion did not change. The initial heart rate, left ventricular systolic and end-diastolic pressure, and left ventricular end-diastolic volumes were not different for those whose wall motion improved versus those whose did not. The increase in the former and fall in the latter three hemodynamic parameters were significant (P less than 0.01) and similar for the two groups. In those whose wall motion abnormalities improved after nitroglycerin, ejection fraction (mean plus or minus se) increased significantly (P less than 0.05), from 0.47 plus or minus 0.025 to 0.62 plus or minus 0.046. In those without improvement, the ejection fraction went from 0.55 plus or minus 0.056 to 0.58 plus or minus 0.051 (NS). Three patients with congestive cardiomyopathy showed no improvement in ventricular wall motion or ejection fraction after nitroglycerin. Left ventricular wall motion abnormalities and ejection fraction improved in some coronary artery disease patients following nitroglycerin. The mechanism for this is unknown; however, ventriculography before and after nitroglycerin may be of potential usefulness for identifying areas of reversible wall motion abnormalities.

Adult↗
PubMed1977

Reappraisal of jugular phlebogram in the diagnosis of tricuspid regurgitation. Relationship between echocardiographic interventricular septal motion and jugular phlebogram.

Little information is available concerning the relationship between the pattern of the jugular phlebogram and interventricular septal motion. We studied 250 patients with various conditons. Abnormal septal motion was observed in only 33% of the patients with tricuspid regurgitation. All the patients having abnormal septal motion and 66% of those having normal septal motion had the jugular pattern of tricuspid regurgitation. After cardiac operation with the incision of cardiac chambers and pericardiotomy, abnormal septal motion was seen from 40 to 89% at early postoperative period. Of the patients studied approximately 1 year after operation, there was reduced incidence of septal abnormality. Septal motion was normal in all the patients who had ligation of a patent ductus arteriosus and who underwent Blalock's operation. Of these, all having paradoxical motion which occurred in the mid-septum at least had the jugular pattern of tricuspid regurgitation. On the other hand, only 20 to 30% of the patients whose septal motion was normal had the jugular pattern of tricuspid regurgitation. Furthermore, all of the 3 patients with coronary artery disease having paradoxical motion of the entire septum had the jugular pattern of tricuspid regurgitation, as well. We conclude that the jugular pattern of tricuspid regurgitation and echocardiographic septal motion abnormality are related to each other and that tricuspid regurgitation should not be diagnosed by jugular phlebogram unless echocardiographic septal motion is examined.

Adolescent↗
PubMed1977

Relation of split apparent motion to metacontrast.

The apparent suppression of the target in metacontrast is often accompanied by "split" apparent motion. In Experiments 1, 4, 5, and 6 "neighboring stimuli" (similar to and flanking the mask stimuli) were added to the display, and subjects rated both metacontrast and split motion. Under some conditions, both split motion and metacontrast were completely eliminated (Experiment 1), supporting the assumption that apparent motion is necessary for metacontrast. However, under other conditions, neighboring stimuli caused a much stronger depression of metacontrast than of split motion (Experiments 4 and 5), sometimes even enhancing the latter (Experiment 6), supporting the assumption that the mechanisms underlying the two phenomena are essentially independent. Further, peripheral presentation and close spacing of target and mask with no neighboring stimuli (Experiments 2 and 3) gave strong metacontrast while completely eliminating split motion, showing clearly that apparent motion is not necessary for metacontrast. Results are interpreted in terms of a "fusion" process underlying metacontrast and a "direction-sensitive unit" underlying apparent motion. Interactions between these two processes that might account for the common co-occurrence of motion and metacontrast are proposed.

Fixation, Ocular↗
PubMed1975

Motility in Echinosphaerium nucleofilum. I. An analysis of particle motions in the axopodia and a direct test of the involvement of the axoneme.

The motion of particles in the axopodia of Echinosphaerium nucleofilum is saltatory. In the present study, photokymograph records of 123 motions from six axopodia have been analyzed. Particles followed rectilinear paths of from 1 to 15 mum while in continuous motion at an average velocity of 0.66 plus or minus 0.32 mum/s. The velocity of the particles was variable in 36% of the cases measured. Some motions were punctuated by pauses either before continuing in the same direction or reversing. Frequently, several particles were moving at the same velocity, but neighboring particles showed no motion or moved in the opposite direction. Two particles occasionally contacted one another and travelled as a unit for varying lengths of time but subsequently moved independently. These motions reflect the underlying mechanism of motive force production. Furthermore, a glass microneedle can be substituted for the microtubular axoneme in the axopodia. In these artificial axopodia, bidirectional particle motions occurred which were similar to those in normal axopodia. Colchicine, at the threshold dose for axonemal dissolution, had no affect on these particel motions. It is concluded that the microtubular axoneme is not responsible for particle motions and also that individual microtubules are unlikely candidates for motive force production in this system.

Animals↗
PubMed1979

Limitations of the cardiokymograph for assessing left ventricular wall motion.

In order to evaluate the reliability and reproducibility of the CKG we studied four groups of patients. In 27 patients with a prior myocardial infarction the CKG recordings were compared to simultaneous wall motion videotracking. Identical wall motion was recorded in 75% of left ventricular sites and most of the discordant sites were false abnormal posterior wall motion recorded by the CKG. The second group consisted of 21 normal subjects studied by CKG only and 35% displayed anterior dyskinesis during expiration. The third group consisted of nine stable patients who were studied on two separate days by CKG and identical wall motion was recorded in only 55% of the sites on the two recordings. The final group consisted of seven patients with mitral regurgitation and all had late systolic outward movement posteriorly. Systolic wall motion was normal postoperatively in the three patients who underwent valve replacement. We conclude that: (1) the usefulness of the CKG is limited by the frequent recording of false wall motion abnormalities in normal subjects, (2) false anterior wall motion abnormalities can be reduced by recording during inspiration, (3) false posterior wall motion abnormalities may be due to systolic left atrial expansion, and (4) cardioxymography recordings are often not reproducible.

Adult↗