Up-Down Asymmetries in Speed Perception

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 6-6 ◽  
Author(s):  
P Thompson ◽  
L S Stone
Keyword(s):  
Spatial Frequency ◽  
Central Point ◽  
The Other ◽  
Upward Motion ◽  
Optokinetic Response ◽  
Downward Motion ◽  
Preliminary Results ◽  
Sinusoidal Gratings ◽  
Speed Perception

We compared speed matches for pairs of stimuli that moved in opposite directions (upward and downward). Stimuli were elliptical patches (2 deg horizontally by 1 deg vertically) of horizontal sinusoidal gratings of spatial frequency 2 cycles deg−1. Two sequential 380 ms foveal presentations were compared. One of each pair of gratings (the standard) moved at 4 Hz (2 deg s−1), the other (the test) moved at a rate determined by a simple up - down staircase. The point of subjectively equal speed was calculated from the average of the last eight reversals. The task was to fixate a central point and to determine which one of the pair appeared to move faster. Eight of ten observers perceived the upward drifting grating as moving faster than a grating moving downward but otherwise identical. On average (N = 10), when the standard moved downward, it was matched by a test moving upward at 94.7± 1.7(SE)% of the standard speed, and when the standard moved upward it was matched by a test moving downward at 105.1± 2.3(SE)% of the standard speed. On extending this paradigm over a range of spatial (1.5 to 13.5 cycles deg−1) and temporal (1.5 to 13.5 Hz) frequencies, preliminary results (N = 4) suggest that, under the conditions of our experiment, upward motion is seen as faster than downward motion for speeds greater than ∼1 deg s−1, but the effect appears to reverse at speeds below ∼1 deg s−1 with downward motion perceived as faster. Given that an up - down asymmetry has been observed by other investigators for the optokinetic response, both perceptual and oculomotor contributions to this phenomenon deserve exploration.

Discrimination between Plaids: Do Oriented Filters Combine Dichoptically?

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 299-299
Author(s):  
L A Olzak ◽  
R L Wong
Keyword(s):  
Spatial Frequency ◽  
Opposite Sign ◽  
Pattern Discrimination ◽  
The Other ◽  
Frequency Content ◽  
Low Contrast ◽  
Combination Process ◽  
Test Conditions ◽  
Sinusoidal Gratings ◽  
Confidence Scale

Two oblique gratings combine perceptually to form a chequerboard appearance under monoptic presentation but not under dichoptic presentation (Georgeson and Meese, 1996 Perception25 Supplement, 121), suggesting an early combination process. Combining processes that operate over orthogonal orientations are also observed in complex pattern discrimination tasks (Olzak and Thomas, 1991 Vision Research31 1885 – 1898). We ask here whether the interactions observed in discrimination tasks occur before or beyond the site of binocular interaction. Observers discriminated between two patterns that differed slightly in their spatial-frequency content. On each trial, one of the two patterns was presented. Observers judged which stimulus had been presented on a 1 – 6 confidence scale. In control conditions, the stimuli were single sinusoidal gratings near 3 cycles deg−1, and were always presented monoptically. In test conditions, a second component was added to the first in each stimulus. The second component was either presented to the same eye as the first component (monoptic presentation), or to the other eye (dichoptic presentation). The second component was either a mask of exactly 3 cycles deg−1, or varied to give a second cue to discrimination. Second cues either varied with the first (both components lower frequency or both higher) or varied in opposite sign (high with low). Rivalry was eliminated by using low contrast (10 × threshold) and small (1.2 deg) patterns. Our results suggest that the combination processes we observe occur beyond the site of binocular combination and differ from those mediating the percept.

Aristotle De Caelo 288a 2–9

1939 ◽  
Vol 33 (1) ◽  
pp. 34-35
Author(s):  
F. M. Cornford
Keyword(s):  
The Other ◽  
Present Problem ◽  
Upward Motion ◽  
Forward Motion ◽  
Downward Motion ◽  
The World ◽  
The Universe

Aristotle is asking why the heaven revolves in one direction rather than the other. His answer is based on his earlier proof that the Universe has a top and a bottom, a right and a left. The upper region, as the place of divinity, is prior or superior to the lower; so upward motion is prior to downward motion. Right is similarly prior and superior to left. The present problem can be solved by supposing that the world has also a front and a back, and hence a forward motion, which will be prior and superior to backward motion. Since Nature always follows the best course, the reason for the direction of the heaven's revolution will be that that direction is forward and therefore better.

Adaptation in single units in visual cortex: The tuning of aftereffects in the spatial domain

1989 ◽  
Vol 2 (6) ◽  
pp. 593-607 ◽  
Author(s):  
A. B. Saul ◽  
M. S. Cynader
Keyword(s):  
Spatial Frequency ◽  
Cortical Neurons ◽  
Frequency Tuning ◽  
Cortical Cell ◽  
Selective Adaptation ◽  
Single Units ◽  
Spatial Frequency Tuning ◽  
Sinusoidal Gratings ◽  
A Cell ◽  
Drift Direction

AbstractCat striate cortical neurons were investigated using a new method of studying adaptation aftereffects. Stimuli were sinusoidal gratings of variable contrast, spatial frequency, and drift direction and rate. A series of alternating adapting and test trials was presented while recording from single units. Control trials were completely integrated with the adapted trials in these experiments.Every cortical cell tested showed selective adaptation aftereffects. Adapting at suprathreshold contrasts invariably reduced contrast sensitivity. Significant aftereffects could be observed even when adapting at low contrasts.The spatial-frequency tuning of aftereffects varied from cell to cell. Adapting at a given spatial frequency generally resulted in a broad response reduction at test frequencies above and below the adapting frequency. Many cells lost responses predominantly at frequencies lower than the adapting frequency.The tuning of aftereffects varied with the adapting frequency. In particular, the strongest aftereffects occurred near the adapting frequency. Adapting at frequencies just above the optimum for a cell often altered the spatial-frequency tuning by shifting the peak toward lower frequencies. The fact that the tuning of aftereffects did not simply match the tuning of the cell, but depended on the adapting stimulus, implies that extrinsic mechanisms are involved in adaptation effects.

scholarly journals Nietzsche’s Dionysos

2017 ◽  
Vol 3 (3) ◽  
pp. 604
Author(s):  
Dieter Mersch
Keyword(s):  
Necessary Conditions ◽  
Central Point ◽  
The Other ◽  
Other Hand ◽  
The Absolute ◽  
The Aesthetic

Nietzsche’s Dionysus, admittedly, represents a direct provocation and an attack on the classical interpretation accepted since Winckelmann, an interpretation that elevates the Apollonian to its central point of focus; Nietzsche’s introduction of another principle to oppose it, rather than representing a genuine invention, in actuality bridges the small gap between Hegel and Hölderlin. If, namely, the Hegelian aesthetic from the very beginning points to Schein and Erscheinung – as necessary conditions of truth, for the truth would not exist if it were not to “superficially appear” (scheinen) and “make its appearance” (erscheinen), writes Hegel – Schein and Erscheinung would still nonetheless be bound up everywhere with the criterium of the absolute; after all, the untruth of the aesthetic rests squarely in the fact that it cannot do other than to draw upon the language of Erscheinung. For Hölderlin, on the other hand, the Dionysian advances to become a metapoetic symbol combining itself – the enigmatic and continually transforming – with the practice of art. Nietzsche follows those very same lines even while giving the metaphor a thoroughly different twist.

Temporal-Discontinuity Detection with Contrast-Modulated Gratings

Perception ◽  
1995 ◽  
Vol 24 (11) ◽  
pp. 1257-1264
Author(s):  
Shigeru Ichihara ◽  
Kenji Susami
Keyword(s):  
Spatial Frequency ◽  
Modulation Frequency ◽  
Sinusoidal Grating ◽  
Local Contrast ◽  
Staircase Method ◽  
Low Contrast ◽  
Discontinuity Detection ◽  
Temporal Discontinuity ◽  
Sinusoidal Gratings ◽  
The Subject

Three experiments on temporal-discontinuity detection were carried out. In experiment 1, temporal-discontinuity thresholds were measured for sinusoidal gratings by the use of the double-staircase method. A sinusoidal grating was presented twice successively. The subject judged whether or not an interval was present. The temporal-discontinuity threshold increased as the spatial frequency of the grating increased, but decreased as the contrast of the grating increased. In experiment 2, contrast-modulated gratings were used instead of the sinusoidal grating. The temporal-discontinuity threshold increased as the carrier frequency increased, and the threshold for each contrast-modulated grating was similar to that for the no-modulation (sinusoidal) grating whose contrast was the same as the maximum local contrast of the contrast-modulated grating. In experiment 3, temporal-discontinuity thresholds were measured for low-contrast (3%) sinusoidal gratings. The thresholds were very low, even for such low-contrast gratings. These results suggest that the low-spatial-frequency channels are not involved in detecting the modulation frequency of the contrast-modulated grating. Rather, the local contrast seems to be the determinant of the detection of the contrast-modulated grating itself.

A Knowledge-Based Approach for Microwire Casting Plant Control

2011 ◽  
pp. 419-437
Author(s):  
S. Zaporojan ◽  
C. Plotnic ◽  
I. Calmicov ◽  
V. Larin
Keyword(s):  
Continuous Casting ◽  
Casting Process ◽  
Video Camera ◽  
The Other ◽  
Advanced Materials ◽  
Casting Plant ◽  
Preliminary Results ◽  
Sensor Applications ◽  
Knowledge Based ◽  
Main Ideas

This chapter presents the main ideas and preliminary results of an applied research project concerning the development of an intelligent plant for microwire casting. The properties of glass-coated microwires are useful for a variety of sensor applications. On the other hand, the process of casting can be one of the methods of nanotechnology and advanced materials. In microwire continuous casting, the main control problem is to maintain the optimum thermal and flow conditions of the process, in order to fabricate the microwire of a given stable diameter. Unlike a conventional casting plant, we propose to use a video camera to take the picture of the molten drop and to control the casting process by means of a knowledge based system. For this reason, a model, that is capable of taking into account the current features of the process and of describing the shape of the drop at each time, is developed. The model presented here should allow us to estimate the geometry of the metal-filled capillary and predict the diameter of microwire at each time during the casting process.

The Values of β-TG During the Anticoagulant Therapy in Patients with Venous Thrombosis and Myocardial Infarction

1979 ◽  
Author(s):  
A. Lucic ◽  
R. Borota ◽  
Z. Radujkov
Keyword(s):  
Myocardial Infarction ◽  
Venous Thrombosis ◽  
Deep Venous Thrombosis ◽  
Anticoagulant Therapy ◽  
The Other ◽  
Prothrombin Activity ◽  
Normal Concentration ◽  
Preliminary Results ◽  
Other Hand

In 38 patients with deep venous thrombosis and 52 patients with myocardial infarction who were on long term anticoagulant therapy, the estimations of β-TG have been done by radioimmunoassay using a kit developed by the Radiochemical Centre, Amersham, England. In the group of patients with deep venous thrombosis, the increased values of β-TG /values which were higher than 80 ng/ml /have been established in 47,3% of the cases and among the patients with myocardial infarction, in 73% of the cases. From the total of 56 patients with increased level of β-TG, in 50 patients the level of prothrombin activity was higher than 20%. On the other hand, in patients with normal concentration of β-TG, the level of prothrombin activity was usually lower than 20%. Our preliminary results suggest the possible use of estimation of β-TG as an important supplementary parameter for evaluation of a substantial efficasy of applied anticoagulant therapy.

Visual Stimuli for Strabismic Suppression

Perception ◽  
1977 ◽  
Vol 6 (5) ◽  
pp. 583-593 ◽  
Author(s):  
Clifton M Schor
Keyword(s):  
Spatial Frequency ◽  
Binocular Vision ◽  
Binocular Rivalry ◽  
Visual Stimuli ◽  
Normal Group ◽  
Sensory Fusion ◽  
Sinusoidal Gratings

The effects of orientation and spatial frequency of grating stimuli upon suppression were examined with a binocular rivalry paradigm in a group of ten strabismic patients and in a control normal group. Duration, frequency, and period of rivalry were examined as functions of differences in orientation and spatial frequency of dichoptic achromatic sinusoidal gratings. Records were made of responses by the sighting and by the nonsighting eye as well as responses during periods of combined binocular vision. Strabismic subjects reported normal binocular rivalry when presented with gratings of dissimilar orientation. Suppression of the deviating eye in strabismic subjects occurred with stimuli of similar orientation and was unaffected by spatial-frequency differences between dichoptic stimuli. Suppression was most intense under conditions that normally stimulate stereopsis and sensory fusion.

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