Coherent Picture on the Pure Spin Transport between Ag/Bi and Ferromagnets

In a joint effort of both experiments and first-principles calculations, we resolve a hotly debated controversy and provide a coherent picture on the pure spin transport between Ag/Bi and ferromagnets. We demonstrate a strong inverse Rashba-Edelstein effect (IREE) at the interface in between Ag/Bi with a ferromagnetic metal (FM) but not with a ferromagnetic insulator. This is in sharp contrast to the previously claimed IREE at Ag/Bi interface or inverse spin Hall effect dominated spin transport. A more than one order of magnitude modulation of IREE signal is realized for different Ag/Bi-FM interfaces, casting strong tunability and a new direction for searching efficient spintronics materials.

Two-dimensional aspect ratio discrimination for shape defined by orientation texture

A pattern of 12,860 short (0.15 x 0.05 deg) texture lines contained an orientation texture-defined (OTD) rectangle of aspect ratio a/b (a was the rectangle's height and b was its width). All the lines within the rectangle had the same orientation and all the lines outside the rectangle had the same orientation. These two orientations were theta deg symmetrically clockwise and anticlockwise of the vertical. The rectangle's visibility was created entirely by the orientation difference 2 theta. Aspect ratio discrimination threshold for the texture-defined rectangle was a U-shaped function of theta that was approximately symmetrical about theta = 45 deg. The lowest values of aspect ratio discrimination threshold were 2.8% (SE = 0.1%), 2.7% (SE = 0.1%) and 5.1% (SE = 0.3%) for three observers. A luminance-defined (LD) rectangle with the same spatial sampling as the OTD rectangle was created by removing all texture lines outside the rectangle. Aspect ratio discrimination threshold for the LD rectangle was 1.1% (SE = 0.1%), 1.7% (SE = 0.1%) and 2.2% (SE = 0.1%)) for the same three observers. Although these discrimination thresholds were not greatly lower than discrimination thresholds for the OTD rectangle, they were significantly lower at the P < 0.001 level. Discrimination thresholds for the OTD rectangle are comparable with the lowest aspect ratio discrimination thresholds for motion-defined (MD) rectangles (2 and 3% for two observers), and for disparity-defined (DD) rectangles (3.1, 3.4, 4.0 and 7.4% for four observers), even though the MD and DD rectangles were much smaller than the 185 deg2 OTD rectangle used in the present study.

Loss of sensitivity to motion-defined form in patients with primary open-angle glaucoma and ocular hypertension

During the past few years many researchers have attempted to find a psychophysical test that will identify at an early stage patients at risk for developing glaucoma. We investigated the ability of a test of motion-defined (MD) form recognition to discriminate between patients with primary open-angle glaucoma (POAG) and control subjects and to identify patients with ocular hypertension (OHT) at risk for developing glaucoma. Performance on two MD tests and three tests of static, luminance-defined (LD) form recognition was compared. Speed thresholds for reading MD letters proved to be the most sensitive test of early glaucomatous damage. 80% of POAG and 38% of OHT patients were abnormal on this test. During a 3-year follow-up period, 50% of these OHT patients developed glaucoma. These psychophysical findings support the hypothesis of early motion deficits in glaucoma.

Recognition and detection of texture-defined letters

We quantified texture segregation by measuring psychophysically the percent correct detection scores for a set of 10 texture-defined (TD) letters using two-alternative forced-choice, and at the same time quantified spatial discrimination of TD form by measuring psychophysically the percent correct letter recognition scores for the 10 letters using 10-alternative forced-choice. Ten levels of task difficulty were created by adding noise dots to the texture patterns. Two kinds of letters were used. Static textures had the same letter and the same texture pattern throughout any given 1-sec presentation. Dynamic textures had the same letter, but a different texture pattern for every one of the 70 frames during any given 1-sec presentation. For both static and dynamic textures, letter recognition scores fell to chance level from a lower number of noise dots than did letter detection scores. Both recognition and detection scores were generally better for dynamic than for static texture patterns. We suggest that, for dynamic textures, subjects were able to enhance the signal-to-noise ratios of the noisy letters by signal averaging.

Defective processing of motion-defined form in the fellow eye of patients with unilateral amblyopia

The following three measurements were made on a group of 20 pediatric and 5 adult patients with unilateral amblyopia: (1) speed threshold for recognizing motion-defined dotted letters; (2) recognition acuity for isolated solid letters of 4% contrast; and (3) Snellen line acuity for high-contrast letters. Normal limits were established with a group of 30 pediatric and 10 adult control subjects. The main finding was that, in amblyopic children, a high percentage (83%, 15 of 18) of fellow eyes showed a degraded ability to recognize motion-defined letters, even though Snellen acuity and 4% letter acuity were normal for age. The fellow eyes of all nine patients with strabismic amblyopia showed this pattern of loss, as did four of six fellow eyes of patients with anisometropic amblyopia and two of three fellow eyes of patients with anisometropic plus strabismic amblyopia. Only two clinically unaffected eyes were normal for motion-defined letters. These eyes belonged to patients with anisometropic amblyopia. Eighteen of the 19 previously amblyopic eyes tested were abnormal for motion-defined letters even though Snellen acuity was within normal limits for 6 of these eyes. In adults, only one of five fellow eyes failed the motion-defined letter test. It was concluded that the degradation of form perception associated with amblyopia can be different for luminance-defined and motion-defined form and that defective processing of motion-defined form is common in the fellow eyes of children with unilateral amblyopia.

Motion-defined letter detection and recognition in patients with multiple sclerosis

Two important distinctions in visual perception are (1) between the detection and recognition of shape (e.g., letters), and (2) between the recognition of shapes defined by a difference in brightness and the recognition of shapes defined by a difference in motion. We report that 6 of 10 patients with multiple sclerosis showed impaired recognition for motion-defined (MD) letters, although the detection of MD letters was normal as were both detection and recognition of luminance-defined letters. We have shown that this was not a function of acuity loss or the loss of ability to detect motion or a general failure of recognition per se, but was confined to a loss of ability to recognize MD letters. The neurological implications of these findings are discussed, and it is suggested that the MD letter test be used by others interested in the central pathology of visual disorders.

Visual processing of motion-defined form: selective failure in patients with parietotemporal lesions

The following psychophysical data were obtained from 13 patients with unilateral cerebral hemispheric lesions and 20 control subjects: speed thresholds for detecting and for recognizing motion-defined letters, speed thresholds for detecting coherent motion and for discriminating its direction, and visual acuity for recognizing letters of 96% and 11% contrast. Acuity was between 6/6 and 6/3 for all patients. Four patients showed a selective loss of ability to recognize motion-defined letters, while the ability to detect those same letters was spared, as was the ability to detect coherent motion and discriminate its direction (type I loss). Three patients showed a loss of ability both to recognize and to detect motion-defined letters, while the ability to detect coherent motion and discriminate its direction was spared (type II loss). All seven patients who failed to recognize motion-defined letters had extensive lesions in parietotemporal white matter underlying Brodmann cortical areas 18, 19, 37, 39, 21, and 22. The lesion was in the left hemisphere for three patients and in the right hemisphere for the remaining four. The region of overlap in these seven patients was not invaded by the lesion in any of the other six patients, and none of these six patients showed a loss of ability to recognize motion-defined letters. Three patients showed selective loss of acuity for low-contrast letters with normal Snellen acuity. The lesions in these three patients extended more posteriorly than in any other patient, and their region of overlap was in white matter underlying areas 18 and 19. We conclude that (1) the loss of ability to recognize letters in seven patients was specific to motion-defined letters rather than being a general loss of letter-recognition ability, (2) this visual loss was specific to motion-defined form rather than being a general failure of motion processing, and (3) the visual loss was not produced by lesions that did not involve the localized cerebral region specified above. To explain the existence of type I and of type II loss with sparing of the detection and discrimination of coherent motion, we propose that motion information is processed hierarchically. We further suggest that homologs of the socalled motion and color/form pathways (i.e., areas V1/MT/MST/7a and areas V1/V4/IT) are interconnected to form a distributed system that is important for the recognition of motion-defined form.(ABSTRACT TRUNCATED AT 400 WORDS)

Visual acuity for optotypes made visible by relative motion

There are several visual mechanisms for analyzing spatial information additional to the much researched mechanism sensitive to luminance contrast. We describe a Snellen-type acuity test for motion-defined (MD) letters. Acuity for these MD letters collapsed at dot speeds slower than 0.05 deg/s, but acuity for contrast-defined (CD) letters was unaffected by speed over the entire 0 to 0.3 deg/s range used. Acuity was a power function of presentation duration for both kinds of letter, but the exponent was higher for MD than for CD letters. Acuity for MD letters was comparatively unaffected by dot density from 50 to 0.05%, below which it suddenly collapsed to zero. On the other hand, acuity for CD letters progressively fell as dot density was reduced from 50%, and below about 0.5% approximated acuity for MD letters.