Leech therapy: when once is not enough.

Venous congestion is a constant threat in the survival of free flaps, pedicled flaps, tissue replantations and traumatized tissue. Leech therapy has proved effective in salvaging much of these compromised tissues. To be effective, leeches must be both readily available and hungry, requirements not always easily met.

Coarse spatial scales constrain the range of binocular fusion on fine scales.

To examine interactions among spatial scales in disparity processing, we have measured the upper disparity limit for binocular single vision (the diplopia threshold) for high-spatial-frequency test stimuli in the presence of cosine gratings of lower spatial frequency that defined a surface in depth. When the frequency of this grating surface was 2.0 octaves below that of the test, the test fusion range was reduced by a factor of 3-4 relative to the condition in which no grating surface was present.

Left-handedness: a marker for decreased survival fitness.

Life span studies have shown that the population percentage of left-handers diminishes steadily, so that they are drastically underrepresented in the oldest age groups. Data are reviewed that indicate that this population trend is due to the reduced longevity of left-handers. Some of the elevated risk for sinistrals is apparently due to environmental factors that elevate their accident susceptibility.

Stereopsis from motion-defined contours.

Random-dot stereograms demonstrate that monocularly visible contours are not necessary for stereopsis, although in the absence of point-for-point correspondence, they are sufficient for stereoscopic combination. The quality of stereopsis from interocularly uncorrelated motion-defined forms was examined here. Results indicate that perceived magnitude of depth is not veridical, and that more depth is seen for crossed than uncrossed disparities.

Frequency difference limens in normal and sensorineural hearing impaired chinchillas.

This study assessed normal frequency discrimination ability in the chinchilla and determined how this ability changes as a function of an experimentally induced sensorineural hearing loss. Four chinchillas were trained by the methods of positive reinforcement to report absolute thresholds and frequency difference limens (FDLs). Subjects were then treated with the aminoglycosidic antibiotic amikacin until a 30-dB hearing loss was measured at 10.

Disparity range for binocular summation.

Binocular summation of contrast and stereopsis have been linked because they both disappear under certain pathological conditions. The dependence of stereopsis on spatial frequency prompted us to examine how binocular summation varies with both spatial frequency and binocular disparity. We therefore measured binocular summation at different disparities using spatially localized stimuli which were also restricted in their Fourier composition.

How contrast affects stereoacuity.

Stereoacuity and its dependence on contrast were measured at four spatial frequencies separated by 1 octave steps. Using a method of adjustment, observers adjusted the retinal disparity of an aperiodic narrow-band stimulus until it appeared in the depth plane defined by two flanking reference lines. Variations in contrast affected stereoacuity (the standard deviation of ten depth settings), with better performance observed at higher contrasts.

Are stereoacuity and binocular rivalry related?

Several lines of evidence suggest that the processes of excitation and inhibition associated with good stereoacuity may also underlie binocular rivalry, implying that performance on these two tasks could be related. To test this possibility, we measured stereoacuity and rivalry under similar stimulus conditions in 40 observers. To estimate stereoacuity, a two-alternative, forced-choice procedure was used, wherein observers determined which of two sinusoidal grating patterns appeared displaced in depth.

What causes stereoscopic tilt from spatial frequency disparity.

A controversy still exists concerning whether the tilt created with interocular spatial frequency disparity arises from a computation of spatial frequency differences or from cumulative positional disparity. In a first experiment, we examined the influence of positional disparity on tilt created with frequency disparity, reasoning that if tilt were computed from spatial frequency differences, the perceived angle should remain unaltered since adding a positional disparity does not change the harmonic content of the stimulus. The results indicated that positional disparity weakened perceived tilt.

Auditory filter shapes in the chinchilla.

Auditory filter shapes were determined for the chinchilla using the notched-noise technique [R. D. Patterson, J.

Magazine versus physicians: the influence of information source on intentions to use oral contraceptives.

College students read either pro or con passages about oral contraceptives. All passages contained the same statistical information, differing only in the way the information was interpreted. The passages were attributed either to a traditional physician, nontraditional physician, traditional magazine, or nontraditional magazine.

Satellite color observations of the phytoplankton distribution in the eastern equatorial pacific during the 1982-1983. El nino.

Dramatic changes in the patterns of satellite-derived pigment concentrations around the Galápagos Islands during February and March 1983 are associated with unusual oceanographic conditions observed during the 1982-1983 El Niño. The redistribution of food resources might have contributed to the reproductive failure of seabirds and marine mammals on these islands during this El Niño.

Age differences in response time to verbal and symbolic traffic signs.

It is well established that verbal skills are maintained at a high level into old age while visuo-spatial skills begin to decline at an earlier age. it was hypothesized that the elderly would therefore respond more quickly to verbal traffic signs than to symbolic ones. In a test of this hypothesis, response times (RT's) to symbolic and verbal traffic signs were obtained from subjects in two age groups (19-29 and 65-77 years).

Oceanographic observations of the 1982 warming of the tropical eastern pacific.

Moored current meter, sea level, hydrographic, and surface drifter measurements show the large changes that took place in the eastern tropical Pacific during the onset of the warm episode of 1982. In August the near-surface flow at 0 degrees , 110 degrees W reversed direction to eastward. By October the sea surface temperature in the equatorial zone increased by 5 degrees Celsius above the long-term monthly mean value, sea level rose by 22 centimeters at the Galápagos Islands, and the thermocline was displaced downward by 50 to 70 meters along the equator and the South American coast.

Wrist subluxation in juvenile rheumatoid arthritis: pathophysiology and management.

Management principles in juvenile rheumatoid arthritis provide for long-term follow-up throughout all phases of disease activity, including apparent remission. Treatment is based on the stage of disease and anatomy and kinesiology of the joints. Palmar subluxation of the wrist requires proximal support by splints for prevention and correction.

The multiple determination of illusory contours: 2. An empirical investigation.

Judgments of contour strength or saliency for twenty-four illusory-contour configurations were subjected to a confirmatory factor analysis. A four-factor model that posited the involvement of simultaneous contrast, linear effects (assimilation and dissimilation), depth/completion cues, and feature analyzers accounted for a substantial proportion of the variance in judgments of illusory-contour strength. The hierarchical addition of a fifth factor, diffuse illusory contours, significantly improved the overall fit of the model, but added little to the proportion of explained variance.

The multiple determination of illusory contours: 1. A review.

Four theories of illusory-contour perception are reviewed--brightness contrast (simultaneous contrast, assimilation, and dissimilation), depth/completion, partial activation of neural feature analyzers, and the diffuse-sharp dichotomy. It is concluded that the processes and mechanisms involved in illusory-contour perception most likely depend upon the stimulus elements used in the illusory-contour display.

Can age-related deficits in spatial memory be attenuated through the use of verbal coding?

In a sequential mental rotation task, women of three age groups (18-28, 50-60, and 70-80) viewed semi-abstract figures which were rotated in the picture plane. To investigate the effects of verbal mediation, each figure was presented under one of four labeling conditions. Errors increased as a function of age.

Subjective towers: depth relationships in multilevel subjective contours.

The perceived depth associated with subjective contours was studied with a three-level subjective contour configuration. An analysis of subjects' size judgments showed significant size-constancy scaling consistent with the prediction that subjects would perceive the various subjective surfaces as superimposed upon one another in depth. Direct depth estimations, however, showed only weak depth effects, easily reversed by conflicting depth cues, and observed with real, as well as subjective contours.