PubMed Health⌕ Search

Biomedical subjects

N Osaka

Publications and source records attributed to N Osaka.

At least 19 recordsLinked to original sources
PubMed1992

Size of saccade and fixation duration of eye movements during reading: psychophysics of Japanese text processing.

The size of saccadic eye movements and eye fixations during Japanese text reading (written in both hirakana phonograms and kanji ideograms) were analyzed. Hirakana is sound based, i.e., it consists of symbols for syllables, but such text was processed differently from English text in terms of saccadic eye movements and fixations. In experiment 1 the reader was asked to read three types of text (hirakana only, kanji-hirakana mixed, and English) in a natural reading manner. The results show that kanji-hirakana-mixed text, which has picturelike symbols, requires shorter eye fixations and longer saccades than those required by hirakana text. The findings show that kanji and hirakana are processed differently. Logographlike kanji text greatly facilitated text processing and understanding during reading. In experiment 2 we found that kanji-based text had a wider perceptual span of reading than did hirakana text. The wider span is consistent with the longer saccade length for kanji-based text found in experiment 1. In experiment 3 we studied the convenient viewing position, i.e., the position within a word where the eye should fixate first for the isolated word to be recognized most quickly. A convenient viewing position was confirmed to exist both for hirakana- and kanji-based words, but for hirakana words the position changed as word length changed, as was expected from the results of experiment 2. In experiment 4 we measured lexical access time for hirakana- and kanji-based words and found that the reaction time to kanji-based words was faster than the reaction time to words written with hirakana.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Long-term prognosis of esophageal variceal cases treated with injection sclerotherapy.

One hundred fifty-two patients with esophageal varices underwent a total of 485 injection sclerotherapy procedures (mean, 3.2 times per each case). During 5 years of observation, 20 cases (13.2%) died following injection sclerotherapy. The 3-year survival rates, based on the Kaplan-Meier method, were 42% for emergency cases, 75% for elective cases and 90% for prophylactic cases. Significant differences (P less than 0.05) by the generalized Wilcoxon test were observed in the survival rates between emergency cases and prophylactic cases, and also between elective cases and prophylactic cases. Two cases (8.6%) of failure to control acute hemostasis were experienced. Twenty cases of bleeding after sclerotherapy were experienced, and 8 died of bleeding. The three-year bleeding rate according to the Kaplan-Meier method was 59% for emergency cases, 25% for elective cases and 7% for prophylactic cases. A significant difference (P less than 0.05) by the generalized Wilcoxon test was observed in the bleeding rate between elective cases and prophylactic cases. Non-bleeding rate (100%-bleeding rate) after sclerotherapy showed almost the same values as the survival rate. These results indicate that upper digestive tract hemorrhage influences the prognosis of patients after sclerotherapy.

Adult↗
PubMed1989

[Studies on the position of the mandibular foramen].

Accurate investigation of the position of the mandibular foramen is important in anatomical and clinical studies, and there are a number of reports about such measurements. In this study, 140 Indian dry skulls, whose dental stages ranged from the stage before deciduous occlusion to the later phase of third molar eruption, were reproduced and the position of the mandibular foramen was measured using laser beams and three-direction photography. The position of the mandibular foramen was defined by the tip of the lingula mandibulae. 1. The angle of the lingula mandibulae was 45 degrees in children and it decreased with ageing. 2. At the later phase of the deciduous occlusion stage, the distance from the occlusal plane to the tip of the lingula mandibulae was high. 3. Each distance increased with the increasing age, height and width of the ramus mandibulae, the front and rear of the lingula mandibulae, and height of the lingula mandibulae. 4. There was little change with age in the ratio of the height of the ramus mandibulae to the height of the lingula mandibulae, and the ratio of the width of the ramus mandibulae to the distance of rear the lingula mandibulae. 5. The method for producing anesthesia in the mandibular foramen of children is as follows. The injection is aimed at the lingula mandibulae, which is 1/2 of the height and 1/2 of the width of the ramus mandibulae, from between the deciduous canine and the first molar on the opposite side, at a 10 angle to occlusal plane and at a 45 angle to the median line. In this manner it is possible to inject into the pterygomandibular space safely and expect certain anesthesia. In this study, the position of the mandibular foramen of children was accurately determined, as well as a safe clinical method for producing anesthesia to the mandibular foramen.

Child↗
PubMed1987

Variation of saccadic suppression with target eccentricity.

Two LEDs separated by 24 degrees from each other were employed as saccadic fixation sources located on a circle about the centre of the saccade path. Either horizontal, vertical or oblique saccade paths were used and a brief test flash was presented at one of five retinal eccentricities during each saccade. The percentage of detected flashes was measured as a function of the location of the test stimulus and of its time delay with respect to the onset of the saccade. The results suggest that saccadic suppression is maximal at the fovea and is significantly decreased as retinal eccentricity increases.

Adolescent↗
PubMed1979

[Brightness power function and equal brightness contour for dark- and light-adapted eye in the peripheral visual field (author's transl)].

To test whether the equal brightness contour at supra-threshold runs parallel with the contour at threshold, magnitude estimation and the staircase procedure were employed for estimating brightness power function under dark- and light-adaptation. The luminance was changed from 43 to 83 dB re 10(-6) cd/m2 with the light adapting luminance at 53 dB. The retinal loci tested were 0 degrees to 70 degrees periphery in steps of 10 degrees. The exponent of the power function gradually increased from .37 to .73 as eccentricity and adapting luminance increased. The equal brightness contour decreased for dark-adaptation and increased for light-adaptation as eccentricity increased at supra-threshold but at threshold did not follow the parallel hypothesis for both adapting conditions.

Adaptation, Ocular↗
PubMed1978

VEP latency and RT as power functions of luminance in the peripheral visual field.

Behavioral correlates of P1 latency of visual evoked potentials (VEPs) were investigated using visual reaction time (RT) as a measure at the fovea, 20 degrees and 40 degrees nasal retinal eccentricities along the horizontal meridian of the right eye. Three luminances of the target in steps of 1 log units were used: 26, 260 and 2600 cd/m2. As luminance increased VEP latency and RT decreased. Further, as eccentricity increased VEP latency and RT increased. The highest product-moment coefficient of correlation (r = 0.998) was found between RT and P1 latency in the fovea, whereas the coefficient of correlation was found to be slightly small in the peripheral loci. The data (both VEPs and RTs) were fitted by the power function of the form: T = kLB + T0 where T, k, L T0 and B indicate VEP latency (or RT, scaling constant, luminance, asymptotic latency and exponent of the power function, respectively. This shows how the VEP latency and the RT can be related to luminance with exponent B. It was found that psychophysical power law governs VEP latency as well as RT with an exponent of about -0.32. It was suggested that both RT AND P1 latencies of VEP originate in the similar nonlinear visual system.

Adult↗
PubMed1978

Brightness exponent for the periphery in the Bloch region.

Using a method of direct magnitude estimation, perceived brightness was measured in the dark-adapted eye with brief flashes of varying duration in the Bloch region (1-100 ms) and retinal lock (0 degrees-40 degrees) for the photopic luminance levels covering the range between 140 and 0.14 cd/m2 in steps of 1 log unit. Perceived brightness increased as a function of flash luminous energy (product of luminance and duration) up to critical duration of approximately 100 ms. The brightness power exponent for brief flash was found to be 0.48 +/- 0.01 in the fovea, whereas about 0.44 +/- 0.01 in the periphery.

Humans↗
PubMed1977

Effect of refraction on perceived locus of a target in the peripheral visual field.

A target of 44 min of arc with luminance of 1.03 log cd/m2 of 50 msec duration was presented to the loci along each of nasal, temporal, superior, and inferior half retinal meridians covering the eccentricity between 10 degrees and 50 degrees in steps of 10 degrees units. Two graduate students, serving as Ss, were instructed to point out the perceived locus where the target had appeared. The visual angles between the perceived and physical locus of the target were increased as a function of retinal eccentricity due to refraction.

Humans↗