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Biomedical subjects

C Casco

Publications and source records attributed to C Casco.

33 records · Page 2Linked to original sources
PubMed1988

Left-right visual field asymmetry in bistable motion perception.

Twelve observers viewed two alternating frames, each consisting of three rectangular bars which were displaced laterally by one cycle in one frame with respect to the other. At long interframe intervals (IFIs) observers perceived a group of three elements moving as a whole (group movement), whereas with IFIs shorter than 40-60 ms the overlapping elements in each frame appeared stationary while the third element appeared to move from one end of the display to the other (end-to-end movement). The percentage of group movement responses in central viewing was compared to those obtained for stimulus presentation in the left and right visual fields (4 deg eccentricity), for opposite horizontal directions of motion. All ten right-handed subjects showed a left-field advantage in sensitivity to group movement. The two left-handed subjects showed a similar advantage in sensitivity with right-field presentation. The effects of monocular vision, hand used in the task, spatial frequency, and contrast on visual field asymmetry were all investigated in two right-handed subjects. None of these factors affected the left-right asymmetry.

Cerebral Cortex↗
PubMed1987

The detection of deviation from straightness in lines.

A wide range of differently shaped perturbations were introduced into long thin straight lines, and threshold amplitude for their detection was measured. This amplitude threshold varies over a 20-fold range, depending on the shape of the cue, but can be economically expressed as just one numerical value, irrespective of the cue shape. This quantity is the area of the largest bump in the target around a least squares regression line axis, and its value is 0.3 arc min2. This value can be related to a fundamental spatial error of 3 arc sec (standard deviation) which is the limiting constraint on shape sensitivity.

Discrimination, Psychological↗
PubMed1987

Detection of moving local density differences in dynamic random patterns by human observers.

The way in which movement enhances target visibility has been investigated by measuring the detectability of the direction of motion of a dot pattern added to a background of dynamic visual noise. When the positions of all the dots were changed randomly from frame to frame, so that there was no dot configuration to define the target area (experiments 1 and 2), the threshold density difference necessary was for direction of motion detection less than 3 dots/frame (between 20% and 50% density difference). The spatial displacement (S) at which optimal detection occurs increased when a target elongated in the direction of motion was used. If S was either larger or smaller than its optimal value, thresholds rose progressively. The rise in threshold when S was smaller than 0.25 deg (the width of the target area) decreased when the target dots had a fixed spatial arrangement (experiment 3). It is suggested that in both fixed and random target configurations there is a grouping of dots with similar trajectories via a global directionally-selective process. The strength of the overall motion signal is greater in the fixed-dot configuration because each target dot has associated with it a vector precisely aligned in the direction of the target motion.

Attention↗
PubMed1984

The relationship between space and time in the perception of stimuli moving behind a slit.

When a shape defined by a set of dots plotted along its contour is presented in a sequence of frames within the boundaries of a slit, and in each frame only one dot (featureless frame) or two dots (feature frame) are displayed, a whole moving dotted shape is perceived. Masking techniques and psychophysical measures have been used to show that a dynamic random-dot mask interferes with shape identification, provided the interframe interval is greater than about 15 ms, and there are no stimulus features for recognition in individual frames. A similar pattern of results was obtained when the observer had only to detect the movement of a single dot or a pair of dots against a dynamic-noise background. It is concluded that the visual system can resolve the correspondence problem in both apparent movement (one moving dot) and aperture viewing (featureless-frame condition) by extracting motion before the extraction of features in each frame. However, the results also show that where feature identification in each frame is possible, it can also be used to identify the moving targets.

Female↗
PubMed1982

Healing of osteitis fibrosa cystica after partial parathyroidectomy despite persistent parathyroid hyperfunction: a case report.

The diagnosis of primary hyperparathyroidism was made in a 55-year-old female with marked hypercalcemia (15 mg/100 ml) and hypercalciuria and skeletal x-rays showing typical lesions of subperiosteal resorption and numerous cystic areas. At surgery a left lower parathyroid adenoma presumably was totally excised. Serum calcium returned to normal levels immediately postoperatively, but 4 months after surgery hypercalcemia (11.5 mg/100 ml) was again found. During the following 18 months the patient was free of symptoms, and radiologic studies revealed complete healing of the subperiosteal resorption and repair of the bone cysts. Cortical bone mineral content also increased. However, elevated levels of serum parathyroid hormone (PTH) and calcium clearly indicated the persistence of primary hyperparathyroidism. Thus, a decrease in the degree of PTH hypersecretion permitted the repair of the skeletal lesions caused by a more severe level of parathyroid hyperfunction.

Bone Resorption↗
PubMed1980

[Reaction time experiment on absolute or relative functional specialization of the cerebral hemispheres in man].

Lateralized presentations of verbal stimuli yield faster reaction times in the right visual field-left hemisphere, whereas nonverbal stimuli yield faster reaction times in the left visual field-right hemisphere. However, the problem of how lateral asymmetries in response latency are determined is still unsolved. The hypothesis of an absolute functional specialization of the two hemispheres suggests that information presented in the visual field connected with the unspecialized hemisphere has to travel along a less direct pathway, implying a crossing through the forebrain commissures, to reach the processing center. The hypothesis of a relative functional specialization assumes that stimuli are processed by the hemisphere contralateral to the field of presentation but speed of processing varies as a function of hemispheric specialization. The present study tried to find empirical evidence in favor of one of the two hypotheses. Choice reaction times to lateralized verbal stimuli were studied in normal subjects. In half of the trials the subjects had to carry out a concomitant task known to interfere selectively with mechanisms responsible of the organization of the responses of the left hemisphere. Both with and without concomitant task reaction times were significantly faster in the right visual field-left hemisphere. While the concomitant task produced an overall lengthening of reaction time, it did not affect interhemispheric asymmetry. This finding was discussed as evidence in favor of the absolute specialization hypothesis.

Acoustic Stimulation↗
PubMedDate not supplied

The treatment of Paget's bone disease with sodium ethidronate.

Of 58 patients with Paget's disease treated with disodium ethane-1-hydroxy-1,1-diphosphonate (EHDP) in doses of 20 and 10 mg/kg/day, a group of 20 patients with the oligostotic form of the disease showed a significantly greater incidence of complications, such as worsening of bone pains, when compared with a group of 38 patients with the polyostotic disease (P less than 0.05). The group of 32 patients that received 20 mg/kg/day showed a greater although not significant incidence of clinical complications than the group of 26 patients treated with 10 mg/kg/day. Bone biopsies performed in one polyostotic and three oligostotic cases who suffered episodes of bone pain worsening during treatment with 20 mg/kg/day disclosed a severe osteomalacia. Both groups treated with 20 and 10 mg/kg showed a highly significant decrease of urinary hydroxyproline (THP) excretion and of serum alkaline phosphatase (P less than 0.01) after two and six months of treatment although the trend comparison between doses was not significant. It is suggested that the dose of EHDP should be related to the extent of the disease.

Adult↗
PubMedDate not supplied

Molecular analysis of p53 tumor-suppressor gene and microsatellites in preneoplastic and neoplastic lesions of the colon and esophagus.

Mutations in exons 4-8 of the p53 gene by the PCR-SSCP analysis in preneoplastic and neoplastic lesions of the colon (n=11) and esophagus (n=18) were screened. p53 overexpression by immunohistochemistry in 11 colonic lesions and 13 microsatellites, in all the patients (n=29), were also studied. A positive result concordancy between the three techniques was found in 1 adenoma and 2 adenocarcinomas of the colon, each with loss of heterozygocity of microsatellites. Metaplastic lesions of esophagus showed biallelic mutations and low frequency of microsatellite alterations. The relationship between genetic alterations in p53, microsatellites and type of colon and esophageal lesions is discussed.

Adenocarcinoma↗