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Biomedical subjects

G Caputo

Publications and source records attributed to G Caputo.

At least 19 recordsLinked to original sources
PubMed2001

Discrimination of an orientation difference in dynamic textures.

We investigated whether the response of a motion sensor was related to the specificity of sensory information (orientation and direction of motion) used to compute motion energy. This was done in two ways. First, we assessed whether orientation discrimination of a target line, which segregated by an orientation difference from a textured background, was improved with two-frame apparent motion stimulation (as compared with static presentation). Second, we investigated whether the amount of improvement (in either orientation or direction of motion discrimination) depends on a particular combination of target orientation and direction of motion (either orthogonal or parallel). We found that the percentage of correct responses in the discrimination task (a) was higher for a moving target than for a static one; (b) was higher when the target was oriented more orthogonally to motion direction than background elements; (c) was little affected by background motion and (d) decreased with frame duration in the direction of motion task whereas it was largely unaffected by frame duration in the discrimination of orientation task. These results suggest that discrimination of moving texture boundaries is based on a motion sensor tuned to a particular combination of orientation and direction of motion, which is capable of signalling the orientation of a moving target more accurately than a static sensor.

Analysis of Variance↗
PubMed2001

The glare effect and the perception of luminosity.

The impression of self-luminosity in the glare effect was studied in two experiments. In experiment 1 the target (CS) was set to the highest luminance of the field and subjects were asked to adjust the luminance ramp of the inducers (R) against five backgrounds (B) to the point where they began to see CS as self-luminous. It was found that there is a linear relationship between background and luminance ramp. Another group of subjects carried out the same task in experiment 2, but this time CS and R were linked together so that CS would always have the same luminance as the highest luminance level of R, as adjustments were performed. It was found that: (i) adjustments were always lower than the highest luminance available; (ii) the linear relationship between background and luminance ramp was confirmed; (iii) observers reported a compelling impression of self-luminous grays. Data are discussed in relation to Bonato and Gilchrist's model for the perception of luminosity. The authors advance the hypothesis that luminance ramps are used at an early stage of encoding for the perception of luminosity.

Contrast Sensitivity↗
PubMed2000

Positron emission tomography with f18-fluorodeoxyglucose in the staging and preoperative evaluation of malignant pleural mesothelioma.

OBJECTIVES: The purpose of this study was to evaluate the utility of positron emission tomography with F18-fluorodeoxyglucose in the preoperative evaluation and staging of malignant mesothelioma in patients who were candidates for aggressive combined modality therapy. METHODS: Eighteen consecutive patients with biopsy-proven malignant mesothelioma underwent positron emission tomographic scanning. The results of positron emission tomographic imaging were compared with results obtained by computed tomography, mediastinoscopy, thoracoscopy, and pathologic examination of surgical specimens. All patients fasted and received an average of 14.5 +/- 2.7 mCi of F18-fluorodeoxyglucose for positron emission tomographic scanning. Attenuation-corrected whole-body and regional emission images of the chest and upper abdomen were acquired and formatted into transaxial, coronal, and sagittal images. RESULTS: All primary malignant mesotheliomas accumulated F18-fluorodeoxyglucose, and the mean standardized uptake value was 7. 6 (range, 3.33-14.85; n = 9). There were no false-negative results of positron emission tomography. Identification of occult extrathoracic metastases by positron emission tomography was the basis for excluding two patients from surgical therapy. There were two false-positive results of positron emission tomography: increased F18-fluorodeoxyglucose uptake in the contralateral chest that was negative by thoracoscopic biopsy (n = 1) and increased abdominal F18-fluorodeoxyglucose uptake after partial colectomy for diverticular disease (n = 1). CONCLUSIONS: Positron emission tomography can identify malignant pleural mesothelioma and appears to be a useful noninvasive staging modality for patients being considered for aggressive combined modality therapy.

Adult↗
PubMed2000

Changes in myocardial cytoskeletal intermediate filaments and myocyte contractile dysfunction in dilated cardiomyopathy: an in vivo study in humans.

AIM: To investigate in vivo the intermediate cytoskeletal filaments desmin and vimentin in myocardial tissues from patients with dilated cardiomyopathy, and to determine whether alterations in these proteins are associated with impaired contractility. METHODS: Endomyocardial biopsies were performed in 12 patients with dilated cardiomyopathy and in 12 controls (six women with breast cancer before anthracycline chemotherapy and six male donors for heart transplantation). Biopsy specimens were analysed by light microscopy and immunochemistry (desmin, vimentin). Myocyte contractile protein function was evaluated by the actin-myosin in vitro motility assay. Left ventricular ejection fraction was assessed by echocardiography and radionuclide ventriculography. RESULTS: Patients with dilated cardiomyopathy had a greater cardiomyocyte diameter than controls (p < 0.01). The increase in cell size was associated with a reduction in contractile function, as assessed by actin-myosin motility (r = -0.643; p < 0.01). Quantitative immunochemistry showed increased desmin and vimentin contents (p < 0.01), and the desmin distribution was disturbed in cardiomyopathy. There was a linear relation between desmin distribution and actin-myosin sliding in vitro (r = 0.853; p < 0.01) and an inverse correlation between desmin content and ejection fraction (r = -0.773; p < 0.02). Negative correlations were also found between myocardial vimentin content and the actin-myosin sliding rate (r = -0.74; p < 0.02) and left ventricular ejection fraction (r = -0.68; p < 0.01). CONCLUSIONS: Compared with normal individuals, the myocardial tissue of patients with dilated cardiomyopathy shows alterations of cytoskeletal intermediate filament distribution and content associated with reduced myocyte contraction.

Actins↗
PubMed1999

Amodal completion in texture visual evoked potentials.

Amodal completion refers to the phenomenological finding of perceiving partly occluded objects as continuing uninterrupted behind an occluder. The outlying problem is how the visual system processes such non-local stimuli because the known processes of early vision are spatially restricted operations which segregate local differences in the visual image, and little is known about their interactions in producing the segmentation of the image into functionally coherent, or global, objects. We recorded human visual evoked potentials (VEPs) to texture stimuli and addressed local/non-local relationships in comparing a condition in which local edges were present, due to texture segregation, with a condition in which, in addition to local edges, textures appeared to continue as surfaces behind gray stripes due to non-local amodal completion. Subtraction of offset from onset responses showed: (1) a difference component due to texture segregation characterized by a negativity with onset at about 95 ms and lasting up to about 280 ms; (2) a further negativity, specifically elicited by amodal completion, with onset at about 142 ms, peaking at 175 ms, and lasting up to about 188 ms. Therefore, amodal completion occurs at an early processing stage of image analysis and the difference component in VEPs can be related to figure-ground perception.

Adult↗
PubMed1999

A visual evoked potential correlate of global figure-ground segmentation.

Human observers discriminated the global orientation of a texture-defined figure which segregated from a texture surround. Global figure discriminability was manipulated through within-figure collinearity, figure-surround interaction, and figure connectedness, while the local orientation contrast at edges between figure and surround was kept constant throughout all the experiments. Visual evoked potentials (VEPs) were recorded during onset-offset stimulation in which the figure cyclically appeared and disappeared from a uniform texture background. A difference component was obtained by subtraction of offset-from onset-VEP. Two negative peaks of the difference component are found with latencies around 140-160 and 200-260 ms, respectively. Enhanced discriminability of the global figure reduced (11-25 ms) the latency of the second peak, hence indicating that the 200-260 ms component was produced by global figure-ground segmentation.

Adult↗
PubMed1999

Edge detection and surface 'filling in' as shown by texture visual evoked potentials.

OBJECTIVES: We designed a stimulation paradigm that was designed to ascertain whether specific components of the texture visual evoked potentials were attributable to edge detection or to surface 'filling-in' processes. METHODS: The stimuli were textures of parallel line elements, which were either uniform (all horizontal or vertical lines) or segregated (checkerboards in which texture line elements of neighbor checks were oriented orthogonally). A sequence of 4 stimuli, two uniform followed by two segregated stimuli, was repeated cyclically. Accordingly, segregation could appear from a uniform display; it could also be maintained, with the checkerboard illusory margin location unchanged but with alteration in the orientation of all line elements. Each stimulus was presented for 487 ms and instantly replaced by the following one. RESULTS: Segregation-related components for segregation-appearance (Sa) and for segregation-maintenance (Sm) conditions were obtained separately by subtraction. In both conditions, a negative component was obtained with a peak latency of about 140-150 ms. However, the onset of Sa was earlier than that of Sm, whereas the respective offsets were almost identical. CONCLUSIONS: We hypothesize that the segregation component in VEPs is composed of two subcomponents: an early part, which is related to the segregation of edges, and a final part, which is related to the 'filling-in' of the homogeneous texture surface within the boundary defined by these edges.

Adolescent↗
PubMed1999

Assessment of pulmonary lesions with 18F-fluorodeoxyglucose positron imaging using coincidence mode gamma cameras.

UNLABELLED: Accurate assessment of lung carcinoma remains a significant clinical problem, often leading to surgical procedures without curative potential. PET with 18F-fluorodeoxyglucose (FDG) has shown promise in differentiating benign from malignant lesions and in staging the extent of disease, resulting in improved treatment at a significant cost savings. This multicenter prospective study used dual-detector coincidence imaging with FDG to categorize pulmonary lesions as benign or malignant. The goal of this study was to determine the sensitivity and specificity of dual-detector coincidence imaging of FDG in patients with pulmonary lesions who were scheduled to have a diagnostic procedure for histopathologic confirmation. METHODS: A total of 96 patients with pulmonary lesions with a lesion size ranging from 1 to 7 cm with a mean of 3.44 cm based on their chest radiograph or CT scan were studied using FDG scans with a dual-detector coincidence detection system. An additional 24 patients were entered as control subjects. The studies of 120 subjects were interpreted in random order by three physicians experienced in the use of FDG in patients with lung cancer. Surgical pathology was used as the standard for identifying malignant lesions. RESULTS: There was 94% agreement between the readers in the independent interpretation of the FDG studies. In the 96 patients with pulmonary lesions, FDG studies were 97% sensitive and 80% specific in identifying proven malignant lesions. CONCLUSION: The results of this prospective study provide evidence that dual-detector coincidence imaging with FDG provides an accurate, sensitive and specific means of diagnosing malignancy in patients with pulmonary lesions.

Case-Control Studies↗
PubMed1999

Investigation on cerebral hemodynamics in patients with carotid disease receiving carotid endarterectomy.

100 patients (pts) receiving CEA (carotid endarterectomy) were evaluated in this study. In some of them postoperative complications were observed, characterized by TIA (transient ischemic attack) and, mostly, by cerebral hyperperfusion. In only two of the pts investigated CEA needed the implantation of a shunt, due to the emergence of intolerance signs at carotid Clamping (C) evaluated by TCD (transcranial Doppler); the preoperative cerebral angiography in the two subjects in question did not show malformations of the circle of Willis. The hyperperfusive phenomenon and the absence of intracranial compensation flows during CEA seemed to be ascribed to a more or less severe impairment of cerebral reserve. Such impairment of the autoregulatory capacity seems to be crucial to the pathogenesis of hemodynamic stroke. Thus the indication to CEA, in pts with severe carotid disease, should take into account also the cerebral reserve (CR) impairment to prevent both thromboembolic and hemodynamic stroke. The predictive and diagnostic role of TCD turns out to be crucial in assessing and selecting pts candidate to CEA.

Blood Pressure↗
PubMed1999

[An analysis of the psychophysiological components in subjects with temporomandibular disorders. Myographic tension and the management of aggressiveness].

BACKGROUND: The stomatognathic literature doesn't sufficiently stress the role of aggressiveness as a modulator of muscular tensions. Our study focused on the hypothesis that 1) original psychological problems related to the modulation of aggressivity could produce 2) chronic muscular tension of the oral district 3) they can become the basis of the malocclusive phenomenon. The investigation was conducted in the laboratory of Clinical Psychophysiology of the University of Rome "La Sapienza". METHODS: We have examined the myographic activity of the temporal and masseter muscles of both sides in 20 women with temporomandibular dysfunction and in the control group comparable by age. The myographic tension was examined in three "stimulus situations": a) closed lips without any teeth contact; b) with light teeth contact; c) with compression of the dental arcade. Moreover, we have examined the style of aggressiveness modulation through Rosenzweig's PFS test. Features of the experimental group were. 1) age between 20 and 30 yrs; 2) presence of condylomeniscal uncoordination; 3) deviation of the median line of incisors; 4) lateral deviation in the opening and/or closing mandible. RESULTS: The experimental group showed a higher score of myographic amplitude for the above-mentioned muscles of both sides in three "stimulus situations". Moreover, it presented at the Rosenzweig's test more elevated scores for the Dominance of Obstacle (O-D); b) less elevated scores for Ego Defence (E-D). CONCLUSIONS: Results are commented on the basis of an integrated psychophysiological model.

Adult↗
PubMed1998

Use of the Parental Bonding Instrument to compare interpretations of the parental bond by adolescent girls with restricting and binge/purging anorexia nervosa.

The Parental Bonding Instrument (PBI) was administered to 62 adolescent female patients (mean age 14.3): 35 with restricting-type anorexia nervosa (RAN), and 27 with binge/purging-type anorexia nervosa (B/PAN) according to the DSM-IV criteria, all at onset and initial diagnosis. The PBI was also administered to a control group (55 subjects) and 22 patients with Crohn's disease or celiac disease. The three groups were matched for age and socioeconomic status. The RAN and B/PAN patients gave significantly different interpretations of the parental bond (PB): for the former, it was adequate with both parents, for the latter it was inadequate, especially with the father. The fact that these differences exist at the onset of anorexia prior to any possible effect of therapy suggests that its structure is determined by different family dynamics.

Adolescent↗
PubMed1998

Attentional selection by distractor suppression.

Selective attention was studied in displays containing singletons popping out for their odd form or color. The target was defined as the form-singleton, the distractor as the color-singleton. The task was to discriminate the length of a longer line inside the target. Target-distractor similarity was controlled using a threshold measurement as dependent variable in experiments in which distractor presence vs absence, bottom-up vs top-down selection (through knowledge of target features), and target-distractor distance were manipulated. The results in the bottom-up condition showed that length threshold was elevated when a distractor was present and that this elevation progressively increased as the number of distractors was increased from one to two. This set-size effect was not accounted by the hypothesis that selective attention intervenes only at the stage of decision before response. Selective attention produced a suppressive surround in which discriminability of neighboring objects was strongly reduced, and a larger surround in which discriminability was reduced by an approximately constant amount. Different results were found in the top-down condition in which target discriminability was unaffected by distractor presence and no effect of target-distractor distance was found. On the other hand, response times in both bottom-up and top-down conditions were slower the shorter the target-distractor distance was. On the basis of the experimental results, selective attention is a parallel process of spatial filtering at an intermediate processing level operating after objects have been segmented. This filtering stage explores high level interactions between objects taking control on combinatorial explosion by operating over only a limited spatial extent: it picks out a selected object and inhibits the neighboring objects; then, non-selected objects are suppressed across the overall image. When no feature-based selection is available in the current behavior, this filtering influences perception in decreasing discriminability of non-selected objects. When feature-based selection is available, spatial interactions are set before stimulus arrival, hence only the unmatching objects have their discriminability diminished.

Attention↗
PubMed1998

Texture brightness filling-in.

The masking procedure by Paradiso and Nakayama (1991) (Vision Research, 31, 1221-1236) was used to investigate brightness filling-in within textures made of line elements: a texture stimulus was masked by a second stimulus containing a square contour. When a uniform texture was presented, the texture region inside the masking square appeared darkened and a small number of texture elements were perceived with a degenerated shape, appearing as dim dots or shorter line elements; it is as if the line element expanded from a bright point to fill the entire region defined by its contour. If the texture stimulus was a texture patch segregating from the surrounding texture by an orientation gradient and this patch was inside the square mask, darkening was not as strong as in the previous condition, and masked line elements preserved their elongated shape. Brightness spreading was measured in two experiments using dichoptic presentations. Experiment 1 used an adjustment task and showed that the brightness of texture line elements spread from equiluminant borders between segregating textures. Experiment 2 used a matching task and demonstrated that spreading was blocked by segregation borders dependent on the orientation gradient between texture line elements. The selectivity for line orientation began 40-80 msec after texture onset and maximal spreading occurred at approximately 120 msec. These findings may indicate that two processes subserve filling-in within textures: the first spreads isotropically the mean stimulus luminance at an initial processing stage of image analysis; at a later stage, the second spreads a texture flow (both brightness and shape of line elements) directed along the orientation of texture line elements. The texture flow mechanism fills in with a texture surface the region bounded by segregation contours.

Fixation, Ocular↗
PubMed1998

Encapsulation of scleral buckling materials. A study of sixty specimens.

OBJECTIVE: The purpose of the study was to obtain information on the encapsulation of two nonabsorbable biomaterials (silicone and hydrogel) used as explants in scleral buckling in retinal detachment surgery. DESIGN: The study design was a histopathologic study on a cohort of capsule fractions and complete eyes. PARTICIPANTS: Fifty-nine patients participated in this study, in which 60 specimens, including 37 hydrogel and 21 silicone capsule specimens as well as 2 whole eyes, were gathered. There were no control subjects. INTERVENTION: The capsule specimens were obtained from eyes operated on previously for scleral buckling for retinal detachment. The two whole eyes were enucleated. All specimens were studied with routine optic microscopy. MAIN OUTCOME MEASURES: Patient characteristics, type of scleral buckling, and number of operations performed were analyzed. Histologically, the capsular structure, its interface with the explant, and its different components also were studied. Remnants of the buckling material also were investigated. RESULTS: There were 45 male and 14 female patients, with a mean age of 49 years. Histologically, capsule specimens had a fibrous matrix with fibroblasts and few inflammatory cells. Eighteen (48.6%) of 37 hydrogel capsule specimens displayed hydrogel fragments surrounded by a foreign body giant cell granuloma in 16 cases. CONCLUSION: Nonabsorbable materials undergo encapsulation after implantation on the eye surface. Giant cell granuloma was observed in some hydrogel capsule specimens in relation to hydrogel fragmentation. The exact origin of this fragmentation remains unknown.

Adolescent↗
PubMed1997

Object grouping contingent upon background.

This study analyzes grouping between singletons (line elements popping out by orientation gradient) when they segregate from textures of uniformly oriented line elements. In the first experiment three adjacent singletons formed a texture bar; in the second experiment the distance between two singletons to be grouped was manipulated. The observer's task was to discriminate the orientation of the global pattern made by the singletons. The results and the explanations suggested are that: (i) an inner gradient within the texture bar (when the singletons are reciprocally orthogonal) operates only at short distances and enhances discrimination, indicating an initial stage of texture segregation based on local processing. (ii) Spatial interactions between parallel singletons are present at short distances and reduce discrimination. (iii) An interruption of background flow (directed along the orientation of background line elements) produced by the grouped pattern when orthogonal to it, enhances discrimination; this effect is present at both short and large distances between singletons, indicating a global process. (iv) Spatial interactions are present between parallel singletons even at large distances and independently of background orientation, suggesting that grouping generates a figural context within which features to be bound together interact. Moreover, flow interruption and figural context were absent in a detection task, thereby suggesting their specific involvement in grouping and figure binding. Overall, the results may indicate that grouping operates on already segmented line elements, across different orientations and over both short and long distances in between.

Analysis of Variance↗
PubMed1997

[Rigid endoscope with Gradient-index lenses. Preliminary studies].

PURPOSE: Endoscopes for use in ophthalmology can be manufactured in dimensions smaller than 0.89 mm. MATERIALS: Gradient-index lenses that give a higher resolution than fiber bundles can be miniaturized down to 0.35 mm. RESULTS: We used this new endoscope in 6 eyes of 6 patients during anterior segment surgery. Preliminary clinical experience has demonstrated the usefulness and practical application of this new instrument. CONCLUSION: The clear views the instrument provides of the ciliary sulcus and ciliary body behind the iris make it useful in secondary posterior chamber intraocular lens implantation, retroprosthetic membrane behind keratoprosthesis, Molteno valve, and in endolaser photocoagulation.

Aged↗
PubMed1996

The role of the background: texture segregation and figure-ground segmentation.

The effects of a texture surround composed of line elements on a stimulus within which a target line element segregates, were studied. Detection and discrimination of the target when it had the same orientation as the surround were impaired at short presentation time; on the other hand, no effect was present when they were reciprocally orthogonal. These results are interpreted as background completion in texture segregation; a texture made up of similar elements is represented as a continuous surface with contour and contrast of an embedded element inhibited. This interpretation is further confirmed with a simple line protruding from an annulus. Generally, the results are taken as evidence that local features are prevented from segmenting when they are parts of a global entity.

Discrimination, Psychological↗