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Biomedical subjects

S Guerra

Publications and source records attributed to S Guerra.

At least 19 recordsLinked to original sources
PubMed2006

The impact of CD14 polymorphisms on the development of soluble CD14 levels during infancy.

CD14 is a receptor involved in the recognition of lipopolysaccharide and other bacterial wall components that may be involved in the balance between infectious and allergic disease and the early polarization towards TH1. Our group has shown an association between polymorphisms in the 5' flanking region of the CD14 gene and plasma soluble CD14 (sCD14) levels at 11 years of age. However, whether this association is present at birth and in infancy remains to be determined. In this study, we measured sCD14 levels in plasma from the umbilical cord (n = 387) and at 3 months (n = 357) and 1 year (n = 312) of age in non-selected healthy infants to assess their relationship with CD14 genotypes at -4190, -2838, -1720 and -260 (relative to translation start site). There was no relation of CD14 genotypes with sCD14 at birth. However, there was a significant association between CD14 genotypes and sCD14 as early as 3 months. Longitudinal analysis suggests that CD14 polymorphisms modulate sCD14 levels up to 1 year of age. This association early in life may have an impact on TH1 polarization and subsequent protection against allergic disease.

Cross-Sectional Studies↗
PubMed2006

Impact of protein kinase PKR in cell biology: from antiviral to antiproliferative action.

The double-stranded RNA-dependent protein kinase PKR is a critical mediator of the antiproliferative and antiviral effects exerted by interferons. Not only is PKR an effector molecule on the cellular response to double-stranded RNA, but it also integrates signals in response to Toll-like receptor activation, growth factors, and diverse cellular stresses. In this review, we provide a detailed picture on how signaling downstream of PKR unfolds and what are the ultimate consequences for the cell fate. PKR activation affects both transcription and translation. PKR phosphorylation of the alpha subunit of eukaryotic initiation factor 2 results in a blockade on translation initiation. However, PKR cannot avoid the translation of some cellular and viral mRNAs bearing special features in their 5' untranslated regions. In addition, PKR affects diverse transcriptional factors such as interferon regulatory factor 1, STATs, p53, activating transcription factor 3, and NF-kappaB. In particular, how PKR triggers a cascade of events involving IKK phosphorylation of IkappaB and NF-kappaB nuclear translocation has been intensively studied. At the cellular and organism levels PKR exerts antiproliferative effects, and it is a key antiviral agent. A point of convergence in both effects is that PKR activation results in apoptosis induction. The extent and strength of the antiviral action of PKR are clearly understood by the findings that unrelated viral proteins of animal viruses have evolved to inhibit PKR action by using diverse strategies. The case for the pathological consequences of the antiproliferative action of PKR is less understood, but therapeutic strategies aimed at targeting PKR are beginning to offer promising results.

Animals↗
PubMed2006

Relationship between physical activity and obesity in children and adolescents.

AIM: The purpose of the present study was to analyze the relationship between physical activity (PA) and obesity in Portuguese children and adolescents. METHODS: The sample consisted of 1341 children and adolescents (8-15 years of age), 634 males (age, 10.6+/-2.3 y; body mass, 40.6+/-12.7 kg; height, 1.431+/-1.41 m) and 707 females (age, 10.9+/-2.4 y; body mass, 50+/-12.4 kg; height, 1.428+/-1.32 m). The sample was divided into quartiles of percentage of body fat (%BF) and physical activity index (PAI), within age and gender. Children in the upper %BF quartile were defined as obese (arbitrary definition). Logistic regression for each PAI quartile was used to determine the odds ratio of obese children and adolescents (> or = P75 of %BF) in comparison to their non-obese counterparts (< P75 of %BF). RESULTS: Males in the lowest PAI quartile have an odds ratio of 2.1 of having obesity in relation to males in the highest PAI quartile. For females any significant result was found between PAI quartiles. CONCLUSIONS: The results obtained in this study add some data to the controversy of PA and obesity relationship youth. Logistical regression shows that males who have a lower PAI have an odds ratio of 2.1 of obesity, in comparison with males that have higher PAI. Those findings were not found in girls.

Adolescent↗
PubMed2005

Rhinitis is an independent risk factor for developing cough apart from colds among adults.

BACKGROUND: In cross-sectional clinical studies, rhinitis has been shown to be strongly associated with co-existing chronic cough. However, to date, this association has been poorly delineated from a prospective and epidemiological standpoint. METHODS: We used data from the 'Pisa Prospective Study', a population-based longitudinal cohort study composed of a baseline and a follow-up survey taken approximately 5 years apart from each other. Information on cough, rhinitis, and other risk factors was collected by standardized questionnaire. Cough apart from colds was defined as either 'chronic' (most days for at least 3 months for at least two consecutive years) or 'occasional' (if the three above temporal conditions were not met). 'Any' cough was defined as the presence of either occasional or chronic cough. RESULTS: Complete information was available for 1670 subjects who were > or =15 years old and had no positive history of cough apart from colds at the baseline survey. Among them, 299 (18%) had rhinitis at baseline. By the follow-up survey, 16% of the subjects with rhinitis had developed any cough apart from colds, as compared with only 10% of the subjects without rhinitis (OR 1.7, 95% CI 1.2-2.5, P < 0.005). After adjustment for age, gender, asthma status, smoking, and occupational exposure, rhinitis remained significantly associated with an increased risk both for any cough (OR 1.8, 95% CI 1.2-2.6) and for occasional and chronic cough separately (OR 2.2, 95% CI 1.1-4.5, and OR 1.7, 95% CI 1.1-2.6, respectively). CONCLUSIONS: Rhinitis is a significant and independent risk factor for developing cough among adults. Further research is needed to assess potential implications in terms of prevention.

Chronic Disease↗
PubMed2003

Migration of antioxidant additives from various polyolefinic plastics into oleaginous vehicles.

The migration of the antioxidant additives pentaerythrityl tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Irganox 1010) and tris(2,4-di-tert-butylphenyl)phosphite (Irgafos 168) from polyolefinic packaging into oily vehicles was investigated. The polyolefins included in the study were from the following classes: isotactic polypropylene homopolymer (PP), ethylene-co-propylene random copolymer (RACO), ethylene-propylene heterophasic copolymer and ethylene-propylene amorphous copolymer blend (EP) and high-density polyethylene (HDPE). Each polymer was additioned with Irganox 1010 (0.15%, w/w) and Irgafos 168 (0.15%, w/w) and processed into blown bottles. To study the antioxidant release process, plastic sheets were cut from the bottles and dipped for various time intervals into a mixture of five oils (caprylic/capric triglyceride, cyclomethicone, dicaprylyl ether, isohexadecane and C(12-15) alkyl benzoate) representative of lipophilic excipients used in pharmaceutical and cosmetic formulations. After exposure to the oil medium, the non-migrated Irganox 1010 and Irgafos 168 were recovered from the polymeric matrices using microwave-assisted extraction with ethyl acetate-hexane and assayed by HPLC. The leaching of the two antioxidants varied remarkably depending on the polyolefin crystallinity and structure. The amount of Irganox 1010 transferred into the contact medium at 25 degrees C decreased in the order EP>RACO>PP>HDPE. The same polyolefin ranking was observed in the case of Irgafos 168, except for PP and HDPE which exhibited similar depletion of this additive. Migration of Irgafos 168 was greater than that of Irganox 1010 and the release of both antioxidants increased at higher temperature (50 degrees C). The obtained data are useful for the selection of polyolefinic matrices as raw-materials for the production of pharmaceutical and cosmetic containers.

Antioxidants↗
PubMed2003

The role of concomitant respiratory diseases on the rate of decline in FEV1 among adult asthmatics.

Several recent reports have presented evidence suggesting that adults with asthma have an accelerated rate of decline in pulmonary function compared with nonasthmatics. However, most of these studies have not taken into account the possible effect of comorbid lung disease in addition to asthma. This study was designed to determine if comorbid respiratory diseases modify or otherwise change the estimates of decline in forced expiratory volume in one second (FEV1). Study subjects were White, non-Mexican, American participants, who were > or = 20 yrs of age at the initial survey and had at least one pulmonary function testing. Respiratory disease status, based on self-reported questionnaires and pulmonary function tests, were assessed during 12 surveys spanning a period of up to 20 yrs. There were 2,926 subjects who met the inclusion criteria, 214 (7.3%) had physician-confirmed asthma, 325 (11.1%) chronic obstructive pulmonary disease (COPD), and 125 (4.3%) both physician-confirmed asthma and COPD. Longitudinal analysis revealed that among those with longstanding asthma, FEV1 values were low but did not decline at a more rapid rate than normal. Likewise, subjects with both asthma and COPD had the lowest levels of FEV1, but also a rate of decline that was not significantly increased. Only those with COPD in the absence of asthma experienced both a low initial FEV1 level and a significantly steeper rate of decline. Based on these findings, the authors conclude that forced expiratory volume in one second does not decline more rapidly in asthmatics or in those with asthma and chronic obstructive pulmonary disease, compared with nonasthmatics.

Adult↗
PubMed2003

Age and gender-related physical activity. A descriptive study in children using accelerometry.

AIM: Precise measures of habitual physical activity are necessary in studies designed to: 1) document the frequency and distribution of physical activity in defined population groups; 2) determine the amount or dose of physical activity requires to influence specific health parameters. The purpose of this study was to document the age and gender-related physical activity levels on a sample of school children. METHODS: The sample for the present study comprised 157 children (boys n=64 and girls n=93), aged 8 to 15 years-old. The CSA activity monitor was used as an objective measure of daily physical activity. Each student in the present study was scheduled to wear the CSA 3 times during the week of monitoring. RESULTS: Boys were involved (p=/<0.05) in more time MVPA than girls. However only in the 11-13 year old group were found significant differences (p=/<0.05). Within gender, significant differences were found out among 11-13 years old (48.7 min) and 14-16 years (72.2 min). The time in MVPA increased across age group in both males and females. Boys participated in more periods of continuous physical activity, bouts of 10 and 20 min respectively, than girls. However no significant differences were found out. CONCLUSION: Our data showed that children under observation, excepted girls in the 11-13 year old group, appear to meet the minimum physical activity level recommended for health. The data also suggested that boys are more active than girls are and that they were significantly more engaged in more time MVPA than girls did. Surprisingly our data showed an increase in MVPA time as age increases. Further studies are needed to compare the different cut off points assessed during daily activity.

Acceleration↗
PubMed2002

Relationship between cardiorespiratory fitness, body composition and blood pressure in school children.

BACKGROUND: The purpose of this comparative and correlational cross-sectional study was to describe the associations between cardiorespiratory fitness, blood pressure and body composition in Portuguese school children. METHODS: The sample comprised 529 children (246 males and 283 females) aged 8-15 years-old. Body height and body mass were determined by standard anthropometric METHODS: Blood pressures were measured with children sitting after at least 5 min rest. The maximal multistage 20 m shuttle run test was carried-out to predict maximal aerobic power. RESULTS: The present study shows that boys were more fit (p= or <0.05) and less fat than girls (p= or <0.05). Multiple regression analysis reveals that weight and age explained significantly (p= or <0.01) the amounts of systolic blood pressure (SBP) and diastolic blood pressure (DBP). In girls, percentage of fat (%F) showed an influence on the variance in SBP (4.9%, p= or <0.05). In addition, weight (14.5%) and age (9.8%) account significantly (p= or <0.01) for the amount of variance to DBP in males. For girls, age (11.4%) and BMI (2.4%) account significantly to the variance found in DBP. However, the independent variables, for both sexes, account less than 50% of the overall variance found in blood pressures values. CONCLUSIONS: In conclusion, the present study shows that boys were more fit and had less fat than girls. The level of cardiorespiratory fitness does not seem to be an important correlate of blood pressure variation across age groups and gender.

Adolescent↗
PubMed2001

Combined analysis of MIB-1 and thyroid transcription factor-1 predicts survival in non-small cell lung carcinomas.

The prognostic value of combined immunohistochemical analysis for the thyroid transcription factor-1 (TTF-1) and the proliferation marker MIB-1 was assessed in a consecutive series of non-small cell lung carcinomas (NSCLC). Tumor immunoreactivity for TTF-1 and MIB-1 was classified in three groups (-,+,++) and in two groups (-,+), respectively. Comparison across groups for TTF-1 reactivity showed significantly different survival curves (P=0.04). In particular, the best prognosis was associated with a TTF-1 negative pattern, whereas the TTF-1 '++' cases showed the worst prognosis. A trend towards better prognosis was observed for MIB-1 negative cases (P=0.09). Multivariate analysis confirmed independent prognostic significance of TTF-1 (P=0.002), MIB-1 (P=0.01) and pStage (P=0.04). Accordingly, analysing TTF-1 and MIB-1 together, a better prediction of survival was obtained (P=0.02), with the poorest prognosis for the 'TTF-1++/MIB-1+' cases.

Antigens, Nuclear↗
PubMed2001

Genome replication and postencapsidation functions mapping to the nonstructural gene restrict the host range of a murine parvovirus in human cells.

The infection outcome of the Parvoviridae largely relies on poorly characterized intracellular factors modulated by proliferation, differentiation, and transformation of host cells. We have studied the interactions displayed by the highly homologous p and i strains of the murine parvovirus minute virus of mice (MVM), with a series of transformed cells of rat (C6) and human (U373, U87, SW1088, SK-N-SH) nervous system origin, seeking for molecular mechanisms governing parvovirus host range. The MVMp infection of C6 and U373 cells was cytotoxic and productive, whereas the other nervous cells behaved essentially as resistant to this virus. In contrast, MVMi did not complete its life cycle in any of the human nervous cells, though it efficiently killed the astrocytic tumor cells by two types of nonproductive infections: (i) normal synthesis of all viral macromolecules with a late defect in infectious virion maturation and release to the medium in U373; and (ii) high levels of accumulation of the full set of viral messenger RNAs and of both nonstructural (NS-1) and structural (VP-1 and VP-2) proteins, under a very low viral DNA amplification, in U87 and SW1088 cells. Further analyses showed that U87 was permissive for nuclear transport of MVMi proteins, leading to efficient assembly of empty viral capsids with a normal phosphorylation and VP1-to-VP2 ratio. The DNA amplification blockade in U87 occurred after conversion of the incoming MVMi genome to the monomeric replicative form, and it operated independently of the delivery pathway used by the viral particle, since it could not be overcome by transfection with cloned infectious viral DNA. Significantly, a chimeric MVMi virus harboring the coding region of the nonstructural (NS) gene replaced with that of MVMp showed a similar pattern of restriction in U87 cells as the parental MVMi virus, and it attained in U373 cultures an infectious titer above 100-fold higher under equal levels of DNA amplification and genome encapsidation. The results suggest that the activity of complexes formed by the NS polypeptides and recruited cellular factors restrict parvovirus DNA amplification in a cell type-dependent manner and that NS functions may in addition determine MVM host range acting at postencapsidation steps of viral maturation. These data are relevant for understanding the increased multiplication of autonomous parvovirus in some transformed cells and the transduction efficacy of nonreplicative parvoviral vectors, as well as a general remark on the mechanisms by which NS genes may regulate viral tropism and pathogenesis.

Animals↗
PubMed2001

Increased frequency dependence of specific airway resistance in patients with laryngeal hemiplegia.

The aim of this study was to investigate whether patients with laryngeal hemiplegia (LH) show a frequency-dependent increase in specific airway resistance (sRaw), measured by body plethysmography. In addition to the flow-volume loop, usually considered in the functional evaluation of upper airway obstructions, variations in sRaw at respiratory frequencies of 30+/-5 (=0.5 Hz), 60+/-5 (=1 Hz) and 90+5 breaths x min(-1) (=1.5 Hz) in 21 never-smoking patients (LH group, mean age+/-SD 55+/-12.09 yrs; 17 females) whose unilateral vocal-cord paralysis was documented by laryngoscopy and who had no signs or symptoms of other respiratory diseases studied. They were compared to 21 healthy control subjects (C group: 50.1+/-15.44 yrs; 10 females). The sRaw values at 30+/-5 breaths min(-1) were similar in the two groups (5.54+/-1.88 versus 5.68+/-1.06 cmH2O x s(-1); p=NS), but at increasing frequencies (30+/-5, 60+/-5 and 90+/-5 breaths min(-1)), they progressively and significantly increased in the LH patients (from 5.54+/-1.88 to 6.63+/-1.96 and 8.05+/-2.6 mH2O x s(-1); p<0.0005), and not significantly in controls (5.68+/-1.06, 5.85+/-0.95 and 5.9+/-1.12 cmH2O x s(-1); p=NS). Linear discriminant analysis using AsRaw (sRaw at 1.5 Hz-sRaw at 0.5 Hz) and forced inspiratory flow at 50% of the vital capacity made it possible to correctly classify all of the controls and 19 of the 21 patients. In conclusion, the multiple, rapid and noninvasive plethysmographical testing of frequency-dependent increase in specific airway resistance with the flow-volume loop, allows the sufficiently satisfactory discrimination of laryngeal hemiplegia patients from controls.

Adult↗
PubMed1999

Myocyte death in the failing human heart is gender dependent.

Cardiovascular disease is delayed and less common in women than in men. Myocyte death occurs in heart failure, but only apoptosis has been documented; the role of myocyte necrosis is unknown. Therefore, we tested whether necrosis is as important as apoptosis and whether myocyte death is lower in women than in men with heart failure. Molecular probes were used to measure the magnitude of myocyte necrosis and apoptosis in 7 women and 12 men undergoing transplantation for cardiac failure. Myocyte necrosis was evaluated by detection of DNA damage with blunt end fragments, whereas apoptosis was assessed by the identification of double-strand DNA cleavage with single base or longer 3' overhangs. An identical analysis of these forms of cell death was performed in control myocardium. Heart failure showed levels of myocyte necrosis 7-fold greater than apoptosis in patients of both sexes. However, cell death was 2-fold higher in men than in women. Heart failure resulted in a 13-fold and 27-fold increase in necrosis in women and men, respectively. Apoptosis increased 35-fold in women and 85-fold in men. The differences in cell death between women and men were confirmed by the electrophoretic pattern of DNA diffusion and laddering of isolated myocytes. The lower degree of cell death in women was associated with a longer duration of the myopathy, a later onset of cardiac decompensation, and a longer interval between heart failure and transplantation. In conclusion, myocyte necrosis and apoptosis affect the decompensated human heart; each contributes to the evolution of cardiac failure. However, the female heart is protected, at least in part, from necrotic and apoptotic death signals.

Apoptosis↗
PubMed1999

Combined yolk sac tumor and adenocarcinoma in a gastric stump: molecular evidence of clonality.

BACKGROUND: Extragonadal yolk sac tumors of the gastrointestinal tract are extremely rare neoplasms. Their greater rarity compared with other extragonadal yolk sac tumors suggests that different pathogenetic mechanisms could be involved according to the site of origin. This report describes a case of a combined yolk sac tumor and adenocarcinoma that arose in a gastric stump in a man age 61 years 43 years after he underwent distal gastric resection and gastrojejunostomy (Billroth II operation) for a benign duodenal ulcer. The coexistence of an adenocarcinomatous component with the yolk sac component suggests that the two histologic patterns may represent distinct phenotypes arising from a common mucosal epithelial cell. METHODS: Immunohistochemical and molecular techniques were used to define the mutation pattern of p53 in both components of the tumor. RESULTS: Single-strand conformation polymorphism and sequencing analyses demonstrated the same pattern of p53 mutation in the adenocarcinomatous and yolk sac tumor components. CONCLUSIONS: This finding suggests that the two tumors could have been derived from the same cellular clone and supports the hypothesis that the two components represented a heterogeneous differentiation of the same tumor.

Adenocarcinoma↗
PubMed1999

Cell death in acromegalic cardiomyopathy.

BACKGROUND: Prolonged untreated acromegaly leads to a nonspecific myopathy characterized by ventricular dysfunction and failure. However, the mechanisms responsible for the alterations of cardiac pump function remain to be defined. Because cell death is implicated in most cardiac disease processes, the possibility has been raised that myocyte apoptosis may occur in the acromegalic heart, contributing to the deterioration of ventricular hemodynamics. METHODS AND RESULTS: Ten acromegalic patients with diastolic dysfunction and 4 also with systolic dysfunction were subjected to electrocardiography, Holter monitoring, 2-dimensional echocardiography, cardiac catheterization, and biventricular and coronary angiography before surgical removal of a growth hormone-secreting pituitary adenoma. Endomyocardial biopsies were obtained and analyzed quantitatively in terms of tissue scarring and myocyte and nonmyocyte apoptosis. Myocardial samples from papillary muscles of patients who underwent valve replacement for mitral stenosis were used for comparison. The presence of apoptosis in myocytes and interstitial cells was determined by confocal microscopy with the use of 2 histochemical methods, consisting of terminal deoxynucleotidyl transferase (TdT) assay and Taq probe in situ ligation. Acromegaly was characterized by a 495-fold and 305-fold increase in apoptosis of myocytes and nonmyocytes, respectively. The magnitude of myocyte apoptosis correlated with the extent of impairment in ejection fraction and the duration of the disease. A similar correlation was found with the magnitude of collagen accumulation, indicative of previous myocyte necrosis. Myocyte death was independent from the hormonal levels of growth hormone and insulin-like growth factor-1. Apoptosis of interstitial cells did not correlate with ejection fraction. CONCLUSIONS: Myocyte cell death, apoptotic and necrotic in nature, may be critical for the development of ventricular dysfunction and its progression to cardiac failure with acromegaly.

Acromegaly↗
PubMed1999

Low folate levels and thermolabile methylenetetrahydrofolate reductase as primary determinant of mild hyperhomocystinemia in normal and thromboembolic subjects.

Several studies have indicated that mild to moderate hyperhomocystinemia is a common cause of arterial occlusive disease. Whether hyperhomocystinemia per se is an independent risk factor for vein thromboembolism (VTE) is still somewhat controversial. Both genetic and nutritional factors influence plasma homocysteine levels. Therefore, we evaluated plasma total homocysteine (tHcy), folate, and vitamin B12 levels and established, by polymerase chain reaction, the presence of the C677T mutation (A223V) in the methylenetetrahydrofolate reductase (MTHFR) gene in 220 cases with VTE without well-established prothrombotic defects. As a control group, 220 healthy subjects from the same geographic area as the cases were investigated. Hyperhomocystinemia was defined as a plasma tHcy level above the 95th percentile in the controls (18.05 micromol/L). Hyperhomocystinemia was found in 16% of cases (odds ratio=3.59; P<0.001); deficiencies of folate (<2.47 ng/mL) or vitamin B12 (<165 pg/mL), defined as values below the 5th percentile in controls, were found in 17.7% (P<0.001) and 12.3% (P=0.015) of cases, respectively. The homozygous condition for the MTHFR mutation (VV) was present in 28.2% of cases and 17.7% of controls (odds ratio=1.82; P=0.013). Comparing only the idiopathic forms of VTE (n=80/220; 36.3%) with normal controls, individuals with hyperhomocystinemia, or individuals homozygous for MTHFR mutation increased the odds ratios to 4.03 (P=0.005) and 2.11 (P=0.018), respectively. No statistically significant difference was observed in the MTHFR genotype distribution of cases and controls with hyperhomocystinemia (P=0.386); however, the normal MTHFR genotype (AA) appeared in control subjects only when tHcy levels were below the 80th percentile (10.57 micromol/L) of the distribution, whereas in case patients, it was present at the highest tHcy levels. A strong association between mutated homozygosity (VV), low folate levels, and hyperhomocystinemia was found in both groups. We conclude that in patients with VTE who do not have coexisting prothrombotic defects, hyperhomocystinemia increases the risk of developing idiopathic and venous thrombosis; the homozygous condition for the MTHFR mutation confers a moderate risk but, together with low folate levels, it is the main determinant of mild hyperhomocystinemia in normal and thromboembolic populations.

Adult↗
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↗