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PubMed1995

Conjunctivitis in a long-term care facility.

OBJECTIVE: To determine the prevalence, incidence, and etiology of conjunctivitis in residents of a long-term care facility. DESIGN: Prospective surveillance of episodes of conjunctivitis during two 6-month periods. SETTING: Three-building, 319-bed, multipurpose, long-term care facility including units for personal care, chronic care, palliative care, rehabilitation, respiratory rehabilitation, and chronic ventilator patients. RESULTS: The incidence of conjunctivitis on different units varied from 0.6 to 3.5 per 1,000 patient-days. One building had a significantly higher rate of acute conjunctivitis and, within that facility, the most highly impaired patients had significantly more disease. Patients with chronic conjunctivitis generally were admitted with conjunctivitis; institutionally acquired conjunctivitis proceeding to chronic conjunctivitis seldom was observed except on the chronic ventilator unit. Residents with chronic conjunctivitis were significantly more likely to have a diagnosis of glaucoma, ectropion, or entropion. Potential bacterial pathogens were isolated from 3 (21%) of 14 and 24 (38%) of 69 acute episodes for which cultures were available in the two study periods. Staphylococcus aureus was the most frequent pathogen isolated. Empiric therapy was usually with topical sodium sulamyd or gentamicin, with substantial interphysician variability in prescribing patterns. Symptom duration did not differ for episodes which did or did not receive topical antimicrobials. CONCLUSION: Conjunctivitis is common in this facility and occurs with increased frequency in more highly impaired residents. Most episodes may not be due to bacterial infection. Further study of optimal management approaches to conjunctivitis is necessary.

Acute Disease↗
PubMed2006

Allergic conjunctivitis in children with asthma, rhinitis and eczema in a secondary outpatient clinic.

Little evidence is available on the prevalence of allergic conjunctivitis in pediatric populations. The objective of this study was to assess the cumulative prevalence of allergic conjunctivitis in children with rhinitis, asthma and eczema in a secondary pediatric outpatient clinic. Children aged 5-15 yr referred during the period of 2002-2004 in whom allergic conjunctivitis, asthma, allergic rhinitis or eczema was diagnosed were included in a retrospective survey. At referral patient characteristics, history, symptoms, signs and results of type 1 allergy tests were entered into an electronic form. Four hundred and fifty-eight children with a mean age of 9.4 yr were studied. Of 316, 324 and 149 children with rhinitis, asthma or eczema, respectively, 133 (42%), 78 (24%) and 45 (30%) had concomitant allergic conjunctivitis. One hundred and thirty-seven (30%) had allergic conjunctivitis, of whom 133 (97%) also had allergic rhinitis, 77 (56%) asthma and 45 (33%) eczema. One hundred and twenty-five (91%) of the children with allergic conjunctivitis had positive allergy tests to one or more allergens, sensitization to house dust mites being more frequent in chronic allergic conjunctivitis than in acute allergic conjunctivitis (95% vs. 53%; p < 0.01). Sensitization to grass was more frequent in children with acute allergic conjunctivitis (78% vs. 57%; p = 0.03). In a secondary pediatric outpatient clinic allergic conjunctivitis is a frequent co-morbidity to allergic rhinitis and to asthma and eczema. Allergic conjunctivitis need to be included as an important co-morbidity in future guidelines on asthma, rhinitis and eczema management.

Allergens↗
PubMed1992

Cytological evaluation of conjunctival scrape smears in cases of conjunctivitis.

The present study was conducted on 130 cases of untreated conjunctivitis and 25 control cases to assess the diagnostic value of cytology. Conjunctival scrapings from all cases were stained with Giemsa and Papanicoloau's stain and categorized cytologically and later correlated with the clinical profile. Normal cytologic profile was obtained in 7 cases (5.4%) of the study group and 14 cases (56%) of the control group. Cytologic diagnosis of trachoma was made in 63 cases (48.5%) including 48 out of 51 clinically diagnosed cases of trachoma, 9 cases of allergic conjunctivitis and 6 cases of acute follicular conjunctivitis, positive clinico cytologic correlation being 76.2%. Mucopurulent conjunctivitis was diagnosed in 24 cases (18.5%) both clinically as well as by cytological technique. Viral conjunctivitis was diagnosed in 24 cases (18.5%) including 19 cases (14.6%) of clinically diagnosed viral conjunctivitis and 5 cases (3.9%) of acute follicular conjunctivitis, positive correlation being 79.2%. Only 2 cases (1.5%) out of 15 clinically diagnosed cases of allergic conjunctivitis were confirmed cytologically. In all the 4 cases (3.1%) of spring catarrh and 6 cases (4.6%) of phlyctenular conjunctivitis the cytologic features were found to be consistent with the clinical diagnosis.

Conjunctiva↗
PubMed2002

Effective treatment of ligneous conjunctivitis with topical plasminogen.

PURPOSE: The etiology of ligneous conjunctivitis is now known to be due to an underlying type 1 plasminogen deficiency. We hereby report the clinical features of three cases and their response to topically administered plasminogen. DESIGN: Observational case series. METHODS: Two Caucasian females aged 5 years and an 18-month male of north African descent presented with a membranous conjunctivitis, which recurred after surgical excision. Case 1 presented before the association with plasminogen deficiency was known with a bilateral chronic membranous mucopurulent conjunctivitis from the age of 14 months associated with bronchiolitis and gingival hyperplasia. A diagnosis of ligneous conjunctivitis was entertained and a number of drops were instituted. At the age of 4 years plasminogen levels were ordered. Case 2 presented at the age of 4 years with a unilateral chronic membranous conjunctivitis. Plasminogen levels were requested as soon as a diagnosis of ligneous conjunctivitis was suspected. Case 3 was born with congenital hydrocephalus. Conjunctivitis was treated with antibiotics from the age of 1 month. He presented to the eye clinic at the age of 5 months when a clinical diagnosis of ligneous conjunctivitis was entertained and treated with a number of medications. Plasminogen levels were available at 9 months of age. RESULTS: The two female patients returned plasminogen levels of 0.25 U/ml and 0.3 U/ml, well below the normal level of 0.7-1.0 U/ml. Functional plasminogen levels in the male infant were not recordable with plasminogen antigen levels of 0.125 U/ml (normal range, 0.52-1.82). All cases have responded well to excision of the membranes and institution of topical plasminogen drops. There has been no recurrence with more than 12 months' follow-up. CONCLUSIONS: With the knowledge of the etiology of ligneous conjunctivitis, efforts are underway to identify the best method of delivery of plasminogen. Topical plasminogen concentrate from fresh frozen plasma holds promise as the definitive treatment for this chronic membranous conjunctivitis

Administration, Topical↗
PubMed2003

Self-inflicted (factitious) conjunctivitis.

PURPOSE: To describe the diagnosis and management of self-inflicted factitious conjunctivitis in conscripted soldiers. DESIGN: Prospective, noncomparative, consecutive case series. PARTICIPANTS: Seventeen conscripted soldiers. METHODS: Soldiers with chronic conjunctivitis (>3 weeks) were referred by ophthalmologists, and cases of shorter duration were referred by primary-care physicians. All cases underwent thorough ophthalmic and systemic history and examination, as well as questioning regarding their military units, military duties, and social background. Exclusion criteria were any condition that may cause conjunctivitis. Inferior fornix specimen microscopy and culture and eye photography were performed in most cases. In cases suspected of self-inflicted conjunctivitis all medication, besides lubricant drops, was stopped. Underlying psychosocial problems were investigated and managed. Cases were followed for at least 3 months after resolution of the conjunctivitis, at which point the diagnosis was confirmed, and the case entered the analysis. MAIN OUTCOME MEASURES: Resolution of the conjunctivitis. RESULTS: Seventeen consecutive cases of self-inflicted conjunctivitis, 8 of long duration and 9 of short duration, were studied. All cases demonstrated inconsistent clinical findings. The ocular signs most suggestive of self-inflicted conjunctivitis were purulent discharge purposely left on the lashes and periorbital skin, discharge more severe than in conjunctival hyperemia, less conjunctival chemosis than in hyperemia, mainly inferior conjunctival involvement, and an uninvolved cornea. Five of the 8 chronic cases had significant underlying psychologic or social problems. Their conjunctivitis resolved only after their underlying problems were addressed. Two cases admitted introducing freshly scraped dental plaque into the lower conjunctival sac. In the remaining 15 the similarity of the clinical findings suggested that a similar method was used. CONCLUSIONS: In the context of a subject standing to gain by assuming the sick role and after exclusion of ocular pathology, self-inflicted conjunctivitis can be reliably diagnosed by noting the characteristic clinical profile. Effective management includes addressing the underlying psychologic and social problems.

Adolescent↗
PubMed2004

An outbreak of conjunctivitis due to a novel unencapsulated Streptococcus pneumoniae among military trainees.

BACKGROUND: Bacterial conjunctivitis usually occurs as sporadic cases; outbreaks are uncommon and usually are associated with school campuses. We report an outbreak of Streptococcus pneumoniae conjunctivitis at a military training facility. METHODS: An outbreak investigation was done. Each case of conjunctivitis was evaluated with an assessment tool including demographic and clinical data. Conjunctival swabs were obtained. Pneumococci underwent standard testing, including serotyping with the Quellung reaction, capsular staining, and multilocus sequence typing. Sequence types were compared with previous reported outbreak strains by construction of dendrograms. Carriage rates of S. pneumoniae were determined among previously undiagnosed case patients with conjunctivitis, and a case-control study was performed. Control measures included education to increase hand washing, distribution of alcohol-based hand gel, and prompt treatment of patients with conjunctivitis. RESULTS: During a 6-week period, 92 cases of conjunctivitis occurred among 3500 persons, with an attack rate of 1.75 cases per 100 person-months. Eighty cases (87%) were due to S. pneumoniae; 45 (49%) were confirmed, and 35 (38%) were probable. Ten percent of recruits surveyed carried the outbreak strain. Twenty-two percent self-reported symptoms consistent with conjunctivitis during the outbreak period; sharing washcloths was associated with conjunctivitis (odds ratio, 11.7; P=.03). The causative organism was resistant to azithromycin but susceptible to telithromycin. The outbreak strain was an unencapsulated S. pneumoniae that has not been previously described; it was most closely related to the sequence type causing the Dartmouth College (Hanover, NH) outbreak of conjunctivitis in 2002. CONCLUSIONS: We report a conjunctivitis outbreak among military trainees caused by a novel, unencapsulated strain of S. pneumoniae.

Adolescent↗
PubMed2003

A qualitative study of patients' perceptions of acute infective conjunctivitis.

BACKGROUND: Acute infective conjunctivitis is a self-limiting condition that commonly presents to primary care. Patients' understanding of conjunctivitis, their reasons for attendance, and their responses to different management strategies, are unknown. AIM: To explore patients' understanding of conjunctivitis and its management. DESIGN OF STUDY: Qualitative study using semi-structured one-to-one interviews. SETTING: Three general practices in Hampshire and Wiltshire. METHOD: Twenty-five patients presenting with conjunctivitis at their general practices were interviewed. Main outcome measures were patients' perceptions of conjunctivities, their experience and knowledge of the disease, beliefs regarding treatment, and their responses to different management strategies and a patient information leaflet. RESULTS: Patients regarded conjunctivitis as a minor illness, although some considered it might become more serious if not treated. Nearly all were confident at recognising conjunctivitis. They stated a preference for not taking medication, but believed that conjunctivitis would not clear up without treatment. However, they were open to alternative management approaches; for example, the delayed prescription approach, because they trusted their general practitioners' (GPs') judgement. Once they were aware of the self-limiting nature of conjunctivitis, patients felt they would prefer to wait a few days to see if the condition improved before seeking medical advice, even if this resulted in a few more days of symptoms. CONCLUSION: Patients who attend their general practices with conjunctivitis present for treatment because they are not aware of its self-limiting nature. Providing patients with this information may enable patients, enhance self-management, and reduce the use of topical antibiotics and the demand for urgent general practice appointments.

Acute Disease↗
PubMed2005

Valid conjunction inference with the minimum statistic.

In logic a conjunction is defined as an AND between truth statements. In neuroimaging, investigators may look for brain areas activated by task A AND by task B, or a conjunction of tasks (Price, C.J., Friston, K.J., 1997. Cognitive conjunction: a new approach to brain activation experiments. NeuroImage 5, 261-270). Friston et al. (Friston, K., Holmes, A., Price, C., Buchel, C., Worsley, K., 1999. Multisubject fMRI studies and conjunction analyses. NeuroImage 10, 85-396) introduced a minimum statistic test for conjunction. We refer to this method as the minimum statistic compared to the global null (MS/GN). The MS/GN is implemented in SPM2 and SPM99 software, and has been widely used as a test of conjunction. However, we assert that it does not have the correct null hypothesis for a test of logical AND, and further, this has led to confusion in the neuroimaging community. In this paper, we define a conjunction and explain the problem with the MS/GN test as a conjunction method. We present a survey of recent practice in neuroimaging which reveals that the MS/GN test is very often misinterpreted as evidence of a logical AND. We show that a correct test for a logical AND requires that all the comparisons in the conjunction are individually significant. This result holds even if the comparisons are not independent. We suggest that the revised test proposed here is the appropriate means for conjunction inference in neuroimaging.

Arousal↗
PubMed2005

Conjunction revisited.

The aim of this note is to revisit the analysis of conjunctions in imaging data. We review some conceptual issues that have emerged from recent discussion (Nichols, T., Brett, M., Andersson, J., Wager, T., Poline, J.-B., 2004. Valid Conjunction Inference with the Minimum Statistic.) and reformulate the conjunction of null hypotheses as a conjunction of k or more effects. Analyses based on minimum statistics have typically used the null hypothesis that k = 0. This enables inferences about one or more effects (k > 0). However, this does not provide control over false-positive rates (FPR) for inferences about a conjunction of k = n effects, over n tests. This is the key point made by Nichols et al., who suggest a procedure based on supremum P values that provides an upper bound on FPR for k = n. Although valid, this is a very conservative procedure, particularly in the context of multiple comparisons. We suggest that an inference on a conjunction of k = n effects is generally unnecessary and distinguish between congruent contrasts that test for the same treatment and incongruent contrasts of the sort used in cognitive conjunctions. For congruent contrasts, the usual inference, k > 0, is sufficient. With incongruent contrasts it is sufficient to infer a conjunction of k >u effects, where u is the number of contrasts that share some uninteresting effect. The issues highlighted by Nichols et al., have important implications for the design and analysis of cognitive conjunction studies and have motivated a change to the SPM software, that affords a test for the more general hypothesis k >u. This more general conjunction test is described.

Arousal↗
PubMed1995

Measurement of IL-4 in tears of patients with seasonal allergic conjunctivitis and vernal keratoconjunctivitis.

To elucidate the mechanism of ocular surface allergic disease, we focused on IL-4, which is one of the key factors in regulating IgE production, and thus determined the concentration of IL-4 in tears. IL-4 concentration was determined in the tears of 15 patients with seasonal allergic conjunctivitis, 15 vernal keratoconjunctivitis (VKC), 10 giant papillary conjunctivitis (GPC), 10 patients with non-allergic conjunctivitis and post-cataract surgical conjunctivitis as intermediate conjunctivitis, and 10 normal subjects using a highly sensitive sandwich ELISA. The mean level of IL-4 in normal controls was low, and seasonal allergic conjunctivitis, VKC and GPC showed a significant elevation (P < 0.05), respectively. IL-4 of VKC and GPC were also significantly higher than allergic conjunctivitis, and non-allergic conjunctivitis and post-cataract surgical conjunctivitis were not higher than normal. These results raise the possibility that the increased level of IL-4 in tears could play a role in allergic disease and its severity in patients.

Adolescent↗
PubMedDate not supplied

Ligneous conjunctivitis: a case report.

BACKGROUND: Ligneous conjunctivitis is a rare condition characterized by chronic, recurrent conjunctivitis associated with pseudomembrane, and it may involve other mucous membranes in the mouth, nasopharynx, trachea, and vagina. We examined and treated a case of presumed ligneous conjunctivitis. CASE: The patient was a 10-year-old boy. His chief complaints were visual impairment, discomfort, and discharge, but no itching in his eyes. His upper eyelids appeared thick without swelling. He had a past history of surgery for lid entropion. His two siblings had similar follicular conjunctivitis. OBSERVATIONS: This case exhibited several characteristics of ligneous conjunctivitis, such as large follicles, recurrent pseudomembrane and normal level IgE in the serum. Indispensable characteristics of vernal keratoconjunctivitis, strong itching, and extensive papillary formation, were not found. In spite of the lack of woody hardness of the conjunctiva, other clinical findings led to the diagnosis of ligneous conjunctivitis. Definite histological diagnosis was not obtained, because of the lack of common histological characteristics among previously reported cases with ligneous conjunctivitis. The boy had developed corticosteroid glaucoma after instillation of dexamethasone 0.1% for 7 months at a previous time. We successfully treated this case with combined instillation of fluorometholon and cyclosporin after trabeculotomy. CONCLUSIONS: Ligneous conjunctivitis must be considered as one type of differential diagnosis of vernal keratoconjunctivitis. Cyclosporin is an effective alternative for the treatment of ligneous conjunctivitis, especially in a case with a possible history of corticosteroid glaucoma.

Child↗
PubMed1997

Conjunctivitis in infants and children.

BACKGROUND: Acute bacterial conjunctivitis, chiefly affecting young children, is generally caused by one of three common pathogens, Haemophilus influenzae, Streptococcus pneumoniae and adenovirus. H. influenzae is the most prevalent causative organism. Some patients presenting initially with conjunctivitis subsequently develop acute otitis media, with H. influenzae the most common etiologic agent of what has been termed the "conjunctivitis-otitis" syndrome. Optimal treatment of acute conjunctivitis would result in a clinical and bacteriologic cure of the conjunctivitis and the prevention of the development of otitis media. Application of topical antimicrobials at 4- to 6-h intervals a day for 1 week to 10 days results in the resolution of the conjunctivitis. However, topical treatment is difficult to administer to toddlers and does not effectively reduce the potential for the development of otitis media. Compared with topical and placebo treatment, oral antibiotics effective against H. influenzae have proved to be most effective in preventing the otitis media associated with conjunctivitis. CONCLUSION: Acute bacterial conjunctivitis is a common disorder in children < 6 years of age. H. influenzae is the most common etiology of the "conjunctivitis-otitis syndrome." The optimal treatment for this condition is still being studied.

Acute Disease↗
PubMed2006

Vasomotor (perennial chronic) conjunctivitis.

PURPOSE OF REVIEW: To increase the awareness of nonimmunoglobulin E-mediated conjunctival disorders similar to those recognized to affect other organs that are targets in immunoglobulin E-mediated disorders. Such conditions may include 'vasomotor' instability, that is vasomotor conjunctivitis, which leads to a more common perennial chronic conjunctivitis. These conditions are not commonly included in the differential diagnosis of allergic conjunctivitis. RECENT FINDINGS: Although there have not been specific recent findings regarding the eye, it appears that evidence for such disorders in the rhinitis literature suggests that they can be involved in more than 25% of chronic conjunctivitis cases. The extrapolation of such conditions to the conjunctival surface clearly reflects these syndromes which have clearly been underappreciated and underdiagnosed. SUMMARY: A significant amount of work remains to be performed to understand perennial chronic conjunctivitis (vasomotor conjunctivitis or nonallergic noninfectious conjunctivitis) as well as other forms of chronic conjunctivitis that can mimic or exist in a comorbid state with ocular allergy. These disorders need to be better defined, categorized and classified to determine the best treatment modalities. Management guidelines and parameters of chronic noninfectious conjunctivitis need to be set on a national and international basis that will advance clinically applicable research results, pharmaceutical development and relief for patients.

Anti-Allergic Agents↗
PubMed2000

Clinical and epidemiological features of acute follicular conjunctivitis with special reference to that caused by herpes simplex virus type 1.

BACKGROUND/AIMS: It is reported by the national surveillance of ocular infectious diseases in Japan that 4.3% of cases of epidemic keratoconjunctivitis (EKC) diagnosed clinically were caused by herpes simplex virus (HSV). Clinical and virological studies of patients with HSV conjunctivitis were carried out. METHODS: The study population consisted of 478 patients with acute follicular conjunctivitis. Virological analysis was carried out for adenovirus (Ad) and HSV by the cell culture method and fluorescein antibody (FA) method. Polymerase chain reaction for Chlamydia trachomatis was also carried out. RESULTS: From 23 patients, HSV type 1 was isolated but Ad or C trachomatis was not isolated. 87% of cases were unilateral. Most cases showed clinical resolution within 9 days. Early corneal lesions and preauricular lymphadenopathy were less frequent in HSV conjunctivitis than in adenoviral conjunctivitis, especially that due to subgenus D. No case showed a positive result for HSV by the FA method using conjunctival swabs; however, the FA test was positive in all strains isolated by cell culture. CONCLUSIONS: These results indicate that it is difficult clinically to differentiate HSV conjunctivitis from adenoviral conjunctivitis in the acute stage, since the clinical features of adenoviral conjunctivitis are similar to those of HSV conjunctivitis. A biological difference may exist between HSV strains causing keratitis and conjunctivitis.

Acute Disease↗
PubMed2003

Multiple cedar pollen challenge diminishes involvement of histamine in allergic conjunctivitis of Guinea pigs.

It has been reported that antihistamines do not fully modify symptoms of allergic conjunctivitis in clinical settings, suggesting that histamine is not the only contributor to symptom generation in the disease. However, in the majority of experimental allergic conjunctivitis models, antihistamines are very effective in the reduction of symptoms. In the present study, we used our recently developed guinea pig model of allergic conjunctivitis and evaluated whether involvement of histamine in the induction of symptoms of allergic conjunctivitis is altered by multiple antigen challenges. Guinea pigs were sensitized by intraperitoneal injection of Japanese cedar pollen extracts adsorbed on aluminum hydroxide gel, and then challenged by dropping a pollen suspension without the adjuvant on each eye once a week until the 15th challenge. The magnitude of the conjunctivitis intensity score (CIS), itch-associated scratching response and albumin leakage were found to increase with repeated challenges. At the 1st-3rd challenges, histamine H(1) receptor antagonist, mepyramine (10 mg/kg, p.o.), strongly reduced all these symptoms. However, symptoms at the 5th-15th challenges were not inhibited by mepyramine. On the other hand, a nitric oxide synthase (NOS) inhibitor, N(omega)-nitro-L-arginine methyl ester (10 mg/kg, i.v.), potently inhibited the increase of CIS and albumin leakage at the 15th challenge. In conclusion, histamine involvement in the induction of conjunctivitis symptoms in our model was diminished by multiple antigen challenges. The allergic conjunctivitis at the chronic stage is partly mediated by nitric oxide (NO) derived from NOSs that may be activated by mediators other than histamine. The histamine-independent allergic conjunctivitis may be useful for analyzing mechanisms underlying chronic conjunctivitis.

Administration, Oral↗
PubMed2001

Dissociations between featural versus conjunction-based texture processing in infancy: analyses of three potential contributing factors.

Many models of object perception posit that adults encode individual features in visual scenes before processing the conjunction relations among these features to generate holistic representations. Prior research suggests that infants detect textural discrepancies based on individual features more readily than those based on feature conjunctions. While these results suggest adult-like qualitative differences in infants' processing of features versus conjunctions, there are potential alternative explanations. We examined three such explanations: (1) failure to process one of the features that constitute the conjunction, (2) failure to encode and remember conjunction information that is necessary to detect conjunction-based textural discrepancies, and (3) the fact that conjunction-based discrepancies involve stimuli that are more similar to original stimuli than those involving feature-based discrepancies. None of these factors could explain 5.5-month-olds' superior processing of featural than conjunction-based textural discrepancies. Thus, in infancy, as in adulthood, features and conjunction relations appear to be processed by qualitatively different mechanisms.

Child Development↗
PubMed2002

Visual feature and conjunction searches of equal difficulty engage only partially overlapping frontoparietal networks.

According to a classical view of visual object recognition, targets are detected "pre-attentively" if they carry unique features, whereas attention has to be deployed serially to object locations for feature binding if the targets can be distinguished from distracters only in terms of their feature conjunctions. Consistent with this view, recent reports suggest a contribution of the posterior parietal cortex (PPC; one major region controlling spatial attention) to conjunction search as opposed to feature search. However, PPC engagement in conjunction search might also reflect feature-based attention or the difficulty of target selection. The present fMRI study compared regions and amplitudes of cortical activity reflecting the attention mechanisms of a conjunction and a feature search of equal difficulty performed during maintenance of fixation. Attention-related activity was assessed by comparing each hard feature and conjunction search with an easy feature search. Hard feature and conjunction search activated overlapping regions in multiple PPC areas and in the frontal eye field (FEF). Most consistent PPC overlaps were located in the anterior and posterior intraparietal sulcus (IPS). The response amplitude of posterior IPS did not differ between both search tasks. However, the IPS junction with the transverse occipital sulcus and the FEF responded at a higher amplitude during conjunction search. Moreover, regions of the prefrontal cortex and the PPC were activated only during either hard feature or conjunction search. These findings suggest that equally difficult visual searches for features and conjunctions are controlled by overlapping frontoparietal networks, but also that both search types involve specific mechanisms.

Adult↗
PubMed2000

Response selection processes for conjunctive targets.

A model is proposed for identification and response selection of cross-dimensional conjunctive stimuli. The model assumes that the formation of conjunction representations involves processes similar to those used in response selection for single-feature targets. It predicts that discrimination between conjunctive targets leads to separate competitions in each of the relevant component dimensions and that detection of a predefined single conjunctive target is done at the conjunctive map level. Experiments 1 and 2 support these two sets of predictions. Experiment 3 demonstrates that responses to conjunctions of features within the orientation dimension are qualitatively different from those for cross-dimensional conjunctive targets. It is speculated that line-orientation conjunctions are handled by the visual object-recognition system, whereas cross-dimensional conjunctions, as exemplified by the model, may be performed by a different system that is closely associated with response selection processes.

Adult↗