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PubMed2007

Air-facilitated three-phase contact formation at hydrophobic solid surfaces under dynamic conditions.

The paper presents results documenting the mechanism of facilitation of the three-phase contact (TPC) formation due to gas entrapped during immersion of hydrophobic (Teflon) plates into distilled water and n-octanol solutions. Collisions, bouncing, the time scale of the TPC formation, and bubble attachment to Teflon plates of different surface roughness were studied using a high-speed camera. Processes occurring during the microscopic wetting film formation at the Teflon plates were monitored using the microinterferometric method (Scheludko-Exerowa cell). A strong relation between the time necessary to form a stable TPC and the roughness of the Teflon was observed. The higher the Teflon roughness was the shorter the time for the TPC formation. This effect can be attributed to two factors: (i) local differences in the thickness of the thinning intervening liquid layer (quicker attainment of rupture thickness at pillars of rough surface) and/or (ii) the presence of gas at the hydrophobic surface. Experimental findings, that (i) prolongation of the plate immersion time resulted in quicker TPC formation, (ii) white irregular and disappearing spots (air pockets) were recorded during the wetting film formation, and (iii) high n-octanol concentration caused prolongation of the time of the TPC formation, show that attachment (TPC formation) of the colliding bubble to hydrophobic surfaces was facilitated by air entrapped at the Teflon plates (and re-distributed) during their immersion into water phase. Thus, on collision instead of solid/gas wetting liquid film a thin gas/liquid/gas foam film was formed which facilitated the TPC formation.

Journal Article↗

PubMed2000

Sentence comprehension is mediated by content-addressable memory structures.

Studies of working memory demonstrate that some forms of information are retrieved by a content-addressable mechanism (McElree & Dosher, 1989; McElree, 1996, 1998), whereas others require a slower search-based mechanism (McElree & Dosher, 1993). Measures of the speed and accuracy of processing sentences with filler-gap dependencies demonstrate that the probability of maintaining a representation of a filler item decreases as additional material is processed, but that the speed with which a preserved representation is accessed is unaffected by the amount of interpolated material. These results suggest that basic binding operations in sentence comprehension are mediated by a content-addressable memory system.

Cognition↗

PubMed2001

Etiology of reading difficulties and rapid naming: the Colorado Twin Study of Reading Disability.

Children with reading deficits perform more slowly than normally-achieving readers on speed of processing measures, such as rapid naming (RN). Although rapid naming is a well-established correlate of reading performance and both are heritable, few studies have attempted to assess the cause of their covariation. Measures of rapid naming (numbers, colors, objects, and letters subtests), phonological decoding, orthographic choice, and a composite variable (DISCR) derived from the reading recognition, reading comprehension, and spelling subtests of the Peabody Individual Achievement Test were obtained from a total of 550 twin pairs with a positive school history of reading problems. Basic DeFries and Fulker (DF) multiple regression models for the analysis of selected twin data confirmed the heritable nature of phonological decoding, orthographic choice, DISCR, and rapid-naming composites. Bivariate DF models were employed to examine the extent to which deficits in the three reading-related measures covary genetically with rapid naming. Significant bivariate heritability estimates for each of the reading measures with the numbers and letters rapid-naming composite were also obtained. As expected, univariate sib-pair linkage analyses indicated the presence of a quantitative trait locus (QTL) on chromosome 6p21.3 for phonological decoding and orthographic choice deficits. Bivariate linkage analyses were then conducted to test the hypothesis that this QTL for reading difficulties is pleiotropic for slower performance on RN tasks. The results obtained from these analyses did not provide substantial evidence that the 6p QTL for reading difficulties has significant effects on rapid naming; however, larger samples would be required to test this hypothesis more rigorously.

Adolescent↗

PubMed2002

Children's recognition of caricatures.

This study examined children's and adults' perception and recognition of facial stimuli that were either systematically exaggerated (caricatures) or de-exaggerated (anticaricatures) relative to a norm face. The results showed that all age groups perceived caricatures as the most distinctive versions of a face and anticaricatures as the least distinctive, although the effect was smallest for 6-year-olds. In general, caricatures were identified as quickly as the veridical faces and faster than the anticaricatures. Across all age groups, participants' familiarity with the stimulus faces interacted with degree of caricature to determine speed of processing as well as choice of best likeness. The results are discussed in relation to the idea that distinctiveness information in a face is represented in relation to a norm.

Caricatures as Topic↗

PubMed1990

Human immunodeficiency virus-type 1 (HIV-1) and the brain.

Infection with human immunodeficiency virus Type-1 (HIV-1), the causative agent of AIDS, can be associated with central nervous system as well as immune system disease. Advanced AIDS can be complicated by a dementia. Short of frank dementia, many AIDS patients manifest neuropsychological (NP) impairment including disturbance in speeded information processing, abstraction, learning, and recall. Data conflict on whether medically asymptomatic HIV-1 carriers have subtle NP deficits. Variations in tests chosen, criterion specification, and sample selection may all be contributing to disparate results. Longitudinal research is needed, and this should examine representative samples of HIV-1 seropositive individuals for whom approximate date of seroconversion is known and in whom sources of comorbidity (e.g., drug abuse, concurrent infections, CNS injuries) can be specified.

AIDS Dementia Complex↗

PubMed1991

Affective influences on partner choice: role of mood in social decisions.

Does mood influence our information search and decision strategies when choosing a partner? In Experiment 1 (N = 60), sad Ss preferred rewarding to competent partners and remembered information supporting that choice better. In Experiment 2 (N = 96), mood effects on information selectivity, decision speed, and processing strategy in partner choices were found. In Experiment 3 (N = 42), a computerized stimulus presentation revealed mood-induced differences in the latency, self-exposure, and eventual recall of interpersonal information. These results are interpreted as evidence for mood-induced selectivity in information search and decision strategies when making realistic partner choices. The implications of the findings for research on interpersonal relations and for contemporary affect-cognition theories are considered.

Adult↗

PubMed1984

A horse race of a different color: Stroop interference patterns with transformed words.

Four experiments investigated Stroop interference using geometrically transformed words. Over experiments, reading was made increasingly difficult by manipulating orientation uncertainty and the number of noncolor words. As a consequence, time to read color words aloud increased dramatically. Yet, even when reading a color word was considerably slower than naming the color of ink in which the word was printed, Stroop interference persisted virtually unaltered. This result is incompatible with the simple horse race model widely used to explain color-word interference. When reading became extremely slow, a reversed Stroop effect--interference in reading the word due to an incongruent ink color--appeared for one transformation together with the standard Stroop interference. Whether or not the concept of automaticity is invoked, relative speed of processing the word versus the color does not provide an adequate overall explanation of the Stroop phenomenon.

Attention↗

PubMed1997

Stroop theory, memory, and prefrontal cortical functioning: reply to Cohen et al. (1997)

In this article, the authors respond to J. D. Cohen, K. O. Dunbar, D. M. Barch and T. S. Braver's (1997) comment on their target article. The present article (a) takes issue with the characterization given by Cohen et al. of the authors' approach as a classical speed-of-processing account of Stroop effects, (b) discusses the value and relevance of other theoretical concepts, such as traditional accounts of working memory and parallel distributed processing (PDP) approaches to Stroop effects, (c) further examines the possibility that the differences the authors observed in Experiment 2 between normal participants' performance and that of participants with schizophrenia may have been due to distractor stimulus degradation, particularly for participants with schizophrenia, and (d) argues for the relevance of the prefrontal cortex, as well as other brain areas, in accounting for their results. The authors conclude with a final theoretical question.

Attention↗

PubMed1988

Training and Stroop-like interference: evidence for a continuum of automaticity.

Three experiments varied the extent of practice in an analog of the Stroop color-work task. Each experiment involved four phases: (a) baseline naming of four familiar colors, (b) training in consistently naming four novel shapes by using the names of the same four colors, (c) naming the colors when they appeared in the form of the shapes, and (d) naming the shapes when they appeared in color. In Experiment 1, with up to 2 hr of training in shape naming, colors were named much faster than shapes. Interference was observed only in Phase 4. In Experiment 2, with 5 hr of training, shape naming sped up, but was still slower than color naming. Nevertheless, there was symmetrical interference in Phases 3 and 4, and this persisted 3 months later without further training. Experiment 3 replicated this pattern and then extended practice to 20 hr, by which time shape and color naming were equally rapid. After 20 hr, interference appeared only in Phase 3, reversing the original asymmetry. The overall pattern is inconsistent with a simple speed of processing account of interference. The alternative idea of a continuum of automaticity--a direct consequence of training--remains plausible, and the implications of this perspective are considered.

Attention↗

PubMed1986

Visual function measured by reflex modification in rats with inherited retinal dystrophy.

Developmental changes in visual function were studied in the Royal College of Surgeons (RCS) rat with inherited retinal degeneration by examining the inhibition of acoustic startle reflexes by visual prestimuli. Compared with a congenic strain of nondystrophic rat, the RCS rats showed an increase in the interstimulus interval between the inhibitory prestimulus and the eliciting stimulus that produced maximal inhibition, a result suggesting a decrease in the speed of processing. The amount of inhibition also decreased over time, which suggests a progressive loss of visual function. Simultaneous presentation of auditory and visual prestimuli was used to demonstrate that the changes in inhibition were related to alterations in visual function and that auditory function was not impaired in these rats. The results show that reflex modification is a suitable test for evaluating visual dysfunction in rats.

Acoustic Stimulation↗

PubMed1994

Young children's performance on a task sensitive to the memory functions of the medial temporal lobe in adults--the delayed nonmatching-to-sample task--reveals problems that are due to non-memory-related task demands.

Delayed nonmatching-to-sample performance was examined in children and found to be poor from 12 months until almost 2 years even at 5-s delay, although 5 s is well within such children's memory capacity. After 12 months of age, performance did not differ by delay (5 or 30 s). Because children's problems seemed largely unrelated to the task's memory demands, the 2 final studies explored the role of other cognitive abilities (deduction of an abstract rule, speed of processing, and resistance to interference or distraction). Telling children the rule or quadrupling sample presentation time had little effect. Because a salient stimulus (the reward) might interfere with keeping one's attention on the sample, the reward was omitted during initial sample presentation. This helped; at the 5-s delay, 15-month-olds performed at least as well as 21-month-olds in the basic condition, and 12-month-olds performed almost as well. Implications for the cognitive abilities improving during the 2nd year and for the functions of the medial temporal lobe are discussed.

Aptitude↗

PubMed2001

Is the dissociability of working memory systems for name identity, visual-object identity, and spatial location maintained in old age?

The dissociability of working memory for name identity (verbal information), visual objects, and spatial location was explored in 3 experiments. Consistent with previous results, the 3 working memory systems were dissociable in younger adults. Both younger and older adults showed involvement of name identity in an object identity task, and older adults showed this involvement in a spatial memory task. Results were interpreted as showing that the systems are generally separable but that involvement of 1 with another is possible and more likely in older adults. A 4th, correlational study showed that there is generalized decline in working memory systems in old age, with the age differences in memory mediated to a moderate extent by age-related differences in speed of processing. It was speculated that the specific, possibly strategic changes are independent of and take place against a backdrop of generalized loss of nervous system integrity.

Acoustic Stimulation↗

PubMed2002

Cognitive and neuropathologic correlates of Stroop Color-Word Test performance in Alzheimer's disease.

The Stroop Color-Word Test (SCWT; C. Golden, 1978) was examined in 59 patients with probable Alzheimer's disease (AD) and in 51 demographically comparable normal control (NC) participants. AD patients produced significantly larger Stroop interference effects than NC participants, and level of dementia severity significantly influenced SCWT performance. Principal-components analyses demonstrated a dissociation in the factor structure of the Stroop trials between NC participants and AD patients, suggesting that disruption of semantic knowledge and speeded verbal processing in AD may be a major contributor to impairment on the incongruent trial. Results of clinicopathologic correlations in an autopsy-confirmed AD subgroup further suggest the invocation of a broad network of integrated cortical regions and executive and language processes underlying successful SCWT performance.

Aged↗

PubMed1986

Self-schematic representation of the type A and B behavior patterns.

Past research has established clear behavioral differences between Type A and B individuals. The purpose of our research was to examine how these behavioral differences are represented in the self-definitions of Type As and Bs. We investigated the existence of Type A and B self-schemata by using two tasks designed to measure the influence of these hypothetical structures on speed of processing and memory interference. During an initial task, Type As and Bs made self-relevant decisions (like me, not like me) in response to trait adjectives previously scaled as Type A, Type B, or neutral in content. Reaction times for the decisions were measured, and results indicated that both Type As and Bs made faster decisions for schema-compatible responses than for schema-incompatible responses. On a second task, Type As and Bs were tested for recognition memory after they attempted to memorize half of the aforementioned trait list. Memory errors were examined and indicated that Type As and Bs made more errors that were compatible with their respective self-schemata. Taken together, these results indicate that a Type A and B distinction forms a reliable organizing framework for the self-definitions of Type As and Bs. The existence of stable cognitive structures that parallel the behavioral differences between Type As and Bs has important implications for both theory and application.

Adult↗

PubMed2005

No, it is not possible to be schizophrenic yet neuropsychologically normal.

Cognitive impairment is well documented in schizophrenia, though some reports have been interpreted to suggest that it is possible to have schizophrenia without neuropsychological impairment. The authors tested this by comparing the neuropsychological profiles of closely matched patients with schizophrenia and healthy comparison participants. Sixty-four patients with schizophrenia and 64 healthy comparison cases, matched to within 3 Full-Scale IQ points, were tested using the Wechsler Adult Intelligence Scale (3rd ed.; D. Wechsler, 1997b) and the Wechsler Memory Scale (3rd ed.; D. Wechsler, 1997c). Neuropsychological profiles for these groups were markedly different, with the group of patients with schizophrenia exhibiting performance deficits in memory and speeded visual processing but superior verbal comprehension and perceptual organization relative to the group of healthy comparison participants matched on Full-Scale IQ. Thus, scoring in the normal range does not preclude neuropsychological abnormality in schizophrenia, confirming that neuropsychological impairment is a core feature of the illness.

Adult↗

PubMed2001

Basic processes in reading: semantics affects speeded naming of high-frequency words in an alphabetic script.

Previous work on single-word naming in university-level readers has shown that semantic factors affect the naming of low frequency words both in an alphabetic script like English, which is often irregular in terms of the spelling-sound correspondences, and in the syllabic Japanese Kana script, in which the spelling-sound correspondences are consistent. The present experiment shows that a semantic factor (imageability) affects naming time to both low- and high-frequency words in an alphabetic script (Persian) when the word is opaque (vowels not specified) but not when it is transparent (vowels specified). Other characteristics of opaque words that promote the use of semantics are discussed. At least in some orthographies, semantics play a larger role in single-word naming than previously thought.

Adult↗

PubMed1999

Antihistamines: models to assess sedative properties, assessment of sedation, safety and other side-effects.

Behavioural changes are produced by any drug that enters the central nervous system. These psychoactive effects include changes in alertness, concentration, attention, memory, cognition, psychomotor accuracy, skilled performance and affect. Changes in psychological performance may affect the safety of both the individuals taking the drug and of those people coming into contact with them. The aims of psychopharmacological performance tests are to describe the nature, extent and severity of these changes and identify drugs without deleterious effects upon performance. Use of traditional antihistamines has until recently been associated with a number of undesirable side-effects, the most troublesome of which is sedation. There are two aspects to sedation. Firstly, an objectively determined one based on the results of psychometric tests from controlled trials and secondly, the subjects response to the administration of a drug. Although the second generation of antihistamines have a much more favourable therapeutic index, use of these agents has also been reported to cause varying degrees of sedation. As antihistamines are largely used by ambulant patients, a complete evaluation of sedation should be performed through standardized objective tests, shown to be sensitive to the central effects of antihistamines as well as reliable ratings of subjective experiences. An extensive review of the literature has identified a number of tests which appear to be sensitive to the central effects of antihistamines. These include tests of psychomotor performance, sensori-motor co-ordination speed, information processing, sensory skills as well as physiological measures and subjective rating scales. Using this battery of cognitive and psychomotor tests, it is evident that only a very limited number of antihistamines can claim to be virtually free of both objective and subjective sedative effects, although the second generation of antihistamines are generally less impairing than the original ones; when prescribed at their recommended doses.

Cognition↗

PubMed1996

Clamp loading, unloading and intrinsic stability of the PCNA, beta and gp45 sliding clamps of human, E. coli and T4 replicases.

BACKGROUND: The high speed and processivity of replicative DNA polymerases reside in a processivity factor which has been shown to be a ring-shaped protein. This protein ("sliding clamp') encircles DNA and tethers the catalytic unit to the template. Although in eukaryotic, prokaryotic and bacteriophage-T4 systems, the processivity factors are ring-shaped, they assume different oligomeric states. The Escherichia coli clamp (the beta subunit) is active as a dimer while the eukaryotic and T4 phage clamps (PCNA and gp45, respectively) are active as trimers. The clamp can not assemble itself on DNA. Instead, a protein complex known as a clamp loader utilizes ATP to assemble the ring around the primer-template. This study compares properties of the human PCNA clamp with those of E. coli and T4 phage. RESULTS: The PCNA ring is a stable trimer down to a concentration below 100 nM (Kd approximately 21 nM). On DNA, the PCNA clamp slides freely and dissociates from DNA slowly (t1/2 approximately 24 min). beta is more stable in solution (Kd < 60 PM) and on DNA (t1/2 approximately 1 h) than PCNA which may be explained by its simpler oligomeric state. The T4 gp45 clamp is a much less stable trimer than PCNA (Kd approximately 250 nM) and requires association with the polymerase to stabilize it on DNA as observed previously. The consequence of this cooperation between clamp and polymerase is that upon finishing a template and dissociation of the polymerase from DNA, the gp45 clamp spontaneously dissociates from DNA without assistance. However, the greater stability of the PCNA and beta clamps on DNA necessitates an active process for their removal. The clamp loaders (RFC and gamma complex) were also capable of unloading their respective clamps from DNA in the presence of ATP. CONCLUSIONS: The stability of the different clamps in solution correlates with their stability on DNA. Thus, the low stability of the T4 clamp explains the inability to isolate gp45 on DNA. The stability of the PCNA and beta clamps predicts they will require an unloading factor to recycle them on and off DNA during replication. The clamp loaders of PCNA and beta double as clamp unloaders presumably for the purpose of clamp recycling.

Bacteriophage T4↗