Biomedical subjects

James A Hampton

Publications and source records attributed to James A Hampton.

6 recordsLinked to original sources

PubMed2005

Comparison and contrast in perceptual categorization.

People categorized pairs of perceptual stimuli that varied in both category membership and pairwise similarity. Experiments 1 and 2 showed categorization of 1 color of a pair to be reliably contrasted from that of the other. This similarity-based contrast effect occurred only when the context stimulus was relevant for the categorization of the target (Experiment 3). The effect was not simply owing to perceptual color contrast (Experiment 4), and it extended to pictures from common semantic categories (Experiment 5). Results were consistent with a sign-and-magnitude version of N. Stewart and G. D. A. Brown's (2005) similarity-dissimilarity generalized context model, in which categorization is affected by both similarity to and difference from target categories. The data are also modeled with criterion setting theory (M. Treisman & T. C. Williams, 1984), in which the decision criterion is systematically shifted toward the mean of the current stimuli.

Color Perception↗

PubMed2005

The prototype effect in recognition memory: intact in autism?

BACKGROUND: There are two accounts of categorization performance in autism: that there is an impairment in prototype formation (Klinger & Dawson, 2001) and that there is an impairment in processing features held in common between stimuli (Plaisted, O'Riordan, & Baron-Cohen, 1998). These accounts, together with central coherence theory (Frith, 1989; Frith & Happé, 1994), imply a reduced or absent prototype effect in autism. METHOD: Children with autism or Asperger syndrome (n = 15) matched on age, gender, and verbal mental age with typically developing children (n = 15) completed a picture recognition task (Experiment 1). These participants also studied categories of cartoon animals possessing either an average prototype structure (Experiment 2) based on (Younger's 1985) stimuli or a modal structure (Experiment 3) based on (Hayes and Taplin's 1993b) stimuli. Following the study phases, participants completed recognition tests comprising prototypes and other exemplars with varying degrees of similarity to the prototypes. RESULTS: For both participant groups, recognition memory appeared intact (Experiment 1) and a full prototype effect in recognition memory was observed in both Experiment 2 and Experiment 3. CONCLUSIONS: The present studies fail to support predictions of impaired prototype effects in autism. The discussion focuses on key methodological differences between these studies and those that support claims that central coherence, prototype formation, and common feature processing are impaired in autism.

Adolescent↗

PubMed2005

In vivo and in vitro effect of baicalein on human prostate cancer cells.

We investigated the in vitro effects of baicalein and baicalin on human umbilical vein endothelial cells (HUVECs) and on human prostate tumor cells (DU-145 and PC3) as well as the effect of orally administered baicalein on the growth of DU-145 cells after subcutaneous injection into SCID mice. In vitro effects of baicalein and baicalin treatment on human prostate cancer cell lines DU-145 and PC-3 were assessed by employing cell proliferation (MTS) assay, cytotoxicity (LIVE/DEAD) assay, and TUNEL assay. In vitro anti-proliferative and anti-angiogenic properties of baicalein and baicalin were studied on HUVECs by sprout assay. The effect of orally administered baicalein on tumor growth in SCID mice was studied in four groups (n=10) of animals injected subcutaneously with DU-145 cells and treated daily for 28 days. The control group received only vehicle (carboxymethylcellulose), whereas the other three groups received escalating doses of baicalein (10, 20, and 40 mg/kg per day). Baicalein and baicalin exhibit dose-dependent growth inhibitory effects on human prostate cancer cells and umbilical vein endothelial cells in vitro. Also, treatment by these two flavonoid compounds significantly decreased the average number and length of sprouts formed by the endothelial cell aggregates in a dose-dependent manner. In vivo, treatment of mice with baicalein demonstrated a statistically significant tumor volume reduction (p<0.01) when compared to the control. This is the first study demonstrating an in vivo growth inhibitory effect of orally administered baicalein on human prostate tumors in mice.

Administration, Oral↗

PubMed2004

Category-based induction: an effect of conclusion typicality.

Category-based induction involves the willingness of a thinker to project some newly learned property of one or more classes of objects to another class on the basis of their shared membership in a common superordinate category. Previous research has established that the perceived strength of arguments of the form "Class A has Property P; therefore, Class B has Property P" is influenced by the similarity of A to B and by the typicality or representativeness of A in a shared category, superordinate to both A and B. (The nature of P is also crucial, but we do not examine it in this study.) There is, however, no prior evidence that the relation between B and the category is influential. Three experiments were designed to test whether the typicality of B in the superordinate category also has an effect on inductive argument strength. By using multiple regression (Experiment 1) and an experimental design (Experiment 3), an effect of conclusion typicality was found, so that people are more willing to project properties to more typical conclusions. Experiment 2 ruled out conclusion familiarity as a potential confounding variable. The results are interpreted in the light of current models of category-based induction.

Cognition↗

PubMed2003

Abstraction and context in concept representation.

This paper develops the notion of abstraction in the context of the psychology of concepts, and discusses its relation to context dependence in knowledge representation. Three general approaches to modelling conceptual knowledge from the domain of cognitive psychology are discussed, which serve to illustrate a theoretical dimension of increasing levels of abstraction.

Cognition↗

PubMed2003

Inhibition of bladder tumor growth by the green tea derivative epigallocatechin-3-gallate.

PURPOSE: We evaluated the green tea derivative epigallocatechin-3-gallate (EGCG) as an intravesical agent for the prevention of transitional cell tumor implantation. MATERIALS AND METHODS: In vitro studies were performed in the AY-27 rat transitional cell cancer and the L1210 mouse leukemia cell lines. Cells were exposed to increasing concentrations of EGCG for 30 minutes to 48 hours. Surviving cell colonies were then determined. A DNA ladder assay was performed in the 2 cell lines. Fisher 344 rats were used for in vivo studies with an intravesical tumor implantation model. Group 1 (12 rats) served as a control (tumor implantation and medium wash only). In group 2 (28 rats) 200 microM EGCG were instilled intravesically 30 minutes after tumor implantation. Rats were sacrificed 3 weeks following treatment. Gross and histological analyses were then performed on the bladders. RESULTS: At 6.0 x 104 cells per 100 mm dish a time dose dependent response was observed. After 2 hours of treatment with EGCG 100% cell lethality of the AY-27 cell line occurred at concentrations greater than 100 microM. Strong banding on the DNA ladder assay was seen with the L1210 mouse leukemia cell line. Only weak banding patterns were found in the AY-27 cell line treated with EGCG (100 and 200 microM) for 24 hours. All 12 controls were successfully implanted with tumors. In group 2 (EGCG instillation) 18 of the 28 animals (64%) were free of tumor (Fisher's exact test p = 0.001). CONCLUSIONS: The clonal assays showed a time dose related response to EGCG. Intravesical instillation of EGCG inhibits the growth of AY-27 rat transitional cells implanted in this model.

Animals↗