Biomedical subjects

Xiangen Hu

Publications and source records attributed to Xiangen Hu.

4 recordsLinked to original sources

PubMed2006

Optimization of a multinomial model for investigating hallucinations and delusions with source monitoring.

Studies of source monitoring have played an important role in cognitive investigations of the inner/outer confusions that characterize hallucinations and delusions in schizophrenia, and multinomial modelling is a statistical/cognitive modelling technique that provides a powerful method for analyzing source monitoring data. The purpose of the current work is to describe how multinomial models can be optimized to answer direct questions about hallucinations and delusions in schizophrenia research. To demonstrate this, we present a reanalysis of previously published source monitoring data, comparing a group of patients with schneiderian first rank symptoms to a group without schneiderian first rank symptoms. The main findings of this analysis were (1) impaired recognition of self-generated items and (2) evidence that impaired source discrimination of perceived items is accompanied by an internalization bias in the target symptom group. Statistical and cognitive interpretations of the findings are discussed.

Cognition Disorders↗

PubMed2005

Impairment of specific episodic memory processes by sub-psychotic doses of ketamine: the effects of levels of processing at encoding and of the subsequent retrieval task.

RATIONALE: The precise nature of the impact of the N-methyl-D-aspartate antagonist, ketamine, upon human episodic memory, has yet to be elucidated fully. OBJECTIVES: This study sought to assess the effects of ketamine on the sub-processes facilitating memory encoding and retrieval. METHODS: We evaluated the effects of the drug on a series of memory performance measures depending upon whether it was administered at the encoding or retrieval stage and on the nature of the encoding task used. Twelve healthy volunteers participated in a double-blind, placebo-controlled, randomized, within-subjects study. Intravenous infusions of placebo, 50 ng/ml ketamine or 100 ng/ml ketamine were administered. We investigated the effects of ketamine on three key aspects of episodic memory: encoding vs retrieval processes, source memory, and depth of processing. Data were analysed using both multinomial modelling and standard measures of item discrimination and response bias. RESULTS: Deleterious effects of ketamine on episodic memory were primarily attributable to its effects on encoding, rather than retrieval processes. Recognition memory was impaired for items encoded at an intermediate level of processing, but preserved for shallowly and deeply encoded items. Increased source guessing bias was also observed when encoding took place under ketamine. CONCLUSIONS: The effects of ketamine upon episodic memory seem, therefore, to predominate at encoding. Furthermore, our results are also consistent with a specific impairment of encoding processes that result in subsequent recollective, as opposed to familiarity-based, retrieval. The observed effects are compatible with memory deficits seen in schizophrenia and thus provide some support for the ketamine model of the disease.

Adolescent↗

PubMed2004

Human use regulatory affairs advisor (HURAA): learning about research ethics with intelligent learning modules.

The Human Use Regulatory Affairs Advisor (HURAA) is a Web-based facility that provides help and training on the ethical use of human subjects in research, based on documents and regulations in United States federal agencies. HURAA has a number of standard features of conventional Web facilities and computer-based training, such as hypertext, multimedia, help modules, glossaries, archives, links to other sites, and page-turning didactic instruction. HURAA also has these intelligent features: (1) an animated conversational agent that serves as a navigational guide for the Web facility, (2) lessons with case-based and explanation-based reasoning, (3) document retrieval through natural language queries, and (4) a context-sensitive Frequently Asked Questions segment, called Point & Query. This article describes the functional learning components of HURAA, specifies its computational architecture, and summarizes empirical tests of the facility on learners.

Artificial Intelligence↗

PubMed2001

Extending General Processing Tree Models to Analyze Reaction Time Experiments.

General processing tree (GPT) models are usually used to analyze categorical data collected in psychological experiments. Such models assume functional relations between probabilities of the observed behavior categories and the unobservable choice probabilities involved in a cognitive task. This paper extends GPT models for categorical data to the analysis of continuous data in a class of response time (RT) experiments in cognitive psychology. Suppose that a cognitive task involves several discrete processing stages and both accuracy (categorical) and latency (continuous) measures are obtained for each of the response categories. Furthermore, suppose that the task can be modeled by a GPT model that assumes serialization among the stages. The observed latencies of the response categories are functions of the choice probabilities and processing times (PT) at each of the processing stages. The functional relations are determined by the processing structure of the task. A general framework is presented and it is applied to a set of data obtained from a source monitoring experiment. Copyright 2001 Academic Press.

Journal Article↗