Biomedical subjects

Xu-Chu Weng

Publications and source records attributed to Xu-Chu Weng.

3 recordsLinked to original sources

PubMed2005

Neural activity associated with cognitive regulation in heroin users: A fMRI study.

Previous research has found heroin addicts to be impulsive. This study employed functional magnetic resonance imaging technology to investigate the differences between heroin addicts and normal controls in neural activity associated with cognitive regulation of behavior. Twenty-one Chinese men participated in this study, 11 of whom were newly admitted heroin-addicted patients and 10 of whom were healthy volunteers. In the experimental task, the subjects were required to first identify the correct directions of arrowheads and then give the opposite answers. Behaviorally, the heroin-dependent patients took a much shorter time to complete the more demanding second part of the task but committed more errors than the normal controls. This pattern of behavior, characteristic of people who are disinhibited and who tend to be impulsive, was consistent with previous reports of impulsivity observed in people who have abused heroin. The neural activity of the patients that was associated with performing the experimental task of cognitive regulation was different to that of the normal controls in terms of the pattern of prefrontal activation, the attenuation of activity in the anterior cingulate, and the additional recruitment of the right inferior parietal region. This study is the first that seeks to understand the neural activity associated with impulsive behavior in people who abuse heroin. The pattern of imaging data obtained resembled the pattern of data observed in immature brains attempting to exercise cognitive control of behavior. Further theoretical and clinical implications of the findings are discussed.

Adult↗

PubMed2005

Functional MRI in attention-deficit hyperactivity disorder: evidence for hypofrontality.

Using event-related functional magnetic resonance imaging to study the Stroop effect on both behavioral and brain activation of ADHD children off or on methylphenidate (MPH). Nine ADHD boys (aged 9.8-14.5 years) and 9 age-matched normal controls were included. A Stroop-like paradigm was used. AFNI (Analysis of Functional NeuroImaging) and its Deconvolution Analysis were used in a descriptive comparison between ADHD and control groups. (1) Both behavioral reaction time and brain activation showed Stroop effect in controls but neither was found in ADHD children off MPH. When MPH was administered, the Stroop effect tended to appear. (2) The activation volume (AV) of prefrontal cortex (PFC) in both the neutral (NC) and interference conditions (IC) in ADHD children off MPH was smaller than in controls. AV of anterior cingulate cortex in the IC in ADHD children off MPH was smaller than that in controls, but was similar in the NC to that in controls. AV of the basal ganglia, insula and cerebellum was also smaller in the IC, but was larger in the NC for ADHD children off MPH compared with controls. These findings are consistent with prior findings of hypofrontality in ADHD children and implicate a compensatory network including basal ganglia, insula and cerebellum for relative lower cognitive load tasks.

Adolescent↗

PubMed2004

Continuous representation of human portraits and natural scenery in human ventral temporal cortex: evidence from functional magnetic resonance imaging.

BACKGROUND: Functional magnetic resonance imaging (fMRI) has become a powerful tool for tracking human brain activity in vivo. This technique is mainly based on blood oxygenation level dependence (BOLD) contrast. In the present study, we employed this newly developed technique to characterize the neural representations of human portraits and natural sceneries in the human brain. METHODS: Nine subjects were scanned with a 1.5 T magnetic resonance imaging (MRI) scanner using gradient-recalled echo and echo-planar imaging (GRE-EPI) pulse sequence while they were visually presented with 3 types of white-black photographs: natural scenery, human portraits, and scrambled nonsense pictures. Multiple linear regression was used to identify brain regions responding preferentially to each type of stimulus and common regions for both human portraits and natural scenery. The relative contributions of each type of stimulus to activation in these regions were examined using linear combinations of a general linear test. RESULTS: Multiple linear regression analysis revealed two distinct but adjacent regions in both sides of the ventral temporal cortex. The medial region preferentially responded to natural scenery, whereas the lateral one preferentially responded to the human portraits. The general linear test further revealed a distribution gradient such that a change from portraits to scenes shifted areas of activation from lateral to medial. CONCLUSIONS: The boundary between portrait-associated and scenery-associated areas is not as clear as previously demonstrated. The representations of portraits and scenes in ventral temporal cortex appear to be continuous and overlap.

Adult↗