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Biomedical subjects

John X Zhang

Publications and source records attributed to John X Zhang.

15 recordsLinked to original sources
PubMed2007

Psychological characteristics and marital quality of infertile women registered for in vitro fertilization-intracytoplasmic sperm injection in China.

OBJECTIVE: To assess the psychological health status and marital quality of Chinese women who were referred for IVF-intracytoplasmic sperm injection (ICSI), to compare the results with a control group, and to test the impact of clinical and sociodemographic determinants on psychological health status and marital quality in this cohort. DESIGN: A descriptive study of psychological health status and marital relationships, comparing infertile women who are registered for IVF or IVF-ICSI with fertile controls. SETTING: An assisted reproductive center of a science and technology institute of family planning. PATIENT(S): Two groups of infertile women (100 registered for IVF, and 100 registered for ICSI), and a control group of 100 women attending a gynecology clinic, who have no known history of infertility. INTERVENTION: Psychometric tests were administered at the first visit of the treatment cycle. MAIN OUTCOME MEASURE(S): Psychological status measured by the Hopkins Symptom Checklist-90 (SCL-90), and marital quality measured by the ENRICH (Evaluating & Nurturing Relationship Issues, Communication & Happiness) marital inventory. RESULT(S): Infertile Chinese women planning to undergo IVF-ICSI scored significantly higher on all subscales of the SCL-90 than did controls. In addition, women in the IVF subgroup had significantly higher scores on depression scales than those in the ICSI subgroup. The study group displayed unstable relationships compared to the control group. Age, yearly income, duration of infertility, and history of unsuccessful IVF treatment had a negative correlation with psychological health status and marital quality. CONCLUSION(S): The stresses associated with infertility and IVF treatment had a negative impact on Chinese women's psychological health status and marital quality. These findings emphasize the need to include psychological and sociocultural considerations with any medical interventions for infertility.

Adult↗
PubMed2006

Age-related differences in response regulation as revealed by functional MRI.

This fMRI study studied age-related differences in neural activities during response regulation. Twenty-one male participants from two age groups, a younger group and an older group (mean ages: 29.9 and 65.2 years, respectively), were scanned while performing a task with response compatibility manipulation. They were presented with a sequence of arrowheads that pointed either upward or downward. In the "Response Compatible" condition, they were required to press an up or a down button consistent with the direction of the arrowhead. In the "Response Incompatible" condition, they were required to press the button opposite to the arrowhead direction so that an upward arrow should elicit a down response, and vice versa. Findings showed age-related differences in response regulation in several brain regions, including the right frontal, the right cingulate, and the left inferior parietal cortexes. The findings suggested a higher level of neural activity in the right prefrontal and left inferior parietal regions during response regulation for the older adults than for the younger adults.

Adult↗
PubMed2006

Thirsty heroin addicts show different fMRI activations when exposed to water-related and drug-related cues.

Relapse to drug use is frequently preceded or caused by craving, an intense desire for drug. Advances in functional brain imaging techniques make it possible to directly investigate this special mental state in vivo and non-invasively. Extant imaging studies on craving have been mostly on cocaine which is the dominant drug abused in the U.S. Employing functional MRI, we examined substance specificity of the neural circuitry underlying craving for heroin. Heroin is the primary drug abused in south-east Asia and has, particularly, become a serious social problem for China in recent years. Following abstinence from water and drug, 14 active heroin addicts (all male, mean age 33.2 years, average drug use history 7.1 years) underwent scanning inside a 1.5T Philips MR scanner during exposure to water-related, drug-related, and neutral cues. Water-related cues elicited anterior cingulate activation (Brodmann's area BA 32/24). Drug-related cues activated bilateral inferior frontal cortex (BA 44/45), confirming the critical role of prefrontal cortex in drug craving. Results suggest heroin craving may involve different neural substrates than do desire from basic physiological drives, such as thirst. As the first fMRI study of heroin craving, our study adds to the scant but much-needed brain imaging literature on heroin addiction.

Adolescent↗
PubMed2005

Differential activity in left inferior frontal gyrus for pseudowords and real words: an event-related fMRI study on auditory lexical decision.

After Newman and Twieg and others, we used a fast event-related functional magnetic resonance imaging (fMRI) design and contrasted the lexical processing of pseudowords and real words. Participants carried out an auditory lexical decision task on a list of randomly intermixed real and pseudo Chinese two-character (or two-syllable) words. The pseudowords were constructed by recombining constituent characters of the real words to control for sublexical code properties. Processing of pseudowords and real words activated a highly comparable network of brain regions, including bilateral inferior frontal gyrus, superior, middle temporal gyrus, calcarine and lingual gyrus, and left supramarginal gyrus. Mirroring a behavioral lexical effect, left inferior frontal gyrus (IFG) was significantly more activated for pseudowords than for real words. This result disconfirms a popular view that this area plays a role in grapheme-to-phoneme conversion, as such a conversion process was unnecessary in our task with auditory stimulus presentation. An alternative view was supported that attributes increased activity in left IFG for pseudowords to general processes in decision making, specifically in making positive versus negative responses. Activation in left supramarginal gyrus was of a much larger volume for real words than for pseudowords, suggesting a role of this region in the representation of phonological or semantic information for two-character Chinese words at the lexical level.

Acoustic Stimulation↗
PubMed2004

Spatial congruence in working memory: an ERP study.

The Simon effect refers to the finding that reaction times are faster when stimulus and response locations are congruent than when they are not, even stimulus locations are task irrelevant. Zhang and Johnson reported a Simon-like spatial congruence effect in working memory. This study examined the neural mechanisms of this memory-based spatial congruence effect by recording event-related potentials to probe stimuli. Behavioral results showed a clear congruence effect. The P300 amplitudes were larger in the congruent condition than in the incongruent condition. The results suggest that the memory-based congruence effect and the classical Simon effect were mediated by similar neural mechanisms and support theories assigning response selection an essential role in spatial congruence effects.

Adolescent↗
PubMed2004

Contagiousness of varicella in vaccinated cases: a household contact study.

CONTEXT: Limited data are available on the contagiousness of vaccinated varicella cases. OBJECTIVES: To describe secondary attack rates within households according to disease history and vaccination status of the primary case and household contacts and to estimate varicella vaccine effectiveness. DESIGN, SETTING, AND PATIENTS: Population-based, active varicella surveillance project in a community of approximately 320,000 in Los Angeles County, California, during 1997 and 2001. Varicella cases were reported by child care centers, private and public schools, and health care clinicians and were investigated to collect demographic, clinical, medical, and vaccination data. Information on household contacts' age, varicella history, and vaccination status was collected. MAIN OUTCOME MEASURES: Varicella secondary attack rate among household contacts; vaccine effectiveness using secondary attack rates in unvaccinated and vaccinated children and adolescents. RESULTS: A total of 6316 varicella cases were reported. Among children and adolescents aged 1 to 14 years, secondary attack rates varied according to age and by disease and vaccination status of the primary case and exposed household contacts. Among contacts aged 1 to 14 years exposed to unvaccinated cases, the secondary attack rate was 71.5% if they were unvaccinated and 15.1% if they were vaccinated (risk ratio [RR], 0.21; 95% confidence interval [CI], 0.15-0.30). Overall, vaccinated cases were half as contagious as unvaccinated cases. However, vaccinated cases with 50 lesions or more were similarly contagious as unvaccinated cases whereas those with fewer than 50 lesions were only one third as contagious (secondary attack rate, 23.4%; RR, 0.32 [95% CI, 0.19-0.53]). Vaccine effectiveness for prevention of all disease was 78.9% (95% CI, 69.7%-85.3%); moderate disease, 92% (50-500 lesions) and 100% (clinician visit); and severe disease, 100%. CONCLUSIONS: Under conditions of intense exposure, varicella vaccine was highly effective in preventing moderate and severe disease and about 80% effective in preventing all disease. Breakthrough varicella cases in household settings were half as contagious as unvaccinated persons with varicella, although contagiousness varied with numbers of lesions.

Adolescent↗
PubMed2004

Is left inferior frontal gyrus a general mechanism for selection?

Converging lines of research in neuroimaging recognize selection as one of the critical functions of prefrontal cortex (e.g., see Annu. Rev. Neurosci. 24, 2001 167). We examined a central thesis of a selection hypothesis (Neuropsychologia 41, 2003 280) that the left inferior frontal gyrus (LIFG) serves as a general mechanism for selecting among competing representations (Annu. Rev. Neurosci. 18, 1995 193). Participants were presented with two sets of letters to remember and then cued to select one set from the two as the target set for subsequent recognition. LIFG showed significantly more activation when the cue elicited a strong need for selection, relative to when it did not, suggesting that the involvement of this area in selection is generalizable beyond semantic retrieval tasks as originally found. This result provides supporting evidence for the selection hypothesis.

Adult↗
PubMed2004

More workload on the central executive of working memory, less attention capture by novel visual distractors: evidence from an fMRI study.

The present study examined the interaction of the central executive in working memory with visual attention. Native Chinese participants were given two versions of a number subtraction task, one of low demand and one of high demand, and were asked to ignore a simultaneously presented peripheral distractor. The distractor could be Chinese or Korean characters, familiar or novel to participants, respectively. Compared with the low-demand subtraction task, brain regions commonly associated with central executive functions, including left middle prefrontal cortex, anterior cingulate cortex, and precentral gyrus/sulcus, were significantly activated in the high-demand task. Critically, there was a significant interaction between distractor type and task demand. Novel distractors captured attention and elicited automatic visual analysis, shown by primary visual cortex activation, only when the subtraction task was of low demand but not when it was of high demand. The results provide confirmatory evidence that the extent to which higher level cognitive resources, specifically, the central executive component of working memory, are absorbed by a cognitive task has an impact upon automatic processing that occurs in response to distracting items.

Adult↗
PubMed2004

Semantic processing of Chinese in left inferior prefrontal cortex studied with reversible words.

This study utilized fast event-related fMRI with reversible words to examine the role of left inferior prefrontal cortex (PFC) in semantic processing of Chinese. As a special linguistic phenomenon in Chinese, a reversible word is a two-character word (AB) that, when read from right to left (BA), opposite to the normal left to right reading direction, is also a real word. The two words, AB and BA, can have very different meanings. Fourteen native Chinese saw a reversible word (BA) and were asked to read it backward silently to obtain the meaning of AB, defined as the target meaning. They then saw two test words and decided which of the two was semantically related to the target meaning. Activity in a subregion of BA47 was found to be modulated by the extent to which irrelevant semantic activation of the distractor word BA interfered with semantic retrieval of the target word AB. This finding demonstrated the involvement of the left inferior PFC in the control processes of semantic retrieval in Chinese. In addition, comparing conditions using reversible with that using nonreversible words, we found evidence suggesting a semantic/phonological functional subdivision in left inferior PFC, consistent with that in English.

Adult↗
PubMed2004

Interference resolution in spatial working memory.

Anterior cingulate and lateral inferior prefrontal cortex (PFC) are considered important for conflict monitoring and interference resolution in many verbal tasks. We studied interference resolution in a spatial working memory task using event-related fMRI. The task required participants to ignore two locations from a set of four initially held in working memory and to remember the remaining two locations as the target set for a subsequent recognition test. Familiarity of nontarget probes was manipulated by drawing the probe from either the ignored locations [high familiarity (HF)] or locations not used in the present trial [low familiarity (LF)]. Precentral sulcus (PrCS) and superior parietal lobe (SPL), two regions commonly associated with motor planning and spatial attention, showed heightened activity in response to increased level of interference from nontargets of high familiarity. Our finding suggests that interference resolution in the spatial domain may involve a different subset of the working memory system from that in the verbal domain.

Adult↗
PubMed2004

Preserved spatial memory over brief intervals in older adults.

Two studies compared young and older adults' memory for location information after brief intervals. Experiment 1 found that accuracy of intentional spatial memory for individual locations was similar in young and older participants for set sizes of 3 and 6. Both groups also encoded individual locations in relation to the larger configuration of locations. Experiment 2 showed that like young adults, older adults' latency to respond to a test probe in a letter working memory task was negatively influenced by spatial information that was irrelevant to the task. This interference effect indicated preserved incidental memory for spatial information in older adults. Together, these data suggest that initial encoding of spatial information for relatively small numbers of items is largely preserved in healthy older adults and that representations of spatial information persist over short intervals.

Adolescent↗
PubMed2004

A memory-based, Simon-like, spatial congruence effect: evidence for persisting spatial codes.

The Simon effect refers to the finding that in a task where stimulus location is irrelevant, reaction time is faster when stimulus and response locations are congruent than when they are not. Dominant theories of the Simon effect have generally attributed this spatial congruence effect to a spatial code automatically generated upon stimulus presentation. A common assumption of these theories is that this spatial code decays in less than a few hundred milliseconds following stimulus onset. We report two working-memory experiments suggesting a reexamination of this assumption--a Simon-like spatial congruence effect persisted over a delay of as long as 2400 ms. We propose that, in addition to generating short-lived perceptual codes, spatial information may be coded in working memory as part of the context associated with stimulus events. When reactivated by cues from the original event, such information may influence response selection and produce spatial congruence effects (in this case, positive when participants made a "yes" response and negative when they made a "no" response).

Female↗
PubMed2003

Frontal activations associated with accessing and evaluating information in working memory: an fMRI study.

To investigate the involvement of frontal cortex in accessing and evaluating information in working memory, we used a variant of a Sternberg paradigm and compared brain activations between positive and negative responses (known to differentially tax access/evaluation processes). Participants remembered two trigrams in each trial and were then cued to discard one of them and maintain the other one as the target set. After a delay, a probe letter was presented and participants made decisions about whether or not it was in the target set. Several frontal areas--anterior cingulate (BA32), middle frontal gyrus (bilateral BA9, right BA10, and right BA46), and left inferior frontal gyrus (BA44/45)--showed increased activity when participants made correct negative responses relative to when they made correct positive responses. No areas activated significantly more for the positive responses than for the negative responses. It is suggested that the multiple frontal areas involved in the test phase of this task may reflect several component processes that underlie more general frontal functions.

Adult↗
PubMed2002

Varicella disease after introduction of varicella vaccine in the United States, 1995-2000.

CONTEXT: Before licensure of varicella vaccine in 1995, varicella was a universal childhood disease in the United States, causing 4 million cases, 11,000 hospitalizations, and 100 deaths every year. OBJECTIVE: To examine population-based disease surveillance data in 3 communities to document the impact of the varicella vaccination program. DESIGN, SETTING, AND SUBJECTS: Active surveillance for varicella conducted among the populations of Antelope Valley, Calif; Travis County, Tex; and West Philadelphia, Pa; from January 1, 1995, to December 31, 2000. Reporting sites included child care centers, schools, universities, physicians, public health clinics, hospitals, emergency departments, and households. MAIN OUTCOME MEASURES: Trends in number and rate of varicella cases and hospitalizations; varicella vaccine coverage. RESULTS: From 1995 through 1998, in each surveillance area, the number of verified varicella cases varied from year to year with marked springtime seasonality. In 1999, the number and rates of varicella cases and hospitalizations declined markedly. From 1995 through 2000, in Antelope Valley, Travis County, and West Philadelphia, varicella cases declined 71%, 84%, and 79%, respectively. Cases declined to the greatest extent among children aged 1 to 4 years, but cases declined in all age groups, including infants and adults. In the combined 3 surveillance areas, hospitalizations due to varicella declined from a range of 2.7 to 4.2 per 100,000 population in 1995 through 1998 to 0.6 and 1.5 per 100,000 population in 1999 and 2000, respectively (P =.15). By 2000, vaccine coverage among children aged 19 to 35 months was 82.1%, 73.6%, and 83.8% in Los Angeles County, Texas, and Philadelphia County, respectively. CONCLUSIONS: Varicella disease has declined dramatically in surveillance areas with moderate vaccine coverage. Continued implementation of existing vaccine policies should lead to further reductions of varicella disease in these communities and throughout the United States.

Adolescent↗