Biomedical subjects

N K Hansell

Publications and source records attributed to N K Hansell.

6 recordsLinked to original sources

PubMed2006

Effect of the BDNF V166M polymorphism on working memory in healthy adolescents.

Brain-derived neurotrophic factor (BDNF) may play a role in modulating memory function and there is growing evidence that the BDNF V166M polymorphism may influence episodic memory in humans. However, previous association studies examining this polymorphism and working memory are inconsistent. The current study examined this association in a large sample of adolescent twin-pairs and siblings (785 individuals from 439 families). A range of measures (event-related potential, general performance and reaction time) was obtained from a delayed-response working-memory task and total association was examined using the quantitative transmission disequilibrium tests (QTDT) program. Analyses had approximately 93-97% power (alpha= 0.05) to detect an association accounting for as little as 2% of the variance in the phenotypes examined. Results indicated that the BDNF V166M polymorphism is not associated with variation in working memory in healthy adolescents.

Adolescent↗

PubMed2005

Linkage analyses of event-related potential slow wave phenotypes recorded in a working memory task.

Working memory is an essential component of wide-ranging cognitive functions. It is a complex genetic trait probably influenced by numerous genes that individually have only a small influence. These genes may have an amplified influence on phenotypes closer to the gene action. In this study, event-related potential (ERP) phenotypes recorded during a working-memory task were collected from 656 adolescents from 299 families for whom genotypes were available. Univariate linkage analyses using the MERLIN variance-components method were conducted on slow wave phenotypes recorded at multiple sites while participants were required to remember the location of a target. Suggestive linkage (LOD > 2.2) was found on chromosomes 4, 5, 6, 10, 17, and 20. After correcting for multiple testing, suggestive linkage remained on chromosome 10. Empirical thresholds were computed for the most promising phenotypes. Those on chromosome 10 remained suggestive. A number of genes reported to regulate neural differentiation and function (i.e. NRP1, ANK3, and CHAT) were found under these linkage peaks and may influence the levels of neural activity occurring in individuals participating in a spatial working-memory task.

Adolescent↗

PubMed2005

Genetic covariation between event-related potential (ERP) and behavioral non-ERP measures of working-memory, processing speed, and IQ.

The aim of this study was to identify genetic covariants for fundamental measures of brain function (event-related potentials (ERPs): P300 latency and slow wave amplitude recorded in a working-memory task) and more complex cognitive measures (behavioral non-ERP measures: working-memory performance, information processing speed, IQ). Data were collected from 252 monozygotic and 297 dizygotic twin pairs aged 16. Multivariate modeling identified two independent genetic factors associated with processing speed that also influenced working-memory performance (one reflected the duration of neural activity required to evaluate target information, the other reflected more general cognitive and speed-related abilities). However, the allocation of neural resources, as assessed by ERP slow wave amplitude measures, was not associated with the other cognitive measures investigated. Thus, of the ERP measures examined, P300 latency, but not slow wave amplitude, may be an informative measure to include (i.e., with working-memory performance) in future multivariate linkage and association analyses of cognitive function.

Cognition↗

PubMed2005

Bladder neck mobility is a heritable trait.

OBJECTIVE: Congenital connective tissue dysfunction may partly be responsible for female pelvic organ prolapse and urinary incontinence. We undertook a heritability study to determine whether mobility of the bladder neck, one of the main determinants of stress urinary incontinence, is genetically influenced. DESIGN: Heritability study using a twin model and structural equation modelling. SETTING: Queensland Institute of Medical Research, Brisbane, Australia. POPULATION: One hundred and seventy-eight nulliparous Caucasian female twins and their sisters (46 monozygotic pairs, 24 dizygotic pairs and 38 sisters) aged 18-24 years. METHODS: We performed translabial ultrasound, supine and after bladder emptying, for pelvic organ mobility. Urethral rotation and bladder neck descent were calculated using the best of three effective Valsalva manoeuvres. MAIN OUTCOME MEASURES: Bladder and urethral mobility on Valsalva assessed by urethral rotation, vertical and oblique bladder neck descent. RESULTS: Genetic modelling indicated that additive genes accounted for up to 59% of the variance for bladder neck descent. All remaining variance appeared due to environmental influences unique to the individual, including measurement error. CONCLUSION: A significant genetic contribution to the phenotype of bladder neck mobility appears likely.

Adolescent↗

PubMed2001

Genetic influence on ERP slow wave measures of working memory.

Individual differences in the variance of event-related potential (ERP) slow wave (SW) measures were examined. SW was recorded at prefrontal and parietal sites during memory and sensory trials of a delayed-response task in 391 adolescent twin pairs. Familial resemblance was identified and there was a strong suggestion of genetic influence. A common genetic factor influencing memory and sensory SW was identified at the prefrontal site (accounting for an estimated 35%-37% of the reliable variance) and at the parietal site (51%-52% of the reliable variance). Remaining reliable variance was influenced by unique environmental factors. Measurement error accounted for 24% to 30% of the total variance of each variable. The results show genetic independence for recording site, but not trial type, and suggest that the genetic factors identified relate more directly to brain structures, as defined by the cognitive functions they support, than to the cognitive networks that link them.

Adolescent↗

PubMed2001

Genetic influence on the variance in P3 amplitude and latency.

The P3(00) event-related potential (ERP) component is widely used as a measure of cognitive functioning and provides a sensitive electrophysiological index of the attentional and working memory demands of a task. This study investigated what proportion of the variance in the amplitude and latency of the P3, elicited in a delayed response working memory task, could be attributed to genetic factors. In 335 adolescent twin pairs and 48 siblings, the amplitude and latency of the P3 were examined at frontal, central, and parietal sites. Additive genetic factors accounted for 48% to 61% of the variance in P3 amplitude. Approximately one-third of the genetic variation at frontal sites was mediated by a common genetic factor that also influenced the genetic variation at parietal and central sites. Familial resemblance in P3 latency was due to genetic influence that accounted for 44% to 50% of the variance. Genetic covariance in P3 latency across sites was substantial, with a large part of the variance found at parietal, central, and frontal sites attributed to a common genetic factor. The findings provide further evidence that the P3 is a promising phenotype of neural activity of the brain and has the potential to be used in linkage and association analysis in the search for quantitative trait loci (QTLs) influencing cognition.

Adolescent↗