Strategies May Mediate Heritable Aspects of Memory Performance: A Twin Study
This study examined use of strategies by twins during cognitive tasks to determine the effects of strategy-use on estimates of heritability.
Performance on many cognitive tasks has been found to be more similar for monozygotic (MZ) than dizygotic (DZ) twins. The cognitive mechanisms mediating these similarities are largely unknown.
Think-aloud protocol analysis was used during 3 cognitive tasks typically considered to have high heritability and susceptibility to strategy-use. In addition, a battery of traditional paper tests was administered to examine potential effects of cognitive abilities.
Performance on 3 cognitive tasks showed effects of strategies, and performance on 2 of the tasks showed a genetic influence. On 1 of these tasks differences in strategies explained a significant portion of the genetic influences. Measures of cognitive ability and metacognitive knowledge could not explain individual differences in strategy use.
This is the first demonstration that the estimated heritability of performance on cognitive tasks is mediated, at least in part, by the use of specific cognitive strategies. Future studies using similar techniques will permit a description of the development of cognitive mechanisms mediating heritable cognitive abilities, and a deeper understanding of the integration of genetic and environmental factors at the level of cognitive strategies and processes.
Available from: Anderson Winkler
- "There is also evidence that heritability estimates for episodic memory are heavily task dependent. For instance, strategy use is genetically influenced; therefore, the degree to which a measure is amenable to strategy use may mediate the heritability of episodic memory performance (Nandagopal and others 2010). Factors such as processing speed constraints may also account for some of the genetic influence on episodic memory, particularly as related to the heritability of age-associated changes (Finkel and others 2009). "
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ABSTRACT: Why do memory abilities vary so greatly across individuals and cognitive domains? Although memory functions are highly heritable, what exactly is being genetically transmitted? Here we review evidence for the contribution of both common and partially independent inheritance of distinct aspects of memory function. We begin by discussing the assessment of long-term memory and its underlying neural and molecular basis. We then consider evidence for both specialist and generalist genes underlying individual variability in memory, indicating that carving memory into distinct subcomponents may yield important information regarding its genetic architecture. And finally we review evidence from both complex and single-gene disorders, which provide insight into the molecular mechanisms underlying the genetic basis of human memory function.
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ABSTRACT: Over the past several years, evidence has accumulated showing that the cerebellum plays a significant role in cognitive function. Here we show, in a large genetically informative twin sample (n=430; aged 16-30years), that the cerebellum is strongly, and reliably (n=30 rescans), activated during an n-back working memory task, particularly lobules I-IV, VIIa Crus I and II, IX and the vermis. Monozygotic twin correlations for cerebellar activation were generally much larger than dizygotic twin correlations, consistent with genetic influences. Structural equation models showed that up to 65% of the variance in cerebellar activation during working memory is genetic (averaging 34% across significant voxels), most prominently in the lobules VI, and VIIa Crus I, with the remaining variance explained by unique/unshared environmental factors. Heritability estimates for brain activation in the cerebellum agree with those found for working memory activation in the cerebral cortex, even though cerebellar cyto-architecture differs substantially. Phenotypic correlations between BOLD percent signal change in cerebrum and cerebellum were low, and bivariate modeling indicated that genetic influences on the cerebellum are at least partly specific to the cerebellum. Activation on the voxel-level correlated very weakly with cerebellar grey matter volume, suggesting specific genetic influences on the BOLD signal. Heritable signals identified here should facilitate discovery of genetic polymorphisms influencing cerebellar function through genome-wide association studies, to elucidate the genetic liability to brain disorders affecting the cerebellum.
Available from: Scott Barry Kaufman
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