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Abstract

There is overwhelming evidence for the existence of substantial genetic influences on individual differences in general and specific cognitive abilities, especially in adults. The actual localization and identification of genes underlying variation in cognitive abilities and intelligence has only just started, however. Successes are currently limited to neurological mutations with rather severe cognitive effects. The current approaches to trace genes responsible for variation in the normal ranges of cognitive ability consist of large scale linkage and association studies. These are hampered by the usual problems of low statistical power to detect quantitative trait loci (QTLs) of small effect. One strategy to boost the power of genomic searches is to employ endophenotypes of cognition derived from the booming field of cognitive neuroscience. This special issue of Behavior Genetics reports on one of the first genome-wide association studies for general IQ. A second paper summarizes candidate genes for cognition, based on animal studies. A series of papers then introduces two additional levels of analysis in the "black box" between genes and cognitive ability: (1) behavioral measures of information-processing speed (inspection time, reaction time, rapid naming) and working memory capacity (performance on on single or dual tasks of verbal and spatio-visual working memory), and (2) electrophyiosological derived measures of brain function (e.g., event-related potentials). The obvious way to assess the reliability and validity of these endophenotypes and their usefulness in the search for cognitive ability genes is through the examination of their genetic architecture in twin family studies. Papers in this special issue show that much of the association between intelligence and speed-of-information processing/brain function is due to a common gene or set of genes, and thereby demonstrate the usefulness of considering these measures in gene-hunting studies for IQ.

Enhancing the Informativeness and Replicability of Imaging Genomics Studies

“…For example, IQ is highly heritable, yet finding genes that affect common variation in intellectual abilities across heterogeneous populations is challenging, likely due to its highly polygenic nature. Until recently, successes were largely limited to de novo or inherited mutations with major effects on cognitive function (11). Nevertheless, large-scale investigations suggest that rare CNVs implicated in developmental neuropsychiatric disorders also affect cognition and neuroanatomy even in control carriers, who do not have psychiatric disease or significant intellectual disability.…”

Implicit association to infant faces: Genetics, early care experiences, and cultural factors influence caregiving propensities

“…We used a paradigm that is less biased than clinical assessments or self-reports, because it reduces the impact of social desirability bias [13,41]: the Single Category Implicit Association Test (SC-IAT). We evaluated (i) implicit preferences toward in-group infant faces compared to out-group infant faces and in-group adult female faces; (ii) whether implicit associations to infant faces are related to genetic polymorphisms, early care experiences (parenting), or the interaction between genetic and early environmental experiences (genetic sensitivity); and (iii) if the latter interaction effect is influenced by infant ethnicity.…”

Impulsivity and comorbid traits: a multi-step approach for finding putative responsible microRNAs in the amygdala

“…With the realization that specific disease symptoms could occur in several diseases, analysis of intermediate traits, known as endophenotypes (Almasy and Blangero, 2001 ; de Geus et al, 2001 ; Loos et al, 2009 ), soon became a popular strategy to find genetic and molecular underpinning of complex phenotypes. This strategy has the advantage that animal models, harboring a fraction of the complexity of the disease, could contribute to solve the puzzle.…”