Genetic foundations of human intelligence

Atypical paroxysmal slow cortical activity in healthy adults: Relationship to age and cognitive performance

Paroxysmal patterns of slow cortical activity have been detected in EEG recordings from individuals with age-related neuropathology and have been shown to be correlated with cognitive dysfunction and blood-brain barrier disruption in these participants. The prevalence of these events in healthy participants, however, has not been studied. In this work, we inspect MEG recordings from 623 healthy participants from the Cam-CAN dataset for the presence of paroxysmal slow wave events (PSWEs). PSWEs were detected in approximately 20% of healthy participants in the dataset, and participants with PSWEs tended to be older and have lower cognitive performance than those without PSWEs. In addition, event features changed linearly with age and cognitive performance, resulting in longer and slower events in older adults, and more widespread events in those with low cognitive performance. These findings provide the first evidence of PSWEs in a subset of purportedly healthy adults. Going forward, these events may have utility as a diagnostic biomarker for atypical brain activity in older adults.

Heritability of cognitive performance in wild Western Australian magpies

Individual differences in cognitive performance can have genetic, social and environmental components. Most research on the heritability of cognitive traits comes from humans or captive non-human animals, while less attention has been given to wild populations. Western Australian magpies (Gymnorhina tibicen dorsalis, hereafter magpies) show phenotypic variation in cognitive performance, which affects reproductive success. Despite high levels of individual repeatability, we do not know whether cognitive performance is heritable in this species. Here, we quantify the broad-sense heritability of associative learning ability in a wild population of Western Australian magpies. Specifically, we explore whether offspring associative learning performance is predicted by maternal associative learning performance or by the social environment (group size) when tested at three time points during the first year of life. We found little evidence that offspring associative learning performance is heritable, with an estimated broad-sense heritability of just -0.046 ± 0.084 (confidence interval: -0.234/0.140). However, complementing previous findings, we find that at 300 days post-fledging, individuals raised in larger groups passed the test in fewer trials compared with individuals from small groups. Our results highlight the pivotal influence of the social environment on cognitive development.

Comparison of three common inbred mouse strains reveals substantial differences in hippocampal GABAergic interneuron populations and in vitro network oscillations

A major challenge in neuroscience is to pinpoint neurobiological correlates of specific cognitive and neuropsychiatric traits. At the mesoscopic level, promising candidates for establishing such connections are brain oscillations that can be robustly recorded as local field potentials with varying frequencies in the hippocampus in vivo and in vitro. Inbred mouse strains show natural variation in hippocampal synaptic plasticity (e.g. long-term potentiation), a cellular correlate of learning and memory. However, their diversity in expression of different types of hippocampal network oscillations has not been fully explored. Here, we investigated hippocampal network oscillations in three widely used inbred mouse strains: C57BL/6J (B6J), C57BL/6NCrl (B6N) and 129S2/SvPasCrl (129) with the aim to identify common oscillatory characteristics in inbred mouse strains that show aberrant emotional/cognitive behaviour (B6N and 129) and compare them to "control" B6J strain. First, we detected higher gamma oscillation power in the hippocampal CA3 of both B6N and 129 strains. Second, higher incidence of hippocampal sharp wave-ripple (SPW-R) transients was evident in these strains. Third, we observed prominent differences in the densities of distinct interneuron types and CA3 associative network activity, which are indispensable for sustainment of mesoscopic network oscillations. Together, these results add further evidence to profound physiological differences among inbred mouse strains commonly used in neuroscience research.

Could olfactory identification be a prognostic factor in detecting cognitive impairment risk in the elderly?

Aging contributes to the deterioration of the olfactory system in humans. Several studies indicate that the olfactory identification test alone may function as a screening test for olfactory dysfunction and they are more feasible to apply in clinical practice. Olfactory identification may be a predictor for cognitive impairment. Multiple studies have considered the use of odor identification as a measure to identify the conversion from normality to mild cognitive impairment or dementia. The objectives were (i) to elucidate the associations between cognitive status and olfactory identification performance in aging; (ii) understand the predictive value of olfactory capacity in identifying subjects with cognitive impairment risk; and (iii) to study how cognitive status and olfactory identification relate with other variables of wellness in aging, such as functional capabilities and clinical measures. For this purpose, a group of 149 participants (77.15 ± 7.29 years; 73 women of 76.7 ± 8 years and 76 men of 77.6 ± 6.52 years) were recruited and were subjected to a sociodemographic questionnaire, a psychological screening tool of general cognitive status, an olfactory identification evaluation, and clinical measures. The participants were divided into groups based on their cutoff scores of previous scientific reports about the Spanish version of Montreal Cognitive Assessment. Our results indicate an age-associated decline in olfactory identification ability and intensity of odor perception. The predictive ability of olfactory identification scores for the risk of mild and severe impairment is around 80%. Olfactory identification decreases with cognitive function. Performance in odor identification is associated with impairment of episodic memory and executive functions. These findings further our current understanding of the association between cognition and olfaction, and support olfactory assessment in screening those at higher risk of dementia.

Social inequalities in child development: the role of differential exposure and susceptibility to stressful family conditions

BACKGROUND

Stressful family conditions may contribute to inequalities in child development because they are more common among disadvantaged groups (ie, differential exposure) and/or because their negative effects are stronger among disadvantaged groups (ie, differential impact/susceptibility). We used counterfactual mediation analysis to investigate to what extent stressful family conditions contribute to inequalities in child development via differential exposure and susceptibility.

METHODS

We used data from the Generation R Study, a population-based birth cohort in the Netherlands (n=6842). Mother's education was used as the exposure. Developmental outcomes, measured at age 13 years, were emotional and behavioural problems (Youth Self-Report), cognitive development (Wechsler Intelligence Scale for Children) and secondary education entry level. Financial and social stress at age 9 years were the putative mediators.

RESULTS

Differential exposure to financial stress caused a 0.07 (95% CI -0.12 to -0.01) SD worse emotional and behavioural problem -score, a 0.05 (95% CI -0.08 to -0.02) SD lower intelligence score and a 0.05 (95% CI -0.05 to -0.01) SD lower secondary educational level, respectively, among children of less-educated mothers compared with children of more-educated mothers. This corresponds to a relative contribution of 54%, 9% and 6% of the total effect of mother's education on these outcomes, respectively. Estimates for differential exposure to social stress, and differential susceptibility to financial or social stress, were much less pronounced.

CONCLUSION

Among children of less-educated mothers, higher exposure to financial stress in the family substantially contributes to inequalities in socioemotional development, but less so for cognitive development and educational attainment.

Can Intelligence Affect Alcohol-, Smoking-, and Physical Activity-Related Behaviors? A Mendelian Randomization Study

People with high levels of intelligence are more aware of risk factors, therefore choosing a healthier lifestyle. This assumption seems reasonable, but is it true? Previous studies appear to agree and disagree. To cope with the uncertainty, we designed a mendelian randomization (MR) study to examine the causal effects of genetically proxied intelligence on alcohol-, smoking-, and physical activity (PA)-related behaviors. We obtained genome-wide association study (GWAS) datasets concerning these variables from separate studies or biobanks and used inverse-variance weighted (IVW) or MR-Egger estimator to evaluate the causal effects according to an MR protocol. The MR-Egger intercept test, MR-PRESSO, and funnel plots were employed for horizontal pleiotropy diagnosis. The Steiger test (with reliability test), Cochran's Q test, MR-PRESSO, and leave-one-out method were employed for sensitivity analysis. We found significant or potential effects of intelligence on alcohol dependence (OR = 0.749, p = 0.003), mental and behavioral disorders due to alcohol (OR = 0.814, p = 0.009), smoking (OR = 0.585, p = 0.005), and smoking cessation (OR = 1.334, p = 0.001). Meanwhile, we found significant or potential effects on walking duration (B = -0.066, p < 0.001), walking frequency (B = -0.055, p = 0.031), moderate PA frequency (B = -0.131, p < 0.001), and vigorous PA frequency (B = -0.070, p = 0.001), but all in a negative direction. In conclusion, our findings reinforce some existing knowledge, indicate the complexity of the health impacts of human intelligence, and underline the value of smoking and alcohol prevention in less intelligent populations. Given the existing limitations in this study, particularly the potential reverse causality in some estimations, re-examinations are warranted in future research.

The Cognitive Profile of Gifted Children Compared to Those of Their Parents: A Descriptive Study Using the Wechsler Scales

The manifestation of performance at the top of a given talent distribution constitutes giftedness. While identifying talented youths based on IQ has been the focus of previous research, examining their cognitive profile is a new endeavor. The present study assessed the IQ and cognitive abilities of a sample of gifted Italian children and compared them to their parents using the Wechsler scales. Fifty-nine gifted children aged 6 to 14 years were administered the WISC-IV while their parents (N = 53 mothers and N = 55 fathers) took the WAIS-IV. The gifted children (IQ ≥ 120) obtained particularly high scores in verbal comprehension (VCI) and visual-perceptual reasoning (PRI). More than two-thirds of the mothers and over half of the fathers also achieved an IQ ≥ 120. The gifted children scored significantly higher than both mothers and fathers in VCI and PRI. The mothers were significantly higher than their children in the processing speed domain. Correlational analyses highlighted that children's IQ was positively related to that of their mothers. In keeping with the literature, the cognitive profile of gifted children was found to vary across cognitive abilities. It follows that the General Ability Index was the WISC-IV index that best matched the potential of gifted youths. Consistent with previous research, our study suggests that intellectual abilities, especially working memory and processing speed, are maintained and presumably passed on from one generation to the next.

General intelligence and executive functioning are overlapping but separable at genetic and molecular pathway levels: An analytical review of existing GWAS findings

Understanding the genomic architecture and molecular mechanisms of cognitive functioning in healthy individuals is critical for developing tailored interventions to enhance cognitive functioning, as well as for identifying targets for treating impaired cognition. There has been substantial progress in uncovering the genetic composition of the general cognitive ability (g). However, there is an ongoing debate whether executive functioning (EF)–another key predictor of cognitive health and performance, is separable from general g. To provide an analytical review on existing findings on genetic influences on the relationship between g and EF, we re-analysed a subset of genome-wide association studies (GWAS) from the GWAS catalogue that used measures of g and EF as outcomes in non-clinical populations. We identified two sets of single nucleotide polymorphisms (SNPs) associated with g (1,372 SNPs across 12 studies), and EF (300 SNPs across 5 studies) at p<5x10^-6. A comparative analysis of GWAS-identified g and EF SNPs in high linkage disequilibrium (LD), followed by pathway enrichment analyses suggest that g and EF are overlapping but separable at genetic variant and molecular pathway levels, however more evidence is required to characterize the genetic overlap/distinction between the two constructs. While not without limitations, these findings may have implications for navigating further research towards translatable genetic findings for cognitive remediation, enhancement, and augmentation.

Number sense: the mediating effect between nonverbal intelligence and children’s mathematical performance

The study explored the mediating effect of number sense between nonverbal intelligence and children’s mathematical performance. The sample consisted of 131 pupils in Shaoxing City of China from grades 1, 3, and 5. The students completed measures of nonverbal intelligence, number sense, basic arithmetic ability, mathematical performance, rapid automatized naming, and working memory. Results show that although all variables significantly relate with each other (all p < .01), only nonverbal intelligence, number sense, and basic arithmetic ability significantly affect children’s mathematical performance (all p < .01). According to multiple-mediation model, nonverbal intelligence significantly predicts children’s mathematical performance through number sense and basic arithmetic ability. These findings suggest that domain-specific mathematical skills play a prominent role in children’s mathematical performance in primary school, rather than domain-general cognitive functions. Educators should pay attention to develop children’s number sense in order to improve children’s mathematical ability.

Psycho-Cognitive Model of Knowledge Creation Theory

Humans perform activities collaboratively or individually, and these activities, more often than not, involve both physical and mental processes. However, irrespective of whether individual or collective functioning, knowledge creation is a personal experience. Nevertheless, the general tenet of this paper is that knowledge is created in a human’s mind and resides in the head. Hence, it posits that knowledge creation is cognitive (associated with the neurological structures of the brain) and psychological (involving consciousness)—a psycho-cognitive process. This study thus employs a “Cognaction” mechanism that is based on the assumptions captured below. The mechanism premised that the human cognitive chamber consists of 3C modes of comprehension (for interpreting stimuli transmitted to the brain by sensory organs), contextualisation (for mindful connecting of chunks to existing schemas), and conceptualisation (for evaluative reflection in a manner that leads to drawing inference and building themes or new concepts). It demonstrates that as diverse skill sets are applied to a task, they generate varieties of effects and outcomes. The outcomes though are distinctive and at the same time are cospecialised. Thus, the psycho-cognitive perspective demonstrates knowledge creation as a cocreation process and sees knowledge as a mix of cocreated, cognitive structures. In view of these, the study provides the missing explanation on how the knowledge archetypes emerged. And it provides the missing link between the belief that “knowledge is created in the head” and knowledge creation theory.

Interdisciplinary Approach to Biological and Health Implications in Selected Professional Competences

Everyday life’s hygiene and professional realities, especially in economically developed countries, indicate the need to modify the standards of pro-health programs as well as modern hygiene and work ergonomics programs. These observations are based on the problem of premature death caused by civilization diseases. The biological mechanisms associated with financial risk susceptibility are well described, but there is little data explaining the biological basis of neuroaccounting. Therefore, the aim of the study was to present relationships between personality traits, cognitive competences and biological factors shaping behavioral conditions in a multidisciplinary aspect. This critical review paper is an attempt to compile biological and psychological factors influencing the development of professional competences, especially decent in the area of accounting and finance. We analyzed existing literature from wide range of scientific disciplines (including economics, psychology, behavioral genetics) to create background to pursuit multidisciplinary research models in the field of neuroaccounting. This would help in pointing the best genetically based behavioral profile of future successful financial and accounting specialists.

Is there still evolution in the human population?

It is often claimed that humanity has stopped evolving because modern medicine erased all selection on survival. Even if that would be true, and it is not, there would be other mechanisms of evolution which could still led to changes in allelic frequencies. Here I show, by applying basic evolutionary genetics knowledge, that we expect humanity to evolve. The results from genome sequencing projects have repeatedly affirmed that there are still recent signs of selection in our genomes. I give some examples of such adaptation. Then I briefly discuss what our evolutionary future has in store for us.

The nature of the self: Neural analyses and heritability estimates of self-evaluations in middle childhood

How neural correlates of self-concept are influenced by environmental versus genetic factors is currently not fully understood. We investigated heritability estimates of behavioral and neural correlates of self-concept in middle childhood since this phase is an important time window for taking on new social roles in academic and social contexts. To do so, a validated self-concept fMRI task was applied in a twin sample of 345 participants aged between 7 and 9 years. In the self-concept condition, participants were asked to indicate whether academic and social traits applied to them whereas the control condition required trait categorization. The self-processing activation analyses (n = 234) revealed stronger medial prefrontal cortex (mPFC) activation for self than for control conditions. This effect was more pronounced for social-self than academic self-traits, whereas stronger dorsolateral prefrontal cortex (DLPFC) activation was observed for academic versus social self-evaluations. Behavioral genetic modeling (166 complete twin pairs) revealed that 25-52% of the variation in academic self-evaluations was explained by genetic factors, whereas 16-49% of the variation in social self-evaluations was explained by shared environmental factors. Neural genetic modeling (91 complete twin pairs) for variation in mPFC and anterior prefrontal cortex (PFC) activation for academic self-evaluations confirmed genetic and unique environmental influences, whereas anterior PFC activation for social self-evaluations was additionally influenced by shared environmental influences. This indicates that environmental context possibly has a larger impact on the behavioral and neural correlates of social self-concept at a young age. This is the first study demonstrating in a young twin sample that self-concept depends on both genetic and environmental factors, depending on the specific domain.

SNAP-25 Single Nucleotide Polymorphisms, Brain Morphology and Intelligence in Children With Borderline Intellectual Functioning: A Mediation Analysis

Borderline intellectual functioning (BIF) is a multifactorial condition in which both genetic and environmental factors are likely to contribute to the clinical outcome. Abnormal cortical development and lower IQ scores were shown to be correlated in BIF children, but the genetic components of this condition and their possible connection with intelligence and brain morphology have never been investigated in BIF. The synaptosomal-associated protein of 25 kD (SNAP-25) is involved in synaptic plasticity, neural maturation, and neurotransmission, affecting intellectual functioning. We investigated SNAP-25 polymorphisms in BIF and correlated such polymorphisms with intelligence and cortical thickness, using socioeconomic status and environmental stress as covariates as a good proxy of the variables that determine intellectual abilities. Thirty-three children with a diagnosis of BIF were enrolled in the study. SNAP-25 polymorphisms rs363050, rs363039, rs363043, rs3746544, and rs1051312 were analyzed by genotyping; cortical thickness was studied by MRI; intelligence was measured using the WISC-III/IV subscales; environmental stressors playing a role in neuropsychiatric development were considered as covariate factors. Results showed that BIF children carrying the rs363043(T) minor allele represented by (CT + TT) genotypes were characterized by lower performance Perceptual Reasoning Index and lower full-scale IQ scores (p = 0.04) compared to those carrying the (CC) genotype. This association was correlated with a reduced thickness of the left inferior parietal cortex (direct effect = 0.44) and of the left supramarginal gyrus (direct effect = 0.56). These results suggest a link between SNAP-25 polymorphism and intelligence with the mediation role of brain morphological features in children with BIF.

Macronutrient Intake in Pregnancy and Child Cognitive and Behavioural Outcomes

Prenatal nutrient exposures can impact on brain development and disease susceptibility across the lifespan. It is well established that maternal macronutrient intake during pregnancy influences foetal and infant development. Therefore, we hypothesise that macronutrient intakes during pregnancy are correlated with cognitive development during early childhood. The current study aimed to investigate the relationship between maternal macronutrient intake during pregnancy and child cognitive and behavioural outcomes at age 4 years. We analysed prospective data from a cohort of 64 Australian mother-child dyads. Maternal macronutrient intake was assessed using a validated 74-item food frequency questionnaire at 2 timepoints during pregnancy. Child cognition and behaviour were measured at age 4 years using the validated Wechsler Preschool and Primary Scale of Intelligence, 3rd version (WPPSI-III) and the Child Behaviour Checklist (CBC). Linear regression models were used to quantify statistical relationships and were adjusted for maternal age, education, pre-pregnancy BMI, breastfeeding duration and birthweight. Child Performance IQ was inversely associated with maternal starch intake (b = -11.02, p = 0.03). However, no other associations were found. Further research is needed to explore the association between different types of starch consumed during pregnancy and child cognitive development.

Apolipoprotein E ε4 and cognitive function after surgery in middle-aged and elderly Danish twins

BACKGROUND

Transient cognitive impairment is common in adult patients of all ages following anaesthesia and surgery. Apolipoprotein E (APOE) ε4 carriers may have a larger deterioration in short-term cognitive function after major surgery compared with APOE ε4 noncarriers.

OBJECTIVES

The aim was to examine the effect of APOE ε4 on the association between exposure to surgery and anaesthesia, and subsequent cognitive functioning. A more pronounced deterioration in cognitive function in APOE ε4 carriers was hypothesised.

DESIGN

An observational cross-sectional and a 6 to 10 years longitudinal twin cohort design.

SETTING

Survey and register study of 2936 Danish twins aged 45 to 92 years.

MAIN OUTCOME MEASURES

Cognitive function was assessed using five age-sensitive cognitive tests. In the cross-sectional study, we compared twins exposed to surgery with a reference group (unexposed). Linear regression models were used adjusting for sex and age and stratified by APOE ε4 carrier status. In the longitudinal cognitive follow-up study 1671 twins participated. Intrapair analyses were also performed using 70 same-sexed twin pairs concordant for APOE ε4 carrier status, but discordant for major surgery.

RESULTS

APOE ε4 carriers had lower cognitive scores compared with noncarriers, and this was statistically significant in elderly twins 70+ years of age (mean difference, -0.67; 95% CI, -1.14 to -0.17). There was no significant impact on cognitive function after surgery according to APOE ε4 carrier status in the cross-sectional study. Similarly, there was no APOE ε4 modification in the longitudinal study. Also, in the intrapair analyses no evidence was found of lower cognitive score after major surgery compared with the nonexposed cotwins among APOE ε4 carriers.

CONCLUSION

No evidence was found of more pronounced long-term deterioration in cognitive function after surgery among APOE ε4 carriers, but elderly APOE ε4 carriers in general performed worse on the cognitive tests than noncarriers.

Genetic copy number variants, cognition and psychosis: a meta-analysis and a family study

The burden of large and rare copy number genetic variants (CNVs) as well as certain specific CNVs increase the risk of developing schizophrenia. Several cognitive measures are purported schizophrenia endophenotypes and may represent an intermediate point between genetics and the illness. This paper investigates the influence of CNVs on cognition. We conducted a systematic review and meta-analysis of the literature exploring the effect of CNV burden on general intelligence. We included ten primary studies with a total of 18,847 participants and found no evidence of association. In a new psychosis family study, we investigated the effects of CNVs on specific cognitive abilities. We examined the burden of large and rare CNVs (>200 kb, <1% MAF) as well as known schizophrenia-associated CNVs in patients with psychotic disorders, their unaffected relatives and controls (N = 3428) from the Psychosis Endophenotypes International Consortium (PEIC). The carriers of specific schizophrenia-associated CNVs showed poorer performance than non-carriers in immediate (P = 0.0036) and delayed (P = 0.0115) verbal recall. We found suggestive evidence that carriers of schizophrenia-associated CNVs had poorer block design performance (P = 0.0307). We do not find any association between CNV burden and cognition. Our findings show that the known high-risk CNVs are not only associated with schizophrenia and other neurodevelopmental disorders, but are also a contributing factor to impairment in cognitive domains such as memory and perceptual reasoning, and act as intermediate biomarkers of disease risk.

A Unifying Theory for Autism: The Pathogenetic Triad as a Theoretical Framework

This paper presents a unifying theory for autism by applying the framework of a pathogenetic triad to the scientific literature. It proposes a deconstruction of autism into three contributing features (an autistic personality dimension, cognitive compensation, and neuropathological risk factors), and delineates how they interact to cause a maladaptive behavioral phenotype that may require a clinical diagnosis. The autistic personality represents a common core condition, which induces a set of behavioral issues when pronounced. These issues are compensated for by cognitive mechanisms, allowing the individual to remain adaptive and functional. Risk factors, both exogenous and endogenous ones, show pathophysiological convergence through their negative effects on neurodevelopment. This secondarily affects cognitive compensation, which disinhibits a maladaptive behavioral phenotype. The triad is operationalized and methods for quantification are presented. With respect to the breadth of findings in the literature that it can incorporate, it is the most comprehensive model yet for autism. Its main implications are that (1) it presents the broader autism phenotype as a non-pathological core personality domain, which is shared across the population and uncoupled from associated features such as low cognitive ability and immune dysfunction, (2) it proposes that common genetic variants underly the personality domain, and that rare variants act as risk factors through negative effects on neurodevelopment, (3) it outlines a common pathophysiological mechanism, through inhibition of neurodevelopment and cognitive dysfunction, by which a wide range of endogenous and exogenous risk factors lead to autism, and (4) it suggests that contributing risk factors, and findings of immune and autonomic dysfunction are clinically ascertained rather than part of the core autism construct.

Chimpanzees' (Pan troglodytes) problem-solving skills are influenced by housing facility and captive care duration

Although a large body of primate cognition research is done in captive institutions, little is known about how much individuals from different facilities vary in their experiences and cognitive skills. Here we present the results of an experimental study investigating how physical cognitive skills vary between chimpanzees in relation to captive settings and their time in captivity. We tested 59 chimpanzees housed at two different captive facilities (a rehabilitation center (sanctuary) and a zoo) in three problem-solving tasks. Our results showed that chimpanzees at the two housing facilities significantly differed in overall task performance. On average, the sanctuary chimpanzees outperformed the chimpanzees housed at the zoo in the detour reaching task and the honey trap task. However, the zoo chimpanzees performed slightly better on average in the learning task. We propose that, for this particular sample, the documented differences result from a combination of factors, such as prior experience with cognitive testing, motivation levels and varying degrees of human exposure. Within the sanctuary sample, we found that chimpanzees who arrived at an earlier age at the sanctuary and had therefore spent a larger percentage of their lives in a captive environment, were better problem-solvers than those that arrived at a later age to the sanctuary. Thus, rehabilitation and time in captivity contributed to improved physical cognitive skills in sanctuary chimpanzees. Our results highlight the importance of studying intraspecific variation and the effect that previous experience and living conditions might have on physical cognitive skills in non-human apes. Accordingly, we should be cautious when extrapolating findings of cognitive studies from one population to the species as a whole.

Using common genetic variation to examine phenotypic expression and risk prediction in 22q11.2 deletion syndrome

The 22q11.2 deletion syndrome (22q11DS) is associated with a 20-25% risk of schizophrenia. In a cohort of 962 individuals with 22q11DS, we examined the shared genetic basis between schizophrenia and schizophrenia-related early trajectory phenotypes: sub-threshold symptoms of psychosis, low baseline intellectual functioning and cognitive decline. We studied the association of these phenotypes with two polygenic scores, derived for schizophrenia and intelligence, and evaluated their use for individual risk prediction in 22q11DS. Polygenic scores were not only associated with schizophrenia and baseline intelligence quotient (IQ), respectively, but schizophrenia polygenic score was also significantly associated with cognitive (verbal IQ) decline and nominally associated with sub-threshold psychosis. Furthermore, in comparing the tail-end deciles of the schizophrenia and IQ polygenic score distributions, 33% versus 9% of individuals with 22q11DS had schizophrenia, and 63% versus 24% of individuals had intellectual disability. Collectively, these data show a shared genetic basis for schizophrenia and schizophrenia-related phenotypes and also highlight the future potential of polygenic scores for risk stratification among individuals with highly, but incompletely, penetrant genetic variants.

Identification of novel loci associated with infant cognitive ability

It is believed that genetic factors play a large role in the development of many cognitive and neurological processes; however, epidemiological evidence for the genetic basis of childhood neurodevelopment is very limited. Identification of the genetic polymorphisms associated with early-stage neurodevelopment will help elucidate biological mechanisms involved in neuro-behavior and provide a better understanding of the developing brain. To search for such variants, we performed a genome-wide association study (GWAS) for infant mental and motor ability at two years of age with mothers and children recruited from cohorts in Bangladesh and Mexico. Infant ability was assessed using mental and motor composite scores calculated with country-specific versions of the Bayley Scales of Infant Development. A missense variant (rs1055153) located in the gene WWTR1 reached genome-wide significance in association with mental composite score (meta-analysis effect size of minor allele βmeta = -6.04; 95% CI: -8.13 to -3.94; P = 1.56×10-8). Infants carrying the minor allele reported substantially lower cognitive scores in both cohorts, and this variant is predicted to be in the top 0.3% of most deleterious substitutions in the human genome. Fine mapping and region-based association testing provided additional suggestive evidence that both WWTR1 and a second gene, LRP1B, were associated with infant cognitive ability. Comparisons with recently conducted GWAS in intelligence and educational attainment indicate that our phenotypes do not possess a high genetic correlation with either adolescent or adult cognitive traits, suggesting that infant neurological assessments should be treated as an independent outcome of interest. Additional functional studies and replication efforts in other cohorts may help uncover new biological pathways and genetic architectures that are crucial to the developing brain.

The Impact of Cesarean and Vaginal Delivery on Results of Psychological Cognitive Test in 5 Year Old Children

Background and objectives: The impact of cesarean and vaginal delivery on cognitive development was analyzed in 5 year old children. Materials and Methods: Two cohorts of 5 year old children born in the years 2013 and 2014 in Karvina (Northern Moravia) and Ceske Budejovice (Southern Bohemia) were studied for their cognitive development related to vaginal (n = 117) and cesarean types of delivery (n = 51). The Bender Visual Motor Gestalt Test (BG test) and the Raven Colored Progressive Matrices (RCPM test) were used as psychological tests. Results: In the comparison of vaginal delivery vs. cesarean section, the children delivered by cesarean section scored lower and, therefore, achieved poorer performance in cognitive tests compared to those born by vaginal delivery, as shown in the RCPM (p < 0.001) and in the BG test (p < 0.001). When mothers' education level was considered, the children whose mothers achieved a university degree scored higher in both the RCPM test (p < 0.001) and the BG test (p < 0.01) compared to the children of mothers with lower secondary education. When comparing mothers with a university degree to those with higher secondary education, there was a significant correlation between level of education and score achieved in the RCPM test (p < 0.001), but not in the BG test. Conclusions: According to our findings, the mode of delivery seems to have a significant influence on performance in psychological cognitive tests in 5 year old children in favor of those who were born by vaginal delivery. Since cesarean-born children scored notably below vaginally born children, it appears possible that cesarean delivery may have a convincingly adverse effect on children's further cognitive development.

Newborn Screening TSH Values Less Than 15 mIU/L Are Not Associated With Long-term Hypothyroidism or Cognitive Impairment

BACKGROUND

It is unclear whether newborns with mild thyrotropin elevation (mTSHe) are at risk of neurocognitive impairment. We assessed whether mTSHe at birth persists during childhood and compared neurocognitive functioning to siblings.

METHODS

This study encompassed children born in the Auckland region (New Zealand) with a newborn screen TSH level of 8 to 14 mIU/L blood, age 6.9 to 12.6 years at assessment, and their siblings. Thyroid function tests (serum TSH and free thyroxine) and neurocognitive assessments were performed, including IQ via the Wechsler Intelligence Scale for Children, fourth edition.

RESULTS

Ninety-six mTSHe individuals were studied, including 67 children recruited with 75 sibling controls. Mean mTSHe newborn TSH level was 10.1 mIU/L blood and 2.4 mIU/L at assessment (range, 0.8-7.0 mIU/L, serum). Although higher newborn TSH levels in the mTSHe group correlated with lower full-scale IQ scores (r = 0.25; P = .040), they were not associated with the magnitude of the IQ difference within sibling pairs (P = .56). Cognitive scores were similar for mTSHe and controls (full-scale IQ 107 vs 109; P = .36), with a minor isolated difference in motor coordination scores.

CONCLUSIONS

Our data do not suggest long-term negative effects of neonatal mild TSH elevation. TSH elevation below the screen threshold appears largely transient, and midchildhood neurocognitive performance of these children was similar to their siblings. We propose that associations between neonatal mild TSH elevation and IQ are due to familial confounders. We caution against the practice of reducing screening CH cutoffs to levels at which the diagnosis may not offer long-term benefit for those detected.

Estimating the heritability of cognitive traits across dog breeds reveals highly heritable inhibitory control and communication factors

Trait heritability is necessary for evolution by both natural and artificial selection, yet we know little about the heritability of cognitive traits. Domestic dogs are a valuable study system for questions regarding the evolution of phenotypic diversity due to their extraordinary intraspecific variation. While previous studies have investigated morphological and behavioral variation across dog breeds, few studies have systematically assessed breed differences in cognition. We integrated data from Dognition.com-a citizen science project on dog cognition-with breed-averaged genetic data from published sources to estimate the among-breed heritability of cognitive traits using mixed models. The resulting dataset included 11 cognitive measures for 1508 adult dogs across 36 breeds. A factor analysis yielded four factors interpreted as reflecting inhibitory control, communication, memory, and physical reasoning. Narrow-sense among-breed heritability estimates-reflecting the proportion of cognitive variance attributable to additive genetic variation-revealed that scores on the inhibitory control and communication factors were highly heritable (inhibitory control: h² = 0.70; communication: h² = 0.39), while memory and physical reasoning were less heritable (memory: h² = 0.17; physical reasoning: h² = 0.21). Although the heritability of inhibitory control is partially explained by body weight, controlling for breed-average weight still yields a high heritability estimate (h² = 0.50), while other factors are minimally affected. Our results indicate that cognitive phenotypes in dogs covary with breed relatedness and suggest that cognitive traits have strong potential to undergo selection. The highest heritabilities were observed for inhibitory control and communication, both of which are hypothesized to have been altered by domestication.

A Large-Scale Genetic Correlation Scan Between Intelligence and Brain Imaging Phenotypes

Limited efforts have been paid to evaluate the potential relationships between structural and functional brain imaging and intelligence until now. We performed a two-stage analysis to systematically explore the relationships between 3144 brain image-derived phenotypes (IDPs) and intelligence. First, by integrating genome-wide association studies (GWAS) summaries data of brain IDPs and two GWAS summary datasets of intelligence, we systematically scanned the relationship between each of the 3144 brain IDPs and intelligence through linkage disequilibrium score regression (LDSC) analysis. Second, using the individual-level genotype and intelligence data of 160 124 subjects derived from UK Biobank datasets, polygenetic risk scoring (PRS) analysis was performed to replicate the common significant associations of the first stage. In the first stage, LDSC identified 6 and 2 significant brain IDPs significantly associated with intelligence dataset1 and dataset2, respectively. It is interesting that NET100_0624 showed genetic correlations with intelligence in the two datasets of intelligence. After adjusted for age and sex as the covariates, NET100_0624 (P = 5.26 × 10-20, Pearson correlation coefficients = -0.02) appeared to be associated with intelligence by PRS analysis of UK Biobank samples. Our findings may help to understand the genetic mechanisms of the effects of brain structure and function on the development of intelligence.

Cortical Surfaces Mediate the Relationship Between Polygenic Scores for Intelligence and General Intelligence

Recent large-scale, genome-wide association studies (GWAS) have identified hundreds of genetic loci associated with general intelligence. The cumulative influence of these loci on brain structure is unknown. We examined if cortical morphology mediates the relationship between GWAS-derived polygenic scores for intelligence (PSi) and g-factor. Using the effect sizes from one of the largest GWAS meta-analysis on general intelligence to date, PSi were calculated among 10 P value thresholds. PSi were assessed for the association with g-factor performance, cortical thickness (CT), and surface area (SA) in two large imaging-genetics samples (IMAGEN N = 1651; IntegraMooDS N = 742). PSi explained up to 5.1% of the variance of g-factor in IMAGEN (F1,1640 = 12.2-94.3; P < 0.005), and up to 3.0% in IntegraMooDS (F1,725 = 10.0-21.0; P < 0.005). The association between polygenic scores and g-factor was partially mediated by SA and CT in prefrontal, anterior cingulate, insula, and medial temporal cortices in both samples (PFWER-corrected < 0.005). The variance explained by mediation was up to 0.75% in IMAGEN and 0.77% in IntegraMooDS. Our results provide evidence that cumulative genetic load influences g-factor via cortical structure. The consistency of our results across samples suggests that cortex morphology could be a novel potential biomarker for neurocognitive dysfunction that is among the most intractable psychiatric symptoms.

Impact of maternal childhood trauma on child behavioral problems: The role of child frontal alpha asymmetry

Childhood trauma is associated with many long-term negative outcomes, and is not limited to the individual experiencing the trauma, but extends to subsequent generations. However, mechanisms underlying the association between maternal childhood trauma and child psychopathology are not well understood. Here, we targeted frontal alpha asymmetry (FAA) as a potential underlying factor of the relationship between maternal childhood trauma and child behavioral problems. Electroencephalography (EEG) was recorded from (N = 45) children (Mean age = 57.9 months, SD = 3.13) during an eyes-closed paradigm in order to evaluate FAA. Mothers reported on their childhood trauma experiences using the Childhood Trauma Questionnaire (CTQ), and on their child's behavior using the child behavior checklist (CBCL). We found that maternal childhood trauma significantly predicted child total, internalizing, and externalizing behavior at age 5 years. We also observed a role for FAA such that it acted as a moderator, but not mediator, for behavioral problems. We found that children with relative more right/less left frontal activity were more at risk to develop behavioral problems when their mother had been exposed to trauma in her childhood. These results indicate that child frontal asymmetry may serve as a susceptibility marker for child behavioral problems.

The genetic relationship between educational attainment and cognitive performance in major psychiatric disorders

Cognitive deficits are a core feature of psychiatric disorders like schizophrenia and bipolar disorder. Evidence supports a genome-wide polygenic score (GPS) for educational attainment (GPSEDU) can be used to explain variability in cognitive performance. We aimed to identify different cognitive domains associated with GPSEDU in a transdiagnostic clinical cohort of chronic psychiatric patients with known cognitive deficits. Bipolar and schizophrenia patients from the PsyCourse cohort (N = 730; 43% female) were used. Likewise, we tested whether GPSs for schizophrenia (GPSSZ) and bipolar disorder (GPSBD) were associated with cognitive outcomes. GPSEDU explained 1.5% of variance in the backward verbal digit span, 1.9% in the number of correctly recalled words of the Verbal Learning and Memory Test, and 1.1% in crystallized intelligence. These effects were robust to the influences of treatment and diagnosis. No significant associations between GPSSZ or GPSBD with cognitive outcomes were found. Furthermore, these risk scores did not confound the effect of GPSEDU on cognitive outcomes. GPSEDU explains a small fraction of cognitive performance in adults with psychiatric disorders, specifically for domains related to linguistic learning and working memory. Investigating such a proxy-phenotype longitudinally, could give intriguing insight into the disease course, highlighting at what time genes play a more influential role on cognitive performance. Better understanding the origin of these deficits might help identify those patients at risk for lower levels of functioning and poor social outcomes. Polygenic estimates may in the future be part of predictive models for more personalized interventions.

Repeat variations in polyglutamine disease-associated genes and cognitive function in old age

Although the heritability of cognitive function in old age is substantial, genome-wide association studies have had limited success in elucidating its genetic basis, leaving a considerable amount of "missing heritability." Aside from single nucleotide polymorphisms, genome-wide association studies are unable to assess other large sources of genetic variation, such as tandem repeat polymorphisms. Therefore, here, we studied the association of cytosine-adenine-guanine (CAG) repeat variations in polyglutamine disease-associated genes (PDAGs) with cognitive function in older adults. In a large cohort consisting of 5786 participants, we found that the CAG repeat number in 3 PDAGs (TBP, HTT, and AR) were significantly associated with the decline in cognitive function, which together accounted for 0.49% of the variation. Furthermore, in an magnetic resonance imaging substudy, we found that CAG repeat polymorphisms in 4 PDAGs (ATXN2, CACNA1A, ATXN7, and AR) were associated with different imaging characteristics, including brain stem, putamen, globus pallidus, thalamus, and amygdala volumes. Our findings indicate that tandem repeat polymorphisms are associated with cognitive function in older adults and highlight the importance of PDAGs in elucidating its missing heritability.

Measuring and understanding individual differences in cognition

Individuals vary in their cognitive performance. While this variation forms the foundation of the study of human psychometrics, its broader importance is only recently being recognized. Explicitly acknowledging this individual variation found in both humans and non-human animals provides a novel opportunity to understand the mechanisms, development and evolution of cognition. The papers in this special issue highlight the growing emphasis on individual cognitive differences from fields as diverse as neurobiology, experimental psychology and evolutionary biology. Here, we synthesize this body of work. We consider the distinct challenges in quantifying individual differences in cognition and provide concrete methodological recommendations. In particular, future studies would benefit from using multiple task variants to ensure they target specific, clearly defined cognitive traits and from conducting repeated testing to assess individual consistency. We then consider how neural, genetic, developmental and behavioural factors may generate individual differences in cognition. Finally, we discuss the potential fitness consequences of individual cognitive variation and place these into an evolutionary framework with testable hypotheses. We intend for this special issue to stimulate researchers to position individual variation at the centre of the cognitive sciences.This article is part of the theme issue 'Causes and consequences of individual differences in cognitive abilities'.

Review and meta-analysis found that prenatal folic acid was associated with a 58% reduction in autism but had no effect on mental and motor development

AIM

The impact of prenatal folic acid on children's neurodevelopment and the risk of autism spectrum disorder (ASD) remain unclear and this review and meta-analysis aimed to quantify any associations.

METHODS

We systematically searched PubMed, Scopus and The Cochrane Library until June 2018 with no language restrictions. Standardised mean differences and odds ratio with 95% confidence intervals are used to describe any associations between folic acid and mental development, motor development and ASD.

RESULTS

The search strategy identified 647 papers and 16 were finally included in the meta-analysis after the application of the exclusion criteria. These provided a total cohort size of 756 365 children aged 11 months to 15 years from 10 countries. The main finding was that prenatal use of folic acid was associated with a 58% reduction in the risk of ASD in children. We were surprised that better scores for mental development were associated with low prenatal exposure to folic acid.

CONCLUSION

Although the results should be interpreted with caution, they showed that routine prenatal supplements of folic acid were associated with significantly lower levels of ASD. Further studies are needed to reach a firm conclusion, given the multifactorial aetiology of neurodevelopment.

Moderating effect of mode of delivery on the genetics of intelligence: Explorative genome-wide analyses in ALSPAC

INTRODUCTION

Intelligence is a core construct of individual differences in cognitive abilities and a strong predictor of important life outcomes. Within recent years, rates of cesarean section have substantially increased globally, though little is known about its effect on neurodevelopmental trajectories. Thus, we aimed to investigate the influence of delivery by cesarean section on the genetics of intelligence in children.

METHODS

Participants were recruited through the Avon Longitudinal Study of Parents and Children (ALSPAC). Intelligence was measured by the Wechsler Intelligence Scale for Children (WISC). Genotyping was performed using the Illumina Human Hap 550 quad genome-wide SNP genotyping platform and was followed by imputation using MACH software. Genome-wide interaction analyses were conducted using linear regression.

RESULTS

A total of 2,421 children and 2,141,747 SNPs were subjected to the genome-wide interaction analyses. No variant reached genome-wide significance. The strongest interaction was observed at rs17800861 in the GRIN2A gene (β = -3.43, 95% CI = -4.74 to -2.12, p = 2.98E-07). This variant is predicted to be located within active chromatin compartments in the hippocampus and may influence binding of the NF-kappaB transcription factor.

CONCLUSIONS

Our results may indicate that mode of delivery might have a moderating effect on genetic disposition of intelligence in children. Studies of considerable sizes (>10,000) are likely required to more robustly detect variants governing such interaction. In summary, the presented findings prompt the need for further studies aimed at increasing our understanding of effects various modes of delivery may have on health outcomes in children.

Meta-analysis of epigenome-wide association studies of cognitive abilities

Cognitive functions are important correlates of health outcomes across the life-course. Individual differences in cognitive functions are partly heritable. Epigenetic modifications, such as DNA methylation, are susceptible to both genetic and environmental factors and may provide insights into individual differences in cognitive functions. Epigenome-wide meta-analyses for blood-based DNA methylation levels at ~420,000 CpG sites were performed for seven measures of cognitive functioning using data from 11 cohorts. CpGs that passed a Bonferroni correction, adjusting for the number of CpGs and cognitive tests, were assessed for: longitudinal change; being under genetic control (methylation QTLs); and associations with brain health (structural MRI), brain methylation and Alzheimer's disease pathology. Across the seven measures of cognitive functioning (meta-analysis n range: 2557-6809), there were epigenome-wide significant (P < 1.7 × 10-8) associations for global cognitive function (cg21450381, P = 1.6 × 10-8), and phonemic verbal fluency (cg12507869, P = 2.5 × 10-9). The CpGs are located in an intergenic region on chromosome 12 and the INPP5A gene on chromosome 10, respectively. Both probes have moderate correlations (~0.4) with brain methylation in Brodmann area 20 (ventral temporal cortex). Neither probe showed evidence of longitudinal change in late-life or associations with white matter brain MRI measures in one cohort with these data. A methylation QTL analysis suggested that rs113565688 was a cis methylation QTL for cg12507869 (P = 5 × 10-5 and 4 × 10-13 in two lookup cohorts). We demonstrate a link between blood-based DNA methylation and measures of phonemic verbal fluency and global cognitive ability. Further research is warranted to understand the mechanisms linking genomic regulatory changes with cognitive function to health and disease.

White matter microstructural development and cognitive ability in the first 2 years of life

White matter (WM) integrity has been related to cognitive ability in adults and children, but it remains largely unknown how WM maturation in early life supports emergent cognition. The associations between tract-based measures of fractional anisotropy (FA) and axial and radial diffusivity (AD, RD) shortly after birth, at age 1, and at age 2 and cognitive measures at 1 and 2 years were investigated in 447 healthy infants. We found that generally higher FA and lower AD and RD across many WM tracts in the first year of life were associated with better performance on measures of general cognitive ability, motor, language, and visual reception skills at ages 1 and 2, suggesting an important role for the overall organization, myelination, and microstructural properties of fiber pathways in emergent cognition. RD in particular was consistently related to ability, and protracted development of RD from ages 1 to 2 years in several tracts was associated with higher cognitive scores and better language performance, suggesting prolonged plasticity may confer cognitive benefits during the second year of life. However, we also found that cognition at age 2 was weakly associated with WM properties across infancy in comparison to child and demographic factors including gestational age and maternal education. Our findings suggest that early postnatal WM integrity across the brain is important for infant cognition, though its role in cognitive development should be considered alongside child and demographic factors.

Archetypes of human cognition defined by time preference for reward and their brain correlates: An evolutionary trade-off approach

Biological systems carry out multiple tasks in their lifetime, which, in the course of evolution, may lead to trade-offs. In fact phenotypes (different species, individuals within a species, circuits, bacteria, proteins, etc.) cannot be optimal at all tasks, and, according to Pareto optimality theory, lay into a well-defined geometrical distribution (polygons and/or polyhedrons) in the space of traits. The vertices of this distribution contain archetypes, namely phenotypes that are specialists at one of the tasks, whereas phenotypes toward the center of the geometrical distribution show average performance across tasks. We applied this theory to the variability of cognitive and behavioral scores measured in 1206 individuals from the Human Connectome Project. Among all possible combinations of pairs of traits, we found the best fit to Pareto optimality when individuals were plotted in the trait-space of time preferences for reward, evaluated with the Delay Discounting Task (DDT). The DDT measures subjects' preference in choosing either immediate smaller rewards or delayed larger rewards. Time preference for reward was described by a triangular distribution in which each of the three vertices included individuals who used a particular strategy to discount reward. These archetypes accounted for variability on many cognitive, personality, and socioeconomic status variables, as well as differences in brain structure and functional connectivity, with only a weak influence of genetics. In summary, time preference for reward reflects a core variable that biases human phenotypes via natural and cultural selection.

A genome-wide pathway enrichment analysis identifies brain region related biological pathways associated with intelligence

Intelligence is an important quantitative trait associated with human cognitive ability. The genetic basis of intelligence remains unclear now. Utilizing the latest chromosomal enhancer maps of brain regions, we explored brain region related biological pathways associated with intelligence. Summary data was derived from a large scale genome-wide association study (GWAS) of human, involving 78,308 unrelated individuals from 13 cohorts. The chromosomal enhancer maps of 8 brain regions were then aligned with the GWAS summary data to obtain the association testing results of enhancer regions for intelligence. Gene set enrichment analysis was then conducted to identify the biological pathways associated with intelligence for 8 brain regions, respectively. A total of 178 KEGG pathways was analyzed in this study. We detected multiple biological pathways showing cross brain regions or brain region specific association signals for human intelligence. For instance, KEGG_SYSTEMIC_LUPUS_ERYTHEMATOSUS pathway presented association signals for intelligence across 8 brain regions (all P value < 0.01). KEGG_GLYCOSPHINGOLIPID_BIOSYNTHESIS_GANGLIO_SERIES was detected for 5 brain regions. We also identified several brain region specific pathways, such as AMINO_SUGAR_AND_NUCLEOTIDE_SUGAR_METABOLISM for Germinal Matrix (P value = 0.009) and FRUCTOSE_AND_MANNOSE_METABOLISM for Anterior Caudate (P value = 0.005). Our study results provided novel clues for understanding the genetic mechanism of intelligence.

How can genetics help understand the relationship between cognitive dysfunction and schizophrenia?

Despite the consistent finding that cognitive dysfunction is a core characteristic of schizophrenia (SCZ), little is known about the underlying pathophysiology. Recent progress in human genetics, driven by large genome-wide association studies (GWAS), has provided new data about the genetic architecture of complex human traits, including cognition and SCZ. Novel analytical tools have provided unprecedented opportunities to leverage the large amount of information from GWAS. Here we review the latest findings related to genetic architecture and risk genes of SCZ and cognitive functions, and recent findings of overlapping genetic factors. The recent GWAS of SCZ implicate over 100 risk gene loci, each with a small effect. A similar genetic architecture seems to be present in cognitive domains, suggesting that these phenotypes are highly polygenic. Further, GWAS have revealed more than 20 gene loci associated with cognitive traits, including intelligence, general cognition (g-factor), reaction time and verbal-numerical reasoning. Several gene loci have been implicated in educational attainment, a proxy measure of cognitive function. Recently, overlapping gene loci were found between education and SCZ, and between SCZ and cognitive traits, suggesting common genetic risk between SCZ and cognitive dysfunction. Mathematical modeling of GWAS of cognition and SCZ indicate that only a fraction of the heritability is identified. The evidence suggests a polygenic architecture for SCZ and cognitive functions, and a large degree of shared genetic risk. This indicates novel molecular genetic mechanisms and strengthens the notion that SCZ is more likely a part of the normal distribution and not a separate entity.

Born to learn: The inspiration, progress, and future of evolved plastic artificial neural networks

Biological neural networks are systems of extraordinary computational capabilities shaped by evolution, development, and lifelong learning. The interplay of these elements leads to the emergence of biological intelligence. Inspired by such intricate natural phenomena, Evolved Plastic Artificial Neural Networks (EPANNs) employ simulated evolution in-silico to breed plastic neural networks with the aim to autonomously design and create learning systems. EPANN experiments evolve networks that include both innate properties and the ability to change and learn in response to experiences in different environments and problem domains. EPANNs' aims include autonomously creating learning systems, bootstrapping learning from scratch, recovering performance in unseen conditions, testing the computational advantages of particular neural components, and deriving hypotheses on the emergence of biological learning. Thus, EPANNs may include a large variety of different neuron types and dynamics, network architectures, plasticity rules, and other factors. While EPANNs have seen considerable progress over the last two decades, current scientific and technological advances in artificial neural networks are setting the conditions for radically new approaches and results. Exploiting the increased availability of computational resources and of simulation environments, the often challenging task of hand-designing learning neural networks could be replaced by more autonomous and creative processes. This paper brings together a variety of inspiring ideas that define the field of EPANNs. The main methods and results are reviewed. Finally, new opportunities and possible developments are presented.

Life-course determinants of cognitive reserve (CR) in cognitive aging and dementia - a systematic literature review

OBJECTIVES

The concept of cognitive reserve (CR) is defined as a moderator, which allows an individual to preserve cognition despite underlying brain pathology. There is no consensus of what potentially modifiable CR determinants are of greatest importance. The aim of this review was to identify life-course factors which protect older individuals from expressing cognitive decline despite the presence of brain pathology.

METHOD

A systematic review search was performed in MEDLINE (1946-06/09/13), EMBASE (1947-06/09/13), and PsycheInfo (1967-06/09/13). We included studies examining CR in the context of the four commonest subtypes of dementia, mild cognitive impairment or healthy aging. Studies which combined measurement of underlying dementia-related neuropathology, cognitive function, and factors providing CR in a single model were accepted. We performed a qualitative synthesis of the results.

RESULTS

Thirty-four studies out of 9229 screened records met our inclusion criteria and were therefore quality assessed and data extracted. Variation in CR definition made comparison across studies difficult. One hundred and forty-four out of 156 models examined education and occupation: overall, 58% of eligible models classified education and 60% occupation as a CR determinant, with 12% and 44% of those, respectively, being of high quality. Within healthy population suitable to inform preventative interventions, there was consistent evidence for education having a protective effect on general cognition in the face of multiple brain burden measures, while occupation presented inconclusive results within cognitive groups.

CONCLUSIONS

Further research on modifiable determinants of CR beyond education/occupation including early-life factors and consensus on CR definition are warranted.

Education and myopia: assessing the direction of causality by mendelian randomisation

OBJECTIVES

To determine whether more years spent in education is a causal risk factor for myopia, or whether myopia is a causal risk factor for more years in education.

DESIGN

Bidirectional, two sample mendelian randomisation study.

SETTING

Publically available genetic data from two consortiums applied to a large, independent population cohort. Genetic variants used as proxies for myopia and years of education were derived from two large genome wide association studies: 23andMe and Social Science Genetic Association Consortium (SSGAC), respectively.

PARTICIPANTS

67 798 men and women from England, Scotland, and Wales in the UK Biobank cohort with available information for years of completed education and refractive error.

MAIN OUTCOME MEASURES

Mendelian randomisation analyses were performed in two directions: the first exposure was the genetic predisposition to myopia, measured with 44 genetic variants strongly associated with myopia in 23andMe, and the outcome was years in education; and the second exposure was the genetic predisposition to higher levels of education, measured with 69 genetic variants from SSGAC, and the outcome was refractive error.

RESULTS

Conventional regression analyses of the observational data suggested that every additional year of education was associated with a more myopic refractive error of -0.18 dioptres/y (95% confidence interval -0.19 to -0.17; P<2e-16). Mendelian randomisation analyses suggested the true causal effect was even stronger: -0.27 dioptres/y (-0.37 to -0.17; P=4e-8). By contrast, there was little evidence to suggest myopia affected education (years in education per dioptre of refractive error -0.008 y/dioptre, 95% confidence interval -0.041 to 0.025, P=0.6). Thus, the cumulative effect of more years in education on refractive error means that a university graduate from the United Kingdom with 17 years of education would, on average, be at least -1 dioptre more myopic than someone who left school at age 16 (with 12 years of education). Myopia of this magnitude would be sufficient to necessitate the use of glasses for driving. Sensitivity analyses showed minimal evidence for genetic confounding that could have biased the causal effect estimates.

CONCLUSIONS

This study shows that exposure to more years in education contributes to the rising prevalence of myopia. Increasing the length of time spent in education may inadvertently increase the prevalence of myopia and potential future visual disability.

The Gene Encoding Protocadherin 9 (PCDH9), a Novel Risk Factor for Major Depressive Disorder

Genomic analyses have identified only a handful of robust risk loci for major depressive disorder (MDD). In addition to the published genome-wide significant genes, it is believed that there are undiscovered 'treasures' underlying the current MDD genome-wide association studies (GWASs) and gene expression data sets, and digging into these data will allow better understanding of the illness and development of new therapeutic approaches. For this purpose, we performed a meta-analytic study combining three MDD GWAS data sets (23andMe, CONVERGE, and PGC), and then conducted independent replications of significant loci in two additional samples. The genome-wide significant variants then underwent explorative analyses on MDD-related phenotypes, cognitive function alterations, and gene expression in brains. In the discovery meta-analysis, a previously unidentified single-nucleotide polymorphism (SNP) rs9540720 in the PCDH9 gene was genome-wide significantly associated with MDD (p=1.69 × 10^-8 in a total of 89 610 cases and 246 603 controls), and the association was further strengthened when additional replication samples were included (p=1.20 × 10^-8 in a total of 136 115 cases and 355 275 controls). The risk SNP was also associated with multiple MDD-related phenotypes and cognitive function impairment in diverse samples. Intriguingly, the risk allele of rs9540720 predicted lower PCDH9 expression, consistent with the diagnostic analysis results that PCDH9 mRNA expression levels in the brain and peripheral blood tissues were reduced in MDD patients compared with healthy controls. These convergent lines of evidence suggest that PCDH9 is likely a novel risk gene for MDD. Our study highlights the necessity and importance of excavating the public data sets to explore risk genes for MDD, and this approach is also applicable to other complex diseases.

Brain region-specific expression of genes mapped within quantitative trait loci for behavioral responsiveness to acute stress in Fisher 344 and Wistar Kyoto male rats

Acute stress responsiveness is a quantitative trait that varies in severity from one individual to another; however, the genetic component underlying the individual variation is largely unknown. Fischer 344 (F344) and Wistar Kyoto (WKY) rat strains show large differences in behavioral responsiveness to acute stress, such as freezing behavior in response to footshock during the conditioning phase of contextual fear conditioning (CFC). Quantitative trait loci (QTL) have been identified for behavioral responsiveness to acute stress in the defensive burying (DB) and open field test (OFT) from a reciprocal F2 cross of F344 and WKY rat strains. These included a significant QTL on chromosome 6 (Stresp10). Here, we hypothesized that the Stresp10 region harbors genes with sequence variation(s) that contribute to differences in multiple behavioral response phenotypes between the F344 and WKY rat strains. To test this hypothesis, first we identified differentially expressed genes within the Stresp10 QTL in the hippocampus, amygdala, and frontal cortex of F344 and WKY male rats using genome-wide microarray analyses. Genes with both expression differences and non-synonymous sequence variations in their coding regions were considered candidate quantitative trait genes (QTGs). As a proof-of-concept, the F344.WKY-Stresp10 congenic strain was generated with the Stresp10 WKY donor region into the F344 recipient strain. This congenic strain showed behavioral phenotypes similar to those of WKYs. Expression patterns of Gpatch11 (G-patch domain containing 11), Cdkl4 (Cyclin dependent kinase like 4), and Drc1 (Dynein regulatory complex subunit 1) paralleled that of WKY in the F344.WKY-Stresp10 strain matching the behavioral profiles of WKY as opposed to F344 parental strains. We propose that these genes are candidate QTGs for behavioral responsiveness to acute stress.

Healthy cognitive ageing in the Lothian Birth Cohort studies: marginal gains not magic bullet

In the face of shifting demographics and an increase in human longevity, it is important to examine carefully what is known about cognitive ageing, and to identify and promote possibly malleable lifestyle and health-related factors that might mitigate age-associated cognitive decline. The Lothian Birth Cohorts of 1921 (LBC1921, n = 550) and 1936 (LBC1936, n = 1091) are longitudinal studies of cognitive and brain ageing based in Scotland. Childhood IQ data are available for these participants, who were recruited in later life and then followed up regularly. This overview summarises some of the main LBC findings to date, illustrating the possible genetic and environmental contributions to cognitive function (level and change) and brain imaging biomarkers in later life. Key associations include genetic variation, health and fitness, psychosocial and lifestyle factors, and aspects of the brain's structure. It addresses some key methodological issues such as confounding by early-life intelligence and social factors and emphasises areas requiring further investigation. Overall, the findings that have emerged from the LBC studies highlight that there are multiple correlates of cognitive ability level in later life, many of which have small effects, that there are as yet few reliable predictors of cognitive change, and that not all of the correlates have independent additive associations. The concept of marginal gains, whereby there might be a cumulative effect of small incremental improvements across a wide range of lifestyle and health-related factors, may offer a useful way to think about and promote a multivariate recipe for healthy cognitive and brain ageing.

Can you teach an old parrot new tricks? Cognitive development in wild kaka (Nestor meridionalis)

Despite recent efforts to characterize innovative individuals within a species, we still know very little about the ontogeny of innovation ability. A number of studies have found that innovation rates are correlated with personality traits, such as neophilia and exploration. Juvenile birds are frequently more neophilic and explorative, yet few studies have found evidence of age-related differences in innovative problem-solving success. Here, we show consistently higher innovation efficiency in juveniles of a wild, omnivorous parrot species across a variety of tasks and contexts. We tested 104 kaka (Nestor meridionalis), ranging in age from four months to 13 years. Twenty-four individuals participated in all three of our problem-solving tasks, two of which involved a familiar feeder and one an entirely novel apparatus. Juveniles were the most efficient problem-solvers in all three tasks. By contrast, the adults' success was context dependent and limited to the novel apparatus, which did not require modification of a pre-learned behavioural response. This suggests greater behavioural flexibility in the juvenile birds, who also showed higher persistence and exploratory diversity than adults. These traits may enable young kaka to discover efficient foraging techniques, which are then maintained throughout adulthood.