APOE genotype, hippocampal volume, and cognitive reserve predict improvement by cognitive training in older adults without dementia: a randomized controlled trial

Cognitive training (CT) programs aim to improve cognitive performance and impede its decline. Thus, defining the characteristics of individuals who can benefit from these interventions is essential. Our objectives were to assess if the cognitive reserve (CR), APOE genotype (e4 carriers/non-carriers) and/or hippocampal volume might predict the effectiveness of a CT program. Participants were older adults without dementia (n = 226), randomized into parallel experimental and control groups. The assessment consisted of a neuropsychological protocol and additional data regarding total intracranial, gray matter, left/right hippocampus volume; APOE genotype; and Cognitive Reserve (CR). The intervention involved multifactorial CT (30 sessions, 90 min each), with an evaluation pre- and post-training (at six months); the control group simply following the center's routine activities. The primary outcome measures were the change in cognitive performance and the predictors of change. The results show that APOE-e4 non-carriers (79.1%) with a larger left hippocampal volume achieved better gains in semantic verbal fluency (R2 = .19). Subjects with a larger CR and a greater gray matter volume better improved their processing speed (R2 = .18). Age was correlated with the improvement in executive functions, such that older age predicts less improvement (R2 = .07). Subjects with a larger left hippocampal volume achieved more significant gains in general cognitive performance (R2 = .087). In conclusion, besides the program itself, the effectiveness of CT depends on age, biological factors like genotype and brain volume, and CR. Thus, to achieve better results through a CT, it is essential to consider the different characteristics of the participants, including genetic factors.Trial registration: Trial retrospectively registered on January 29th, 2020-(ClinicalTrials.gov -NCT04245579).

Working Memory Training for Children Using the Adaptive, Self-Select, and Stepwise Approaches to Setting the Difficulty Level of Training Activities: Protocol for a Randomized Controlled Trial

BACKGROUND

A common yet untested assumption of cognitive training in children is that activities should be adaptive, with difficulty adjusted to the individual's performance in order to maximize improvements on untrained tasks (known as transfer). Working memory training provides the ideal testbed to systematically examine this assumption as it is one of the most widely studied domains in the cognitive training literature, and is critical for children's learning, including following instructions and reasoning.

OBJECTIVE

This trial aimed to examine children's outcomes of working memory training using adaptive, self-select (child selects difficulty level), and stepwise (difficulty level increases incrementally) approaches to setting the difficulty of training activities compared to an active control condition immediately and 6-month postintervention. While the aim is exploratory, we hypothesized that children allocated to a working memory training condition would show greater improvements: (1) on near transfer measures compared to intermediate and far transfer measures and (2) immediately postintervention compared to 6-month postintervention.

METHODS

This double-blinded, active-controlled, parallel-group randomized trial aimed to recruit 128 children aged 7 to 11 years from 1 metropolitan primary school in Melbourne, Australia. Following baseline testing, children were randomized into 1 of 4 conditions: adaptive, self-select, or stepwise working memory training, or active control. An experimental intervention embedded in Minecraft was developed for teachers to deliver in class over 2 consecutive weeks (10 × 20-minute sessions). The working memory training comprised 2 training activities with processing demands similar to daily activities: backward span and following instructions. The control comprised creative activities. Pre- and postintervention, children completed a set of working memory tests (near and intermediate transfer) and the Raven's Standard Progressive Matrices (far transfer) to determine training outcomes, as well as motivation questionnaires to determine if motivations toward learning and the intervention were similar across conditions. Caregivers completed the ADHD-Rating Scale-5 to measure their child's attention (far transfer). Statistical analysis will include traditional null hypothesis significance testing and Bayesian methods to quantify evidence for both the null and alternative hypotheses.

RESULTS

Data collection concluded in December 2022. Data are currently being processed and analyzed.

CONCLUSIONS

This trial will determine whether the adaptive approach to setting the difficulty of training activities maximizes cognitive training outcomes for children. This trial has several strengths: it adopts best practices for cognitive training studies (design, methods, and analysis plan); uses a range of measures to detect discrete levels of transfer; has a 6-month postintervention assessment; is appropriately powered; and uses an experimental working memory training intervention based on our current understanding of the cognitive mechanisms of training. Findings will inform future research and design of cognitive training interventions and highlight the value of the evidence-based principles of cognitive training.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry, ACTRN12621000990820; https://www.anzctr.org.au/ACTRN12621000990820.aspx.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/47496.

Exploring Genetic and Neural Risk of Specific Reading Disability within a Nuclear Twin Family Case Study: A Translational Clinical Application

Imaging and genetic studies have characterized biological risk factors contributing to specific reading disability (SRD). The current study aimed to apply this literature to a family of twins discordant for SRD and an older sibling with reading difficulty. Intraclass correlations were used to understand the similarity of imaging phenotypes between pairs. Reading-related genes and brain region phenotypes, including asymmetry indices representing the relative size of left compared to right hemispheric structures, were descriptively examined. SNPs that corresponded between the SRD siblings and not the typically developing (TD) siblings were in genes ZNF385D, LPHN3, CNTNAP2, FGF18, NOP9, CMIP, MYO18B, and RBFOX2. Imaging phenotypes were similar among all sibling pairs for grey matter volume and surface area, but cortical thickness in reading-related regions of interest (ROIs) was more similar among the siblings with SRD, followed by the twins, and then the TD twin and older siblings, suggesting cortical thickness may differentiate risk for this family. The siblings with SRD had more symmetry of cortical thickness in the transverse temporal and superior temporal gyri, while the TD sibling had greater rightward asymmetry. The TD sibling had a greater leftward asymmetry of grey matter volume and cortical surface area in the fusiform, supramarginal, and transverse temporal gyrus. This exploratory study demonstrated that reading-related risk factors appeared to correspond with SRD within this family, suggesting that early examination of biological factors may benefit early identification. Future studies may benefit from the use of polygenic risk scores or machine learning to better understand SRD risk.

A multi-faceted role of dual-state dopamine signaling in working memory, attentional control, and intelligence

Genetic evidence strongly suggests that individual differences in intelligence will not be reducible to a single dominant cause. However, some of those variations/changes may be traced to tractable, cohesive mechanisms. One such mechanism may be the balance of dopamine D1 (D₁R) and D2 (D₂R) receptors, which regulate intrinsic currents and synaptic transmission in frontal cortical regions. Here, we review evidence from human, animal, and computational studies that suggest that this balance (in density, activity state, and/or availability) is critical to the implementation of executive functions such as attention and working memory, both of which are principal contributors to variations in intelligence. D1 receptors dominate neural responding during stable periods of short-term memory maintenance (requiring attentional focus), while D2 receptors play a more specific role during periods of instability such as changing environmental or memory states (requiring attentional disengagement). Here we bridge these observations with known properties of human intelligence. Starting from theories of intelligence that place executive functions (e.g., working memory and attentional control) at its center, we propose that dual-state dopamine signaling might be a causal contributor to at least some of the variation in intelligence across individuals and its change by experiences/training. Although it is unlikely that such a mechanism can account for more than a modest portion of the total variance in intelligence, our proposal is consistent with an array of available evidence and has a high degree of explanatory value. We suggest future directions and specific empirical tests that can further elucidate these relationships.

Change by challenge: A common genetic basis behind childhood cognitive development and cognitive training

The interplay of genetic and environmental factors behind cognitive development has preoccupied multiple fields of science and sparked heated debates over the decades. Here we tested the hypothesis that developmental genes rely heavily on cognitive challenges-as opposed to natural maturation. Starting with a polygenic score (cogPGS) that previously explained variation in cognitive performance in adults, we estimated its effect in 344 children and adolescents (mean age of 12 years old, ranging from 6 to 25) who showed changes in working memory (WM) in two distinct samples: (1) a developmental sample showing significant WM gains after 2 years of typical, age-related development, and (2) a training sample showing significant, experimentally-induced WM gains after 25 days of an intense WM training. We found that the same genetic factor, cogPGS, significantly explained the amount of WM gain in both samples. And there was no interaction of cogPGS with sample, suggesting that those genetic factors are neutral to whether the WM gains came from development or training. These results represent evidence that cognitive challenges are a central piece in the gene-environment interplay during cognitive development. We believe our study sheds new light on previous findings of interindividual differences in education (rich-get-richer and compensation effects), brain plasticity in children, and the heritability increase of intelligence across the lifespan.

Sustained and transient gray matter volume changes after n-back training: A VBM study

Working memory training causes functional adaptations in the brain, which include changes in activation and functional connectivity that remain stable over time. Few studies have investigated gray matter (GM) changes after working memory training, and they have produced heterogeneous results without clarifying the stable effects of training. The present study was designed to test for sustained and transient anatomic changes after only 200 min of working memory training. The voxel-based morphometry technique was used in order to investigate the GM changes produced by a brief single n-back training, immediately and 5 weeks after finishing it. The sample was composed by 59 human participants who underwent MRI scanning and were assigned to either a training group or a passive control group. Results showed sustained GM volume enlargement in the right superior parietal cortex and a transient GM decrease in the right putamen. The brain adaptation in the right superior parietal cortex was stronger in individuals who showed greater improvements in performance. The results provide further evidence that a brief working memory training is able to produce brain plasticity in structures related to the trained task.

Working memory training effects across the lifespan: Evidence from human and experimental animal studies

Working memory refers to a cognitive function that provides temporary storage and manipulation of the information necessary for complex cognitive tasks. Due to its central role in general cognition, several studies have investigated the possibility that training on working memory tasks could improve not only working memory function but also increase other cognitive abilities or modulate other behaviors. This possibility is still highly controversial, with prior studies providing contradictory findings. The lack of systematic approaches and methodological shortcomings complicates this debate even more. This review highlights the impact of working memory training at different ages on humans. Finally, it demonstrates several findings about the neural substrate of training in both humans and experimental animals, including non-human primates and rodents.

Within-session verbal learning slope is predictive of lifespan delayed recall, hippocampal volume, and memory training benefit, and is heritable

Memory performance results from plasticity, the ability to change with experience. We show that benefit from practice over a few trials, learning slope, is predictive of long-term recall and hippocampal volume across a broad age range and a long period of time, relates to memory training benefit, and is heritable. First, in a healthy lifespan sample (n = 1825, age 4-93 years), comprising 3483 occasions of combined magnetic resonance imaging (MRI) scans and memory tests over a period of up to 11 years, learning slope across 5 trials was uniquely related to performance on a delayed free recall test, as well as hippocampal volume, independent from first trial memory or total memory performance across the five learning trials. Second, learning slope was predictive of benefit from memory training across ten weeks in an experimental subsample of adults (n = 155). Finally, in an independent sample of male twins (n = 1240, age 51-50 years), learning slope showed significant heritability. Within-session learning slope may be a useful marker beyond performance per se, being heritable and having unique predictive value for long-term memory function, hippocampal volume and training benefit across the human lifespan.

The Effectiveness of Working Memory Training for Children With Low Working Memory

OBJECTIVES

Subgroups of children may benefit more from working memory training than others. In this study, we aimed to examine whether response to the Cogmed Working Memory Training program differed for children with low IQ and elevated attention-deficit/hyperactivity disorder, emotional and behavioral symptoms, special health care needs, or by sex.

METHODS

We used data from the Memory Maestros trial, a population-based randomized controlled trial of the Cogmed program delivered at school (n = 226) compared to usual teaching (n = 226) in grade 1 children (mean age 6.9 years; SD 0.4) with low working memory. Cogmed comprises 20 to 25 sessions of 45-minute duration over 5 to 7 weeks. Children completed subtests from the Automated Working Memory Assessment to measure change in working memory from baseline to 6 months postrandomization.

RESULTS

After training, improved working memory standard scores (>1 SD) from baseline to 6 months were observed for approximately one-third of the children, with more than half maintaining stable scores (within 1 SD). However, similar outcomes were observed for children receiving usual teaching. Differential effect of Cogmed versus usual teaching was evident for children with elevated hyperactivity and/or inattention, who were less likely to show improved visuospatial working memory, but not for other subgroups studied.

CONCLUSIONS

Children with elevated hyperactivity and/or inattention were less likely to show clinically meaningful improvement after Cogmed; however, differential effects were not evident for children with low IQ and elevated emotional and behavioral symptoms, special health care needs, or by sex. More research is needed to determine if training can improve working memory and, if so, for whom.

Evidence for the contribution of COMT gene Val158/108Met polymorphism (rs4680) to working memory training-related prefrontal plasticity

BACKGROUND

Genetic factors have been suggested to affect the efficacy of working memory training. However, few studies have attempted to identify the relevant genes.

METHODS

In this study, we first performed a randomized controlled trial (RCT) to identify brain regions that were specifically affected by working memory training. Sixty undergraduate students were randomly assigned to either the adaptive training group (N = 30) or the active control group (N = 30). Both groups were trained for 20 sessions during 4 weeks and received fMRI scans before and after the training. Afterward, we combined the data from the 30 participants in the RCT study who received adaptive training with data from 71 additional participants who also received the same adaptive training but were not part of the RCT study (total N = 101) to test the contribution of the COMT Val158/108Met polymorphism to the interindividual difference in the training effect within the identified brain regions.

RESULTS

In the RCT study, we found that the adaptive training significantly decreased brain activation in the left prefrontal cortex (TFCE-FWE corrected p = .030). In the genetic study, we found that compared with the Val allele homozygotes, the Met allele carriers' brain activation decreased more after the training at the left prefrontal cortex (TFCE-FWE corrected p = .025).

CONCLUSIONS

This study provided evidence for the neural effect of a visual-spatial span training and suggested that genetic factors such as the COMT Val158/108Met polymorphism may have to be considered in future studies of such training.

Interaction Between Prematurity and the MAOA Gene on Mental Development in Children: A Longitudinal View

This study aimed to examine the association of dopamine-related genes with mental and motor development and the gene-environment interaction in preterm and term children. A total of 201 preterm and 111 term children were examined for their development at 6, 12, 18, 24, and 36 months and were genotyped for 15 single-nucleotide polymorphisms (SNPs) in dopamine-related genes (DRD2, DRD3, DAT1, COMT, and MAOA). An independent sample of 256 preterm children was used for replication. Since the developmental age trends of preterm children differed from those of term children, the analyses were stratified by prematurity. Among the 8 SNPs on the MAOA gene examined in the whole learning sample, the results of linkage disequilibrium analysis indicated that they were located in one block (all D' > 0.9), and rs2239448 was chosen as the tag (r² > 0.85). In the analysis of individual SNPs in each dopamine-related gene, the tag SNP (rs2239448) in MAOA remained significantly associated with the mental scores of preterm children for the interaction with age trend (p < 0.0001; largest effect size of 0.65 at 24 months) after Bonferroni correction for multiple testing. Similar findings for rs2239448 were replicated in the independent sample (p = 0.026). However, none of the SNPs were associated with the motor scores of preterm children, and none were related to the mental or motor scores of term children. The genetic variants of the MAOA gene exert influence on mental development throughout early childhood for preterm, but not term, children.

MAOA-VNTR genotype affects structural and functional connectivity in distributed brain networks

Previous studies have linked the low expression variant of a variable number of tandem repeat polymorphism in the monoamine oxidase A gene (MAOA‐L) to the risk for impulsivity and aggression, brain developmental abnormalities, altered cortico‐limbic circuit function, and an exaggerated neural serotonergic tone. However, the neurobiological effects of this variant on human brain network architecture are incompletely understood. We studied healthy individuals and used multimodal neuroimaging (sample size range: 219–284 across modalities) and network‐based statistics (NBS) to probe the specificity of MAOA‐L‐related connectomic alterations to cortical‐limbic circuits and the emotion processing domain. We assessed the spatial distribution of affected links across several neuroimaging tasks and data modalities to identify potential alterations in network architecture. Our results revealed a distributed network of node links with a significantly increased connectivity in MAOA‐L carriers compared to the carriers of the high expression (H) variant. The hyperconnectivity phenotype primarily consisted of between‐lobe (“anisocoupled”) network links and showed a pronounced involvement of frontal‐temporal connections. Hyperconnectivity was observed across functional magnetic resonance imaging (fMRI) of implicit emotion processing (p_FWE = .037), resting‐state fMRI (p_FWE = .022), and diffusion tensor imaging (p_FWE = .044) data, while no effects were seen in fMRI data of another cognitive domain, that is, spatial working memory (p_FWE = .540). These observations are in line with prior research on the MAOA‐L variant and complement these existing data by novel insights into the specificity and spatial distribution of the neurogenetic effects. Our work highlights the value of multimodal network connectomic approaches for imaging genetics.

Becoming a balanced, proficient bilingual: Predictions from age of acquisition & genetic background

Genetic variants related to dopamine functioning (e.g., the ANKK1/TaqIa polymorphism within the DRD2 gene and the Val158Met polymorphism within the COMT gene) have previously been shown to predict cognitive flexibility and learning (e.g., Colzato et al., 2010; Stelzel et al., 2010). Additionally, researchers have found that these genetic variants may also predict second language learning (Mamiya et al., 2016), although this relationship may change across the lifespan (Sugiura et al., 2011). The current study examined the role of the ANKK1/TaqIa and Val158Met polymorphisms along with age of second language acquisition (AoA) in order to predict levels of bilingual proficiency in Spanish-English bilinguals. Results indicated a three-way interaction such that the relationship between the genetic variants and bilingual proficiency depended on AoA. At earlier AoAs, having the genetic variant associated with higher levels of subcortical dopamine (A1+) predicted the highest levels of bilingual proficiency. At later AoAs, individuals with the genetic variant associated with cortical dopamine levels that are balanced between stability and flexibility (Val/Met) predicted the highest levels of bilingual proficiency. These results fit with theories about the development of language as a subcortical process early in life and as a cortical process later in life (Hernandez & Li, 2007), as well as the importance of both stability and flexibility in bilingual language development (Green & Abutalebi, 2013). Finally, this study raises questions about the direction of causality between bilingualism and cognitive control, which is central to the debate over the "bilingual advantage."

Local and Global Feature Learning for Blind Quality Evaluation of Screen Content and Natural Scene Images

The blind quality evaluation of screen content images (SCIs) and natural scene images (NSIs) has become an important, yet very challenging issue. In this paper, we present an effective blind quality evaluation technique for SCIs and NSIs based on a dictionary of learned local and global quality features. First, a local dictionary is constructed using local normalized image patches and conventional -means clustering. With this local dictionary, the learned local quality features can be obtained using a locality-constrained linear coding with max pooling. To extract the learned global quality features, the histogram representations of binary patterns are concatenated to form a global dictionary. The collaborative representation algorithm is used to efficiently code the learned global quality features of the distorted images using this dictionary. Finally, kernel-based support vector regression is used to integrate these features into an overall quality score. Extensive experiments involving the proposed evaluation technique demonstrate that in comparison with most relevant metrics, the proposed blind metric yields significantly higher consistency in line with subjective fidelity ratings.

Interaction between striatal volume and DAT1 polymorphism predicts working memory development during adolescence

There is considerable inter-individual variability in the rate at which working memory (WM) develops during childhood and adolescence, but the neural and genetic basis for these differences are poorly understood. Dopamine-related genes, striatal activation and morphology have been associated with increased WM capacity after training. Here we tested the hypothesis that these factors would also explain some of the inter-individual differences in the rate of WM development.

We measured WM performance in 487 healthy subjects twice: at age 14 and 19. At age 14 subjects underwent a structural MRI scan, and genotyping of five single nucleotide polymorphisms (SNPs) in or close to the dopamine genes DRD2, DAT-1 and COMT, which have previously been associated with gains in WM after WM training. We then analyzed which biological factors predicted the rate of increase in WM between ages 14 and 19.

We found a significant interaction between putamen size and DAT1/SLC6A3 rs40184 polymorphism, such that TC heterozygotes with a larger putamen at age 14 showed greater WM improvement at age 19.

The effect of the DAT1 polymorphism on WM development was exerted in interaction with striatal morphology. These results suggest that development of WM partially share neuro-physiological mechanism with training-induced plasticity.

Antipsychotic Drug Responsiveness and Dopamine Receptor Signaling; Old Players and New Prospects

Antipsychotic drugs targeting dopamine neurotransmission are still the principal mean of therapeutic intervention for schizophrenia. However, about one third of people do not respond to dopaminergic antipsychotics. Genome wide association studies (GWAS), have shown that multiple genetic factors play a role in schizophrenia pathophysiology. Most of these schizophrenia risk variants are not related to dopamine or antipsychotic drugs mechanism of action. Genetic factors have also been implicated in defining response to antipsychotic medication. In contrast to disease risk, variation of genes coding for molecular targets of antipsychotics have been associated with treatment response. Among genes implicated, those involved in dopamine signaling mediated by D2-class dopamine receptor, including DRD2 itself and its molecular effectors, have been implicated as key genetic predictors of response to treatments. Studies have also reported that genetic variation in genes coding for proteins that cross-talk with DRD2 at the molecular level, such as AKT1, GSK3B, Beta-catenin, and PPP2R2B are associated with response to antipsychotics. In this review we discuss the relative contribution to antipsychotic drug responsiveness of candidate genes and GWAS identified genes encoding proteins involved in dopamine responses. We also suggest that in addition of these older players, a deeper investigation of new GWAS identified schizophrenia risk genes such as FXR1 can provide new prospects that are not clearly engaged in dopamine function while being targeted by dopamine-associated signaling molecules. Overall, further examination of genes proximally or distally related to signaling mechanisms engaged by medications and associated with disease risk and/or treatment responsiveness may uncover an interface between genes involved in disease causation with those affecting disease remediation. Such a nexus would provide realistic targets for therapy and further the development of genetically personalized approaches for schizophrenia.

Using the research domain criteria (RDoC) to conceptualize impulsivity and compulsivity in relation to addiction

Nomenclature for mental disorder was updated in 2013 with the publication of the fifth edition of the Diagnostic and Statistical Manual (DSM-5). In DSM-5, substance use disorders are framed as more dimensional. First, the distinction between abuse and dependence is replaced by substance use. Second, the addictions section now covers both substances and behavioral addictions. This contemporary move toward dimensionality and transdiagnosis in the addictions and other disorders embrace accumulating cognitive-affective neurobiological evidence that is reflected in the United States' National Institutes of Health Research Domain Criteria (NIH RDoC). The RDoC calls for the further development of transdiagnostic approaches to psychopathy and includes five domains to improve research. Additionally, the RDoC suggests that these domains can be measured in terms of specific units of analysis. In line with these suggestions, recent publications have stimulated updated neurobiological conceptualizations of two transdiagnostic concepts, namely impulsivity and compulsivity and their interactions that are applicable to addictive disorders. However, there has not yet been a review to examine the constructs of impulsivity and compulsivity in relation to addiction in light of the research-oriented RDoC. By doing so it may become clearer as to whether impulsivity and compulsivity function antagonistically, complementarily or in some other way at the behavioral, cognitive, and neural level and how this relationship underpins addiction. Thus, here we consider research into impulsivity and compulsivity in light of the transdiagnostic RDoC to help better understand these concepts and their application to evidence-based clinical intervention for addiction.

The Role of Working Memory for Cognitive Control in Anorexia Nervosa versus Substance Use Disorder

Prefrontal cortex executive functions, such as working memory (WM) interact with limbic processes to foster impulse control. Such an interaction is referred to in a growing body of publications by terms such as cognitive control, cognitive inhibition, affect regulation, self-regulation, top-down control, and cognitive–emotion interaction. The rising trend of research into cognitive control of impulsivity, using various related terms reflects the importance of research into impulse control, as failure to employ cognitions optimally may eventually result in mental disorder. Against this background, we take a novel approach using an impulse control spectrum model – where anorexia nervosa (AN) and substance use disorder (SUD) are at opposite extremes – to examine the role of WM for cognitive control. With this aim, we first summarize WM processes in the healthy brain in order to frame a systematic review of the neuropsychological, neural and genetic findings of AN and SUD. In our systematic review of WM/cognitive control, we found n = 15 studies of AN with a total of n = 582 AN and n = 365 HC participants; and n = 93 studies of SUD with n = 9106 SUD and n = 3028 HC participants. In particular, we consider how WM load/capacity may support the neural process of excessive epistemic foraging (cognitive sampling of the environment to test predictions about the world) in AN that reduces distraction from salient stimuli. We also consider the link between WM and cognitive control in people with SUD who are prone to ‘jumping to conclusions’ and reduced epistemic foraging. Finally, in light of our review, we consider WM training as a novel research tool and an adjunct to enhance treatment that improves cognitive control of impulsivity.

DRD2: Bridging the Genome and Ingestive Behavior

Recent work highlights the importance of genetic variants that influence brain structure and function in conferring risk for polygenic obesity. The neurotransmitter dopamine (DA) has a pivotal role in energy balance by integrating metabolic signals with circuits supporting cognitive, perceptual, and appetitive functions that guide feeding. It has also been established that diet and obesity alter DA signaling, leading to compulsive-like feeding and neurocognitive impairments. This raises the possibility that genetic variants that influence DA signaling and adaptation confer risk for overeating and cognitive decline. Here, we consider the role of two common gene variants, FTO and TaqIA rs1800497 in driving gene × environment interactions promoting obesity, metabolic dysfunction, and cognitive change via their influence on DA receptor subtype 2 (DRD2) signaling.

Influence of Dopamine-Related Genes on Neurobehavioral Recovery after Traumatic Brain Injury during Early Childhood

The present study examined the association of dopamine-related genes with short- and long-term neurobehavioral recovery, as well as neurobehavioral recovery trajectories over time, in children who had sustained early childhood traumatic brain injuries (TBI) relative to children who had sustained orthopedic injuries (OI). Participants were recruited from a prospective, longitudinal study evaluating outcomes of children who sustained a TBI (n = 68) or OI (n = 72) between the ages of 3 and 7 years. Parents completed ratings of child executive function and behavior at the immediate post-acute period (0-3 months after injury); 6, 12, and 18 months after injury; and an average of 3.5 and 7 years after injury. Thirty-two single nucleotide polymorphisms (SNPs) in dopamine-related genes (dopamine receptor D2 [DRD2], solute carrier family 6 member 3 [SLC6A3], solute carrier family 18 member A2 [SLC18A2], catechol-o-methyltransferase [COMT], and ankyrin repeat and kinase domain containing 1 [ANKK1]) were examined in association with short- and long-term executive function and behavioral adjustment, as well as their trajectories over time. After controlling for premorbid child functioning, genetic variation within the SLC6A3 (rs464049 and rs460000) gene was differentially associated with neurobehavioral recovery trajectories over time following TBI relative to OI, with rs464049 surviving multiple testing corrections. In addition, genetic variation within the ANKK1 (rs1800497 and rs2734849) and SLC6A3 (rs464049, rs460000, and rs1042098) genes was differentially associated with short- and long-term neurobehavioral recovery following TBI, with rs460000 and rs464049 surviving multiple testing corrections. The findings provide preliminary evidence that genetic variation in genes involved in DRD2 expression and density (ANKK1) and dopamine transport (SLC6A3) plays a role in neurobehavioral recovery following pediatric TBI.

Adaptive working memory training improved brain function in human immunodeficiency virus-seropositive patients

Objective

We aimed to evaluate the effectiveness of an adaptive working memory (WM) training (WMT) program, the corresponding neural correlates, and LMX1A‐rs4657412 polymorphism on the adaptive WMT, in human immunodeficiency virus (HIV) participants compared to seronegative (SN) controls.

Methods

A total of 201 of 206 qualified participants completed baseline assessments before randomization to 25 sessions of adaptive WMT or nonadaptive WMT. A total of 74 of 76 (34 HIV, 42 SN) completed adaptive WMT and all 40 completed nonadaptive WMT (20 HIV, 20 SN) and were assessed after 1 month, and 55 adaptive WMT participants were also assessed after 6 months. Nontrained near‐transfer WM tests (Digit‐Span, Spatial‐Span), self‐reported executive functioning, and functional magnetic resonance images during 1‐back and 2‐back tasks were performed at baseline and each follow‐up visit, and LMX1A‐rs4657412 was genotyped in all participants.

Results

Although HIV participants had slightly lower cognitive performance and start index than SN at baseline, both groups improved on improvement index (>30%; false discovery rate [FDR] corrected p < 0.0008) and nontrained WM tests after adaptive WMT (FDR corrected, p ≤ 0.001), but not after nonadaptive WMT (training by training type corrected, p = 0.01 to p = 0.05) 1 month later. HIV participants (especially LMX1A‐G carriers) also had poorer self‐reported executive functioning than SN, but both groups reported improvements after adaptive WMT (Global: training FDR corrected, p = 0.004), and only HIV participants improved after nonadaptive WMT. HIV participants also had greater frontal activation than SN at baseline, but brain activation decreased in both groups at 1 and 6 months after adaptive WMT (FDR corrected, p < 0.0001), with normalization of brain activation in HIV participants, especially the LMX1A‐AA carriers (LMX1A genotype by HIV status, cluster‐corrected‐p < 0.0001).

Interpretation

Adaptive WMT, but not nonadaptive WMT, improved WM performance in both SN and HIV participants, and the accompanied decreased or normalized brain activation suggest improved neural efficiency, especially in HIV‐LMX1A‐AA carriers who might have greater dopaminergic reserve. These findings suggest that adaptive WMT may be an effective adjunctive therapy for WM deficits in HIV participants. ANN NEUROL 2017;81:17–34

The Association of DRD2 with Insight Problem Solving

Although the insight phenomenon has attracted great attention from psychologists, it is still largely unknown whether its variation in well-functioning human adults has a genetic basis. Several lines of evidence suggest that genes involved in dopamine (DA) transmission might be potential candidates. The present study explored for the first time the association of dopamine D2 receptor gene (DRD2) with insight problem solving. Fifteen single-nucleotide polymorphisms (SNPs) covering DRD2 were genotyped in 425 unrelated healthy Chinese undergraduates, and were further tested for association with insight problem solving. Both single SNP and haplotype analysis revealed several associations of DRD2 SNPs and haplotypes with insight problem solving. In conclusion, the present study provides the first evidence for the involvement of DRD2 in insight problem solving, future studies are necessary to validate these findings.

Grit Is Associated with Structure of Nucleus Accumbens and Gains in Cognitive Training

There is a long-standing interest in the determinants of successful learning in children. “Grit” is an individual trait, reflecting the ability to pursue long-term goals despite temporary setbacks. Although grit is known to be predictive of future success in real-world learning situations, an understanding of the underlying neural basis and mechanisms is still lacking. Here we show that grit in a sample of 6-year-old children (n = 55) predicts the working memory improvement during 8 weeks of training on working memory tasks (p = .009). In a separate neuroimaging analysis performed on a partially overlapping sample (n = 27), we show that interindividual differences in grit were associated with differences in the volume of nucleus accumbens (peak voxel p = .021, x = 12, y = 11, z = −11). This was also confirmed in a leave-one-out analysis of gray matter density in the nucleus accumbens (p = .018). The results can be related to previous animal research showing the role of the nucleus accumbens to search out rewards regardless of delays or obstacles. The results provide a putative neural basis for grit and could contribute a cross-disciplinary connection of animal neuroscience to child psychology.

The neuroscience of working memory capacity and training

Working memory - the ability to maintain and manipulate information over a period of seconds - is a core component of higher cognitive functions. The storage capacity of working memory is limited but can be expanded by training, and evidence of the neural mechanisms underlying this effect is accumulating. Human imaging studies and neurophysiological recordings in non-human primates, together with computational modelling studies, reveal that training increases the activity of prefrontal neurons and the strength of connectivity in the prefrontal cortex and between the prefrontal and parietal cortex. Dopaminergic transmission could have a facilitatory role. These changes more generally inform us of the plasticity of higher cognitive functions.

Central and peripheral pathogenetic forms of type 2 diabetes: a proof-of-concept study

HYPOTHESIS

Previous studies provide evidence that glycated haemoglobin (HbA1c) and fasting plasma glucose (FPG) should not be considered as interchangeable alternatives in the diagnosis of the same type 2 diabetes, but as indicators of its different pathogenetic subtypes. This study was conducted to determine whether a particularly high amount of glucose in either HbA1c form or in fasting plasma would be found in diabetic patients genetically predisposed for either intensive cognitive or intensive muscle metabolic activity, respectively.

METHODS

HbA1c and FPG levels, polymorphisms of genes indicating the predisposition to different cognitive activity (the dopamine D2 receptor (DRD2/ANKK1)), muscle activity (peroxisome proliferator-activated receptor gamma, coactivator 1 alpha (PGC1A(PPARGC1A))), and vascular regulation of general metabolic activity (the angiotensin 1 converting enzyme (ACE)) were assessed in diabetic patients and nondiabetic controls.

RESULTS

DRD2/ANKK1 polymorphism that affects baseline central arousal determined HbA1c variations uncorrelated with FPG in total and clinical groups. The mutation of PGC1A mainly affecting peripheral glucose metabolism had an effect on FPG correlated or uncorrelated with HbA1c depending on the effect assessment in the total sample or in the nondiabetic group, respectively. ACE insertion/deletion (I/D) gene polymorphism was associated with both HbA1c and FPG fluctuations, but only in diabetic patients.

CONCLUSION

The findings provide evidence that the HbA1c and FPG may predict the risks for different subtypes of type 2 diabetes associated with either brain or muscle metabolic activity in genetically vulnerable people.

Genetic variation and dopamine D2 receptor availability: a systematic review and meta-analysis of human in vivo molecular imaging studies

The D2 dopamine receptor mediates neuropsychiatric symptoms and is a target of pharmacotherapy. Inter-individual variation of D2 receptor density is thought to influence disease risk and pharmacological response. Numerous molecular imaging studies have tested whether common genetic variants influence D2 receptor binding potential (BP) in humans, but demonstration of robust effects has been limited by small sample sizes. We performed a systematic search of published human in vivo molecular imaging studies to estimate effect sizes of common genetic variants on striatal D2 receptor BP. We identified 21 studies examining 19 variants in 11 genes. The most commonly studied variant was a single-nucleotide polymorphism in ANKK1 (rs1800497, Glu713Lys, also called 'Taq1A'). Fixed- and random-effects meta-analyses of this variant (5 studies, 194 subjects total) revealed that striatal BP was significantly and robustly lower among carriers of the minor allele (Lys713) relative to major allele homozygotes. The weighted standardized mean difference was -0.57 under the fixed-effect model (95% confidence interval=(-0.87, -0.27), P=0.0002). The normal relationship between rs1800497 and BP was not apparent among subjects with neuropsychiatric diseases. Significant associations with baseline striatal D2 receptor BP have been reported for four DRD2 variants (rs1079597, rs1076560, rs6277 and rs1799732) and a PER2 repeat polymorphism, but none have yet been tested in more than two independent samples. Our findings resolve apparent discrepancies in the literature and establish that rs1800497 robustly influences striatal D2 receptor availability. This genetic variant is likely to contribute to important individual differences in human striatal function, neuropsychiatric disease risk and pharmacological response.

New Perspectives for the Rescue of Cognitive Disability in Down Syndrome

Down syndrome (DS) is a relatively common genetic condition caused by the triplication of human chromosome 21. No therapies currently exist for the rescue of neurocognitive impairment in DS. This review presents exciting findings showing that it is possible to restore brain development and cognitive performance in mouse models of DS with therapies that can also apply to humans. This knowledge provides a potential breakthrough for the prevention of intellectual disability in DS.

Perceptual quality measurement of 3D images based on binocular vision

Three-dimensional (3D) technology has become immensely popular in recent years and widely adopted in various applications. Hence, perceptual quality measurement of symmetrically and asymmetrically distorted 3D images has become an important, fundamental, and challenging issue in 3D imaging research. In this paper, we propose a binocular-vision-based 3D image-quality measurement (IQM) metric. Consideration of the 3D perceptual properties of the primary visual cortex (V1) and the higher visual areas (V2) for 3D-IQM is the major technical contribution to this research. To be more specific, first, the metric simulates the receptive fields of complex cells (V1) using binocular energy response and binocular rivalry response and the higher visual areas (V2) using local binary patterns features. Then, three similarity scores of 3D perceptual properties between the reference and distorted 3D images are measured. Finally, by using support vector regression, three similarity scores are integrated into an overall 3D quality score. Experimental results for two public benchmark databases demonstrate that, in comparison with most current 2D and 3D metrics, the proposed metric achieves significantly higher consistency in alignment with subjective fidelity ratings.

Association between Dopamine Receptor D2 (DRD2) Variations rs6277 and rs1800497 and Cognitive Performance According to Risk Type for Psychosis: A Nested Case Control Study in a Finnish Population Sample

Background

There is limited research regarding the association between genes and cognitive intermediate phenotypes in those at risk for psychotic disorders.

Methods

We measured the association between established psychosis risk variants in dopamine D2 receptor (DRD2) and cognitive performance in individuals at age 23 years and explored if associations between cognition and these variants differed according to the presence of familial or clinical risk for psychosis. The subjects of the Oulu Brain and Mind Study were drawn from the general population-based Northern Finland 1986 Birth Cohort (NFBC 1986). Using linear regression, we compared the associations between cognitive performance and two candidate DRD2 polymorphisms (rs6277 and rs1800497) between subjects having familial (n=61) and clinical (n=45) risk for psychosis and a random sample of participating NFBC 1986 controls (n=74). Cognitive performance was evaluated using a comprehensive battery of tests at follow-up.

Results

Principal components factor analysis supported a three-factor model for cognitive measures. The minor allele of rs6277 was associated with poorer performance on a verbal factor (p=0.003) but this did not significantly interact with familial or clinical risk for psychosis. The minor allele of rs1800497 was associated with poorer performance on a psychomotor factor (p=0.038), though only in those at familial risk for psychotic disorders (interaction p=0.049).

Conclusion

The effect of two DRD2 SNPs on cognitive performance may differ according to risk type for psychosis, suggesting that cognitive intermediate phenotypes differ according to the type (familial or clinical) risk for psychosis.

Genetic Influence on Slope Variability in a Childhood Reflexive Attention Task

Individuals are not perfectly consistent, and interindividual variability is a common feature in all varieties of human behavior. Some individuals respond more variably than others, however, and this difference may be important to understanding how the brain works. In this paper, we explore genetic contributions to response time (RT) slope variability on a reflexive attention task. We are interested in such variability because we believe it is an important part of the overall picture of attention that, if understood, has the potential to improve intervention for those with attentional deficits. Genetic association studies are valuable in discovering biological pathways of variability and several studies have found such associations with a sustained attention task. Here, we expand our knowledge to include a reflexive attention task. We ask whether specific candidate genes are associated with interindividual variability on a childhood reflexive attention task in 9–16 year olds. The genetic makers considered are on 11 genes: APOE, BDNF, CHRNA4, COMT, DRD4, HTR4, IGF2, MAOA, SLC5A7, SLC6A3, and SNAP25. We find significant associations with variability with markers on nine and we discuss the results in terms of neurotransmitters associated with each gene and the characteristics of the associated measures from the reflexive attention task.

Benefits of a working memory training program for inattention in daily life: a systematic review and meta-analysis

BACKGROUND

Many common disorders across the lifespan feature impaired working memory (WM). Reported benefits of a WM training program include improving inattention in daily life, but this has not been evaluated in a meta-analysis. This study aimed to evaluate whether one WM training method has benefits for inattention in daily life by conducting a systematic review and meta-analysis.

METHODS

We searched Medline and PsycINFO, relevant journals and contacted authors for studies with an intervention and control group reporting post-training estimates of inattention in daily life. To reduce the influence of different WM training methods on the findings, the review was restricted to trials evaluating the Cogmed method. A meta-analysis calculated the pooled standardised difference in means (SMD) between intervention and control groups.

RESULTS

A total of 622 studies were identified and 12 studies with 13 group comparisons met inclusion criteria. The meta-analysis showed a significant training effect on inattention in daily life, SMD=-0.47, 95% CI -0.65, -0.29, p<.00001. Subgroup analyses showed this significant effect was observed in groups of children and adults as well as users with and without ADHD, and in studies using control groups that were active and non-adaptive, wait-list and passive as well as studies using specific or general measures. Seven of the studies reported follow-up assessment and a meta-analysis showed persisting training benefits for inattention in daily life, SMD=-0.33, 95% CI -0.57 -0.09, p=.006. Additional meta-analyses confirmed improvements after training on visuospatial WM, SMD=0.66, 95% CI 0.43, 0.89, p<.00001, and verbal WM tasks, SMD=0.40, 95% CI 0.18, 0.62, p=.0004.

CONCLUSIONS

Benefits of a WM training program generalise to improvements in everyday functioning. Initial evidence shows that the Cogmed method has significant benefits for inattention in daily life with a clinically relevant effect size.

Polymorphic variation in the epigenetic gene DNMT3B modulates the environmental impact on cognitive ability: a twin study

BACKGROUND

Though cognitive abilities in adulthood are largely influenced by individual genetic background, they have also been shown to be importantly influenced by environmental factors. Some of these influences are mediated by epigenetic mechanisms. Accordingly, polymorphic variants in the epigenetic gene DNMT3B have been linked to neurocognitive performance. Since monozygotic (MZ) twins may show larger or smaller intrapair phenotypic differences depending on whether their genetic background is more or less sensitive to environmental factors, a twin design was implemented to determine if particular polymorphisms in the DNMT3B gene may be linked to a better (worse) response to enriched (deprived) environmental factors.

METHODS

Applying the variability gene methodology in a sample of 54 healthy MZ twin pairs (108 individuals) with no lifetime history of psychopathology, two DNMT3B polymorphisms were analyzed in relation to their intrapair differences for either intellectual quotient (IQ) or working memory performance.

RESULTS

MZ twin pairs with the CC genotype for rs406193 SNP showed statistically significant larger intrapair differences in IQ than CT pairs.

CONCLUSIONS

Results suggest that DNMT3B polymorphisms may explain variability in the IQ response to either enriched or impoverished environmental conditions. Accordingly, the applied methodology is shown as a potentially valuable tool for determining genetic markers of cognitive plasticity. Further research is needed to confirm this specific result and to expand on other putative genetic markers of environmental sensitivity.

DRD2/ANKK1 polymorphism modulates the effect of ventral striatal activation on working memory performance

Motivation is important for learning and cognition. Although dopaminergic (D2) transmission in the ventral striatum (VS) is associated with motivation, learning, and cognition are more strongly associated with function of the dorsal striatum, including activation in the caudate nucleus. A recent study found an interaction between intrinsic motivation and the DRD2/ANKK1 polymorphism (rs1800497), suggesting that A-carriers of rs1800497 are significantly more sensitive to motivation in order to improve during working memory (WM) training. Using data from the two large-scale imaging genetic data sets, IMAGEN (n=1080, age 13-15 years) and BrainChild (n∼300, age 6-27), we investigated whether rs1800497 is associated with WM. In the IMAGEN data set, we tested whether VS/caudate activation during reward anticipation was associated with WM performance and whether rs1800497 and VS/caudate activation interact to affect WM performance. We found that rs1800497 was associated with WM performance in IMAGEN and BrainChild. Higher VS and caudate activation during reward processing were significantly associated with higher WM performance (p<0.0001). An interaction was found between the DRD2/ANKK1 polymorphism rs1800497 and VS activation during reward anticipation on WM (p<0.01), such that carriers of the minor allele (A) showed a significant correlation between VS activation and WM, whereas the GG-homozygotes did not, suggesting that the effect of VS BOLD on WM is modified by inter-individual genetic differences related to D2 dopaminergic transmission.

Childhood cognitive development as a skill

Theories view childhood development as being either driven by structural maturation of the brain or being driven by skill-learning. It is hypothesized here that working memory (WM) development during childhood is partly driven by training effects in the environment, and that similar neural mechanisms underlie training-induced plasticity and childhood development. In particular, the functional connectivity of a fronto-parietal network is suggested to be associated with WM capacity. The striatum, dopamine receptor D2 (DRD2) activity, and corticostriatal white-matter tracts, on the other hand, seem to be more important for plasticity and change of WM capacity during both training and development. In this view, the development of WM capacity during childhood partly involves the same mechanisms as skill-learning.