Attention deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental disorder characterized by age-inappropriate symptoms of inattention, impulsivity, and hyperactivity that persist into adulthood in the majority of the diagnosed children. Despite several risk factors during childhood predicting the persistence of ADHD symptoms into adulthood, the genetic architecture underlying the trajectory of ADHD over time is still unclear. We set out to study the contribution of common genetic variants to the risk for ADHD across the lifespan by conducting meta-analyses of genome-wide association studies on persistent ADHD in adults and ADHD in childhood separately and jointly, and by comparing the genetic background between them in a total sample of 17,149 cases and 32,411 controls. Our results show nine new independent loci and support a shared contribution of common genetic variants to ADHD in children and adults. No subgroup heterogeneity was observed among children, while this group consists of future remitting and persistent individuals. We report similar patterns of genetic correlation of ADHD with other ADHD-related datasets and different traits and disorders among adults, children, and when combining both groups. These findings confirm that persistent ADHD in adults is a neurodevelopmental disorder and extend the existing hypothesis of a shared genetic architecture underlying ADHD and different traits to a lifespan perspective.Neuropsychopharmacology (2020) 0:1-10; https://doi.

We usually look at an object when we are going to manipulate it. Thus, eye tracking can be used to communicate intended actions. An effective human-machine interface, however, should be able to differentiate intentional and spontaneous eye movements. We report an electroencephalogram (EEG) marker that differentiates gaze fixations used for control from spontaneous fixations involved in visual exploration. Eight healthy participants played a game with their eye movements only. Their gaze-synchronized EEG data (fixation-related potentials, FRPs) were collected during game's control-on and control-off conditions. A slow negative wave with a maximum in the parietooccipital region was present in each participant's averaged FRPs in the control-on conditions and was absent or had much lower amplitude in the control-off condition. This wave was similar but not identical to stimulus-preceding negativity, a slow negative wave that can be observed during feedback expectation. Classification of intentional vs. spontaneous fixations was based on amplitude features from 13 EEG channels using 300 ms length segments free from electrooculogram contamination (200–500 ms relative to the fixation onset). For the first fixations in the fixation triplets required to make moves in the game, classified against control-off data, a committee of greedy classifiers provided 0.90 ± 0.07 specificity and 0.38 ± 0.14 sensitivity. Similar (slightly lower) results were obtained for the shrinkage Linear Discriminate Analysis (LDA) classifier. The second and third fixations in the triplets were classified at lower rate. We expect that, with improved feature sets and classifiers, a hybrid dwell-based Eye-Brain-Computer Interface (EBCI) can be built using the FRP difference between the intended and spontaneous fixations. If this direction of BCI development will be successful, such a multimodal interface may improve the fluency of interaction and can possibly become the basis for a new input device for paralyzed and healthy users, the EBCI “Wish Mouse.”

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Attention-deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental disorder with a complex genetic background, hampering identification of underlying genetic risk factors. We hypothesized that combining linkage analysis and whole-exome sequencing (WES) in multi-generation pedigrees with multiple affected individuals can point toward novel ADHD genes. Three families with multiple ADHD-affected members (N total = 70) and apparent dominant inheritance pattern were included in this study. Genotyping was performed in 37 family members, and WES was additionally carried out in 10 of those. Linkage analysis was performed using multi-point analysis in Superlink Online SNP 1.1. From prioritized linkage regions with a LOD score ≥ 2, a total of 24 genes harboring rare variants were selected. Those genes were taken forward and were jointly analyzed in gene-set analyses of exome-chip data using the MAGMA software in an independent sample of patients with persistent ADHD and healthy controls (N = 9365). The gene-set including all 24 genes together, and particularly the gene-set from one of the three families (12 genes), were significantly associated with persistent ADHD in this sample. Among the latter, gene-wide analysis for the AAED1 gene reached significance. A rare variant (rs151326868) within AAED1 segregated with ADHD in one of the families. The analytic strategy followed here is an effective approach for identifying novel ADHD risk genes. Additionally, this study suggests that both rare and more frequent variants in multiple genes act together in contributing to ADHD risk, even in individual multi-case families.

Gangliosides are glycosphingolipids, which are abundant in brain, are known to modulate ion channels and cell-to-cell communication. Deficiencies can result in aberrant myelination and altered immune responses, which can give rise to neurodevelopmental psychiatric disorders. However, to date, little mechanistic data is available on how ganglioside deficiencies contribute to the behavioural disorders. In humans, the loss of lactosylceramide-alpha-2,3-sialyltransferase (ST3Gal5) leads to a severe neuropathology, but in ST3Gal5 knock-out ( St3gal5−/− ) mice the absence of GM3 and associated a-, b- and c-series gangliosides is partially compensated by 0-series gangliosides and there is no overt behavioural phenotype. Here, we sought to examine the behavioural and molecular consequences of GM3 loss more closely. Mutants of both sexes exhibited impaired conditioned taste aversion in an inhibitory learning task and anxiety-like behaviours in the open field, moderate motor deficits, abnormal social interactions, excessive grooming and rearing behaviours. Taken together, the aberrant behaviours are suggestive of an autism spectrum disorder (ASD)-like syndrome. Molecular analysis showed decreased gene and protein expression of proteolipid protein-1 ( Plp1 ) and over expression of proinflammatory cytokines, which has been associated with ASD-like syndromes. The inflammatory and behavioural responses to lipopolysaccharide (LPS) were also altered in the St3gal5−/− mice compared to wild-type, which is indicative of the importance of GM3 gangliosides in regulating immune responses. Together, the St3gal5−/− mice display ASD-like behavioural features, altered response to systemic inflammation, signs of hypomyelination and neuroinflammation, which suggests that deficiency in a- and b-series gangliosides could contribute to the development of an ASD-like pathology in humans.

Bacterial intoxication associated with inflammatory conditions during development can impair brain functions, in particular evolutionarily novel forms of memory, such as explicit learning. Little is known about the dangers of early-life inflammation on more basic forms of learning, for example, the acquisition of motor escape abilities, which are generally better preserved under pathological conditions. To address this limitation in knowledge, an inflammatory response was elicited in Wistar pups by lipopolysaccharide (LPS) injections (25 μg/kg) on postnatal days P15, P18 and P21. The acquisition of escape behaviour was tested from P77 by active avoidance footshock model and water maze. Open-field behaviour and blood corticosterone levels were also measured. Rat brain tissue was collected from pups 2 h post-injection and from adult rats which either underwent escape training on P77–P81 or remained untrained. mRNA levels of developmental brain plasticity factors MMP-9 and TIMP-1 were investigated in the medial prefrontal cortex and ventral/dorsal hippocampus. LPS-challenged rats displayed moderately deficient escape responses in both memory tests, increased freezing behaviour and, surprisingly, reduced blood cortisol levels. Mmp9 and Timp1, and their ratio to one another, were differentially altered in pups versus adult untrained rats but remained unchanged overall in rats trained in either learning task. Together, our data indicate that systemic pro-inflammatory response during early postnatal development has long-lasting effects, including on the acquisition of motor escape abilities and plasticity factor expression, into adulthood. Our data suggest that altered stress response could possibly mediate these deviations and repeated training might generate positive effects on plasticity under the employed conditions.Electronic supplementary materialThe online version of this article (doi:10.1007/s12640-017-9720-2) contains supplementary material, which is available to authorized users.

Brain serotonin (5-hydroxytryptamine, 5-HT) system dysfunction is implicated in exaggerated fear responses triggering various anxiety-, stress-, and trauma-related disorders. However, the underlying mechanisms are not well understood. Here, we investigated the impact of constitutively inactivated 5-HT synthesis on context-dependent fear learning and extinction using tryptophan hydroxylase 2 ( Tph2 ) knockout mice. Fear conditioning and context-dependent fear memory extinction paradigms were combined with c-Fos imaging and electrophysiological recordings in the dorsal hippocampus (dHip). Tph2 mutant mice, completely devoid of 5-HT synthesis in brain, displayed accelerated fear memory formation and increased locomotor responses to foot shock. Furthermore, recall of context-dependent fear memory was increased. The behavioral responses were associated with increased c-Fos expression in the dHip and resistance to foot shock-induced impairment of hippocampal long-term potentiation (LTP). In conclusion, increased context-dependent fear memory resulting from brain 5-HT deficiency involves dysfunction of the hippocampal circuitry controlling contextual representation of fear-related behavioral responses.

The interaction between brain serotonin (5-HT) deficiency and environmental adversity may predispose females to excessive aggression. Specifically, complete inactivation of the gene encoding tryptophan hydroxylase-2 (Tph2) results in the absence of neuronal 5-HT synthesis and excessive aggressiveness in both male and female null mutant (Tph2−/−) mice. In heterozygous male mice (Tph2+/−), there is a moderate reduction in brain 5-HT levels, and when they are exposed to stress, they exhibit increased aggression. Here, we exposed female Tph2+/− mice to a five-day rat predation stress paradigm and assessed their emotionality and social interaction/aggression-like behaviors. Tph2+/− females exhibited excessive aggression and increased dominant behavior. Stressed mutants displayed altered gene expression of the 5-HT receptors Htr1a and Htr2a, glycogen synthase kinase-3 β (GSK-3β), and c-fos as well as myelination-related transcripts in the prefrontal cortex: myelin basic protein (Mbp), proteolipid protein 1 (Plp1), myelin-associated glycoprotein (Mag), and myelin oligodendrocyte glycoprotein (Mog). The expression of the plasticity markers synaptophysin (Syp) and cAMP response element binding protein (Creb), but not AMPA receptor subunit A2 (GluA2), were affected by genotype. Moreover, in a separate experiment, naïve female Tph2+/− mice showed signs of enhanced stress resilience in the modified swim test with repeated swimming sessions. Taken together, the combination of a moderate reduction in brain 5-HT with environmental challenges results in behavioral changes in female mice that resemble the aggression-related behavior and resilience seen in stressed male mutants; additionally, the combination is comparable to the phenotype of null mutants lacking neuronal 5-HT. Changes in myelination-associated processes are suspected to underpin the molecular mechanisms leading to aggressive behavior.