IcelandEnvironmentGene-Environment InteractionNeuronal PlasticityGenetic Predisposition to DiseaseGenotypeRisk FactorsBreedingPanicumQuantitative Trait, HeritableWeaningTwin Studies as TopicModels, GeneticGenetic PleiotropyHybrid VigorSocial EnvironmentPhenotypeQuantitative Trait LociAnimal HusbandryCrosses, GeneticReceptors, Dopamine D4PoaceaeSelection, GeneticEpistasis, GeneticDiseases in TwinsSerotonin Plasma Membrane Transport ProteinsGenetic VariationCattleTwinsBody WeightAllelesAnalysis of VarianceTriticumChromosome MappingSeasonsPolymorphism, Single NucleotideReproductionLife Change EventsRegression AnalysisModels, StatisticalAnimal FeedLinear ModelsGenetic MarkersPolymorphism, GeneticModels, BiologicalLong-Term PotentiationSynapsesHippocampusNeuronsSynaptic TransmissionLearning