4 aminobutyric acid 1 4 aminobutyric acid metabolism 1 Alzheimer disease 1 Alzheimer’s disease 1 Article 1 GABA 1 adult 1 aged 1 amnesia 1 apolipoprotein E4 1 apolipoprotein ε4 1 brain size 1 choline 1 cohort analysis 1 creatine 1 directed forgetting task 1 disease association 1 episodic memory 1 female 1 fluid-attenuated inversion recovery imaging 1 glutamic acid 1 glutamine 1 heterozygote 1 hippocampus 1 homocarnosine human 1 human experiment 1 image analysis 1 image segmentation 1 male 1