PSEN1 and Alzheimer disease: The effect of AD onset on GABAergic synapses has also been studied, and an increased number of GABAergic projections towards the CA1 hippocampal region [81] has been observed in APPPS1 mice, together with a potentiation of GABAergic synaptic activity observed in transgenic mice overexpressing hAPP carrying the Swedish and Indiana FAD mutations [82,83].