APP and amyloidosis: To evaluate hippocampal circuit function in a mouse model of Aβ-amyloidosis at an age when both Aβ plaque deposition (Fig. 1a, b) and hippocampal-dependent memory impairments are robust14–18, we applied somatic calcium imaging (Fig. 1c–e) and simultaneous ipsilateral LFP recording (Fig. 1f) in the hippocampal CA1 region of APP/PS1 transgenic mice (12.4 ± 1.2 months) and littermate controls (12.1 ± 2.3 months), as animals explored a linear track and subsequently rested in their home cage (Fig. 1g, h).