Contextual fear conditioning causes PAP retraction after 4 h in WT but not in APP/PS1 mice. (A) Representative images showing WT home cage (HC), APP/PS1 HC, WT delayed shock (DS) and APP/PS1 DS conditions. Astrocyte is pseudo-colored in purple. Outline of the pre-synapse is indicated with the red dashed line, the outline of the post-synapse is indicated by the blue dashed line. Scale bar, 100 nm. (B) Shared contact between the astrocyte (Astro) and pre-synapse, relative (rel.) to the pre-synapse perimeter and expressed as percentages (%). (C) Shared contact between the astrocyte and post-synapse, relative to the post-synapse perimeter and expressed as percentages. (D) Quantification of the length of the PAP tip protruding toward the synaptic cleft. (E) Frequency distribution plots of WT HC and WT DS conditions of the data presented in panel (D). (F) Quantification of the distance between the PAP-tip and PSD. (G) Frequency distribution plots of WT HC and WT DS conditions of the data presented in panel (F). Data is presented as mean ± SEM. *P ≤ 0.05; ***P ≤ 0.001; ****P ≤ 0.0001. (B) WT HC n = 5/158, APP/PS1 HC n = 5/108, WT DS n = 5/164, APP/PS1 DS n = 5/156; c: WT HC n = 5/168, APP/PS1 HC n = 5/107, WT DS n = 5/173, APP/PS1 DS n = 5/169; d + f; WT HC n = 5/104, APP/PS1 HC n = 5/67, WT DS n = 5/94, APP/PS1 DS n = 5/98. Statistical details are reported in Supplementary Table 1.