“…In addition, TPU-evoked signals can be expected to be localized to the stimulated GC spine: there is no Ca 2+ influx into the adjacent dendritic shaft upon TPU, as we have shown in GC Ca 2+ imaging experiments that were performed previously (dye 100 µM OGB-1, average amplitude ratio ∆F/F spine:dendrite 46:2 Bywalez et al, 2015 ) and also interleaved with the MC recordings in this study, using a low-affinity dye (100 µM OGB-6F, ratio ∆F/F spine:dendrite 24:2, Ona Jodar et al, 2020 ). Finally, we also tested via Ca 2+ imaging whether neighboring GC spines of the same GC could sense uncaged glutamate (n = 11 spine pairs, average distance between stimulated and non-stimulated spine heads 4.1 ± 2.2 µm, range 1.5–6.8 µm, Figure 1—figure supplement 1C,D,E ).…”