A critical initialization for biological neural networks

All experimental procedures were conducted according to the Institutional Animal Care and Use Committee (IACUC) at Howard Hughes Medical Institute (HHMI) Janelia. Data analysis and simulations were performed in Python using pytorch and numpy, and figures were made using matplotlib and jupyter-notebooks 61 , 62 , 63 , 64 , 65 . Data acquisition Animals All experimental procedures were conducted according to IACUC ethics approval received from the IACUC board at HHMI Janelia Research Campus. We performed 18 recordings in cortex in: (1) 12 mice bred to express jGCaMP8s 66 in excitatory neurons: TetO-jGCaMP8s × Camk2a-tTA mice (available as JAX 037717 and JAX 007004); (2) 3 mice bred to express jGCaMP8s 66 in the somas of excitatory neurons: riboL1–jGCaMP8s × Slc17a7-Cre (similar to JAX 039267 without IRES; and JAX 037512) and (3) 3 mice bred to express tdTomato in inter-neurons VGAT-CRE × Ai14 (JAX 016962; JAX 007914) with injections of a dual virus Thy1s:TTA (AAV9, 1.64 × 10 13 vector genomes ml −1 ) and TRE3G:RiboL1–jGCaMP8s (AAV9, 2.45 × 10 13 vector genomes ml −1 ) as in ref. 67 , see also ref. 68 . We also performed eight recordings in hippocampal CA1 in six mice bred to express GCaMP6f in excitatory neurons: Thy1-GCaMP6f GP5.17 mice (JAX 025393) 69 , as well as in two wild-type C57 mice (JAX 000664) with injections of the same RiboL1-jGCaMP8s virus combination described above. These mice were male and female, and ranged from 2 to 12 months of age. …