Animals.
Male C57Bl6/J mice (Charles River Laboratories, France) aged between 60 and 90 days were used. To identify FSIs, mice expressing the fluorescent tomato protein in parvalbumin neurons were generated by crossing B6;129P2-Pvalbtm1(cre)Arbr/J strain with B6.Cg-Gt(ROSA)26Sortm9(CAG-tdTomato)Hze/J strain from Jackson Laboratory11The initial proposal planned to use wild type mice. The use of transgenic mice expressing tomato protein in parvalbumin neurons was introduced to identify the fast spiking interneurons in cortical slices. This changes in the protocol received editorial approval prior to data collection, on 9 Feb 2022.. All procedures were in accordance with European Union recommendations for animal experimentation (2010/63/UE). Mice were housed in groups of up to five in standard laboratory cages and were kept on a 12-hour light/dark cycle (at a constant temperature of 22°C) with food and water ad libitum.