Specific expansion of motor cortical projections in a singing mouse

Mouse husbandry All experiments were approved and conducted in accordance with the Cold Spring Harbor Laboratory Institutional Animal Care and Use Committee. All animals used were adult (>3 months) male and female mice. Laboratory mice were acquired from The Jackson Laboratory (C57BL/6J). Colonies of laboratory and singing mice were maintained at 20–22 °C, 30–70% humidity and a 12–12 h light–dark cycle. Behavioural recordings and analysis A female of each species was muted by synaptic silencing of the caudolateral PAG using tetanus-toxin light chain 7 , 50 and allowed 2 weeks for protein expression. For five sessions per species, the mute female was placed with a conspecific male in a clean cage for interaction (Thoren Systems 8; 30.8 × 40.6 × 22.2 cm) lined with Alpha-pad cotton paper (Shepherd Specialty Papers). Audio of each dyad was recorded for 1–2 h using two Avisoft CM16/CMPA microphones positioned above the cage with high and low gain settings and sampling at 250 kHz (digitized with Avisoft UltraSoundGate 116H). Vocalizations were segmented from the audio using USVSEG 69 software for MATLAB (v.09r2), and parameters were optimized to the sounds emitted by each species. For singing mice, songs and their individual notes were also detected using custom code in Python. Segmented sounds were manually curated in a customized spectrogram browser derived from the open-source MATLAB graphical user interface DeepSqueak 70 . …