Recording techniques were based on a previous study6 (link). Briefly, we recorded extracellularly from VTA using a custom-built, screw-driven microdrive containing six or eight tetrodes (Sandvik, Palm Coast, Florida) glued to a 200 µm optic fibre (ThorLabs). Tetrodes were affixed to the fibre so that their tips extended 300–600 µm from the end of the fibre. Neural and behavioural signals were recorded with a DigiLynx recording system (Neuralynx) or a custom-built system using a multi-channel amplifier chip (RHA2116, Intan Technologies LLC) and data acquisition device (PCIe-6351, National Instruments). Broadband signals from each wire were filtered between 0.1 and 9000 Hz and recorded continuously at 32 kHz. To extract spike timing, signals were band-pass-filtered between 300 and 6000 Hz and sorted offline using SpikeSort3D (Neuralynx) or MClust-3.5 (A. D. Redish). At the end of each session, the fibre and tetrodes were lowered by 40–80 µm to record new units the next day.
To be included in the dataset, a neuron had to be well-isolated (L-ratio36 < 0.05) and recorded within 0.5 mm of a light-identified or putative dopamine neuron, to ensure that it was recorded in VTA. Recording sites were also verified histologically with electrolytic lesions using 10–15 s of 30 µA direct current.
To be included in the dataset, a neuron had to be well-isolated (L-ratio36 < 0.05) and recorded within 0.5 mm of a light-identified or putative dopamine neuron, to ensure that it was recorded in VTA. Recording sites were also verified histologically with electrolytic lesions using 10–15 s of 30 µA direct current.