But in the other scan, the phone on the right ear was switched on, muted, and set to receive a lengthy recorded message.
Scroll through the many recorded messages, listening for the voice we recognised.
The phone on the left ear was turned off, while the one on the right received a 50-minute recorded message.
They turned it on, and replayed the previously recorded signal from CA1 — like a recorded message from the brain. The rats remembered.