In our earliest work with a single lever it was noted that while the subject would lever-press at a steady rate for stimulation to various brain sites, the current could be turned off entirely and he would continue lever-pressing at the same rate (for as many as 2000 responses) until told to stop.
It is of interest that the introduction of an attractive tray of food produced no break in responding, although the subject had been without food for 7 hours, was noted to glance repeatedly at the tray, and later indicated that he knew he could have stopped to eat if he wished. Even under these conditions he continued to respond without change in rate after the current was turned off, until finally instructed to stop, at which point he ate heartily.
https://en.wikipedia.org/wiki/Brain_stimulation_reward
https://doi.org/10.1126/science.140.3565.394
https://sci-hub.hkvisa.net/10.1126/science.140.3565.394