The lever-pull task in head-restrained mice. A, A mouse is shown in the task device. Top, The head of the mouse was fixed under an objective, and the right forelimb was available to grasp and pull the movable lever. The left forelimb grasped a fixed pole to keep the posture relaxed. A waterspout for reward delivery was near the mouth. Bottom, The mouse with the head plate was smoothly inserted into the body holder. The head plate (inset) slid through an open space in the body holder wall and was fixed between the head holders. B, Schematic diagram of the lever-pull task. Before pulling the lever, mice had to wait for >3 s. After the lever pull was maintained for T_set, a drop of water was dispensed and the lever was then rapidly pushed to the wait position by a solenoid pole. The lever was immobilized for 2 s in the wait position (green bar). When an animal did not maintain the lever pull for T_set or did not wait at least 3 s before the level pull, a reward was not given and the mechanical lever push did not engage. C, The mean pull time increased over the 9 d training session (n = 35 mice) until the imaging experiment (Ex) was performed (n = 21 mice). D, The number of successful trials during the 9 d training session and imaging experiment. E, The median waiting time before successful trials decreased during the training sessions and 5.3 ± 0.3 s (n = 21 mice) during the imaging session. F, Representative traces of EMG activity of the right forelimb muscle (top) and lever trajectory (bottom) during task performance. G, H, EMG power coincided with the start (G) and end (H) of the pull movement.