Isometric forelimb task behavioral training v1

This is the standard protocol for behavioral training of the Isometric Two Action task developed and used for Rodrigues-Vaz and Athalye et al, 2025. This task is a self-paced task in which mice are reinforced for using their forelimb to apply force to an immobile joystick exceeding a threshold of duration and force. In this task mice receive a 10% sucrose drop when they perform correct action. This task has a trial structure as follows: There is an inter-trial-interval (ITI) that lasts for 1 second during which no reinforcement will be delivered. At the end of ITI if the force is below 3g threshold, the trial initiates. If force is above threshold, a new ITI is initiated. Once a trial is initiated, mice execute task actions – actions that cross task defined force threshold (4g or 6 g) for task defined duration (20 or 50 ms). If a task action occurs, mice receive a delayed reinforcement. If force crosses the force threshold for less time than the task duration, the task re-enters ITI phase (1). After reinforcement, the task re-enters ITI (1) or ends – according to task duration and number of task actions executed. This task was developed and trained to study minimal motor actions and their encoding in striatum. There are 3 blocks to this task, performed in sequence: block Both, block A and block B – in which both actions or one action is reinforced (more details below). Action A is defined as the action that the animal performs less during the last session in Block Both. Action B is defined as the action the animal performs more during the last session of Block Both.