Figure 1.

Different tasks in an assay to measure the effects of pressure pain. (A) Resting task where the person sits and is instructed to remain as still as possible. (B) Drawing task where the person draws a line connecting digits and letters in a specified order (1 A, 2 B, etc.) from beginning to end. (C) Pointing task, where the person is asked to point to a target (the full loop of forward motion to the target and backward motion toward rest). The second backward segment occurs spontaneously, without instruction, while the first motion toward the target is instructed. (D) The grooved peg task where the person picks up a grooved peg and aims it at the grooved hole on the board to insert it in the appropriate orientation. This task requires orienting the grooved peg to match the grooved hole, similar to opening a door by inserting a key into the lock. (E) Experimental assay to probe the control condition vs. the pain condition. For each task (using the pointing task as an example), the person performs the task normally, without any pain (control case). A blood pressure cuff is then placed on the non-dominant arm (the arm that is not performing the task) and inflated to 200 mmHg for the entirety of the task to ensure lingering discomfort that produces the sensation of physical pressure pain. The person performs the task under pain (pain condition), and lastly, the person performs the task after the pain disappears (post-pain condition).