<qa>  What is the amount of cash accumulated in a session?Participants will perform a monetary reward task while lying in an MRI scanner. The task is similar to playing a computer video game with the possibility of winning cash. The amount of cash is largely dependent on the subjects performance. The accumulated amount of cash earned in a session will fluctuate depending on the subjects continuing performance level. That is, during a single session, a subject could lose money earned early in the session if his or her performance later in the session is not as good as earlier. 