Anterior prefrontal cortex activities during the inhibition of stereotyped responses in a neuropsychological rock-paper-scissors task.

Stereotyped responses must be suppressed at certain times during daily life, which can be difficult for patients with lesions in the frontal cortices. Neuropsychologists have used the rock-paper-scissors (RPS) task to evaluate patients' ability to suppress a stereotyped response. In this study, we measured functional magnetic resonance imaging signals to investigate how frontal cortex activities change corresponding to subjects' performance as they tried to lose (successfully inhibiting the typical response to win) when presented with a gesture signifying rock, paper, or scissors. Performance rates ranged from 50% to 100%, and results indicated that activation in the bilateral anterior part of the prefrontal cortex increased parametrically corresponding to subjects' successful performance. This result implies that the anterior prefrontal cortex plays a key role in the successful completion of a modified RPS task and may play a role in the suppression of stereotyped responses.