Right hemisphere brain damage impairs strategy updating.

Our behavior is predicated on mental models of the environment that must be updated to accommodate incoming information. We had 13 right-brain-damaged (RBD) patients and 10 left-brain-damaged (LBD) patients play the children's game "rock, paper, scissors" against a computer opponent that covertly altered its strategy. Healthy age-matched controls and LBD patients quickly detected extreme departures from uniform play ("paper" chosen on 80% of trials), but the RBD patient group did not. Seven RBD patients presented with neglect and although this was associated with greater impairment in strategy updating, there were exceptions: 2 of 7 neglect patients performed above the median of the patient group and 1 of the 6 nonneglect participants was severely impaired. Although speculative, lesion analyses contrasting high and low performing patients showed that severe impairments were associated with insula and putamen lesions. Interestingly, relative to the controls, the LBD group tended to "maximize" choices in the strongly biased condition (i.e., optimal strategy chosen on 100% of the trials), whereas controls "matched" the computer's strategy (i.e., optimal strategy chosen on 80% of the trials). We conclude that RBD leads to impaired updating of mental models to exploit environmental changes.