Novel decision making in patients with prefrontal or posterior brain damage.

Patients with lesions of the frontal lobes experience greater difficulties in performing nonroutine tasks, but their ability to cope with novel situations has not been studied. We assessed novel and previously practiced decisions in normal subjects and patients with frontal or posterior brain damage using a unimanual two-choice response time test. Patients with frontal damage had a dramatic impairment on novel decision, whereas practiced decision was normal. Relative Judgment Theory analysis suggested that the basic disorder concerns the ability to create internal referents that are determined from instructions and are subsequently required to associate the current stimulus with the appropriate response. The results of the study suggest that the prefrontal cortex is critical for novel decision making and that it operates mainly at the stage of creation of internal referents that associate some subsequent event with the selection of appropriate processing. This basic disorder may underlie some behavioral changes such as apathy and difficulty on tests that are sensitive to frontal damage.