Contribution of subregions of human frontal cortex to novelty processing.

Novelty processing was studied in patients with lesions centered in either OFC or lateral pFC (LPFC). An auditory novelty oddball ERP paradigm was applied with environmental sounds serving as task irrelevant novel stimuli. Lesions to the LPFC as well as the OFC resulted in a reduction of the frontal Novelty P3 response, supporting a key role of both frontal subdivisions in novelty processing. The posterior P3b to target sounds was unaffected in patients with frontal lobe lesions in either location, indicating intact posterior cortical target detection mechanisms. LPFC patients displayed an enhanced sustained negative slow wave (NSW) to novel sounds not observed in OFC patients, indicating prolonged resource allocation to task-irrelevant stimuli after LPFC damage. Both patient groups displayed an enhanced NSW to targets relative to controls. However, there was no difference in behavior between patients and controls suggesting that the enhanced NSW to targets may index an increased resource allocation to response requirements enabling comparable performance in the frontal lesioned patients. The current findings indicate that the LPFC and OFC have partly shared and partly differential contributions to the cognitive subcomponents of novelty processing.