IMPAIRED ESTIMATION OF WORD OCCURRENCE FREQUENCY IN FRONTAL-LOBE PATIENTS

Neuroanatomical correlates of the estimation of occurrence frequency h ave received little attention. This study investigates the possible ro le of the frontal lobe in estimating word occurrence frequency. A samp le of 27 patients with frontal lesions were matched with normal contro ls by sex, age and years of education. Significant differences between patients and controls were found for frequency estimation, but not fo r item recognition. Studying accuracy of estimation as a function of a ctual frequency, the frontal group performed worse, especially at high frequencies of occurrence. As far as lesion lateralization is concern ed, the right frontal subgroup performed worse than the control group in the estimation of frequency. Our results suggest that the prefronta l cortex plays a role in estimating word occurrence and that there is a dissociation between frequency memory and recognition memory, pointi ng to the involvement of two different cerebral systems. (C) 1997 Else vier Science Ltd.