Estimation of frequency of occurrence of abstract designs after frontal or temporal lobectomy.

Patients with unilateral frontal- or temporal-lobe excisions and normal control subjects were shown a series of abstract designs. Within the series, the designs differed in the number of times that they appeared. The frontal-lobe groups (right more so than left) were impaired in recalling the frequency of occurrence of the designs. Recognition deficits were found only in the patients with right temporal-lobe lesions. The impairment in frequency estimation may reflect a disorderly search process in memory, or a deficit in cognitive estimation, or both.