The hippocampal contribution to verbal fluency in patients with temporal lobe epilepsy

We report the effects of hippocampal and non-hippocampal temporal-lobe dysfunction on verbal fluency performance. Quantitative aspects of semantic and phonemic fluency performance were examined in 46 patients with right- or left-temporal-lobe epilepsy and 20 healthy controls. A pattern of fewer words generated on semantic rather than phonemic fluency tasks was found among patients with damage to hippocampal structures. This pattern was not obtained in patients with non-hippocampal temporal-lobe damage, suggesting that the hippocampus plays a crucial role in semantic fluency performance. An interesting lateralization effect was obtained. Among patients with left temporal-lobe involvement, fluency performance was impaired regardless of whether the hippocampus was involved. In contrast, among patients with right temporal-lobe involvement, fluency performance was impaired only when the hippocampus was involved.