Role of the frontal lobes in implicit and explicit retrieval tasks.

While the role of the frontal lobes in explicit retrieval tasks is well supported, the findings for implicit tasks are less conclusive. We investigated the role of the frontal lobes in perceptual and conceptual implicit priming. Three memory paradigms were given under both implicit and explicit retrieval instructions, using word fragment completion, picture fragment completion and category exemplar generation. Three groups of individuals with frontal lesions were compared to normal controls: Left dorsolateral lesions (n = 5), right dorsolateral lesions (n = 4), and medial lesions (n = 9). Word fragment completion priming was impaired by left dorsolateral lesions, with other priming tests unaffected by any lesion. Explicit performance showed a different pattern, with category exemplar cued recall impaired by left dorsolateral and medial lesions. These findings support the role of the frontal lobes in both implicit and explicit retrieval mechanisms under certain conditions requiring strategy application or lexical retrieval.