Directed forgetting deficits in patients with temporal lobe epilepsy: An information processing perspective

Although mesial temporal lobe brain damage is frequently associated with me mory loss, it is unclear whether the deficit results entirely from a disrup tion in the processing of relevant information or whether it also reflects interference from irrelevant information. Directed forgetting is one proced ure that can be used, along with standard tests of memory, to investigate t his distinction. Seventeen patients with a diagnosis of complex-partial sei zures of temporal lobe origin and 17 healthy volunteers were compared on le xical decision, free recall, and recognition tests in a directed-forgetting paradigm. These tests created a memory profile to measure the influence of task relevant and irrelevant information in implicit and explicit memory. Compared with healthy volunteers, the patients were significantly impaired on the memory tasks overall [F(5,25) = 5.01, p <.01]. Specifically, directe d forgetting in lexical decision and recognition both discriminated between the groups [stepdown F(1,26) = 6.84, eta(2) =.26, p <.05 and stepdown F(1, 25) = 5.36, eta(2) =.13, p <.05, respectively]. The results suggest that in terictal memory performance in temporal lobe epilepsy may be disrupted in p art because of a deficit in the differential processing of task relevant an d task irrelevant information, particularly at retrieval.