Although mesial temporal lobe brain damage is frequently
associated with memory loss, it is unclear whether the
deficit results entirely from a disruption in the processing
of relevant information or whether it also reflects interference
from irrelevant information. Directed forgetting is one
procedure that can be used, along with standard tests of
memory, to investigate this distinction. Seventeen patients
with a diagnosis of complex–partial seizures of temporal
lobe origin and 17 healthy volunteers were compared on
lexical 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, directed forgetting
in lexical decision and recognition both discriminated between
the groups [stepdown F(1,26) = 6.84,
η2 = .26, p < .05 and stepdown
F(1,25) = 5.36, η2 = .13, p
< .05, respectively]. The results suggest that
interictal memory performance in temporal lobe epilepsy
may be disrupted in part because of a deficit in the differential
processing of task relevant and task irrelevant information,
particularly at retrieval. (JINS, 1999, 5,
549–555.)
