Accelerated long-term forgetting (ALF) is a form of memory impairment in which learning
and initial retention of information appear normal but subsequent forgetting is excessively
rapid. ALF is most commonly associated with epilepsy and, in particular, a form of lateonset
epilepsy called transient epileptic amnesia (TEA). ALF provides a novel opportunity
to investigate post-encoding memory processes, such as consolidation. Sleep is implicated
in the consolidation of memory in healthy people and a deficit in sleep-dependent memory
consolidation has been proposed as an explanation for ALF. If this proposal were correct,
then sleep would not benefit memory retention in people with ALF as much as in healthy
people, and ALF might only be apparent when the retention interval contains sleep. To test
this theory, we compared performance on a sleep-sensitive memory task over a night of
sleep and a day of wakefulness. We found, contrary to the hypothesis, that sleep benefits
memory retention in TEA patients with ALF and that this benefit is no smaller in magnitude
than that seen in healthy controls. Indeed, the patients performed significantly more
poorly than the controls only in the wake condition and not the sleep condition. Patients
were matched to controls on learning rate, initial retention, and the effect of time of day on
cognitive performance. These results indicate that ALF is not caused by a disruption of
sleep-dependent memory consolidation. Instead, ALF may be due to an encoding abnormality
that goes undetected on behavioural assessments of learning, or by a deficit in
memory consolidation processes that are not sleep-dependent