Investigating the Utility of the WMS-IV with Novel Procedures as an Assessment Tool for Accelerated Long Term Forgetting in Temporal Lobe Epilepsy

Research suggests some individuals with Temporal Lobe Epilepsy (TLE)
experience an increased rate of forgetting for new information; currently defined
as ‘Accelerated Long-Term Forgetting’ or ALF (Butler & Zeman, 2008). This
novel construct goes undetected by standard neuropsychological measures and
only becomes apparent after longer testing delays. However, as yet there have
been no specific measures developed for the assessment of ALF.
Consequentially, it is often undetected in TLE and research (relying on various
novel or adapted measures) is yielding inconsistent findings.
The present study aimed to build upon the findings of a previous research project
(Crowley, 2014) by adapting an existing and widely used neuropsychological
measure (Wechsler Memory Scale - Fourth UK Edition [WMS-IVUK]; Wechsler,
2010) in an attempt to assess its utility at detecting ALF in TLE. 25 TLE
participants and 26 unaffected controls were administered selected WMS-IVUK
subtests with an additional one-week recall and recognition delay. Participants
also completed a comprehensive neuropsychological battery of cognitive and
non-cognitive measures. Data was analysed at the group and individual level,
and the contribution of non-memory cognitive and non-cognitive variables was
considered.
When analysed at the group level, TLE participants displayed evidence of verbal
and visual ALF on selected WMS-IVUK subtests, even when the mediating role of
non-memory variables was considered. Individual analysis revealed a range of
memory profiles in the TLE group. Some participants displayed primary difficulty
in the encoding/retrieval of new information, assessed across standard delays. It
was unclear whether these individuals also experienced accelerated forgetting.
Other individuals displayed a memory profile consistent with current definitions of
ALF and performed worse than controls at the extended delay despite
performance being comparable at the standard delay. Evidence of ALF was
observed for all three WMS-IVUK subtests, on tasks of recall and recognition.
Findings suggest the utility of the WMS-IVUK at detecting ALF in TLE.