Abstracts

Conventional memory assessment might fail to identify memory dysfunction that is characterized by intact recall for a relatively brief period, but rapid forgetting thereafter. A recent study of auditory and visual selective reminding test performance revealed that temporal lobe epilepsy (TLE) patients demonstrated poorer memory ability than controls, but there were no group differences in rate of information loss at the 30-minute and 24-hour delay trials (Bell et al., 2005). In addition, at the individual level of analysis accelerated forgetting over 24 hours was not more common in TLE patients compared to controls. In this study, we assessed Wechsler Memory Scale-3rd ed. (WMS-III) Logical Memory subtest () performance, including immediate memory and recall after 30-minute and 14-day delays, in a control group (n = 25) and a group of individuals with TLE (n = 25). The mean age of epilepsy onset was 11 years (SD = 8). Individuals with a history of right, left, bilateral or indeterminate TLE laterality were included and five of the TLE patients had undergone a left anterior temporal lobectomy (ATL) at the time of this study. The results described below were unchanged when the ATL patients were excluded. [italic]Group analysis[/italic]: A 2 X 3 (Group X Trial) univariate ANOVA for LM free recall raw scores revealed main effects of group and trial, but no significant group X trial interaction effect. [italic]T[/italic] tests revealed that the control group performed significantly better than the TLE group on the immediate, 30-minute delay, and 14-day delay trials. [italic]Individual analysis[/italic]: Memory impairment was defined as a score [underline][gt][/underline] 1 standard deviation below the control group mean. Examination of raw scores revealed that the TLE group had a significantly higher percentage of individuals with impairment at the immediate and 30-minute delay trials, but not at the 14-day delay. Moreover, none of the TLE patients versus three controls (12%) showed memory impairment solely at the 14-day trial. When examining percent retention scores, only 4% of the individuals with TLE versus 20% of the controls were unimpaired after 30 minutes but impaired after 14 days. Accelerated forgetting over a 14-day delay was not present on a widely used story memory test (WMS-III LM) in a group of individuals with TLE. This evidence suggests that the conventional 30-minute delay utilized in clinical neuropsychological evaluations typically is sufficient for measuring memory functioning in TLE patients. Future study of word list retention after a delay of weeks in subsets of TLE patients with clearly lateralized seizures would further test this hypothesis. (Supported by NIH grants NS 37738, NS 42251, and MO1 RR03186 (General Clinical Research Center).)