Development of a new test of accelerated long-term forgetting in epilepsy

Abstract

Accelerated long-term forgetting (ALF) is a novel form of memory impairment in which epilepsy patients demonstrate intact recall and recognition after standard delays, but they show an accelerated rate of forgetting in comparison to controls when the retention period is extended. ALF has been evidenced in children with idiopathic generalised epilepsy (IGE), who showed ALF for verbal material over a period of 1 week. Use of a minimum-learning criterion revealed that poorer initial learning was mediating the effect of ALF. The current study aimed to further investigate rates of forgetting in 5 children with IGE in comparison to 13 healthy controls, whilst developing a new spatial object-locations task to be used as a non-verbal measure of ALF. When tested immediately and at 30 minutes, memory for 2 stories was equivalent between groups but at 1 week there was a strong trend (approaching significance) for IGE participants to recall less verbal material than controls and there was a significant main effect of group and delay. IGE and control group participants did not differ in the number of trials required to reach criterion. Neither of the 2 measures of non-verbal, spatial memory revealed significant group differences, nor were there were group differences in verbal or non-verbal recognition performance. The findings are interpreted in relation to previous research and theories of memory consolidation. Directions for future research and further development of the spatial object-locations task are considered.