Topographical memory in transient epileptic amnesia

Transient Epileptic Amnesia (TEA) is an epilepsy syndrome characterised by amnestic seizures and inter-ictal memory problems affecting remote autobiographical memory, retention of new information (accelerated long-term forgetting), and topographical memory. While studies to-date have focused on the first two of these memory changes, no objective investigation has been undertaken into topographical memory complaints.

Sixteen patients with TEA were compared with 26 age-matched healthy control participants. All participants completed a comprehensive neuropsychological battery, self-report questionnaires to rate frequency and level of difficulties with both place memory and route-finding, and an objective measure of allocentric spatial memory: the Four Mountains Test.

There were no significant group differences in predicted full scale IQ, processing speed, working memory, visuoconstructional or broader visual memory skills. The TEA group, however, performed significantly below controls on the Four Mountains Test and self-reported more frequent problems with recognising places and recalling familiar routes. The level of self-reported difficulty with route-finding was also significantly greater in people with TEA than controls. While the self-reported measures were significantly correlated with each other, no significant relationship was found between the subjective and objective measures of topographical memory.

These results provide the first empirical evidence of topographical memory impairment in people with TEA, regarding allocentric spatial memory, place memory and route-finding. This further supports theoretical models linking TEA to disruption of hippocampal and medial temporal lobe networks critical for allocentric spatial representation. Future research should extend the objective measurement to include additional aspects of topographical memory.