SPATIAL MEMORY DEFICITS IN PATIENTS WITH UNILATERAL DAMAGE TO THE RIGHT HIPPOCAMPAL-FORMATION

Patients with unilateral temporal lobe damage resulting from intractab le temporal lobe epilepsy (TLE, n = 30) or from temporal lobe resectio n (temporal lobectomy, TLR, n = 47) were investigated on the Nine-box Maze. The task, analogous to the radial arm maze, was designed to comp are spatial mapping and working memory theories of the functions of th e hippocampus. The task provides measures of spatial, object, working and reference memory, incorporated into a within subjects design. The spatial component was designed to encourage the formation of allocentr ic rather than egocentric spatial representations. Spatial memory defi cits were found (across working and reference memory components) in bo th TLE and TLR patients with right temporal lobe damage, with intact s patial memory in patients with corresponding left temporal lobe damage . Performance on the matched nonspatial (object) working memory compon ent was equal to healthy controls for all groups. However all patient groups showed a deficit on object reference memory. These findings are discussed in relation to the underlying temporal lobe pathology and p articularly atrophy of the hippocampal formation. Overall, the results support the cognitive mapping theory of hippocampal function, with th e demonstration of a selective (and probably allocentric) spatial memo ry deficit in patients with right hippocampal damage. Copyright (C) 19 96 Elsevier Science Ltd.