Object location performance: detection of functional impairment in right temporal lobe epilepsy

A prominent role of the right temporal lobe in nonverbal memory and visuospatial memory is widely accepted. A variety of neuropsychological tests have been shown to be sensitive to functional deficits related to right temporal lobe epilepsies mainly after surgical interventions, whereas preoperative deficits were seldom used to demonstrate test sensitivities. Furthermore, compensation processes or additional cognitive deficits related to left temporal or extratemporal dysfunctions are often not adequately taken into account. We used a modified object location task to demarcate preoperative visuospatial memory deficits of right temporal origin against such processes in patients with clinically verified right temporal, left temporal, or extratemporal lobe epilepsies. Healthy subjects served as controls. By using 8 "unnameable" objects, the positional memory accuracy of patients with right temporal lobe epilepsy was significantly lower than the positional memory performance of patients with left temporal and extratemporal lobe epilepsies, while object location memory performance differentiated patients with right temporal and extratemporal lobe epilepsies from patients with left temporal lobe epilepsy. Our version of a classical object location task might be a useful tool to detect mnestic deficits specifically related to right temporal lobe dysfunction. Future studies should focus on the refinement of testing conditions in order to detect differences induced by more distinct structural or functional deficits.