Spatial and non-spatial contextual working memory in patients with diencephalic or hippocampal dysfunction.

Damage to the medial temporal lobe (MTL) and diencephalon results in impaired long-term memory, which relies on the binding of multiple, mostly contextual, features. Recent neuroimaging and patient studies have suggested that impairments may also be present in working memory after MTL or diencephalic damage. To examine whether patients with damage to these brain structures have impairments in working memory for contextual information, 15 patients with damage to the diencephalon due to Korsakoff's syndrome and 12 patients with unilateral MTL lesions, and 30 age-matched healthy controls performed a delayed match-to-sample (DMS) task in which they had to maintain either object-location associations, color-number associations, single colors or single locations. Compared to their age-matched controls, performance on the DMS task was generally impaired in both patient groups, whereas no deficits were found on standard neuropsychological span tasks that do not rely on maintenance aspects of working memory. The patients did not show disproportionate impairments on the binding condition. In all, the results clearly show that impairments in working memory maintenance are present in patients with MTL or diencephalic lesions. However, we did not find a disproportionate inability in maintaining spatial or non-spatial associations within working memory as previously demonstrated in long-term memory.