Dissociation between declarative and procedural learning in dementia and depression

Declarative and procedural learning were assessed in patients with probable Alzheimer's Disease (AD) and major depression, patients with AD and no depression, patients with major depression but no dementia, and a group of age-comparable nondemented and nondepressed normal controls. AD patients showed significant deficits in declarative but not in procedural learning, while depressed nondemented patients showed the opposite pattern (i.e., a significantly worse procedural than declarative learning). Patients with both AD and major depression showed a similar learning pattern to the AD nondepressed group (relatively preserved procedural learning but severe deficits in declarative memory). These findings provide further evidence for the independence between declarative and procedural learning, and demonstrate their different vulnerability in dementia and depressive-like states.