Procedural memory in Korsakoff's disease under different movement feedback conditions

Within the field of cognitive neuroscience, it has become widely accepted to distinguish between declarative and nondeclarative memory, with different neurobiological substrates subserving these memory structures. This distinction has been inferred from the study of amnesic patients, including those suffering from Korsakoff's syndrome. It is commonly agreed that Korsakoff patients demonstrate intact memory for motor and perceptual skills (nondeclarative) whereas memory of various forms of factual knowledge (declarative) is severely impaired. In the present study, Korsakoff patients and a group of age-matched controls learned a new bimanual motor skill whereby performance was assessed in the presence and absence of augmented visual information feedback. Findings demonstrated that Korsakoff patients were able to learn and retain this skill when directive augmented information feedback was provided while no learning occurred at all in the absence of this information. These observations shed new light on the conditions required for preserved memory in amnesic patients and challenge the classic view that nondeclarative memory is invariably preserved. Instead, the quality of memory across both motor and cognitive dimensions appears to depend on the availability of task-specific information to guide performance, presumably allowing amnesic patients to bypass affected brain areas. This prompts for a reevaluation of current notions about procedural memory capacity in Korsakoff patients.