"Do not take that medication": negative prospective memory in Korsakoff’s syndrome

Background: While prospective memory (i.e., the ability to execute a future plan) has been extensively researched, little is known about negative prospective memory (i.e., the ability to remember not to execute a future plan) in Korsakoff's syndrome (KS). We thus evaluated both prospective memory and negative prospective memory in KS, as well as the relationship between both types of prospective memory and inhibition. Methods: Patients with KS and control participants were invited to press a button on the keyboard (i.e., prospective memory) or not to press a button when a cue word (e.g., negative prospective memory) was encountered. Results: The analysis demonstrated that patients with KS had more prospective memory errors (i.e., forgetting to click the keyboard when the instruction was to do so) than control participants. The analysis also demonstrated that patients with KS had more negative prospective memory errors (i.e., clicking the keyboard when the instruction was not to do so) than control participants. Similar levels of commissions and omissions were observed in patients with KS than in control participants. Interestingly, prospective and negative prospective performances were significantly correlated with performance on an inhibition assessment task. Discussion: Our study demonstrates that KS is characterized by not only difficulty in remembering to execute a future intention but also by difficulty in remembering not to execute a future intention. A decline in negative prospective memory in KS can be associated with difficulty in inhibiting no longer appropriate previously learned intentions.