Wakeful rest benefits before and after encoding in anterograde amnesia

Objective: Studies have shown that patients with anterograde amnesia forget less episodic information after a delay if encoding is immediately followed by an unfilled period of wakeful rest. This benefit has been attributed to the reduced interference with the consolidation process. However, this account cannot directly explain improved retention in healthy adults resulting from pre-encoding rest. While benefits resulting from pre- and post-encoding rest can be alternatively explained via improved distinctiveness at retrieval, it has yet to be established whether both benefits are observable in amnesics. The aim of the current study was to assess whether amnesic patients showed improved retention of prose material after 10 minutes following both pre- and post-encoding unfilled intervals of wakeful rest.

Method: Twelve patients with anterograde amnesia were recruited. Participants completed four conditions. A short prose passage was aurally presented in each condition. Prose presentation was preceded and followed by a 9-minute delay interval. Delay intervals were either filled (spot-the-difference task) or unfilled (wakeful rest). Prose retention was assessed immediately after presentation and after 10 minutes.

Results: Prose retention was consistently better when wakeful rest followed prose encoding in comparison to a condition where an effortful task was encountered both before and after encoding.

Conclusions: Post-encoding wakeful rest alone substantially improves retention in amnesic patients. While pre-encoding wakeful rest elicits inconsistent benefits in amnesics, reduced retention following both pre- and post-encoding task engagement suggests that pre-encoding activity may still be relevant. Overall, our findings support consolidation interference explanations of forgetting in anterograde amnesia.