Word-pair association task.

To test declarative memory consolidation, the word-pair association task was used in an adapted version consisting of 46 related word pairs presented randomly on a 15 inch computer screen for 5000 ms, followed by a 100 ms blank screen using the Presentation® software (word-pair list and procedures were identical to the ones used by [18]). Four additional word pairs at the beginning and end of the task served to buffer primacy and recency effects. The word pairs were presented repeatedly until the subject remembered at least 60% in a cued-recall test, i.e. stating the word matching the first word of the previously learned word pairs. Variables measuring declarative memory encoding on day 1 (baseline) were the number of trials to criterion as well as the number of correctly retrieved word pairs in the last trial. Memory consolidation was calculated as the percentage of correctly retrieved words at recall referred to the number of correctly encoded words in the learning session (retention rate, %). Cued-recall was performed one single time without further learning 24 hrs and 7 days after initial acquisition and the number of correctly recalled words was assessed.