• Gislaine de Almeida Valverde Zanini, Sérgio Tufik, Monica Levy Andersen, Raquel Cristina Martins da Silva, Orlando Francisco Amodeo Bueno, Camila Cruz Rodrigues, and Sabine Pompéia.
• Universidade Federal de São Paulo, UNIFESP, São Paulo, Brazil.
• Sleep. 2012 Feb 1;35(2):223-30.

Study ObjectivesOne task that has been used to assess memory effects of prior total sleep deprivation (TSD) is the immediate free recall of word lists; however, results have been mixed. A possible explanation for this is task impurity, since recall of words from different serial positions reflects use of distinct types of memory (last words: short-term memory; first and intermediate words: episodic memory). Here we studied the effects of 2 nights of TSD on immediate free recall of semantically unrelated word lists considering the serial position curve.DesignRandom allocation to a 2-night TSD protocol followed by one night of recovery sleep or to a control group.SettingStudy conducted under continuous behavioral monitoring.Participants24 young, healthy male volunteers.Intervention2 nights of total sleep deprivation (TSD) and one night of recovery sleep.Measurements And ResultsParticipants were shown five 15 unrelated word-lists at baseline, after one and 2 nights of TSD, and after one night of recovery sleep. We also investigated the development of recall strategies (learning) and susceptibility to interference from previous lists. No free recall impairment occurred during TSD, irrespective of serial position. Interference was unchanged. Both groups developed recall strategies, but task learning occurred earlier in controls and was evident in the TSD group only after sleep recovery.ConclusionPrior TSD spared episodic memory, short-term phonological memory, and interference, allowed the development of recall strategies, but may have decreased the advantage of using these strategies, which returned to normal after recovery sleep.

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