Retrieval from semantic memory during a night without sleep

It has been demonstrated that retrieval performance from semantic memory varies during the day. Specifically, the retrieval of low- relative to high-dominance category members is slower in the morning compared to later in the day. It has been suggested that the effect is related to a circadian arousal rhythm, which steadily rises during the day and rapidly declines at night. This study examines retrieval from semantic memory during the night. Sixteen subjects performed a semantic classification task once every hour throughout one night without sleep. Classification latencies became progressively slower, and the time taken to retrieve low- relative to high-dominance category members increased from midnight to 4 a.m. The trend reversed between 4 and 7 a.m. The pattern of results closely parallels the hypothesised circadian arousal rhythm. It is suggested that the variation in retrieval performance as a function of time of day may be related to fluctuations in a circadian arousal rhythm.