Priming recognition in good sleepers and in insomniacs

Insomniacs often report memory and concentration problems, but these complaints have not been consistently supported by performance measurements. Furthermore, while the majority of studies have addressed explicit memory, few have investigated the implicit domain, and very little is known concerning other types of implicit memory besides procedural memory, such as priming. Thus, the purpose of the study was to investigate priming effect for visual stimuli in insomniacs and good sleepers. Twenty-three insomniacs and 20 good sleepers performed a visual priming task in which they were asked to name new and old pictures presented at nine ascending levels of spatial filtering. Both neutral and sleep-related stimuli were used, as previous research evidenced an attentional bias for sleep-related stimuli. Visual priming effect was observed in both groups, suggesting that poor sleep quality does not affect this type of implicit memory. However, the identification process in insomniacs is influenced by the nature of the stimulus to identify: insomniacs recognized both new and old sleep-related stimuli at lower spatial frequencies compared with good sleepers. The tendency to selectively attend to sleep-related stimuli may influence top-down processes occurring during identification of filtering stimuli, by determining a pre-allocation of attentional resources and facilitating identification processes even when sensorial information is scant. Differences in the identification processes of sleep-related stimuli compared with neutral ones should be carefully taken into account as possible pre-clinical markers of insomnia in poor sleepers.