Hypnotic Medications and Sleep-dependent Memory Consolidation: the Effect of Variable Drug Exposure During the Night

A growing body of evidence has demonstrated that sleep promotes memory consolidation in healthy individuals. However, little research has been conducted regarding the effect of hypnotics on sleep-dependent memory. One study found that zopiclone (7.5 mg), but not brotizolam (0.25 mg), impaired sleep-dependent memory consolidation in normal sleepers. Another study reported significant impairment of sleep-dependent memory on a motor task with triazolam (0.375 mg), but not with zolpidem immediate release (10 mg). These studies provide some evidence that sedative-hypnotic drugs may impair sleep-dependent memory consolidation, but further investigation is clearly needed in this area. Because hypnotics are commonly prescribed for insomnia, it is important to determine if there is a significant risk of impairment in sleep-dependent memory consolidation associated with these medications. Further, investigation of alternative doses and drug regimens upon memory consolidation appears warranted.

The purpose of the current study is to determine the effect of two hypnotic medications on sleep-dependent memory consolidation in normal sleepers. Zolpidem extended release, which will be active for most of the sleep period when administered at bedtime, will be compared to zaleplon, which will be active for half of the sleep period when administered in the middle of the night. This comparison allows us to address the question of whether a few hours of drug-free sleep results in better memory consolidation than sleep with drug throughout the night.