Fischer Stefan, Wilhelm Ines, Born Jan
Innsbruck Medical University, Innsbruck, Austria.
J Cogn Neurosci. 2007 Feb;19(2):214-27. doi: 10.1162/jocn.2007.19.2.214.
Sleep crucially contributes to the off-line consolidation of memories. Although this view was confirmed in numerous studies in adults, it is not known whether it can be generalized to sleep during development. Here, we examined effects of sleep on implicit memory formation considered of particular relevance in children, because brain structures underlying implicit learning develop earlier in ontogeny than structures supporting explicit learning. Subjects were 7- to 11-year-old children (n = 14) and 20- to 30-year-old adults (n = 12) tested on a serial reaction time task before (learning) and after (retest) equal length retention periods of overnight sleep and daytime wakefulness. At learning, after eight training blocks, all subjects had acquired implicit knowledge of the probabilistic rules underlying the sequential stimulus materials, as indicated by a substantial difference in response time to grammatical versus nongrammatical trials in two test blocks that followed the training blocks. At learning, this response time difference was greater in children (48.49 +/- 6.08 msec) than adults (28.02 +/- 3.65 msec, p < .01), but did not differ between sleep and wake retention conditions in either age group. Consistent with previous studies, retesting in the adults revealed that the reaction time differences between grammatical and nongrammatical trials increased by 9.78 +/- 4.82 msec after sleep, but decreased by -12.76 +/- 5.49 msec after the wake retention period (p < .01). Contrary to this finding in adults, sleep in children did not lead to an increase, but to a decrease in the reaction time difference averaging -26.68 +/- 12.25 msec (p < .05), whereas across the wake retention interval the reaction time difference remained nearly unchanged. The sleep-dependent deterioration in measures of implicit sequence knowledge in children was in striking contrast to the gain of such knowledge in the adults during sleep (p < .01). Our findings indicate that the functional role of sleep in implicit memory consolidation depends on age. We speculate that the overnight decrease of implicit knowledge in children reflects a preferential effect of sleep toward the enhancement of explicit aspects of task performance that interferes with implicit performance gains.
睡眠对记忆的离线巩固起着至关重要的作用。尽管这一观点在针对成年人的众多研究中得到了证实，但睡眠在发育过程中是否也具有同样作用尚不清楚。在此，我们研究了睡眠对儿童内隐记忆形成的影响，鉴于内隐学习的脑结构在个体发育中比支持外显学习的结构发育得更早，所以认为这一影响对儿童尤为重要。研究对象为7至11岁儿童（n = 14）和20至30岁成年人（n = 12），他们在经历了时长相等的夜间睡眠和白天清醒的保持期前后，分别进行了序列反应时任务测试（学习阶段和重测阶段）。在学习阶段，经过八个训练块后，所有受试者都掌握了序列刺激材料背后概率规则的内隐知识，这一点从训练块之后的两个测试块中对符合语法和不符合语法试验的反应时间存在显著差异可以看出。在学习阶段，儿童的这种反应时间差异（48.49 ± 6.08毫秒）大于成年人（28.02 ± 3.65毫秒，p <.01），但在两个年龄组中，睡眠和清醒保持条件下的反应时间差异并无不同。与之前的研究一致，对成年人进行重测发现，睡眠后符合语法和不符合语法试验之间的反应时间差异增加了9.78 ± 4.82毫秒，但在清醒保持期后减少了 -12.76 ± 5.49毫秒（p <.01）。与成年人的这一发现相反，儿童睡眠后反应时间差异并未增加，反而平均减少了 -26.68 ± 12.25毫秒（p <.05），而在整个清醒保持期内，反应时间差异几乎没有变化。儿童内隐序列知识测量指标中依赖睡眠的恶化与成年人在睡眠期间此类知识的增加形成了鲜明对比（p <.01）。我们的研究结果表明，睡眠在内隐记忆巩固中的功能作用取决于年龄。我们推测，儿童夜间内隐知识的减少反映了睡眠对任务表现外显方面增强的优先作用，这干扰了内隐表现的提升。
