Stickgold R, Scott L, Rittenhouse C, Hobson J A
Massachusetts Medical Health Center, Harvard Medical School, 74 Fenwood Road, Boston, MA 02115, USA.
J Cogn Neurosci. 1999 Mar;11(2):182-93. doi: 10.1162/089892999563319.
The notion that dreaming might alter the strength of associative links in memory was first proposed almost 200 years ago. But no strong evidence of such altered associative links has been obtained. Semantic priming can be used to quantify the strength of associative links between pairs of words; it is thought to measure the automatic spread of activation from a "node" representing one word to nodes representing semantically related words. Semantic priming could thus be used to test for global alterations in the strengths of associative links across the wake-sleep cycle. Awakenings from REM and nonREM (NREM) sleep produce a period of state carry-over during which performance is altered as a result of the brain's slow transition to full wakefulness, and cognitive testing in this period can provide information about the functioning of the brain during the prior sleep period. When subjects were tested across the night--before and after a night's sleep as well as immediately following forced awakenings from REM and NREM sleep--weak priming (e. g., thief-wrong) was found to be state dependent (p = 0.016), whereas strong priming (e.g., hot-cold) was not (p = 0.89). Weak primes were most effective in the presleep and REM sleep conditions and least effective in NREM and postsleep conditions. Most striking are analyses comparing weak and strong priming within each wake-sleep state. Contrary to the normal pattern of priming, subjects awakened from REM sleep showed greater priming by weak primes than by strong primes (p = 0.01). This result was seen in each of three protocols. In contrast, strong priming exceeded weak priming in NREM sleep. The shift in weak priming seen after REM sleep awakenings suggests that cognition during REM sleep is qualitatively different from that of waking and NREM sleep and may reflect a shift in associative memory systems, a shift that we hypothesize underlies the bizarre and hyperassociative character of REM-sleep dreaming. Known changes in brainstem activity that control the transition into and maintenance of REM sleep provide a possible explanation of this shift.
做梦可能会改变记忆中联想联系的强度这一观点几乎在200年前就首次被提出。但尚未获得这种改变的联想联系的有力证据。语义启动可用于量化单词对之间联想联系的强度；它被认为是测量激活从代表一个单词的“节点”自动扩散到代表语义相关单词的节点的过程。因此，语义启动可用于测试整个清醒-睡眠周期中联想联系强度的全局变化。从快速眼动（REM）睡眠和非快速眼动（NREM）睡眠中醒来会产生一段状态延续期，在此期间，由于大脑缓慢过渡到完全清醒，表现会发生改变，在此期间的认知测试可以提供有关前一晚睡眠期间大脑功能的信息。当在夜间对受试者进行测试时——在一晚睡眠前后以及在从REM和NREM睡眠中被强制唤醒后立即进行测试——发现弱启动（例如，小偷-错误）具有状态依赖性（p = 0.016），而强启动（例如，热-冷）则不具有状态依赖性（p = 0.89）。弱启动在睡前和REM睡眠条件下最有效，而在NREM睡眠和睡眠后条件下最无效。最引人注目的是在每个清醒-睡眠状态下比较弱启动和强启动的分析。与正常的启动模式相反，从REM睡眠中醒来的受试者表现出弱启动比强启动产生更大的启动效应（p = 0.01）。在三个实验方案中的每一个中都观察到了这一结果。相比之下，在NREM睡眠中强启动超过了弱启动。REM睡眠唤醒后弱启动的变化表明，REM睡眠期间的认知在质上不同于清醒和NREM睡眠期间的认知，可能反映了联想记忆系统的转变，我们假设这种转变是REM睡眠梦境奇异和超联想特征的基础。已知控制进入和维持REM睡眠的脑干活动变化为这种转变提供了一种可能的解释。
