We’re all familiar with songs getting stuck in our head while we’re awake, but it turns out this can happen during sleep as well. A new study investigating the phenomenon indicates that earworms invading our brains at night could cause problems in getting to sleep and staying asleep.

“Our brains continue to process music even when none is playing, including apparently while we are asleep,” says neuroscientist Michael Scullin from Baylor University.

He and colleagues used surveys of 199 people, as well as a sleep lab test involving 50 volunteers, to measure how listening to music before bedtime affects sleep. In particular, the team focused on catchy earworms, technically known as “involuntary musical imagery.”

In the survey part of the study, participants who frequently listened to music during the day were more likely to report persistent nighttime earworms, which then had a negative effect on sleep quality through the night.

For the lab test, individuals were played instrumental or standard versions of “Shake It Off” by Taylor Swift, “Call Me Maybe” by Carly Rae Jepsen, and “Don’t Stop Believin’” by Journey. Polysomnography tests were used to measure subsequent sleep quality.

Earworms were reported throughout the night by participants, with those catching an earworm taking longer to fall asleep, spending more time in the light stages of sleep, and waking up more times during the night. Surprisingly, the instrumental versions of the songs caused about twice as many earworms (and more subsequent sleep problems) than the versions with vocals.

“We thought that people would have earworms at bedtime when they were trying to fall asleep, but we certainly didn’t know that people would report regularly waking up from sleep with an earworm,” says Scullin. “But we saw that in both the survey and experimental study.”

Brain scans showed more slow oscillations during sleep in the people who reported getting an earworm — a sign of memory reactivation. The brain region involved, the primary audio cortex, is also linked to earworm processing when people are awake.

Past studies have linked late-night music listening with better sleep in those with insomnia, perhaps because it can relax the body. The researchers behind the new study suggest that actually it might be worse for our sleep — that even after the tunes stop, our brains continue to process them for several hours.

Words to Learn 相关词汇

【振波】 zhènbō oscillation a flow of electricity changing periodically from a maximum to a minimum

【失眠】shīmián insomnia a common sleep disorder that can make it hard to fall asleep, hard to stay asleep, or wake up too early

我们在清醒时应该都有过歌曲旋律在大脑中挥之不去的经历，但事实证明，这种“耳虫”现象在睡觉时也会出现。针对这一现象的新研究表明，夜里“入侵”大脑的耳虫可能会导致睡眠问题，让人睡不安稳。

贝勒大学的神经科学家迈克尔•斯卡林说：“即使外界没有播放音乐，我们的大脑也会继续处理音乐，包括睡觉的时候。”

为了衡量睡前听音乐对睡眠的影响，斯卡林和同事们调查了199个人，并对50名志愿者开展了睡眠实验。研究小组特别关注所谓的洗脑神曲，学名叫作“被动音像"。

调查发现，白天经常听音乐的参与者更有可能在夜里“耳虫上脑”，而夜间耳虫会对一整晚的睡眠质量造成负面影响。

在实验室测试中，研究人员为参与者播放了泰勒•斯威夫特的《摆脱》、卡莉•雷•杰普森的《打电话给我》和Journey乐队的《不要放弃信念》，并使用多导睡眠监测来评测他们接下来的睡眠质量。

据参与者报告，一整晚都有耳虫现象出现，那些耳虫上脑的人需要更长时间才能入睡，浅睡眠时间更长，而且夜里醒来的次数更多。令人惊讶的是，混声版本的歌曲引发的耳虫现象次数是人声演唱版本的两倍左右，导致的睡眠问题也更多。

斯卡林说：“我们原以为，人们在试图入睡时会被耳虫困扰，但是我们不知道，人们在夜里会时常被耳虫吵醒。但是我们从调查和实验中都发现了这一点。”

大脑扫描显示，自称遭遇耳虫困扰的人在睡眠期间大脑出现更多慢速振动，这是记忆被重新激活的迹象。所涉及的大脑区域是初级听觉皮层，这也是人们清醒时大脑处理耳虫的相关区域。

过去的研究曾将深夜听音乐与改善失眠者的睡眠质量联系在一起，这或许是因为听音乐可以让身体放松。这项新研究背后的研究人员指出，实际上，睡前听音乐可能对我们的睡眠更不利，因为即使在曲子停止播放后，我们的大脑仍会花数个小时继续对其进行处理。

(chinadaily.com.cn)