Using brain images of people listening to short symphonies by an obscure 18th-century composer, a research team from the Stanford University School of Medicine has gained valuable insight into how the brain sorts out the chaotic world around it. Beyond understanding the process of listening to music, their work has far-reaching implications for how human brains sort out events in general. The researchers caught glimpses of the brain in action using functional magnetic resonance imaging, or fMRI, which gives a dynamic image showing which parts of the brain are working during a given activity. The goal of the study was to look at how the brain sorts out events, but the research also revealed that musical techniques used by composers 200 years ago help the brain organize incoming information. "In a concert setting, for example, different individuals listen to a piece of music with wandering attention, but at the transition point between movements, their attention is arrested," said the paper's senior author Vinod Menon, PhD, associate professor of psychiatry and behavioral sciences and of neurosciences. "I'm not sure if the baroque composers would have thought of it in this way, but certainly from a modern neuroscience perspective, our study shows that this is a moment when individual brains respond in a tightly synchronized manner," Menon said. The team used music to help study the brain's attempt to make sense of the continual flow of information the real world generates, a process called event segmentation. The brain partitions information into meaningful chunks by extracting information about beginnings, endings and the boundaries between events. "These transitions between musical movements offer an ideal setting to study the dynamically changing landscape of activity in the brain during this segmentation process," said Devarajan Sridharan, a neurosciences graduate student trained in Indian percussion and first author of the article. No previous study, to the researchers' knowledge, has directly addressed the question of event segmentation in the act of hearing and, specifically, in music. To explore this area, the team chose pieces of music that contained several movements, which are self-contained sections that break a single work into segments. They chose eight symphonies by the English late-baroque period composer William Boyce (1711-79), because his music has a familiar style but is not widely recognized, and it contains several well-defined transitions between relatively short movements. The study focused on movement transitions - when the music slows down, is punctuated by a brief silence and begins the next movement. These transitions span a few seconds and are obvious to even a non-musician - an aspect critical to their study, which was limited to participants with no formal music training. The researchers attempted to mimic the everyday activity of listening to music, while their subjects were lying prone inside the large, noisy chamber of an MRI machine. Ten men and eight women entered the MRI scanner with noise-reducing headphones, with instructions to simply listen passively to the music. In the analysis of the participants' brain scans, the researchers focused on a 10-second window before and after the transition between movements. They identified two distinct neural networks involved in processing the movement transition, located in two separate areas of the brain. They found what they called a "striking" difference between activity levels in the right and left sides of the brain during the entire transition, with the right side significantly more active. In this foundational study, the researchers conclude that dynamic changes seen in the fMRI scans reflect the brain's evolving responses to different phases of a symphony. An event change - the movement transition signaled by the termination of one movement, a brief pause, followed by the initiation of a new movement - activates the first network, called the ventral fronto-temporal network. Then a second network, the dorsal fronto-parietal network, turns the spotlight of attention to the change and, upon the next event beginning, updates working memory. "The study suggests one possible adaptive evolutionary purpose of music," said Jonathan Berger, PhD, professor of music and a musician who is another co-author of the study. Music engages the brain over a period of time, he said, and the process of listening to music could be a way that the brain sharpens its ability to anticipate events and sustain attention. According to the researchers, their findings expand on previous functional brain imaging studies of anticipation, which is at the heart of the musical experience. Even non-musicians are actively engaged, at least subconsciously, in tracking the ongoing development of a musical piece, and forming predictions about what will come next. Typically in music, when something will come next is known, because of the music's underlying pulse or rhythm, but what will occur next is less known, they said. Having a mismatch between what listeners expect to hear vs. what they actually hear - for example, if an unrelated chord follows an ongoing harmony - triggers similar ventral regions of the brain. Once activated, that region partitions the deviant chord as a different segment with distinct boundaries. The results of the study "may put us closer to solving the cocktail party problem - how it is that we are able to follow one conversation in a crowded room of many conversations," said one of the co-authors, Daniel Levitin, PhD, associate professor of psychology and music from McGill University, who has written a popular book called This Is Your Brain on Music: The Science of a Human Obsession. These findings will be published in the Aug. 2 issue of Neuron. | 斯坦福大学医学院的研究人员利用大脑成像技术，研究 18 世纪一位人们不太熟悉的作曲家的交响乐对听众大脑的影响，对大脑如何从周围杂乱的世界中获得有意义的信息这一问题，获得了有价值的理解。 该研究团队发现音乐影响大脑涉及注意力、预期和更新记忆的区域。大脑的活动高峰发生在音乐段落之间短暂的停顿期，这段时间表面上似乎什么也没发生。 除理解大脑听音乐的过程之外，他们的工作对理解人类大脑在一般情况下如何获得有意义的信息这一问题具有深远的意义。 研究者通过功能核磁共振成像技术（fMRI）观察活动中的大脑。研究者利用该技术能够获得在指定的活动过程中大脑的动态图像，以确定大脑的活动区域。该项研究的目的是了解大脑如何理解外界事件，同时，研究也发现 200 年前作曲家采用的音乐技巧有助于大脑组织来自外界的信息。 “在音乐厅里，每个听众欣赏音乐时的注意力都是游移的，但是在音乐段落之间的停顿期，他们的注意力被吸引了，” 文章的主要作者 Vinod Menon 博士说，他是精神病与行为科学以及神经科学副教授。 “我不知道巴洛克风格的作曲家是否有意为之，但是从现代神经科学的观点来看确定无疑，我们的研究表明，这一时刻不同听众的大脑以一种密切同步的方式作出反应，” Menon 说。 该研究小组利用音乐来帮助研究大脑如何赋予现实世界产生的连续信息流以明确意义。这一过程称为事件分割。通过获取关于开始、结束和事件间分界的信息，大脑将连续信息分割成有意义的片段。 “音乐段落之间的停顿期提供了一个理想的机会来研究在事件分割过程中，大脑活动动态变化的图景，” 神经科学研究生 Devarajan Sridharan 说，他学习过印第安打击乐器，是文章的第一作者。 据该项研究的科研人员所知，此前还没有研究者直接研究听觉活动中，特别是听音乐过程中的事件分割过程。为了探索该领域，该科研小组选择了几支包含若干乐章的音乐，每段乐章本身又分成了若干片段。他们选择由英国后巴洛克时期作曲家 William Boyce (1711-1779) 谱曲的八支交响乐。因为他的音乐具有大家熟悉的风格但是并未广泛流传，同时也因为他的音乐在小段落之间具有清晰的停顿期。 该项研究关注音乐段落之间的停顿--当音乐慢下来，接着是短暂的停顿期，然后又开始新的段落。这些停顿持续几秒钟，对于没有受过音乐训练的人来说也是非常明显的--这对他们的研究非常关键，研究对象仅限于没有受过正式音乐训练的人。 研究人员想要模拟日常听音乐的环境，他们的研究对象俯卧在一个大的，充满噪声的 MRI 机房间里。十个男性和八个女性带着降噪耳机接受了MRI 扫描，并按照指示简单被动地接受音乐。 在分析大脑扫描图像过程中，研究人员集中研究音乐停顿期十秒和后十秒的图像。他们找到了两个不同的因音乐停顿而产生反应的神经网络，分别位于大脑的两个不同区域。在整个停顿期，他们发现大脑左右区域活动级别显著不同，右边区域更为活跃。 在这项基础研究中，研究人员认为，在 fMRI 扫描图像中的动态变化反映了大脑对交响乐不同段落作出的动态响应。当某个事件发生变化-- 音乐停顿 -- 将激活第一个网络，称为背侧额叶-顶叶网络（ ventral fronto-temporal network）。接着，第二个网络，称为腹侧额颞网络（ dorsal fronto-parietal network），将注意力集中于这一改变，并且在下一事件的开始时更新记忆。 “该项研究提出了音乐的一个可能的适应演化功能， ” Jonathan Berger 博士说，他是音乐教授兼作曲家，也是该项研究的合作者之一。他说，让大脑沉浸在音乐中一段时间，听音乐的过程能够加强大脑预测事件和维持注意力的能力。 研究人员声称，他们的发现扩展了先前有关预期的大脑功能成像的研究，这是音乐体验的核心。即使没有受过正规音乐训练的人，至少在潜意识里，也会积极去追随乐章发展的轨迹，并且形成对下一个的音符的预测。他们指出，在欣赏音乐时，人们知道下个音符会什么时候出现，因为音乐具有基本的节率，但下一个音符是什么人们却知之甚少。 如果所预期的和实际听到的不匹配--比如，将一个不相关的音符插入到一段和谐的音乐当中--同样会触发背侧额叶-顶叶网络（即上面提到的第一个网络）。一经触发，该网络会将那个不协调的音符归于带有明显边界的另外的片段中。 该项研究的结果可能使我们进一步理解“鸡尾酒会问题”--为什么我们能够在一个拥挤吵杂的房间进行谈话而不会受其他人谈话的影响--合作者之一，来自 McGill 大学心理学和音乐副教授， Daniel Levitin 博士说，他写过一本畅销书《欣赏音乐的大脑：为什么会着迷？》（This Is Your Brain on Music: The Science of a Human Obsession）。 这些研究发表在2007年8月2日出版的《神经元》（Neuron）杂志上。 |
