The structure and function of the brain pose the ultimate challenge to human understanding of nature and of themselves. What make human species unique among all living organisms is the brain – its unique capability that allow us to survive in diverse environments, to change the environments to our benefit, and to build a society that accumulates and transmits the learned experience over generations. How do these unique capacities of the human brain evolve within a relatively short period of human evolution? How do these unique capacities emerge from the structure of the human brain? How individual experiences shape postnatal development of diverse capabilities among different human beings? These are some of the outstanding questions that have attracted the attention of scientists over the ages.
In the past century, the research on brain structure and function consists of two major approaches. First, the identification of brain regions responsible for specific brain functions. This was achieved by recognizing the impairment of specific brain functions caused by trauma and diseases that affect specific brain regions in humans and experimental animals. Thanks to the recent advances in non-invasive brain imaging methods, the involvement of different brain regions during the execution of normal human brain functions could now be examined. Second, through anatomical and physiological studies of animal brains at the cellular and tissue level, we have learned the properties and functions of individual building blocks of the brain, the nerve cells, and how neural networks formed by different types of nerve cells can perform elementary functions in sensory processing, motor coordination, and simple cognitive functions. However, despite the enormous progress in these two approaches – the top-down understanding of the localization of brain function and the bottom-up understanding of the nerve cells and neural network functions, there is an enormous gap in our understanding. We do not even know how complex neural networks that composed of millions of nerve cells in your brain perform the simple functions, e.g., remembering the face of your grandmother, recognizing her when you see her, or telling her how much you love her.
As I will describe in this lecture, there is rapid progress in various areas of brain research over the past decade in both our understanding of macroscopic brain functions and microscopic neural circuit properties. Yet, the gap between these two levels of understanding remains largely unfilled, there the mysteries of the brain reside. The task facing brain scientists in the coming decades is enormous, because the solution of the mysteries of the brain requires integration of experimental approaches from diverse disciplines and new conceptual frameworks (which are largely absent at present) that bridge understandings at different levels. Why it is so important to bridge the missing gap between macroscopic and microscopic understanding of the brain? Because this is the goal of modern science - to understand nature is to understand how a natural phenomenon emerges from the properties of its constituent parts. Thus, any description of a neural phenomenon, whether it is at the cognitive, circuit, cellular, or molecular level, is incomplete and unsatisfactory without addressing its causal links to the phenomena at a higher or lower level. Now few neuroscientists are satisfied with the description that certain brain areas are involved in a particular brain function. We need to know the neural circuits underlying the function, the neuron types and synaptic connections shaping these circuits, the neuronal and synaptic properties giving rise to the circuit functions, and the genetic and molecular mechanisms responsible for the development, function, and plasticity of individual neurons and synapses. The advances of brain science introduced in my lecture represent several windows into the secrets of the brain. To crack these secrets are the most exciting and challenging tasks facing scientists of future few generations, including young participants of this WCS Science Camp.
對大腦結構與功能的理解是人類認知自然界及自身的終極挑戰。大腦以其卓絕的能力使人類能夠在各種環境下生存，能改造自然以趨利避害，並且能建立一個能將知識進行積累和傳承的社會形態；因此，正是大腦使得人類能夠從萬物中脫穎而出。人類大腦這些獨特的能力是如何在一個相對較短的進化過程中演化而來的呢？這些獨特的能力又是如何在大腦結構的基礎上產生的呢？因人而異的經歷如何塑造了個人不同的個性與能力呢？這些有意思的問題已讓科學家們著迷多年。
在過去的一個世紀中，主要通過兩種途徑對大腦的結構和功能進行了研究。第一種途徑是去發現特定的腦功能是由哪些腦區負責的。以前，這一途徑是通過識別人類（實驗動物）中針對特定腦區的腦損傷或腦疾病會對哪些特定腦功能造成傷害而實現的。而如今，得益於近期腦成像技術所取得的進展，已經實現對參與了執行正常腦功能的各個腦區非侵入性的識別。在第二種途徑中，通過對動物大腦在細胞層次的解剖學和生理學研究，我們不僅了解了構建大腦的基石--神經細胞的特性和功能，而且了解了由特定神經細胞組成的神經網絡如何能夠進行感覺信號處理中運動的協調和一些簡單的認知功能。雖然這兩種途徑取得的巨大進展實現了自上而下（top-down）的對腦功能定位的了解，以及自下而上（bottom-up）的對神經細胞和神經網絡功能的理解；在這兩層面的了解之間仍然存在著一個巨大的溝壑。我們甚至還不清楚在我們腦中由成千上萬個神經元組成的神經網絡具體是如何實現一些簡單的功能。比如說如何記住你奶奶的面容，下次見到她時如何能認識她，或者告訴她你愛她。
在過去的數十年中，不論是對宏觀腦功能還是微觀神經環路特性的理解，腦科學研究在各個領域均取得了快速的進展。然而，這兩個層次的研究之間的溝壑仍然有待填補，而那裡正是大腦奧秘的所在。在未來數十年中，腦科學家將要面對大量而困難的工作，因為揭開大腦奧秘需要整合不同學科的實驗手段和一些新的概念構架（目前這些基本還沒有）來聯繫在不同層次對大腦的了解。為什麼在大腦的宏觀和微觀理解之間那尚未填補的溝壑上架起一座橋樑是如此重要呢？因為這是現代科學的目標— 理解自然就是要理解一個自然現像如何從它組成部分的特性中呈展產生。所以，任何從認知、環路、細胞‧分子等單一層次上對一個神經的現象進行的描述，若不能聯繫上與更高或更低層次上的因果關係，這種描述都是不完整的，也不可能令人滿意。目前，神經科學家對某些腦區參與了某個特定腦功能的這種描述已不會感到滿意。我們更需要知道的是實現這些腦功能的神經環路，神經元類型和塑造這些神經環路的突觸聯繫方式，以及負責這些個體神經元發育、功能和可塑性的遺傳和分子機制。如何破解這些大腦的奧秘正是未來幾代人，可能您自己，所要面對的最令人興奮和最具挑戰性的任務。
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