工具的制造和使用对于人类的生存具有重要意义，也一直被认为是现代智人区别于其它动物的显著特征之一。与人类复杂的工具制造、使用能力相对应，人类加工工具类客体的脑网络基础是怎样的？这一问题一直为心理学和认知神经科学等学科所关注。我们从两个方面来对此进行考察，一方面，成人加工工具类客体具有怎样的脑网络模式？先前研究发现成人在皮层区域存在对于工具类客体特异性加工的脑网络。考虑到工具制造和使用对于人类的重要意义，工具类客体脑网络模式是否涉及更广泛的区域？具体来说，对于皮下区域是否存在对于工具类客体的特异性激活，及其与皮层区域之间存在怎样的连接模式（脑网络）缺乏考察。另一方面，成人加工工具类客体的脑网络是如何形成的，受先天(Nature)还是后天(Nurture)影响？有多个相关但有差异的角度可以对该问题进行回答：系统发育(phylogeny)，个体发育(ontogeny)以及遗传。先前研究发现成人对于工具的加工在区域（即顶下小叶）水平有物种特异性基础，但缺乏网络水平的研究。对于工具类客体脑网络是否已经在人类新生儿中存在以及是否受到遗传影响，当前缺乏相关研究证据。从上述几个角度出发，我们的研究主要检测人类的工具类客体脑网络是否受先天影响。如果人类工具类客体脑网络具有一定的物种特异性基础（跨物种比较分析）、在发育早期阶段存在（人类新生儿脑网络结构解析）、受遗传影响（双生子遗传学研究）则表明和先天相关。在先天还是后天影响框架下，我们也关注工具与其它人类核心认知能力间关系，以增加对于工具加工的进一步理解。语言的大脑加工也受到先天因素影响，那么大脑对工具类客体的加工及对语言的加工是否受到共同的先天因素影响？具体而言，是否存在大脑区域在工具加工与语言加工时受到共同遗传因素影响尚且不知。回答这一系列问题，可以更加深入地理解人类加工工具类客体的脑网络基础。同时，以工具加工为切入口，帮助我们更好地理解在演化过程中大脑的相关规律，更好地理解“何以为人”。

针对上述研究问题及现状，本论文通过系列实验设计及分析，试图系统性探究人类加工工具类客体的脑网络基础。具体来说，本论文五个研究分别是：

研究一：成人的工具类客体脑网络模式识别。本研究通过多个功能磁共振激活实验、静息态功能连接数据以及任务态动态因果分析，对成人的工具类客体脑网络模式进行识别。具体来说，我们考察皮下区域丘脑枕是否存在对于工具类客体的特异性激活，刻画其激活模式以及其与皮层区域间的连接模式（脑网络）。结果显示工具类客体（对比其它客体范畴），在丘脑枕存在特异性激活，且表现出左半球偏侧化激活模式。静息态功能连接分析发现丘脑枕和工具类客体皮层加工区域间的连接模式与丘脑枕对工具类客体的激活模式间存在显著相关。任务态动态因果分析表明丘脑枕不只接受皮层信息，也传递信息至皮层区域。特别是丘脑枕与顶叶间，存在着从丘脑枕到顶叶区域传递的优势效应。本研究表明与人类复杂的工具制造与使用能力相适应，成人大脑存在专门的工具类客体加工脑网络。其涉及脑区包括皮下区域，它们呈现出与成人的工具类客体皮层加工区域相似的偏侧化特点，与皮层加工区域一起构成成人的工具类客体脑网络。

研究二：工具类客体静息态脑网络跨物种比较分析。本研究通过跨物种配准手段将成人大脑的工具类客体皮层加工区域配准得到猕猴大脑的工具类客体（同源）区域，考察这些区域间的静息态功能连接模式。结果显示，在猕猴大脑中不存在独立的工具类客体（同源）脑网络。同时，工具类客体（同源）区域间网络拓扑模式在猕猴与任一人类群体间相似性均显著低于人类不同群体间相似性。进一步地，额叶运动前回与顶叶之间连接在猕猴与人类群体间最不相似。表明成人的工具类客体脑网络具有一定的物种特异性基础，特别是运动前回与顶叶之间连接对此起到重要作用。

研究三：人类新生儿工具类客体静息态脑网络的结构解析。本研究通过跨群体配准手段将成人大脑的工具类客体皮层加工区域进行配准得到人类新生儿的工具类客体（同源）区域，考察和比较这些区域间的静息态功能连接模式。结果显示，在人类新生儿大脑中，存在着与成人类似的工具类客体（同源）网络。同时，工具类客体（同源）区域间网络拓扑模式在成人和人类新生儿群体间具有很高的相似性。进一步地，额叶运动前回与顶叶之间连接在成人和人类新生儿间最相似。表明人类在有个体经验前，已经存在工具类客体脑网络原型，运动前回与顶叶间连接对此起到重要作用。

研究四：基于双生子的工具类客体脑网络遗传学研究。本研究采用双生子研究设计，结合公开数据库中功能磁共振数据及静息态功能连接数据，考察成人的工具类客体脑网络是否受到遗传影响。结果显示，成人的工具类客体脑网络受到遗传影响，特别是额叶与顶叶间连接表现出遗传作用趋势。进一步地，功能激活分析发现，大脑对于工具类客体激活模式也存在遗传作用，这种遗传作用既包含皮层区域，也包含皮下区域。该研究表明成人的工具类客体脑网络具有受遗传影响的特点。 

研究五：成人大脑工具加工与语言加工的共同遗传作用研究。本研究采用双生子设计，结合多套任务态功能磁共振数据，来考察是否存在区域对工具类客体的加工和对语言的加工受到共同遗传作用影响。结果显示，对于双侧基底节，存在对于语言、工具类客体及身体部位激活的遗传作用；对于右半球颞上回，存在对于语言及工具类客体激活的遗传作用。进一步模型分析表明，这些区域存在对于语言及工具的共同成份的遗传作用。该研究表明成人对于工具的加工在演化过程中可能存在着与其它人类核心认知能力（语言）的密切交互，它们相互影响，共同帮助人类适应环境。

基于上述发现，本论文更深入地回答了人类加工工具类客体的脑网络基础问题。与人类复杂的工具制造与使用能力相适应，成人大脑存在专门的工具类客体脑网络。该网络不仅包含皮层区域，也包含皮下区域。在网络形成问题上，成人的工具类客体脑网络受到先天因素影响，具有如下具体特点：具有一定的物种特异性基础、在发育早期阶段已经开始出现、受遗传影响。特别地，除工具加工自身外，本论文进一步发现存在对于工具加工与语言加工有共同遗传作用的大脑区域。本论文的发现一定程度支持和拓展了关于客体加工的反应映射假说，即人类具有独特且复杂的工具制造和使用行为系统，支持该系统的皮层-皮下脑网络在演化过程中具有先天性特点，表现出具有一定的物种特异性基础、在发育阶段早期已经开始出现、受遗传影响等特点。支持该反应系统的知觉系统在演化过程中与其它人类核心认知能力（语言）存在共享的认知成分。本论文的发现也加深了对于人类大脑演化的理解，即以工具类客体为切入点，为研究其它人类核心认知能力脑网络的形成提供启发与借鉴作用，更好地刻画大脑相应的演化规律，同时也促进了客体加工相关理论的发展。

Tool making and tool use are crucial for human survival and have long been argued to be unique to homo sapiens. Accordingly, what is the brain network underlying tool object processing? This issue has long been of interest to fields such as psychology and cognitive neuroscience. We investigated this question from two perspectives. Firstly, what is the brain network pattern in human adults engaged in processing tool objects? According to previous research, human adults exhibit cortical brain networks specific to tool objects. Considering the significant impact of tool making and use on human evolution, it raises the question whether the tool-processing network includes more widespread areas. Do subcortical regions also respond specifically to tool objects? Are there connections between subcortical and cortical regions? Secondly, how does the tool-processing network form, and is it influenced by nature or nurture? This can be approached from various perspectives, each with its unique but interconnected aspects: phylogeny, ontogeny, and a genetic perspective. Prior research has found a species-specific basis for the processing of tools in the inferior parietal lobule, but there is a lack of research at the network level. Meanwhile, there is currently a lack of evidence regarding whether the tool-processing (homologous) network already exists in human neonates and is influenced by genetics. From the above-mentioned perspectives, our research mainly aims to investigate whether the tool-processing network is influenced by nature. The existence of a species-specific basis (from a phylogenetic perspective), existence in early developmental stages (from an ontogenetic perspective), and the potential influence of genetics (from a genetic perspective) all suggest an association with nature. In addition to the tool-processing network itself, our research also explores the relationship between tool abilities and other key cognitive abilities in humans. Since language ability is known to be influenced by nature, do the tool-processing and language-processing in the human brain share common natural factors? Specifically, we aim to determine whether certain brain regions share common genetic factors that contribute to both tool processing and language processing. Answering this series of questions can enhance our comprehension of brain mechanisms involved in processing tool objects and provide insights into the evolution of the brain.

In response to the above research questions, this paper proposes a series of experimental designs and analyzes to systematically explore the brain network underlying tool processing. In summary, this paper includes five studies:

Study 1: Human adult tool-processing brain network pattern recognition. This study identified the pattern of the adult tool-processing brain network through multiple fMRI experiments, resting-state functional connectivity data, and task-based dynamic causal model analysis. Specifically, we examined whether the subcortical region (i.e., pulvinar) shows significant, consistent activity patterns specifically associated with tools, and whether it is functionally connected with corresponding tool-processing cortical regions. The results showed that, compared to other object domains, tools elicited specific activation in the subcortical region, with left hemisphere lateralized activation pattern. Resting-state functional connectivity analysis revealed a significant correlation between the cortico-pulvinar connectivity and the pulvinar activation pattern for tools. Task-based dynamic causal model analysis revealed that the subcortical regions not only received information from cortical regions, but also transmitted information to cortical regions. Particularly, there was a prominent effect in the transmission from the subcortical region (i.e. pulvinar) to the parietal region. Together, these results demonstrate that a specialized tool-processing brain network exists in the human adult brain, including the subcortical regions that exhibit lateralization similar to those of tool-processing cortical regions. This specialized network is necessary to human complex tool making and use.

Study 2: Cross-species comparative analysis of tool-processing resting-state brain network. In this study, we used cross-species registration methods to register the tool-processing cortical regions in human adult brains to macaque brains. The resulting homologous regions in macaque brains allowed us to investigate the resting-state functional connectivity pattern between tool-processing areas. The results showed that there was no independent tool-specific brain network in the macaque brain. Additionally, the network topology pattern was significantly less similar between macaques and any human group compared to that between different human groups. Moreover, the connection between the premotor gyrus and the parietal was the least similar between macaques and human populations. These findings suggest that there is a species-specific basis for the adult tool brain network, and the connection between the premotor gyrus and the parietal plays an important role in this specificity.

Study 3: Analysis of the tool resting-state brain network in human neonates. In this study, we registered the tool-processing cortical regions in human adult brains to human neonate brains, to examine and compare the resting-state functional connectivity patterns between these areas. The results showed that there was a homologous network underlying tool processing in the neonatal brain, similar to that in adults. Moreover, the network topology patterns were highly similar between human adults and human neonates. Additionally, the connection between the premotor gyrus and the parietal was most similar between adults and human neonates. This finding indicates that there is a tool-processing brain network prototype in humans before individual experience, and the connection between the premotor gyrus and the parietal plays an essential role in developing this prototype.

Study 4: Twin-design based genetic research on the tool-processing brain network. In this study, we used the twin research design, along with fMRI data and resting-state functional connectivity data from public databases, to investigate whether the adult tool brain network is genetically influenced. The results showed that the adult tool brain network was indeed genetically influenced, particularly in the connection between the frontal and parietal lobes. Additionally, the functional activation analysis showed that there was a genetic influence on the activation pattern for tools, which included both cortical and subcortical regions. Together, these findings suggest that the adult tool-processing brain network is genetically influenced.

Study 5: Shared genetic effect on the tool processing and language processing in adult brains. In this study, we utilized a twin research design, in combination with multiple task-based fMRI data, to investigate whether there was shared genetic effect on the activation of language and tools for some regions. The findings revealed the existence of genetic influence on the activation of the bilateral basal ganglia regions for tools, language and body parts, and the right superior temporal gyrus region for tools and language. Further common path model analysis indicated that these regions shared genetic components for language processing and tool processing. These results suggest that adult tool ability may have played a critical role in the evolution of human cognition and its interaction with other core cognitive abilities, such as language, which in turn helped humans adapt to their environment.

Based on the findings above, the present paper has provided a comprehensive understanding of the dedicated tool-processing brain network in the adult human brain. In light of the complex tool making and use of humans, a dedicated tool-processing brain network exists in the adult brain, including both cortical and subcortical areas. The adult tool-processing brain network is influenced by innate factors and has specific characteristics such as a species-specific basis, early-developmental-stage appearance, and genetic influence. Interestingly, this paper also reveals that there are shared genetic effects between tool processing and language processing within certain brain regions. These findings support and expand the response system mapping hypothesis, which argues that human possess a cortical-subcortical brain network underlying unique and complex tool-making and use behavior. The network is influenced by nature in a species-specific, early-development-stage-appeared, and genetically-influenced manner. Additionally, the perceptual system supporting this response system shares cognitive components with other human core cognitive abilities, including language ability during evolution. Moreover, this paper deepens our comprehension of human brain evolution, characterizes the brain's evolutionary laws better, and leads to a more profound understanding of what it means to be human.