Mind Wandering And Its Neural Correlates

We individuals' mind are always occupied with some internal representations,which generate involuntarily and unrelated to the immediate environment and the task we are doing. We call this process "Mind Wandering". Mind wandering is a very universal conscious phenomenon, and it's existence show that besides reacting to the external world and the immediate task, the individual's cognitive system has many spontaneous and involuntary internal processing and which play a big role in mind. The research about mind wandering has important meaning in exploring the structure and mechanism of consciousness and understanding the operation manner of our cognitve system and internal spirit world. Furthermore, the study about the neural correlats of mind wandering ,especially its relationship to the resting brain and the Default Network of brain, will facilitate the understanding of the working manner of brain.Ignoring the nature of mind wandeing and studing its corresponding brain work without the understanding of its characteristic is the most dinstinct shortcoming in the research about mind wandering . We study mind wandering from a new point of view and adopt some new method, deconstructing the mind wandering and analyzing its core feature, and developing simulative mind wandeing experiments corresponding to its main elements, and reaching to the brain activation map of every element. We integrate the result of these simultive experiment and come to the general understanding about the neural correlats of mind wandering , and discuss the role of the Default Network during mind wandering.Our study include four parts. First, we sample the experience of mind wandering in nature circumstance and resting state by experience-sampled method, and obtain the main components and its corresponding feature of mind wandering. Then we design three simultative mind wandering fMRI experiments corresponding to its main components: involuntary episodici thinking, involuntary inner speech and involuntary visual imagery.The main findings of this study are as follows:1) Mind wanding is an universal phenomenon. More than 30% conscious experience in nature circumstance and more than 80% conscious experience in resting state are occupied with mind wandering, and task and other environmental stimuli can not prevent its happening. Human individuals have the tendency to process the internal information spontaneously, involuntarily and constantly. Mind wandering in daily lift and resting state have similar characteristic: a) Mind wandering is a compound cogntitive process composed of multiple elements, and the main components are involuntary episodic thinkng, involuntary inner speech and involuntary visual imaery. And involuntary episodic thinking is the predominate process;b) There is some clue causing mind wandering including external stimuli and internal processing;c) There is close relationship between mind wandering and individuls experience.2) The brain regions activated in our simulative mind wandering are as follows:a) PCC, parahippocamal gyrus and left precuneus are activated in involuntary episodic thinking;b) The region between left precuneus and PCC is activated during involuntary inner speech;c) Occipital asscioatve cortex(BA19), left precuneus and PCC are activated in involuntary visual imagery;d) PCC has important role in the involuntary emergence of internal information.3) The Default Network and mind wanderingThe activation of brain's default network during resting state is related to mind wandering. The core hub of default network-PCC-particpates in the main components of mind wandering and we suggest that PCC is important in the involuntary emergence of internal information, and the parahippocampal gyrus participates the predominant process of mind wandering-episodicthinking.