The Development Of Brain Functional Networks In Pre-school Children

Recent years, resting state functional magnetic resonance imaging (rs-fMRI）wasdeveloped based on the traditional fMRI, and it becomes research topics in the field ofneuroscience, nuero and mental disease et al. Early researchers found that the lowfrequen（t<0.1Hz）fluctuation of the blood oxygenation level dependent (BOLD) fMRIsignal was still highly synchronized and correlated in the bilateral motor area.A term “default mode” proposed to describe a baseline or default state of the brain.The core brain areas of default mode are the medial prefrontal cortex (MPFC),posterior cingulate/retrosplenial cortex (PCC/Rsp), and left and right inferior parietallobules (IPLs). In early studies, investigators suggested that, the brain‘s default modesupports self-referential‘‘or introspective‘‘mental activity. Subsequently, regionsof the default network have been more specifically related to the self consciousnessactivities. Research results found two separate default modes of brain function,including task-positive network and task-negative network. However, most ofprevious studies about introspection performed on adults or adolescents. However, sofar, it is still little known about the two separate default modes in young children,especially in pre-school children.We examine both correlations and anti-correlations in spontaneous BOLDfluctuations associated with PCC, the predefined region of interest. Functional MRimages of30healthy preschool children aged at3and5years old were acquired (15children in each age group) while they were in natural sleep state, without anygoal-directed, attention-demanding activity during the scanning sessions. WithROI-based functional connectivity analysis, two separate default mode networks weredetected in very young children. The PCC (BA23/31) and ventral MFPC werecorrelated positively with PCC (centered at [0,-56,30]) in both groups; of note, alarge area of the right prefrontal cortex positively correlated with PCC in5-year old group was observed. That is, more regions in the right prefrontal cortex are cruciallyinvolved so as to complete normal mental or extrospective activities in5years old. In5-year old group, bilateral Angular Gyrus participated in the network, and developedthe frontoparietal network that is probably vital to the introspective network.Presumably, the development of task-negative network in5-year old group isconsistent with the progress of―theory of mind‖in young children, which experiencesa sharp improvement during the period from3to5years old. However, both thefrontoparietal and cinguloopercular connectivity involved in task-positive networkhave basically developed in3-year old. According to the results of LIs, it is notablethat task-negative networks show a trend from left-lateralized to bilateral, and thattask-positive networks show a trend from strongly right-lateralized to bilateral as agegrows. Combined with the large area of the right prefrontal cortex, it is obvious thatmore brain areas in the right cerebral hemisphere are required with the age growing,which signifies both hemispheres make joint contribution to perform special tasks.The increased GMV in5-year old group shows a pattern similar to the comparison offunctional connectivity，and the findings suggest the rapid structural development ofsome brain areas with important cognitive function.