Variability Difference Of Functional Activity Between Gyri And Sulci Based On FMRI

One of the most prominent morphological features of the cerebral cortex is its highly convoluted surface into convex gyri and concave sulci.In the past decades,extensive studies have consistently revealed substantial differences between gyri and sulci in terms of genetics,anatomy,morphology,axonal fiber connections and function,which reflect the close relationship between brain structure and function.With the fast development of functional neuroimaging techniques such as magnetic resonance imaging(MRI),the study of functional differences between gyri and sulci using the non-invasive in vivo functional MRI(fMRI)has gained increasing interests in recent years.However,to the best of our knowledge,the existing studies on the functional differences between gyri and sulci have the following four limitations:(1)Previous studies assumed the temporal stationarity of fMRI signals during the scanning,while ignoring the variability of brain functional activity.Therefore,it is not clear whether there is variability difference of functional activity between gyri and sulci.(2)Although interesting findings have been reported that the variability of functional activity is associated with individual difference in learning and higher-order cognitive functions,the relationship between the functional characteristics in gyri/sulci and cognitive function and behavior remains to be explored.(3)Previous studies focused on the intrinsic or task-induced gyral/sulcal functional differences based on resting state fMRI or task-based fMRI,while such difference under natural stimulus fMRI remains unclear.(4)Previous studies used 3T fMRI data to explore the functional differences between gyri and sulci,while the reproducibility of such difference remains to be verified using 7T fMRI data.In order to address the above four limitations,this study firstly adopted the 3T resting state fMRI from 819 subjects in the publicly released Human Connectome Project(HCP)S900 data to analyze the intrinsic gyral-sulcal variability at global and local scales,respectively.Secondly,the correlation and elastic network regression model were used to analyze the relationship between the intrinsic gyral-sulcal variability and certain behavioral and cognitive scales at global and local scales,respectively.Finally,the gyralsulcal variability under natural stimulus as well as such difference compared to resting state were analyzed based on the 7T resting state and natural stimulus(movie-watching)fMRI data from 171 subjects provided by HCP.Experimental results found that,at the global scale,the cortical gyral variability was significantly larger than sulcal one,and the vertices showing significant correlation with fluid intelligence located more on gyri than on sulci.At the local scale,the gyral variability was significantly larger than sulcal one in the neocortex,while significantly smaller than sulcal one in the limbic cortex.Next,by using the gyral-sulcal variability to predict 30 behavioral and cognitive scales provided by HCP through the elastic net regression model,there were five scales(fluid intelligence,crystallize cognition,hand grip strength,dexterity and sleep quality)that were effectively predicted.Moreover,there were differences in the gyral and sulcal weighting coefficients for the prediction of those behavioral cognitive scales,reflecting the different involvement of specific brain regions with different cognitive behaviors.In addition,there were significant differences of gyral-sulcal variability in specific brain regions during natural stimulus state.Furthermore,such difference scale was smaller than that of resting state in DMN(default mode network)regions,while larger in movie-watching related brain regions.Moreover,same results were found in the 7T resting state fMRI as in the3 T one,indicating that the intrinsic gyral-sulcal variability differences were not affected by the magnetic field strength.In summary,this study systematically investigated the variability differences of functional activity between gyri and sulci,as well as their relationship with specific behavioral and cognitive scales based on different fMRI data modalities(resting state and natural stimulation)and different magnetic field strengths(3T and 7T).It provides a solid foundation for better understanding of the functional differences between gyri and sulci in the future,and a novel insight to explore the role of such gyral-sulcal functional differences in the working mechanisms of the brain.