Modification of Sulcal Geometry Reconstruction Results Based on Spherical Harmonics Coefficients

This paper describes a modeling approach for 3D brain reconstruction that may be useful for controlled studies of these approximate effects. The general approach is to model the brain surface with spherical harmonic expansion and then modify the expansion coefficient to selectively and smoothly control the groove width. This paper first describes and evaluates a method for experimentally selecting two sets of spherical harmonic coefficients in a specified range that can simultaneously affect selected gyro samples. For the coefficients in the first set, the widths of all gyroscopes in the sample are increased by enlarging the corresponding coefficients for each spherical harmonic, but for each coefficient in the second set, this adjustment results in a simultaneous decrease in the width of the sampling gyroscope. The experimental results show that most of the sulcus and gyrus widths are simultaneously adjusted according to the desired effect. At the same time, this paper attempts to construct a volumetric mesh starting from a modified spherical harmonic surface, which proved to be particularly challenging since most surface models in our study have self-intersection points. We used a well-known mesh processing package (ISO2Mesh) to successfully remove all self-intersects from the surface, but this process seems to create small holes on the model surface. Despite these holes, with a few exceptions, the width of most of the grooves (gaps) still increases (decreases) simultaneously with the adjustment of the coefficients. This result provides a direction for further research on the influence of controlling partial volume problem on tCS modeling.