“…An affinity matrix was constructed with a normalized angle kernel, and eigenvectors were estimated via diffusion map embedding ( Figure 1A ), a nonlinear dimensionality reduction technique ( Coifman and Lafon, 2006 ) that projects connectome features into low-dimensional manifolds ( Margulies et al, 2016 ). This technique is only controlled by a few parameters, computationally efficient, and relatively robust to noise compared to other nonlinear techniques ( Errity and McKenna, 2007 ; Gallos et al, 2020 ; Hong et al, 2020 ; Tenenbaum et al, 2000 ), and has been extensively used in the previous gradient mapping literature ( Hong et al, 2019 ; Hong et al, 2020 ; Huntenburg et al, 2017 ; Larivière et al, 2020a ; Margulies et al, 2016 ; Müller et al, 2020 ; Paquola et al, 2019a ; Park et al, 2021b ; Valk et al, 2020 ; Vos de Wael et al, 2020a ). It is controlled by two parameters α and t , where α controls the influence of the density of sampling points on the manifold (α = 0, maximal influence; α = 1, no influence) and t controls the scale of eigenvalues of the diffusion operator.…”