International audienceThe study of brain functions using fMRI often requires an accuratematching of cortical surface data for comparing brain activation acrossa population. In this context, several tasks are critical, such as surface in-flation for cortical visualizations and measurements, surface matching andalignment of functional data for group-level analyses. Present methods typicallytreat each task separately and can be computationally expensive. It takesfor example several hours to smooth and match a single pair of cortical surfaces.Furthermore, conventional methods rely on anatomical features to drivethe alignment of functional data across individuals, whereas their relation tofunction can vary across a population. To address these issues, we proposeBrain Transfer, a spectral framework that unifies cortical smoothing, pointmatching with confidence regions, and transfer of functional maps, all withinminutes of computation. Spectral methods have the advantage of decomposingshapes into intrinsic geometrical harmonics, but suffer from the inherentinstability of these harmonics. This limits their direct comparison in surfacematching, and prevents the spectral transfer of functions. Our contributionsconsist of, first, the optimization of a spectral transformation matrix, whichcombines both, point correspondence and change of eigenbasis, and second,a localized spectral decomposition of functional data, via focused harmonics.Brain Transfer enables the transfer of surface functions across interchangeablecortical spaces, accounts for localized confidence, and gives a new way toperform statistics on surfaces. We illustrate the benefits of spectral transfersby exploring the shape and functional variability of retinotopy, which remainschallenging with conventional methods. We find a higher degree of accuracyin the alignment of retinotopy, exceeding those of conventional methods