Introduction A precise knowledge of functional organization in the neocortex relies on comparisons between functional mapping and anatomical structures. In classical neuroscience, such comparisons were often made between electrophysiological recording of neural response and postmortem histological staining of myelin . MRI can augment this knowledge with comparisons between BOLD fMRI and structural MRI such as T1 mapping that reveals cortical myeloarchitecture . In particular, previous anatomical studies suggest that interhemispheric somatosensory connections are spatially heterogeneous, and they end in specific myelin-poor bands in the cortical area 3b, which is part of primary somatosensory cortex (SI) of the nonhuman primate common marmoset . This structural organization suggests that ipsilateral functional responses may also center on these myelinpoor zones, but this possibility was not explored in previous functional imaging studies [3-5]. We therefore study ipsilateral responses in awake marmosets, with a methodological advance in combining high-resolution BOLD fMRI with T1 mapping. Methods All fMRI measurements were performed in awake adult marmosets that were trained but received no pharmacological agents (n = 3, age = 1.5 yr). Each animal was first anesthetized with 2% isoflurane to take 3D MRI of the head scalp. The animal then went through 3 weeks of acclimatization process. Animal head was secured rigidly by one top and one bottom helmet pieces starting from the 3rd week of acclimatization and throughout the real MRI sessions. The 3D shapes of the helmet were designed to tightly fit the 3D shape of head, which was obtained from the 3D MRI.