A probabilistic atlas of finger dominance in the primary somatosensory cortex

With the advent of ultra-high field (7T), high spatial resolution functional MRI (fMRI) has allowed the differentiation of the cortical representations of each of the digits at an individual-subject level in human primary somatosensory cortex (S1). Here we generate a probabilistic atlas of the contralateral SI representations of the digits of both the left and right hand in a group of 22 right-handed individuals. The atlas is generated in both volume and surface standardised spaces from somatotopic maps obtained by delivering vibrotactile stimulation to each distal phalangeal digit using a travelling wave paradigm. Metrics quantify the likelihood of a given position being assigned to a digit (full probability map) and the most probable digit for a given spatial location (maximum probability map). The atlas is validated using a leave-one-out cross validation procedure. Anatomical variance across the somatotopic map is also assessed to investigate whether the functional variability across subjects is coupled to structural differences. This probabilistic atlas quantifies the variability in digit representations in healthy subjects, finding some quantifiable separability between digits 2, 3 and 4, a complex overlapping relationship between digits 1 and 2, and little agreement of digit 5 across subjects. The atlas and constituent subject maps are available online for use as a reference in future neuroimaging studies. •Here we present a probabilistic atlas of the hand and digits in the primary somatosensory cortex.•The atlas was created by combining multiple 7 T fMRI datasets where a travellingwave paradigm to map the digits was employed.•Maps are reproducible across sessions and show large overlap across subjects in template anatomical spaces•Maps are reproducible across sessions and show large overlap across subjects inThe atlas shows that non-invasive electrophysiological data can be separated according to digits stimulated.•The atlas is publically available and will be refined with additional data over time.The atlas is publically available and will be refined with additional data over time.