Fast event-related mapping of fingertip population receptive fields in human somatosensory and motor cortex at 7T

Abstract The majority of fMRI studies investigating somatotopic body representations in the human cortex have used either block or phase-encoding stimulation designs. Event-related (ER) designs allow for more natural and flexible stimulation sequences, while enabling the independent estimation of responses to different body parts in the same cortical location. Here we compared an efficiency-optimized fast ER design (2s inter stimulus interval, ISI) to a slow ER design (8s ISI) for mapping fingertip voxelwise tuning properties in the sensorimotor cortex of 6 participants at 7 Tesla. The fast ER design resulted in similar, but more robust, estimates compared to the slow ER design. Concatenating the fast and slow ER data, we demonstrate in each individual brain the existence of two separate somatotopically-organized representations of the fingertips, one in S1 on the post-central gyrus and the other at the border of the motor and pre-motor cortices on the pre-central gyrus. In both post-central and pre-central representations, fingertip tuning width increases progressively, from narrowly-tuned Brodmann areas 3b and 4a respectively, towards parietal and frontal regions responding equally to all fingertips. Key PointsFingertip population receptive fields (pRFs) in sensorimotor cortex can be efficiently mapped using a fast event-related design (ISI = 2 s) at 7T.Somatotopically-organized tactile maps were found not only in primary somatosensory cortex but also at the border between motor and premotor cortex.pRF size, reflecting the degree of integration between fingertips, increases from primary Brodmann areas 3b and 4a towards higher-order parietal and frontal regions.