Within-finger maps of tactile and nociceptive input in the human parietal cortex

The spatial representation of nociceptive input in the human parietal cortex is not fully understood. For instance, it is known that the primary somatosensory cortex (S1) contains a representation of nociceptive-selective input to different fingers, but it is unclear whether S1 subdivisions contain finer-grained, within-finger maps of nociceptive input. It is also unknown whether within-finger maps of somatosensory input exist in intraparietal regions. Therefore, we used high-field 7T functional MRI to reveal within-finger maps of nociceptive and tactile inputs in the human parietal cortex. Although we replicated the previous findings of between-finger maps of nociceptive input spanning S1 subdivisions, we found weak and inconsistent evidence for within-finger maps of nociceptive input in S1 subdivisions. In the same subjects, we found mirrored, within-finger maps of tactile input in areas 3a, 3b, and 1. Importantly, we discovered a within-finger map of nociceptive input, but not of tactile input, in the human intraparietal area 1 (hIP1). In conclusion, our study indicates that the spatial representation of nociceptive input in the parietal cortex partly differs from that of tactile input and reports the discovery of a within-finger map of nociceptive input in hIP1. New & Noteworthy We report the discovery of a fine-grained map of nociceptive input to finger segments in the human intraparietal area 1.