Representational similarity scores of digits in the sensorimotor cortex are associated with behavioral performance

Previous studies aimed to unravel a digit-specific somatotopic organization in the primary sensorimotor (SM1) cortex. It is, however, yet to be determined whether such digit somatotopy is associated with motor performance (i.e., effector selection) and digit enslaving (unintentional co-contraction of fingers) during different types of motor tasks. Here, we adopted multivariate representational similarity analysis, applied to high-field (7T) MRI data, to explore digit activation patterns in response to online finger tapping. Sixteen young adults (7 males, mean age: 24.4 years) underwent MRI, and additionally performed an offline choice reaction time task (CRTT) to assess effector selection. During both the finger tapping task (FTT) and the CRTT, force sensor data of all digits were acquired. This allowed us to assess digit enslaving (obtained from CRTT & FTT), as well as digit interference (i.e., erroneous effector selection; obtained from CRTT) and correlate these variables with digit representational similarity scores of SM1. Digit enslaving during finger tapping was associated with contralateral SM1 representational similarity scores of both hands. During the reacton time task, digit enslaving of the right hand only was associated with representational similarity scores of left SM1. Additionally, right hand digit interference was associated with representational similarity scores of left S1. In conclusion, we demonstrate a cortical origin of digit enslaving, and uniquely reveal that effector selection performance is predicted by digit representations in the somatosensory cortex.