A visual representation of the hand in the resting somatomotor regions of the human brain

Hand visibility affects motor control, perception, and attention, as visual information is integrated into an internal model of somatomotor control. Spontaneous brain activity, i.e., at rest, in the absence of an active task, is correlated among somatomotor regions that are jointly activated during motor tasks. Recent studies suggest that spontaneous activity patterns do not only replay task activation patterns but also maintain a model of the statistical regularities (priors) of the body and environment, which may be used to predict upcoming behavior. We test whether spontaneous activity in the human somatomotor cortex is modulated by visual stimuli that display hands vs. non-hand stimuli and by the use/action they represent. We analyzed fMRI activity and multivariate pattern analysis to examine the similarity between spontaneous activity patterns and task-evoked patterns to the presentation of natural hands, robot hands, gloves, or control stimuli (food). In the left somatomotor cortex, we observed a stronger (multivoxel) spatial correlation between resting-state activity and natural hand picture patterns compared to other stimuli. We did not observe any task-rest similarity in the visual cortex. We conclude that spontaneous activity patterns in somatomotor brain regions code for the visual representation of human hands and their use.