The effect of motor familiarity during simple finger opposition tasks

Humans are more familiar with performing (and observing) index-thumb than with any other finger to thumb grasping and the effect of familiarity has not been tested specifically with simple and intransitive actions. The study of simple and intransitive motor actions (i.e. simple actions without need of object interaction) provides the opportunity to investigate specifically the brain motor regions reducing the effect of non-motor aspects that are related with more complex and/or transitive motor actions. The aim of this study is to evaluate brain activity patterns during the execution of simple and intransitive finger movements with different degrees of familiarity. With this in mind, a functional Magnetic Resonance Imaging (fMRI) study was performed in which participants were asked to execute finger to thumb opposition tasks with all the different fingers (index, middle, ring and little) with a fixed frequency (1 Hz) determined by a visual cue. This movement is considered as the pantomime of a precision grasping action. Significant activity was identified in the Sensory Motor Cortex (SMC), posterior parietal and premotor regions for all simple conditions (index-finger>control, middle-finger>control, ring-finger>control and little-finger>control). However, a linear trend contrast (index