Effector-dependent activity in the left dorsal premotor cortex in motor imagery

Although right- and left-hand motor imagery (MI) typically results in lateralized cortical activation patterns in various areas, such an effect has never been observed in the left premotor cortex (PMC). Using functional magnetic resonance imaging we tested whether the left PMC, which is supposed to be effector independent, i.e. it is activated irrespective of the hand used for MI, shows differential activation during right- and left-hand MI of ecologically valid everyday actions. Results showed that the left dorsal PMC was activated more strongly during right- than left-hand MI, and that the co-varying quality of imagination could not explain the observed effects. We conclude that the left dorsal PMC incorporates effector-dependent functionality and therefore is not fully generic for MI, as has been suggested before. Implications for clinical research are discussed.