Hands on the future: facilitation of cortico-spinal hand-representation when reading the future tense of hand-related action verbs

Reading action-related verbs brings about sensorimotor neural activity, suggesting that the linguistic representation of actions impinges upon neural structures largely overlapping with those involved in actual action execution. While studies of direct action observation indicate that motor mirroring is inherently anticipatory, no information is currently available on whether deriving action-related knowledge from language also takes into account the temporal deployment of actions. Using transcranial magnetic stimulation, here we sought to determine whether reading action verbs conjugated in the future induced higher cortico-spinal activity with respect to when the same verbs were conjugated in the past tense. We recorded motor-evoked potentials (MEPs) from relaxed hand and leg muscles of healthy subjects who were reading silently hand- or leg-related action, sensorial (non-somatic) and abstract verbs conjugated either in future or past tense. The amplitude of MEPs recorded from the hand was higher during reading hand-related action verbs conjugated in the future than in the past. No future-related modulation of leg muscles activity was found during reading leg-related action verbs. In a similar vein, no future-related change of hand or leg muscles reactivity was found for abstract or sensorial verbs. These results indicate that the anticipatory mirroring of hand actions may be triggered by linguistic representations and not only by direct action observation.