Spontaneous movement tempo is influenced by observation of rhythmical actions

Observation of people performing movements facilitates motor planning, execution and memory formation. Tempo, a crucial aspect involved in the execution of rhythmic movements, is normally perceived and learned through auditory channels. In this work, we ascertained whether: first, the frequency of self-paced finger movements (SPMs), which in normal subjects is around 2 Hz, is modified by prior observation of movements performed at either 1 or 3 Hz; second, such changes are lasting; third, there is an effect of time interval between observation and performance. We finally determined the effect of providing explicit information about the upcoming motor task. Seventy-two normal subjects (12 groups) performed a simple finger sequence at different intervals after observation of videos of either landscapes or finger opposition movements. Both with and without information about the upcoming task, observation influenced the tempo of SPMs and led to memory formation. With knowledge of the upcoming task, such changes occurred at all observation-execution intervals, while without instructions, changes took place only when SPMs were performed immediately after observation. Compared to explicit instructions, the absence of instructions produced tempo's changes that more closely resembled the observed rhythms. We conclude that learning requires a prompt comparison between visual and sensorimotor representations of movements; moreover, learning with explicit instructions is more efficient, as activity in both the dorsal and ventral streams might be potentiated by the chatecholaminergic attentional systems that promote long-term potentiation. These results provide the bases for novel neurorehabilitation strategies in terms of temporal re-organization of movement.