The effects of combined action observation and motor imagery on corticospinal excitability and movement outcomes: Two meta-analyses.

Motor simulation interventions involving motor imagery (MI) and action observation (AO) have received considerable interest in the behavioral sciences. A growing body of research has focused on using AO and MI simultaneously, termed 'combined action observation and motor imagery' (AOMI). The current paper includes two meta-analyses that quantify changes in corticospinal excitability and motor skill performance for AOMI compared to AO, MI and control conditions. Specifically, the first meta-analysis collated and synthesized existing motor evoked potential (MEP) amplitude data from transcranial magnetic stimulation studies and the second meta-analysis collated and synthesized existing movement outcome data from behavioral studies. AOMI had a positive effect compared to control and AO but not MI conditions for both MEP amplitudes and movement outcomes. No methodological factors moderated the effects of AOMI, indicating a robust effect of AOMI across the two outcome variables. The results of the meta-analyses are discussed in relation to existing literature on motor simulation and skill acquisition, before providing viable directions for future research on this topic.