title: Formation of a motor memory by action observation.
abstract: Mirror neurons discharge with both action observation and action execution. It has been proposed that the mirror neuron system is instrumental in motor learning. The human primary motor cortex (M1) displays mirror activity in response to movement observation, is capable of forming motor memories, and is involved in motor learning. However, it is not known whether movement observation can lead directly to the formation of motor memories in the M1, which is considered a likely physiological step in motor learning. Here, we used transcranial magnetic stimulation (TMS) to show that observation of another individual performing simple repetitive thumb movements gives rise to a kinematically specific memory trace of the observed motions in M1. An extended period of observation of thumb movements that were oriented oppositely to the previously determined habitual directional bias increased the probability of TMS-evoked thumb movements to fall within the observed direction. Furthermore, the acceleration of TMS-evoked thumb movements along the principal movement axis and the balance of excitability of muscle representations active in the observed movements were altered in favor of the observed movement direction. These findings support a role for the mirror neuron system in memory formation and possibly human motor learning.
authors.affiliation: National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Katja
authors.initials: K
authors.lastname: Stefan
authors.forename: Leonardo G
authors.initials: LG
authors.lastname: Cohen
authors.forename: Julie
authors.initials: J
authors.lastname: Duque
authors.forename: Riccardo
authors.initials: R
authors.lastname: Mazzocchio
authors.forename: Pablo
authors.initials: P
authors.lastname: Celnik
authors.forename: Lumy
authors.initials: L
authors.lastname: Sawaki
authors.forename: Leslie
authors.initials: L
authors.lastname: Ungerleider
authors.forename: Joseph
authors.initials: J
authors.lastname: Classen
mesh_terms: D000328:Adult; D004574:Electromagnetic Fields; D004576:Electromyography / Q000379:methods; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008568:Memory / Q000502:physiology*; D008875:Middle Aged; D009044:Motor Cortex / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods*; D011597:Psychomotor Performance / Q000502:physiology*