Unraveling the visual and motor properties of mirror neurons in human and nonhuman primates

Mirror neurons respond when a subject performs an action and also
when the subject sees another actor performing an action. Ever since
their discovery almost three decades ago in the premotor cortex of
macaque monkeys, mirror neurons are most likely one of the most
studied and most fascinating neurons in the brain. The association of
mirror activity with action recognition, imitation of others and even
empathy continues to have a significant impact on neuroscience and
beyond. However, many questions about the properties of mirror
neurons remain unanswered. Even after thousands of studies on
mirror activity, it is still unclear what mirror neurons respond to when
observing an action. Even more intriguingly, we do not know where
mirror neurons project to in the brain. Some reports have identified
mirror neurons that project directly to the spinal cord and must
therefore play a role in the generation of skilled movements, but it is
unclear whether the motor system is the main output of mirror
neurons in premotor cortex. We want to use a combination of largescale
neuronal recordings in different cortical areas, electrical
microstimulation and functional imaging in macaque monkeys and
humans to address these crucial research questions. With a set of
carefully controlled visual stimuli and with precisely targeted
microstimulation during motor tasks, we aim to clarify what mirror
neurons respond to and what is their main output target.