Mirror Neurons

What are Mirror Neurons? Mirror neurons are cells that fire when a monkey (or person?) performs an action or when it views another animal performing that same action

What are Mirror Neurons? Located in conjunction with a frontoparietal action planning network: posterior inferior frontal pre-motor areas that represent impending actions Many cells are “motor dominant”: they fire when monkey grasps or reaches, but are independent of visual input inferior parietal sensory area that integrates somatosensory, visual and auditory signals Many cells are “visuo-dominant” or “visuomotor-dominant”: they fire when monkey sees a graspable object or a stimulus that could be interacted with These regions are densely interconnected

What are Mirror Neurons? Mirror neurons are in regions immediately adjacent to these frontal and parietal areas Motor properties of mirror neurons are same as “non-mirror” neurons but… Sensory properties are different These cells do not fire when monkey sees a graspable object They do fire when monkey sees another monkey (or a person!) perform actions relative to objects

What can Mirror Neurons Represent? Some cells are precisely tuned to the specific actions e.g. using two fingers to pick up an object Others are broadly tuned to any action that accomplishes the same goal E.g. using any combination of hand and fingers to pick up an object

What can Mirror Neurons Represent? Mirror neurons represent abstract actions and goals Cells will not fire when grasping is pantomimed Cells will fire when grasping is real and visible Cells will also fire when grasping happens behind an occluding screen, as long as the monkey has seen that there is an object to be grasped behind the screen!

What can Mirror Neurons Represent? Mirror neurons represent abstract actions and goals Some mirror neurons will even fire in response to the sound of an action being performed e.g. the sound of breaking a peanut shell

What can Mirror Neurons Represent? Mirror neurons represent intended actions Some cells fire more when monkey grasps food with intention to eat it – or when monkey observes a human grasping food to eat it Some cells fire more when monkey grasps food with intention to place it in a container – or when monkey observes a human placing food in a container

Mirror Neurons in Humans? The existence of mirror neurons in humans is inferred We don’t record directly from human cortex!

Mirror Neurons in Humans? fMRI studies have found evidence for two brain regions associated with imitative actions Task 1: watch action Task 2: perform action Task 3: imitate action

Mirror Neurons in Humans? Based on work with monkeys, it was presumed that mirror neuron areas would exhibit a specific pattern of BOLD response: Task 1 < Task 2 < Task 3 Two regions exhibited such a response

Mirror Neurons in Humans? Mirror Neuron System (MNS) in Humans seems to be part of a system that mediates empathy fMRI data revealed MNS areas plus limbic areas became activated during observation of emotional faces MNS areas became more activated during imitation of an emotional facial expression

Mirror Neurons Dysfunction in Autism? Some evidence supports a theory (speculation?) that a dysfunction of the MNS underlies social isolation disorders such as autism spectrum disorder (ASD) Some structural abnormalities MEG data shows abnormal propagation of signals in the MNS when imitating lip movements in individuals with Asperger’s Syndrome fMRI data shows that BOLD signal in MNS during viewing and imitating emotional expressions is negatively correlated with severity of Autism Spectrum Disorder