“ The mirror neuron system and the consequences of its dysfunktion ”

1. “The mirror neuron system and the consequences of its dysfunktion” Fördjupningsarbete för Neurokognition 7,5 HP VT 09

2. Lateral surface of left cerebral hemisphere, (viewed from the side) top (superior) front (anterior) back (posterior)

3. The primate MNS • Due to research done on primates with the help of TMS, PET and fMRI… • mirror neurons fire during goal-directed actions • mirror neurons fire during observation of similar action • mirror neurons do not fire during observation of pantomimed action • mirror neurons fire when observed action is partly hidden • It therefore follows that prior knowledge allows the mirror neurons to discriminate between real and faked situations, and therefore to code highly abstract aspects of a situation/the actions of others

4. The primate MNS (continued) • Due to research done on primates with the help of TMS, PET and fMRI… • two thirds of recorded mirror neurons discharge differently according to the perceived intention of an observed action • the same two thirds discharge accordingly during the performance of similar actions •  It follows that the MNS codes the intention associated with the observed action of others

5. The primate MNS (continued) • Due to research done on primates with the help of TMS, PET and fMRI… • some mirror units discharge during the observation of ingestive or communicative mouth actions • this is of importance with regards to the hypothesis that the MNS is vital for the understanding of emotional states in others (which are mostly communicated by facial expression) • the MNS is not active during initial observations of humans handling objects (food) with the help of tools (sticks, pliers) • some mirror neurons start firing after repeated observation •  This is evidence for the fact that the MNS can be shaped by experience and accounts for observational learning

6. The human MNS (and imitation) • Research done on humans by means of fMRI shows that… • Broca’s area plays an important role in imitation • mirror neurons are more active during “mirror”-imitation than in anatomically correct imitation • The MNS seems to be crucial for imitation early in live

7. The human core-circuit for imitation (Shown on the lateral surface of left cerebral hemisphere) top (superior) parietal comp. of MNS: motoric aspects frontal comp. of MNS: goal of action front (anterior) back (posterior) STS: higher order visual description

8. The human MNS (and imitation) • Research done on humans by means of fMRI shows that… • the MNS interacts with motor preparation areas and the dorsolateral prefrontal cortex during imitative learning • there are two functionally divided sectors in the frontal component of the human MNS, of which only one is properly mirror •  The so called forward model draws the conclusion that the ventral part might have a functional significance during imitational actions

9. The human MNS (and social cognition) • Research done on humans by means of fMRI shows that… • during imitation and observation of emotional faces the network of MNS, amygdala and insula was activated • as earlier mentioned the MNS codes abstract aspects of an action, like the intention of it • the more one can relate to the observed action, the more action can be recorded in the mirror neurons •  The MNS plays a key role in social cognition

10. The dysfunctional MNS • morphometric studies have revealed structural abnormalities in MNS in patients with autism • the activation of the core-circuit for imitation (slide 7) is delayed in patients with autism • autistic children showed reduced MNS activity during observation and imitation of emotional facial expressions •  The data supports the hypothesis that MNS dysfunction is the core deficit in autism