“The mirror neuron system
and the consequences of its
dysfunktion”
Fördjupningsarbete
för Neurokognition 7,5 HP
VT 09
Lateral surface of left cerebral hemisphere,
(viewed from the side)
top (superior)
front
(anterior)
back
(posterior)
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
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
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
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
The human core-circuit for imitation
(Shown on the lateral surface of left cerebral hemisphere)
top (superior)
frontal comp. of
MNS: goal of action
front
(anterior)
parietal comp. of MNS:
motoric aspects
back
(posterior)
STS: higher order visual
description
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
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
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