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
• Brocas 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