Mirror Neurons

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Mirror Neurons
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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

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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

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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

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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

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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!

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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

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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

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Mirror Neurons in Humans?

• The existence of mirror neurons in humans is
  inferred
• We dont record directly from human cortex!

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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
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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 lt Task 2 lt Task 3
• Two regions exhibited such a response

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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

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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 Aspergers Syndrome
• fMRI data shows that BOLD signal in MNS during
  viewing and imitating emotional expressions is
  negatively correlated with severity of Autism
  Spectrum Disorder