Mirror Neurons

1
Mirror Neurons
2
What are mirror neurons?

• In the early 90s, a research group at the
  Università di Parma discovered cells in area F5
  of the macaque brain that fire both when the
  animal performs an action and when it observes
  that action being performed by another
• These cells, and other cells with so-called
  mirror properties, have been claimed to be
  necessary for
• Understanding actions (Gallese Goldman, 1998
  Rizzolatti Craighero, 2004 Rizzolatti,
  Fogassi, Gallese, 2001)
• Imitation (Jeannerod, 1994)
• Evolution of language (Rizzolatti Craighero,
  2004)
• Social cognition (Gallese, Keysers, Rizzolatti,
  2004)
• Esthetic reactions to art (Freedberg Gallese,
  2007)

3
Area F5
Rizzolatti et al., 1996, Cogn Brain Res

• F5 is arguably the monkey homologue of the pars
  opercularis in humans, a region involved in the
  production of language
• Also movements of the hand and mouth

4
The basic paradigm
di Pellegrino et al., 1992, Exp Brain Res
5
The basic paradigm
Gallesse et al., 1996, Brain
6
The basic paradigm
Rizzolatti et al., 1996, Cogn Brain Res
7
MNs are specific to specific actions
Rizzolatti et al., 1996, Cogn Brain Res
8
MNs respond even if the action cant be observed
directly
Umiltà et al., 2001, Neuron
9
MNs respond even if the action cant be observed
directly
Kohler et al., 2002, Science
10
Mirror Neurons Appearto Exist in Humans
Iacoboni et al., 1999, Science
11
Greater activation in IFG with observation of
meaningful than meaningless actions
Decety et al., 1997, Brain
12
Putative MNs in humans do not respond to actions
we can not perform
Buccino et al., 2004, J Cogn Neurosci
13
Action Understanding

• As a result of these data, it has been claimed
  that MNs are crucial for action understanding
• Our main claim is that the fundamental mechanism
  at the basis of the experiential understanding of
  others actions is the activation of the mirror
  neuron system (Gallesse, Keysers, Rizzolatti,
  2004, TICS)
• Well call this embodied simulation (ES)
• This is what Vittorio Gallesse calls it

14
Action Understanding

• Butwhy?
• Lets review
• MNs fire when
• performing a specific motor act, especially with
  the hands or mouth
• observing the same specific motor act
• the act itself can not be observed, but can be
  inferred
• MNs do not fire when observing acts that we can
  not perform

15
Action Understanding

• Some theoretical problems
• Actions can be ambiguous, so ES cant be
  sufficient for action understanding
• ES makes some weird predictions
• We shouldnt be able to understand actions we
  cant perform
• Why does a dog bark?
• Why does a pigeon take flight?
• How do infants understand action?
• We shouldnt be able to understand more than one
  action at a time (assuming the actions are not
  simultaneously performable)
• Activation of the mirror neuron system has never
  been shown to improve action understanding!
• In the experiments with unseen actions, the
  animals had extensive experience viewing the
  action before it was performed out of sight
• How could you simulate an action whose motor
  instantiation is unknown?

16
So what are MNs doing, then?

• An alternative account of mirror neuron
  functionmental simulation of action
• It has been well demonstrated that people use the
  motor system to mentally simulate actions
• So, does mental simulation activate the putative
  mirror neuron region of the IFG?

17
10 and 20Hz oscillating frequencies are
suppressed during action observation and
performance
Muthukumaraswamy Johnson, 2004, Clin Neurophys
18
The 20Hz frequency appears to be in primary motor
cortex
Salmelin et al., 1995, Neuroimage
19
Motor Evoked Potentials

• Transcranial Magnetic Stimulation of the primary
  motor cortex induces muscle contractions
• These are enhanced during action observation

Fadiga et al., 1995, J Neurophysiol
20
Spinal reflexes are also changed during motor
imagery
Oishi et al., 1994, BBR
21
Motor Imagery

• During motor imagery motor cortex is activated
• Overt movement is inhibited at the spinal cord
• Sowhat about the IFG?

22
IFG is active during motor imagery
Hanakawa et al., 2003, J Neurophysiol
23
Action observation activates IFG
Hand Actions
Foot Actions
Buccino et al., 2001, Euro J of Neurosci
24
Mental Simulation

• IFG activation is greater under conditions that
  should lead to more mental simulation
• Instructions to imitate (Grèzes et al., 1998
  Iacoboni et al., 1999)
• During observation of object-oriented actions vs
  meaningless pantomimes (Grèzes et al., 1998)
• During observation of possible versus impossible
  apparent limb movements (Stevens, Fonlupt,
  Shiffrar, Decety, 2000)
• When trained classical and capoeira dancers
  observed the type of dance with which they were
  familiar, as opposed to the other dance
  (Calvo-Merino, Glaser, Grèzes, Passingham,
  Haggard 2005)
• Glaser on this study

25
So

• Wheres the evidence for action understanding?
• Critically, action understanding lies at the
  foundation of many of the other claims being made
  about mirror neurons

26

• The Ramachandran Show