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Three routes to self perception by 3TGsB50a

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									• I will be at a conference May 7-13.
  – The final class, scheduled for May 12th, will be
    postponed until May 19th
  – The class will be held in William Guild F31 at
    10am on Wednesday May 19th
  – Since this falls in the study period, this final
    class will be a review class and an opportunity
    to ask clarification questions
Action, mirror neurons and
     communication
          Week 10
       April 28th, 2010
            Mirror neurons
• Why are they important?
• Why are they controversial?
      Understanding the
       actions of others
• Essential to social interaction
• Essential to communication
• Intuitive ease belies complexity of underlying
  processes
• Need to be able to perceive, understand, and make
  intuitive leaps about a complex, dynamic, and
  infinitely variable sequence of events
Action understanding is essential
      for communication
• My goal as sender is to replicate some
  aspect of my own brain’s state in your brain
  as accurately as I can.
• Your goal as receiver is to attend to and
  attempt to simulate/understand the message,
  and to enrich and/or question the message.
• Action (usually speech) is the medium
     Three key concepts from
 previous lectures to keep in mind
1: From week 3: Common
  coding theory (Hommel et
  al., 2001). Perceptual
  representations are stored
  together with the motor
  responses they elicit.
Tight coupling of perception
  of action and action itself.
2: Blakemore et al. (2001)’s model of action control
                         Desired
            GOAL
                          State
                                Affordances
                       Controllers
                     (perception to
                       movement)
                                        Predictors/
                                                       Predicted
                                      Efference copy
                                                         state
                                      (movement to
                         Motor         perception)
                       Commands

                       Movement
                   Actual state / effect
                   Sensory feedback

                       Estimated
                       actual state
         GOAL           Desired
                         State
                                         Inverse
                       Controllers       Model
                     (perception to
                       movement)
The inverse model
is a “guess” about
what sequence of        Motor
actions will bring    Commands
about the desired
state.
                     Movement
                 Actual state / effect
                 Sensory feedback

                      Estimated
                      actual state
GOAL      Desired
           State
         Controllers
       (perception to
         movement)
   Forward models providePredictors/
                                            Predicted
   information about how   Efference copy
                                              state
   whether the inverse (movement to
           Motor
   model will work and/or perception)
         Commands
   is working, so it can be
   corrected or fine-tuned.
         Movement
     Actual state / effect
      Sensory feedback

         Observed
          Action
          3. Embodiment illusions
            (e.g. Leggenhager et al., 2007)
Assignment of ownership
to a perceived body or
body part is flexible and
easily distorted.

The gulf between
perception of self and
perception of other is
perhaps not very wide.
 What does communication have
   to do with action control?
• The neural system that allows us to understand the actions
  of others may depend on the system that allows us to
  control our own actions
• When we perceive our own actions, we automatically
  match the consequences with the intended consequences
  and correct if we perceive an error.
• When we observe the actions of others we could use the
  same mechanism to infer their intention, i.e. what was the
  goal state they were attempting to achieve?
       Inter-brain concept transfer
         Me                          You




“Act” the concept.          Automatically match
Label, describe, gesture.   perceived actions with
Self-monitor action to      underlying intention (i.e.
determine if intended       what concept would I be
message is conveyed.        trying to describe if I
Correct if unclear.         said those words?)
        Crucial to this theory of
     communication: Mirror Neurons
                               A: monkey watches the
                               experimenter picking up
                               a raisin, neuron
                               responds



                               B: monkey picks up the
                               raisin, same neuron
                               responds


From Rizzolatti et al., 1996
Area F5: ventral premotor cortex
            Di Pellegrino et al., 1992:
            Out of 184 F5 neurons sampled, almost
            all were active during movements.
            12 of these neurons (6%) responded to
            the same action when executed as when
            observed (classic mirror neuron)
            17 more (9%) responded to logically
            related or visually similar actions
               Neurons with similar properties have
               since also been observed parietal area
               IPS Fogossi et al., 2005.
                    Desired
            GOAL
                     State

                     Sensorimotor
                    transformation

Mirror neurons?
                    Observed         Of self
                   Actual state      AND of
                                     other?
     What are mirror neurons for?
      (at least) three proposals
1. Imitation learning - seeing the action automatically
activates the motor system required to do that action
     What are mirror neurons for?
      (at least) three proposals
2. Mediate understanding of the actions of others, a
rudimentary theory of mind. Basis for social reasoning,
theory of mind, empathy. “Tranforms visual information
into knowledge.” (Rizzolatti & Craighero, 2004, page 172)
    What are mirror neurons for?
3. Language (Rizzolatti & Arbib, 1998). Rostral F5 in monkey is at or
   near human area 44, AKA Broca’s area.
      - Is the mirror neuron system an evolutionary precursor to
      language? An imitation reflex could lead to a primitive dialogue,
      and then lead to language
      - But does speech comprehension depend on speech production?
      Children with cerebral palsy have a smaller vocabulary (Bishop et
      al., 1990) but it is not devastating.
      - TMS over tongue/lip areas of primary motor cortex slows manual
      responses to corresponding phonemes presented auditorily
      (D’Ausillo et al., 2009)
     Are there mirror neurons in
              humans?
• EEG: Desynchronization of mu (a specific EEG rhythm)
  occurs during action and observation of action
• TMS: Motor-evoked potentials (MEPs): observing action
  leads to activation of MEPs in muscles corresponding to
  the observed action when TMS is applied over motor
  cortex. Suggests a “motor resonance”
• fMRI: Observing actions activates two motor areas, rostral
  IPL and posterior IFG: the “core of the human mirror
  neuron system”
[But are these appropriate tools for isolating subpopulations
  of neurons within multimodal, complex frontal regions?]
                 Mirror neurons:
               Mountain or molehill?
• Imitation learning, empathy, theory of mind, social
  reasoning, communication -- a lot riding on a few
  neurons!
• Difficult to rule out other interpretations - responses
  of mirror neurons needs to be selective for these two
  disparate stimulus types, which is hard to establish
• A causal relationship between mirror neurons and
  action understanding in monkey has not been
  established.
   – Lesion studies would establish causality, but have not been
     tried for 3 reasons (Rizzolatti & Craighero, 2004)
       • Mirror neuron system too large and diffuse to lesion completely
       • Other mechanisms may mediate action understanding
       • Other cognitive deficits would interfere with measuring outcome
   [This argument alone suggests F5/mirror neurons are neither
     necessary nor sufficient for action understanding.]
                   Mirror neurons:
                  Where is the pony?
• Link from mirror neurons to a human “mirror system” is
  tenuous; no evidence of connectivity or what the functions of
  various components may be.
• Attempts to demonstrate mirror neurons in fMRI in humans
  have not been overwhelmingly positive*.
• Unlikely that noninvasive brain imaging techniques and/or
  TMS could reveal classic mirror neurons anyway, given that
  they are rare and sparse.
• There are dissociations of action control and action
  understanding in patient populations. Apraxic patients cannot
  produce certain actions but can make judgments about them.
  E.g., case study of a deaf apraxic who cannot sign, but can
  understand sign language (Poizner, Klima & Bellugi, 1987)
      *fMRI adaptation (Dinstein et al., 2007)
When you use the same region twice,
 it gets “adapted”.


                                 Within-modal adaptation is
                                 robust, but cross-modal is not.




If areas involved in observing
and executing overlap, should
show adaptation when one
follows the other.
     Mirror neurons: golden
   goose or wild goose chase?
• The “mirror system” is an intuitively appealing idea that
  can inspire and motivate targeted research
• It can also mislead or blinker researchers into asking
  certain questions or interpreting data in a certain light
• Important to keep an open mind to the function of mirror
  neurons
• Also important to give fair weight to other mechanisms
  that could support action
  understanding/communication/theory of mind, e.g.
  learning
Are mirror neurons evidence for common coding theory?
Lower-level sensory and motor processes are separated and
independent, but perception and action are coded together at
some level.




                                 From Hommel, Prinz & Aschersleben, 2001
 Why would perception and action
      be coded together?
• The ultimate purpose of perceiving is action
• Action relies on perceptual information
• Action produces perceptual information
 “Mirror system”: fact or fiction?
• Action is the medium for communication / social
  interaction
• The “mirror system” is a powerfully intuitive idea: if we
  understand ourselves we understand others
• Could be useful idea if approached with caution. Not be a
  panacea for understanding human language, theory of
  mind, imitation, empathy . . . .
• Behavioural results supporting idea of mirror neuron
  system may be construed as also providing support for
  perception/action links

								
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