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From Perception to Action

From Perception to Action. And what’s in between?. A thought problem. “Hold it!”, you shout, because you spot the problem immediately…. The brain exhibits functional specialization, but the functions are complex and dynamic E.g. catching a ball, driving a car, reading a book, running

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From Perception to Action

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  1. From Perception to Action And what’s in between?

  2. A thought problem • “Hold it!”, you shout, because you spot the problem immediately…

  3. The brain exhibits functional specialization, but the functions are complex and dynamic • E.g. catching a ball, driving a car, reading a book, running • Each example requires tight integration of perception and action

  4. “motor systems” are perception systems as well

  5. Complexities of modularity • Some cells in “association” cortex exhibit properties that cannot be described without reference to both input and output systems

  6. For example… • Some cells in basal ganglia have visual receptive fields that are locked to arm location rather than

  7. Mirror Neurons The perception – action system

  8. 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

  9. 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

  10. 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

  11. What can Mirror Neurons Represent? • Some cells are precisely tuned to the specific actions (strictly congruent – about 1/3 of cells) • e.g. using two fingers to pick up an object • Others are broadly tuned to any action that accomplishes the same goal (broadly congruent – about 2/3 of cells) • E.g. using any combination of hand and fingers to pick up an object

  12. 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!

  13. 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

  14. What are mirror neurons for? • Two theories: • Action imitation • Understanding actions of others

  15. Mirror Neurons in Humans? • The existence of mirror neurons in humans is inferred • We don’t record directly from human cortex!

  16. Mirror Neurons in Humans? • EEG and MEG evidence suggests a Mu desynchronization (9 – 12 Hz over premotor areas) when someone observes grasping • TMS evidence shows that observed grasping decreases the threshold for triggering motor potentials for grasping muscles in the hand.

  17. The putative Mirror Neuron System in humans Iacoboni et al (2006)

  18. 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

  19. 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 < Task 2 < Task 3 • Two regions exhibited such a response

  20. Mirror Neurons Dysfunction in Autism? • Some evidence supports a theory that a dysfunction of the MNS underlies social isolation disorders such as autism spectrum disorder (ASD) • Some structural abnormalities revealed with anatomical MRI

  21. Mirror Neurons Dysfunction in Autism? • fMRI data shows that BOLD signal in MNS during viewing and imitating emotional expressions is negatively correlated with severity of Autism Spectrum Disorder

  22. Mirror Neurons Dysfunction in Autism? • Some evidence supports a theory that a dysfunction of the MNS underlies social isolation disorders such as autism spectrum disorder (ASD) • MEG data shows abnormal propagation of signals in the MNS when imitating lip movements in individuals with Asperger’s Syndrome

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