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Explore the role of mirror neurons in movement perception and adaptation in the motor cortical areas through cortical activation, brain regions involved, and specificity in fMRI responses.
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Motor cortical areas: the homunculus The motor system
Major Cortical areas involved in planning and execution of “purposeful” movements
P.D. Directional Tuning of MI Cells Movement onset (Georgopoulos et al 1982)
Set related responses in Pre-motor Cortex Prepare LEFT movement Prepare RIGHT movement
Mirror neurons Rizzolatti et al., 1996
Basic properties of the Mirror Neurons Rizzolatti et al. 1996
Mirror neurons in the Parietal cortex: Intention understanding?
Mirror neurons show the same specificity when actions are preformed by the experimenter
What is represented by the MN?Actions or goals? unit210 unit199 opening Hand Umlita et al., 2008 closure
The mirror system – abstract representation of movement goals? • Recordings from 37 mirror neurons in F5 in a “hidden action” paradigm • 19/37 mirror neurons responded significantly in the hidden condition. • 7/19 – strong responses (hidden=visual) Full vision Hidden vision (Umilta et al., 2001).
Cortical activation during observation of mouth hand and foot action
Viewed-Hand identity effects in parietal cortex Shmuelof & Zohary 2006
Specificity of visually defined “hand areas” to motor actions
Human mirror system fMRI response Dinstein, J. Neuroscience (2008) Executed Observed
Hang loose mirror neuron The finger mirror neuron Hang loose Fist The finger Thumbs up
Monkey mirror neurons Gallese, Brain (1996)
Mirror regions should be active both during viewing action and motor action Mirror neurons should show cross-modal adaptation
Adaptation First presentation Repeated presentation
Movement selective adaptation Repeats Non-repeats
Visual adaptation Repeats Non-repeats Observe Observe Observe Observe
Motor adaptation Repeats Non-repeats Execute Execute Execute Execute
Cross-modal adaptation Repeats Non-repeats Execute Observe Execute Observe
Cross-modal adaptation Repeats Non-repeats Observe Execute Observe Execute
Rock paper scissors Dinstein 2008 Get extra $10 if you win more than you lose!
Game Timeline Observe Time
Game Timeline Observe Execute Time
Game Timeline Observe Execute Time Repeat Non-repeat
Game Timeline Observe Execute Time Repeat Non-repeat
Game Timeline Observe Execute Time Repeat Non-repeat
Game Timeline Observe Execute Time Repeat Non-repeat
Game Timeline Observe Execute Time Repeat Non-repeat
Game Timeline Observe Execute Time Repeat Non-repeat
Visual adaptation Mirror system areas Green: observed non-repeat > repeat
Motor adaptation Mirror system areas Purple: executed non-repeat > repeat
Motor & visual adaptation Mirror system areas Yellow: overlap of motor and visual adaptation
Motor & visual adaptation Mirror system areas Yellow: overlap of motor and visual adaptation No cross modal adaptation
Adaptation summary Selectivity for movements in “Mirror system” areas. Adaptation may be taking place in a single population of mirror neurons and/or in two separate populations of visual and motor neurons adapting independently. We now have a way of studying movement selective responses; the critical feature of neural populations involved in movement perception. Dinstein J. Neurophysiology 2007
Classification Typical mirror region = ~ 300 voxels fMRI response Executed Observed
Classification No specificity in the overall fMRI signal (across voxels) fMRI response Executed
Classification Specificity in the fMRI signal (within voxels)
Movement selective patterns Activation level Strong Weak
Are patterns distinct & reproducible? Execute Execute Execute Trial #1 Trial #2 Trial #3 Trial #4 …. …. ….