Motor cortical areas: the homunculus The motor system

Major Cortical areas involved in planning and execution of “purposeful” movements

Directional Tuning of MI Cells Movement onset (Georgopoulos et al 1982) P.D.

Set related responses in Pre-motor Cortex Prepare LEFT movementPrepare RIGHT movement

Mirror neurons Rizzolatti et al., 1996

Basic properties of the Mirror Neurons Rizzolatti et al. 1996

A multimodal representation of action

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? Hand unit210unit199 Umlita et al., 2008 closure opening

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) (Umilta et al., 2001). Full vision Hidden vision

The mirror system in humans

Cortical activation during observation of mouth hand and foot action

Shmuelof & Zohary 2006 Viewed-Hand identity effects in parietal cortex

Visual and motor hand areas in the human parietal cortex

Specificity of visually defined “hand areas” to motor actions

Human mirror system Dinstein, J. Neuroscience (2008) Execute d Observe d fMRI response

Selectivity

FistHang loose Thumbs up The finger Hang loose mirror neuron The finger mirror neuron

Monkey mirror neurons Gallese, Brain (1996)

A deeper understanding of “mirror like voxels”

Mirror neurons should show cross-modal adaptation Mirror regions should be active both during viewing action and motor action

Adaptation First presentation Repeated presentation

Movement selective adaptation RepeatsNon-repeats

Visual adaptation Observe RepeatsNon-repeats

Motor adaptation Execute RepeatsNon-repeats

Cross-modal adaptation ExecuteObserveExecuteObserve RepeatsNon-repeats

Cross-modal adaptation ObserveExecuteObserveExecute RepeatsNon-repeats

Rock paper scissors Dinstein 2008 Get extra $10 if you win more than you lose!

Game Timeline Observe Time

Execute Time Game Timeline Observe

RepeatNon-repeat Execute Time Game Timeline Observe

RepeatNon-repeat Execute Time Game Timeline Observe

RepeatNon-repeat Execute Time Game Timeline Observe

RepeatNon-repeat Execute Time Game Timeline Observe

RepeatNon-repeat Execute Time Game Timeline Observe

RepeatNon-repeat Execute Time Game Timeline

Visual adaptation Green: observed non-repeat > repeat Mirror system areas

Motor adaptation Purple: executed non-repeat > repeat Mirror system areas

Motor & visual adaptation Yellow: overlap of motor and visual adaptation Mirror system areas

Motor & visual adaptation Yellow: overlap of motor and visual adaptation No cross modal adaptation Mirror system areas

ROI Analysis

Adaptation summary 1.Selectivity for movements in “Mirror system” areas. 2.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. 3.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 ExecutedObserved fMRI response

Classification Executed fMRI response No specificity in the overall fMRI signal (across voxels)

Classification Specificity in the fMRI signal (within voxels)

Movement selective patterns StrongWeak Activation level

Are patterns distinct & reproducible? Trial #1 …. Execute Trial #2 Trial #3 Trial #4

Are patterns distinct & reproducible? Trial #1 …. Observe Trial #2 Trial #3 Trial #4

Classify movement patterns Decoding accuracy R P S Execute d Observe d R P S Primary motor & somatosensory

Classify movement patterns Decoding accuracy R P S Execute d Observe d R P S Early visual areas

Classify movement patterns Decoding accuracy R P S Execute d Observe d R P S Ventral premotor

Classify movement patterns Decoding accuracy LeftRight R P S Execute d Observe d Execute d Observe d Anterior intraparietal sulcus

Different patterns across modalities Executed to observed Observed to executed R P S Left aIPSRight aIPS

Execute Different patterns across modalities Observe