Motor cortical areas: the homunculus The motor system

Motor cortical areas: the homunculusThe 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 movement Prepare 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

unit210 unit199

Umlita et al., 2008closure

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)

Executed

Observed

fMR

I re

spon

se

Selectivity

FistHang loose

Thumbsup

The finger

Hang loosemirror neuron

The fingermirror 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

Repeats Non-repeats

Visual adaptation

Observe Observe Observe Observe

Repeats Non-repeats

Motor adaptation

Execute Execute Execute Execute

Repeats Non-repeats

Cross-modal adaptation

Execute Observe Execute Observe

Repeats Non-repeats

Cross-modal adaptation

Observe Execute Observe Execute

Repeats Non-repeats

Rock paper scissorsDinstein 2008

Get extra $10 if you win more than you lose!

Game Timeline

Observe

Time

Execute

Time

Game Timeline

Observe

Repeat Non-repeat

Execute

Time

Game Timeline

Observe

Repeat Non-repeat

Execute

Time

Game Timeline

Observe

Repeat Non-repeat

Execute

Time

Game Timeline

Observe

Repeat Non-repeat

Execute

Time

Game Timeline

Observe

Repeat Non-repeat

Execute

Time

Game Timeline

Observe

Observe

Repeat Non-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

ClassificationTypical mirror region

= ~ 300 voxels

Executed Observed

fMR

I re

spon

se

Classification

Executed

fMR

I re

spon

se

No specificity in the overall fMRI signal (across voxels)

Classification

Specificity in the fMRI signal (within voxels)

Movement selective patterns

Strong Weak

Activation level

Are patterns distinct & reproducible?

Trial #1

.… .… .…

Execute Execute Execute

Trial #2

Trial #3

Trial #4

Are patterns distinct & reproducible?

Trial #1

.… .… .…

Observe Observe Observe

Trial #2

Trial #3

Trial #4

Classify movement patternsD

ecod

ing

accu

racy

R P SExecute

dObserved

R P S

Primary motor & somatosensory

Classify movement patternsD

ecod

ing

accu

racy

R P SExecute

dObserved

R P S

Early visual areas

Classify movement patternsD

ecod

ing

accu

racy

R P SExecute

dObserved

R P S

Ventral premotor

Classify movement patternsD

ecod

ing

accu

racy Left Right

R P S

R P S

R P S

R P SExecute

dObserved

Executed

Observed

Anterior intraparietal sulcus

Different patterns across modalities

Executed to observed

Observed to executed

R P S

R P S

R P S

R P S

Left aIPS Right aIPS

Execute

Different patterns across modalities

Observe