NeuroImage 50 (2010) 1148–1167

ALE meta-analysis of action observation and imitation in the human brain

Svenja Caspers,Karl Zillesa, Angela R.Laird, SimonB.Eickhoff

Background

• Mirror neuron system in the macaque brain (Gallese et al., 1996)

• Evidence for possible “mirror areas” in humans based on functional neuroimaging experiments

• Observation and imitation are closely related

• Are observation and imitation sustained by the same neuronal networks?

AIM

Identification of cortical areas consistently involved in action observation and imitation…

… by a quantitive (coordinate based) meta-analysis of the current neuroimaging literature

Materials & Methods• 139 experiments (fMRI and PET),1289 subjects, 1932 activation foci ( Talairach, MNI coordinates)

• Tasks, effectors and instructions

Material & MethodsActivation likelihood estimation (ALE) algorithm

1 study

1 Map

Foci from all studies

Many foci Each foci = centre of a 3D Gaussian probability distribution

Input Output

Union activation modelled map (MA)

Voxel-wise ALE scores

True convergence?Comparison of “true” scores with scores in null distribution (baseline activation)

Symmetrical activation across both hemispheres

Action Observation Network

Action Observation Network……subanalysis for effectors

No FFA/FBA activation BA45 only in right hemisphere

As hand observation but with lower statistical power

FFA/FBA only in right hemisphere hIP3 only in left hemisphere (the only consistent parietal activation)

As nonHand observation No consistent SMA activation

Contrast analysis between hand action observation and observation of non-hand actions

A: hand observationC : non-hand observation

Action Observation Network……subanalysis for instructions

Comparable network to main analysis

No parietal activation Consistent activation of dPMC-BA6, pMTG and extrastriate areas

Contrast analysis between the two instructions

No stronger activation for the instruction “observe to imitate” in any region BUT only 8 experiments were used

A: passively observeB : observe to imitate

Action Observation Network……subanalysis for object-related hand actions

Bilaterally: BA 44, BA6, IPL-PFt, SPL (7a), pMTG,V5 Right hemisphere: S1, IPS-hIP3

Activation of temporo-occipital areas

Contrast analysis between object-related hand actions and non-object-related hand action

A: object-related hand actionB : non-object-related hand action

Action Imitation Network

Bilaterally: BA 44, BA 6, SMA, SFG, S1 (area 2), IPL-PFt, V5 Left hemisphere: pMTG Right hemisphere: IPL-PFcm, FFA/FBA, frontal aspect of insular cortex

Action Imitation Network……subanalysis for effectors

Comparable to the main analysis

Comparable to the main analysis pMTG bilaterally activated

Activation of BA 4, BA 6, BA 44 SFG No temporo-occipital activation

Conjunction analyses

Bilaterally: BA 44, BA 6, SMA, PFt, PFop, S1 (area 2), V5 Left hemisphere: pMTG Right hemisphere: FFA/FBA

Contrast analyses

Observation Imitation

Rostro-dorsal part of BA 44 (area BA45- bilaterally)

Caudo-ventral part of BA 44 (bilaterally)

BA 6, pMTG, V5 (bilaterally)

IPL-PFt/Pfop (left hemisphere)

SPL (right hemisphere) S1 (area 2),IPL-PFt, FFA/FBA (right hemisphere)

DiscussionMethodological considerations

• Coordinate based meta-analysis vs. image based meta-analysis

• Potential presence of confounding factors

• No information for the strength of resulting activation

• Account for sample size

DiscussionAreas involved in each network

• Expanded Mirror Neuron System• In humans, observation and imitation networks are similar, if not the same (differences in macaque brain)• BA 44 and PFt/hIP3 homolog to F5 and PFG/PF of macaque respectively • BA 44 => initiation and termination of simple actions (imitation) BA 45 =>supraordinate aspect of action• SMA mainly activated in non-hand tasks• pMTG involved in the processing of biological motion• V5 involved in motion perception • FFA/FBA serves as an encoder of facial and body stimuli• S1-top down modulation from associative areas

DiscussionNeural correlates of action observation

• Transient inactivation of observation network- related areas result in impairment of action observation ability• Somatotopy of the involved parts of observation network?• Activation’s independency from the effectors• Possible functions of the network: - Feedback control of an action (SPL, IPS, BA 6)-optic ataxia - Implicit processing of object features and their integration within the observed motor act (fronto-parietal areas) - Composition of the appropriate motor program (dPMC)

Neural correlates of action imitation

• Bilateral pattern of activation

Thank

you!