17292
Hand and Foot Action Perception in Autism
Most mirror neurons in monkey demonstrate only a broad congruence between observed and executed actions (e.g. a neuron firing during the execution of a precision grip will respond to the observation of the object being grasped with the mouth or foot). These broadly congruent mirror neurons are though to encode the goal of perceived actions irrespective of the mean used to accomplish the action. About 1/3rd of mirror neurons however fire solely when the observed action is performed the same way as during execution. These strictly congruent mirror neurons may encode the mean used to accomplish a goal (e.g. with the hand or foot).
Objectives:
Testing whether individuals with autism re-enact both the goal and the mean of others' actions in parietal and premotor cortices
Methods:
Sixteen participants with autism and 18 controls matched for age, IQ, and handedness watched short movies of hand and foot actions while their cerebral activity was recorded in a 3T MRI scanner (EPI sequence with TR=2s, TE=28ms, 39 slices 3.5mm thick). Participants watched 16 blocks of hand and 16 blocks of foot actions. Hand and foot actions were performed on the same objects with the same goal (e.g. squishing a foam ball), and were paired-matched for duration. At the second level, age, laterality and IQ scores were used as cofactor in a mixed design model with factors group and effector. SPMs were thresholded at P < 0.001 uncorrected, and activity in regions of interests was tested with P-FWE=0.05. Sleepiness was monitored with a camera during the entire session and evaluated on a 10-point scale. Participants' attention to the movies was further evaluated with 24 questions presented at the end of the scanning session.
Results:
Participants in both groups were well awake during the movies (9/10) and answered the verification questions with the same accuracy. In both groups, large portions of the parietal and premotor cortices were equally active during the perception of hand and foot actions. In addition, both groups showed similar effector effects in parietal lobe hand and foot regions. Finally, a significant interaction between group and effector was found in the left inferior frontal gyrus, where there was more activity for hand than foot in autism, but more activity for foot than hand in controls.
Conclusions:
The results so far suggest that individuals with autism activate the mirror neuron system like typically developing subjects during action perception. However, there might be subtle differences in the activation of strictly congruent mirror neurons involved in encoding the mean used to accomplish an action.