title: Neural processing of observed oro-facial movements reflects multiple action encoding strategies in the human brain.
abstract: In this experiment, the oscillatory responses of the MEG were characterized during the observation of four viewing conditions: (a) observation of mouth movements, (b) observation of a non-biological motion stimulus (a mechanical aperture opening and shutting), (c) observation of object-directed mouth movements and (d) observation of speech-like mouth movements. Data were analyzed using synthetic aperture magnetometry (SAM) in three frequency bands, beta (15-35 Hz), gamma (35-70 Hz) and alpha/mu (8-15 Hz). Results showed that observations of biological motion resulted in beta desynchronization over lateral sensorimotor areas, while observations of non-biological motion resulted in a more medial desynchronization, an effect that may be related to the processing of a structured event sequence. Observation of linguistic movements resulted in less alpha/beta desynchronization in posterior brain regions in comparison to biological motion stimuli, suggesting that linguistically-relevant stimuli are processed with different neuronal systems than those recruited by normal action observation. We suggest that non-linguistic actions recruit dorsal systems while linguistic actions engage ventral processing systems. Object-directed movements showed the largest sensorimotor activations, suggesting that, as is the case for observations of hand movements, motoric processing is particularly sensitive to the viewing of goal-directed actions. Taken together, the results indicate that the brain utilizes multiple action encoding strategies, tailored to the function of the observed movement.
authors.affiliation: Department of Psychology, University of Auckland, Auckland, New Zealand. smut008@psynov1.auckland.ac.nz
authors.forename: Suresh D
authors.initials: SD
authors.lastname: Muthukumaraswamy
authors.forename: Blake W
authors.initials: BW
authors.lastname: Johnson
authors.forename: William C
authors.initials: WC
authors.lastname: Gaetz
authors.forename: Douglas O
authors.initials: DO
authors.lastname: Cheyne
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D005260:Female; D007839:Functional Laterality; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D015225:Magnetoencephalography; D008297:Male; D008875:Middle Aged; D009039:Motion Perception / Q000502:physiology*; D009055:Mouth / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology; D013997:Time Factors