title: Post-movement beta rebound abnormality as indicator of mirror neuron system dysfunction in autistic spectrum disorder: an MEG study.
abstract: The mu rhythm is regarded as a physiological indicator of the human mirror neuron system (MNS). The dysfunctional MNS hypothesis in patients with autistic spectrum disorder (ASD) has often been tested using EEG and MEG, targeting mu rhythm suppression during action observation/execution, although with controversial results. We explored neural activity related to the MNS in patients with ASD, focusing on power increase in the beta frequency band after observation and execution of movements, known as post-movement beta rebound (PMBR). Multiple source beamformer (MSBF) and BrainVoyager QX were used for MEG source imaging and statistical group analysis, respectively. Seven patients with ASD and ten normal subjects participated in this study. During the MEG recordings, the subjects were asked to observe and later execute object-related hand actions performed by an experimenter. We found that both groups exhibited pronounced PMBR exceeding 20% when observing and executing actions with a similar topographic distribution of maximal activity. However, significantly reduced PMBR was found only during the observation condition in the patients relative to controls in cortical regions within the MNS, namely the sensorimotor area, premotor cortex and superior temporal gyrus. Reduced PMBR during the observation condition was also found in the medial prefrontal cortex. These results support the notion of a dysfunctional execution/observation matching system related to MNS impairment in patients with ASD, and the feasibility of using MEG to detect neural activity, in particular PMBR abnormalities, as an index of MNS dysfunction during performance of motor or cognitive tasks.
authors.affiliation: Department of Psychiatry, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
authors.forename: Eiko
authors.initials: E
authors.lastname: Honaga
authors.forename: Ryouhei
authors.initials: R
authors.lastname: Ishii
authors.forename: Ryu
authors.initials: R
authors.lastname: Kurimoto
authors.forename: Leonides
authors.initials: L
authors.lastname: Canuet
authors.forename: Koji
authors.initials: K
authors.lastname: Ikezawa
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Takahashi
authors.forename: Takayuki
authors.initials: T
authors.lastname: Nakahachi
authors.forename: Masao
authors.initials: M
authors.lastname: Iwase
authors.forename: Ichiro
authors.initials: I
authors.lastname: Mizuta
authors.forename: Toshiki
authors.initials: T
authors.lastname: Yoshimine
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Takeda
mesh_terms: D000328:Adult; D001611:Beta Rhythm; D001921:Brain / Q000503:physiopathology*; D001931:Brain Mapping; D002659:Child Development Disorders, Pervasive / Q000503:physiopathology*; D002675:Child, Preschool; D003071:Cognition / Q000502:physiology; D005260:Female; D006225:Hand / Q000502:physiology; D006801:Humans; D007100:Imitative Behavior / Q000502:physiology*; D015225:Magnetoencephalography; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D009483:Neuropsychological Tests; D012815:Signal Processing, Computer-Assisted; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult