title: Children and adolescents with autism exhibit reduced MEG steady-state gamma responses.
abstract: BACKGROUND
  Recent neuroimaging studies of autism have indicated reduced functional connectivity during both cognitive tasks and rest. These data suggest long-range connectivity may be compromised in this disorder, and current neurological theories of autism contend disrupted inter-regional interactions may be an underlying mechanism explaining behavioral symptomatology. However, it is unclear whether deficient neuronal communication is attributable to fewer long-range tracts or more of a local deficit in neural circuitry. This study examines the integrity of local circuitry by focusing on gamma band activity in auditory cortices of children and adolescents with autism.
  
  
  METHODS
  Ten children and adolescents with autism and 10 matched controls participated. Both groups listened to 500 ms duration monaural click trains with a 25 ms inter-click interval, as magnetoencephalography was acquired from the contralateral hemisphere. To estimate 40 Hz spectral power density, we performed time-frequency decomposition of the single-trial magnetic steady-state response data using complex demodulation.
  
  
  RESULTS
  Children and adolescents with autism exhibited significantly reduced left hemispheric 40 Hz power from 200-500 ms post-stimulus onset. In contrast, no significant between group differences were observed for right hemispheric cortices.
  
  
  CONCLUSIONS
  The production and/or maintenance of left hemispheric gamma oscillations appeared abnormal in participants with autism. We interpret these data as indicating that in autism, particular brain regions may be unable to generate the high-frequency activity likely necessary for binding and other forms of inter-regional interactions. These findings augment connectivity theories of autism with novel evidence that aberrations in local circuitry could underlie putative deficiencies in long-range neural communication.
authors.affiliation: Department of Psychiatry, Neuromagnetic Imaging Center, University of Colorado, Health Sciences Center, Denver, Colorado 80262, USA. Tony.Wilson@uchsc.edu
authors.forename: Tony W
authors.initials: TW
authors.lastname: Wilson
authors.forename: Donald C
authors.initials: DC
authors.lastname: Rojas
authors.forename: Martin L
authors.initials: ML
authors.lastname: Reite
authors.forename: Peter D
authors.initials: PD
authors.lastname: Teale
authors.forename: Sally J
authors.initials: SJ
authors.lastname: Rogers
mesh_terms: D000161:Acoustic Stimulation; D000293:Adolescent; D001303:Auditory Cortex / Q000502:physiology / Q000503:physiopathology; D001306:Auditory Pathways / Q000502:physiology* / Q000503:physiopathology; D001307:Auditory Perception / Q000502:physiology*; D001321:Autistic Disorder / Q000503:physiopathology*; D016022:Case-Control Studies; D002648:Child; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D015225:Magnetoencephalography; D016555:Matched-Pair Analysis; D012016:Reference Values