title: Atypical excitation-inhibition balance in autism captured by the gamma response to contextual modulation.
abstract: Atypical visual perception in people with autism spectrum disorders (ASD) is hypothesized to stem from an imbalance in excitatory and inhibitory processes in the brain. We used neuronal oscillations in the gamma frequency range (30-90 Hz), which emerge from a balanced interaction of excitation and inhibition in the brain, to assess contextual modulation processes in early visual perception. Electroencephalography was recorded in 12 high-functioning adults with ASD and 12 age- and IQ-matched control participants. Oscillations in the gamma frequency range were analyzed in response to stimuli consisting of small line-like elements. Orientation-specific contextual modulation was manipulated by parametrically increasing the amount of homogeneously oriented elements in the stimuli. The stimuli elicited a strong steady-state gamma response around the refresh-rate of 60 Hz, which was larger for controls than for participants with ASD. The amount of orientation homogeneity (contextual modulation) influenced the gamma response in control subjects, while for subjects with ASD this was not the case. The atypical steady-state gamma response to contextual modulation in subjects with ASD may capture the link between an imbalance in excitatory and inhibitory neuronal processing and atypical visual processing in ASD.
authors.affiliation: Department of Experimental Psychology, Helmholtz Institute, Utrecht University, P.O. Box 80140, 3508 TC Utrecht, The Netherlands ; Department of Developmental Psychology, Utrecht University, P.O. Box 80140, 3508 TC Utrecht, The Netherlands ; Radboud University Nijmegen, Donders Institute for Brain, Cognition and Behaviour, Centre for Cognitive Neuroimaging, P.O. Box 9101, NL-6500 HB Nijmegen, The Netherlands ; Radboud University Nijmegen, Centre for Language Studies, P.O. Box 9103, NL-6500 HD Nijmegen, The Netherlands.
authors.forename: Tineke M
authors.initials: TM
authors.lastname: Snijders
authors.forename: Branka
authors.initials: B
authors.lastname: Milivojevic
authors.forename: Chantal
authors.initials: C
authors.lastname: Kemner
keywords: Asperger's disorder; EEG; GABA; Gamma oscillations; Surround suppression; Visual perception