Transient and steady-state auditory gamma-band responses in first-degree relatives of people with autism spectrum disorder

Magnetoencephalography (MEG) recordings in 21 parents who had a child with an autism spectrum disorder (pASD) and 20 healthy adult control subjects (HC) were obtained. Gamma-band phase locking factor (PLF), and evoked and induced power to 32, 40 and 48 Hz amplitude-modulated sounds were measured for transient and steady-state responses. Participants were also tested on a number of behavioral and cognitive assessments related to the broad autism phenotype (BAP).Reliable group differences were seen primarily for steady-state responses. In the left hemisphere, pASD subjects exhibited lower phase-locked steady-state power in all three conditions. Total γ-band power, including the non-phase-locked component, was also reduced in the pASD group. In addition, pASD subjects had significantly lower PLF than the HC group. Correlations were seen between MEG measures and BAP measures.The reduction in steady-state γ-band responses in the pASD group is consistent with previous results for children with ASD. Steady-state responses may be more sensitive than transient responses to phase-locking errors in ASD. Together with the lower PLF and phase-locked power in first-degree relatives, correlations between γ-band measures and behavioral measures relevant to the BAP highlight the potential of γ-band deficits as a potential new autism endophenotype.Autism spectrum disorders (ASD) are clinically defined by impairments in social interaction and communication and by restricted/stereotyped behaviors. The prevalence for ASD, which includes autistic disorder, Asperger's syndrome and pervasive developmental disorder - not otherwise specified, is estimated to be as high as 1 in 110 [CDC, [1]]. Although diagnosable medical conditions, including genetic syndromes, are estimated to account for as many as 10% of cases, most cases remain idiopathic [2,3]. Family studies indicate that idiopathic ASD is highly heritable [4,5], with an estimated heritability as high as 90%. Studies of first-degree re