P3-7. Neurophysiological profile of acoustic startle response in Japanese children with autism spectrum disorders

The acoustic startle response (ASR) is considered the promising neurophysiological measurements for translational research in psychiatry. A numbers of individuals with autism spectrum disorders (ASD) exhibit enhanced auditory perception; however, ASR to weak stimuli remains unclear. Here, we evaluated the basic profile of ASR with weak and strong stimuli in Japanese children with ASD. The subjects were 10 Japanese children with ASD and 34 with typical development (TD). The electromyographic activity of the left orbicularis oculi muscle to pulse stimuli of 65–110 dB SPL, in increments of 5 dB, was measured to evaluate ASR. The electroencephalogram (EEG) was also recorded during the testing. Quantitative autistic traits were assessed by Social Responsive Scale (SRS). Magnitude of ASR to weak stimuli (70 dB) was greater in ASD individuals, and was associated with SRS social awareness subscale scores. The peak startle latency was prolonged in ASD individuals, and was associated with SRS social cognition and autistic mannerism subscales. The EEG current source density distribution was atypical in ASD compared to TD group. A comprehensive investigation of ASR, including the magnitude of startle responses to weak stimuli and peak startle latency, might enhance understanding of the atypical neurophysiological mechanisms underlying ASD.