The Relation Between Locomotor Dynamics and the Acoustic Startle Response and Its Modulation in Children with Typical Development and Those with Autism Spectrum Disorders
Objectives: The objective of this study was to investigate the relationship between locomotor dynamics and the profile of the acoustic startle response (ASR) and its modulation in children with ASD and typical development (TD).
Methods: ASR and its modulation, including prepulse inhibition (PPI), was investigated in 14 children with ASD and 13 children with TD. The electromyographic activity of the left orbicularis oculi muscle to acoustic stimuli of 65 to 105 dB sound pressure level, in increments of 10 dB, was measured to evaluate ASR. Average eyeblink magnitude for each acoustic stimuli intensity and average peak startle latency of ASR was evaluated. Locomotor activity i.e. spontaneous physical activity in daily life, was also continuously measured by a watch-type actigraph during a long school vacation. We examined sleep measures, including sleep latency, as well as locomotor activity statistics, including the mean and skewness of all day and daytime activity.
Results: Compared to in the TD group, among ASD children the skewness of all day activity was negative and highly statistically significant, while the skewness of daytime activity was also negative but at a borderline level of statistical significance. For all children combined, actigraph measured sleep latency was significantly related to PPI at the prepulse intensity of 70 dB (PPI70). Increased mean and higher negative skewness values for all day activity were significantly related to reduced PPI70, while for daytime activity these values were associated with a greater ASR magnitude to weak stimuli of 65 dB. Conclusions: Hyper-reactivity, examined as ASR magnitude to weak stimuli was related to locomotor activity, characterized by higher mean and higher negative skewness values during daytime, and reduced sensorimotor gating examined as PPI, to these values occurring all day. PPI was also related to sleep latency. The comprehensive investigation of locomotor activity as well as ASR and its modulation, including PPI, might extend understanding of the neurophysiological basis underlying ASD and other psychiatric problems in children.
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