Abstract
Autism spectrum disorder (ASD) is characterized by hypersensitivities to sensory stimuli which may result from deficits in habituation, i.e., encoding temporal regularities in the environment and adapting predictions accordingly. Here, we investigate whether changes in pupil dilation—decreases of pupil diameter (PD) over time—are a useful biomarker for attenuated habituation to multisensory stimuli in young children with ASD.
Neurotypical (n = 27, M = 44.58 mos., SD = 14.14) and ASD (n = 7, M = 50.37 mos., SD = 15.76) participants viewed repeated audio-visual stimuli of varying complexity: from discrete beeps with continuous optic flow field to naturalistic movies. PD changes were tracked with the remote Eyelink 1000 plus tracker that allows free head movement. We extended preprocessing pipelines in the PsychoPhysiological Modeling toolbox to clean data and correct for blinks, saccades, and system artifacts.
Regression modeling indicated that neurotypical (NT) and ASD participants showed different PD trajectories with trial repetitions depending on stimulus complexity. In the lowest complexity condition (beeps), both groups showed attenuation of PD responses throughout the experiment. The time course and structure, however, differed: NT participants’ PD decreased linearly over time, while ASD participants’ PD followed a quadratic trajectory, i.e., pupil size increased through the first third of the experiment and decreased thereafter. In the more complex audio-visual animation condition, PD decreased quadratically with time in both groups. Neither group showed PD habituation to the most complex stimulus—the naturalistic movie scene.
These results provide preliminary evidence that pupillary responses can measure differences in sensory processing and habituation between NT and ASD groups. Our results also suggest that habituation differs for low and highly complex stimuli. Next, we will use computational modeling to identify finer-grained group differences in habituation to complex stimuli, with the goal of establishing a biomarker for habituation deficits in autism.