Effects of Sensory Distractors on Interoceptive Processing in ASD

Background: Our sense of our body’s internal signals (“interoception”) influences our emotional states, so it is a parsimonious target of study to understand both sensory and emotional processing in autism spectrum disorders (ASD). There is emerging evidence that individuals with ASD show nuanced strengths and weaknesses in this sensory system compared to typical development (TD), and these nuances have been linked to emotional outcomes such as anxiety. However, the few studies of this sensory system in ASD so far have mostly considered interoception in isolation from other senses. This study aims to investigate the extent to which individuals attend to interoceptive cues in the presence of competing, external sensory information, as we are always processing our internal signals in the context of ongoing sights, sounds, or touch. Though individuals with ASD are generally more distracted by competing sensory information, prior data from our lab looking at heartbeat counting over different temporal intervals suggests that individuals’ with ASD may show more “sticky” attention to their internal signals (Schauder et al., 2015).

Objectives: The objective of this study was to investigate how a competing tactile signal affects the ability to perceive one’s heartbeat, compared in ASD versus TD.

Methods: N=45 participants (ASD: N=23, ages 8-43, TD: N=22, ages 6-53) completed a heartbeat counting task across each of four temporal intervals (25s, 35s, 45s, and 100s). Participants completed one block with distracting, 25 Hz vibrations of either “low” or “high” amplitude (randomized by participant) applied to their finger via a device, plus one block without any vibrotactile input. Reported number of heartbeats was compared to actual heartbeats, measured with a pulse oximeter. Accuracy data was analyzed with a mixed effects model predicting accuracy by distractor level per diagnostic group, including covariates of age by diagnosis (as in Mash et al., 2017) and IQ.

Results: The TD group showed resilience in performance across lengths and distractor levels (all coefficients n.s.). Qualitatively, the group showed a slight performance decrement in the high distractor condition (t=-0.39), consistent with the expected difficulty of this condition. Conversely, the ASD group showed a trend of worse performance in the low distractor condition (t=-1.90, p=0.058) but relatively better performance in the high distractor condition, compared to low. The results suggest a preliminary difference in the level of distractor to which the ASD group is most susceptible to distraction, compared to TD.

Conclusions: While this pattern of results is inconsistent with an overall group difference in tracking internal signals when distracted by other cues, they do suggest that the level that is most distracting may be different in ASD versus TD. The ASD group showed the greatest performance decrement in response to the low tactile distractor, whereas the TD group only showed somewhat of a decrement in response to the high tactile distractor. While this effect requires follow-up to confirm, future work will also consider the timing of low versus high pulses relative to the individual’s heartbeat, as the timing of multisensory inputs crucially affects their integration versus competition.