SPLTRAK Abstract Submission
Behavioral and Neurophysiological Mechanisms Underlying Responses to Olfactory Volatility in Autism
Valentina Parma1,2, Michele Furlan2, David N Top3, Kevin Stephenson3, Mikle South3
1William James Center for Reseach, Lisbon, Portugal
2International School for Advanced Studies, Trieste, Italy
3Brigham Young University, Provo, UT, United States

Odor stimuli are naturally volatile and dynamic stimuli, and constitute a test-bed for the volatility of sensory environmen often overestimated by adults with autism spectrum disorder (ASD). At the behavioral level, overestimating the change in sensory environment should correspond to longer times and reduced accuracy in discrimination tasks. At the neural level, this behavior is expected to be grounded in the functioning of areas known to preferentially encode features (e.g., quality) and sensitive to repeated exposures (i.e., piriform cortex). We assessed these hypotheses by asking to 20 adults with ASD (8F) and 14 (8F) typical controls (TD) to participate to a discrimination task and an fMRI a cross-adaptation task. Participants smelled 40 pairs of odorants that could share the same perceptual quality (e.g., minty/floral) or the same chemical group (e.g., ketones/alcohols) to decide whether the two odorants were different. As expected, individuals with ASD are slower than TD in discriminating the same quality, and as slow as TD in discriminating different qualities. Discriminating chemical group takes longer in ASD. The accuracy for the different odor qualities in the ASD group is reduced compared to the TD group. Whole-brain and representational similarity analyses, with specific interest in the piriform cortex, are ongoing. Preliminary data suggest suppression of activity following the presentation of two stimuli sharing one feature in the TD but not in the ASD group. The odor­ evoked activity in posterior piriform cortex significantly decreased (cross­-adapted) in response to qualitatively similar, but not to chemically similar, odorant pairs in TD, but not in ASD. Our findings offer novel insights into the behavioral and physiological mechanisms underlying sensory volatility in ASD.