Deficits in Taste Identification, in the Context of Intact Taste Sensitivity, in Autism Spectrum Disorder

Background: Atypical sensory processing is widely appreciated as a symptom of autism spectrum disorder (ASD). Experimental data exists across all sensory domains, with a dearth of studies in the domain of gustation (i.e., taste) compared to other sensory domains (e.g., vision, audition). Gustation is important to consider in ASD, not only in the context of sensory processing, but also because atypical taste perception could contribute to the known feeding difficulties associated with ASD (e.g., picky eating). In addition, it remains unknown if taste perception differences exist more broadly across family members with ASD, or if they are specific to individuals with ASD. Taste perception can be evaluated at two levels, taste sensitivity and identification. Taste sensitivity is associated with brainstem functioning whereas taste identification relies on cortical processing networks. Assessing taste at these levels allows us to test for possibly dissociable differences in neural functioning in the context of gustation.

Objectives:  The purpose of this study was to assess gustation, at the level of both taste sensitivity and taste identification, across three groups: individuals with ASD, unaffected siblings of individuals with ASD, and typically developing (TD) controls.

Methods:  81 children, adolescents, and young adults (ages 10-25) with well-characterized ASD, 51 unaffected siblings, and 69 age- and IQ-matched TD controls completed two tasks assessing gustation. Electrogustometry was used to estimate taste sensitivity thresholds on both sides of the tongue using an adaptive staircase procedure. Taste identification was evaluated via “Taste Strips,” which assessed identification of sweet, sour, salty, and bitter stimuli, each presented at four concentration levels. A 3 (group) x 2 (side of tongue) mixed-model ANOVA was used to test for differences in taste sensitivity. A 3 (group) x 4 (taste) mixed-model ANOVA investigated differences in taste identification abilities. Follow-up tests were conducted accordingly.

Results: Analyses revealed similar electrogustometry thresholds across groups (F = 2.46, p > .05). In contrast, there were significant group differences in taste identification accuracy (main effect of group: F = 14.99, p < .001), with post-hoc Tukey tests indicating that individuals with ASD had significant deficits in overall taste identification compared to both unaffected siblings (p < .001) and TD controls (p < .001). However, there was no group x taste interaction (F = .63, p > .05), suggesting consistent impairment in ASD participants across all individual tastes.

Conclusions:  This study showed impaired taste identification in the context of intact taste sensitivity in ASD. This suggests that while brainstem functioning seems intact, cortical networks required for taste identification may be selectively disrupted ASD. Unaffected siblings were strikingly similar to TD controls, suggesting that deficits in taste identification is specific to the ASD phenotype and not represented more broadly in family members. Ongoing analyses are exploring gustatory misperceptions (via confusion matrix analyses) and examining how differences in taste perception impact restricted food preferences and vary in the parents of individuals with ASD.