*3.2. ROI Analyses*

Table 2 shows the *k*icer values in striatal ROIs and their associations with the AQ total and subscale scores. We found no significant differences in the striatal *k*icer values between ASD and controls. Moreover, within the control sample, and within the combined ASD and control sample, we found no significant associations between the AQ scores and striatal *k*icer values. In contrast, in the ASD sample, *k*icer values in the whole striatum, putamen, and nucleus accumbens were significantly negatively associated with AQ attention to detail subscale scores. These associations remained negative when we examined the results without adjusting for confounders or for the two PET/CT scanners separately, although they became statistically non-significant. No other statistically significant associations were observed.

**Table 2.** Striatal [18F]-FDOPA uptake (*k*icer min−1) in ASD adults and controls, and its association with self-reported autistic traits.


ASD, autism spectrum disorder; AQ, autism spectrum quotient; SD, standard deviation; ROI, region of interest; total, AQ total scores; social, AQ social interaction subscale scores; and detail, AQ attention to detail subscale scores. Analyses adjusted for age, sex, smoking status, and PET/CT scanner type. a, as reported in [9].

> Bayesian analyses supported the observed null findings over the alternative hypotheses (Supplementary Method S2 and Supplementary Table S1). Notably, these analyses also did not provide support for a relationship between AQ attention to detail subscale scores and *k*icer values.
