HTR1A and sudden infant death syndrome: Figure 1 shows an example of these features while Table 3 shows the prevalence of these abnormalities in the original report (8) and in the SIDS analytic cohort from this report that have medullary 5-HT1A data. Of note, the prevalence of clusters of immature cells in the subgranular layer was higher (73.2% vs. 53.5%, p = 0.04) in the current SIDS cases compared to the prevalence in the published cases (Table 3). This may be due to sampling variation. The prevalences of the other hippocampal features were similar for the Kinney et al. (8) and present study.