Corrigendum to ‘Psilocybin induces spatially constrained alterations in thalamic functional organizaton and connectivity’: Neuroimage 2022 Oct 15;260:119434 (NeuroImage (2022) 260, (S1053811922005511), (10.1016/j.neuroimage.2022.119434))

The authors are writing to provide a correction to this article. Among other findings, we reported the results of correlations between subjective effects of psilocybin that were rated by study participants and measures of both thalamic engagement (section 3.2.3, Figure 5) and between-network connectivity (section 3.3.2, Figure 7) assessed using data derived from thalamic parcellation. Associations of interest were identified using a standard R-squared effect size ≥ 0.2 (accounting for 20% of explained variance). In the article, we did not report any p-values associated with those effect sizes. Upon further analysis, while several effects are significant before multiplicity correction, none of the reported correlations survive correction for multiple comparisons at alpha = 0.05, assessed using Bonferonni correction, correction for False Discovery Rate, and permutation analysis. This is likely due to a lack of power in our dataset (n=18), combined with the large number of comparisons being made (98 in Figure 5, 252 in Figure 7). We find more significant (uncorrected) associations (approximately 11%) than what would be expected by chance at alpha = 0.05 (5%), which suggests that a subset of the reported associations likely reflect relationships between subjective effects and psylocibin-associated changes in intra-thalamic and thalamo-cortical connectivity. However, it is not possible to distinguish which of those association are real versus spurious. Our analysis requires verification and replication in a well-powered sample. Alternatively, a multivariate approach may be a more appropriate lens through which to examine the associations between subjective effects of psilocybin and the brain changes we quantified, given that the individual measures within each domain are likely strongly interrelated. As a proof of concept, we performed a canonical correlation analysis (CCA) between the reported subjective effects and thalamic engagement counts, and found that the first canonical direction was significant at p = 0.03 based on a permutation test. This CCA revealed statistically significant multivariate patterns of association between changes to the functional organization of the thalamus and the subjective effects of psilocybin (with joy, equanimity, and overall strength of drug effect loading positively, and sacredness and fusion loading negatively on the first canonical direction).