Intrinsic timescale develops hierarchically from sensorimotor to association cortex in youth and stabilizes in adulthood

Key results

1. 01

   ShownIn the Human Connectome Project-Development (HCPD) cohort, cortex-wide mean timescale rises with age from 8 to 22 years. The rise comes from association regions while sensorimotor regions stay stable, so regional age effects follow the sensorimotor-association (S-A) axis.

   Whole-brain generalized additive model (GAM) partial R^2 = 0.047, p_anova = 1.25 x 10^-7 (n=565; sex and mean framewise displacement as covariates); regional age effects vs S-A axis rank rs = 0.41, p_spin = 0.001; a within-subject S-A differentiation index also rose with age (partial R^2 = 0.025, p_anova = 0.0007; direct t-value version 0.026, p_anova = 9.36 x 10^-5). · Neurodevelopmental patterns in intrinsic…; Generalized Additive Model (GAM); Sensorimotor-association timescale…; Figure legends

2. 02

   ShownThe pattern replicates in the independent Healthy Brain Network (HBN) cohort, but with weaker S-A alignment and fewer significant regions than HCPD. In both cohorts, the S-A alignment of age-related change peaks in early-to-mid adolescence.

   HBN (n=729) whole-brain partial R^2 = 0.037, p_anova = 1.13 x 10^-7; age effects vs S-A axis rs = 0.19, p_spin = 0.02; HCPD vs HBN age-effect maps rs = 0.30, p_spin = 0.0002; regions significant after false discovery rate (FDR) correction 46.5% (HCPD) vs 22.5% (HBN), overlap Dice = 0.42, p_spin = 0.0008; peak S-A alignment at 14.6 years (HCPD) and 12.8 years (HBN). · Findings replicate in an independent…; Age of maximum alignment between age-related…; Figure legends

3. 03

   ShownIn Human Connectome Project-Young Adults (HCPYA) participants aged 22-37, the mean timescale map still follows the S-A axis. Age effects, however, are small, mostly non-significant and not organized along the axis.

   HCPYA (n=973): mean map vs S-A axis rs = 0.4, p_spin = 0.01; association vs sensorimotor t = 7.5, p_spin = 0.02; whole-brain partial R^2 = −0.004, p_anova = 0.04; 11.7% of regions with significant age effects; age effects vs S-A axis rs = −0.1, p_spin = 0.58. · Timescale remains relatively stable in adulthood; Figure legends

4. 04

   ShownIn both youth cohorts, average timescale is longer in association than in sensorimotor cortex, and the two group maps agree. However, the map's correlation with the continuous S-A axis ranking is significant only in HCPD.

   Association vs sensorimotor: HCPD t = 7.8, p_spin = 0.01; HBN t = 6.6, p_spin = 0.04 (two-tailed). HCPD vs HBN mean maps rs = 0.76, p_spin = 0.0002. Mean map vs S-A axis: HCPD rs = 0.37, p_spin = 0.03; HBN rs = 0.27, p_spin = 0.12. · Intrinsic timescale is longer in association…; Figure legends

5. 05

   SuggestedAge effects held across covariate, atlas, site and subsample checks and two other full-autocorrelation definitions. Lag-1 temporal autocorrelation (lag-1 TA) gave a different mean map and age effects without significant S-A alignment, and the main measure's age effects rest mostly on long-lag autocorrelation.

   HCPD Schaefer-200: whole-brain partial R^2 = 0.041, p_anova = 9.86 x 10^-7; results consistent with estimated total intracranial volume as covariate, CovBat-GAM site harmonization and two N=600 HBN subsets. HCPD lag-1 TA: whole-brain partial R^2 = 0.008, p_anova = 0.03; 28.2% of regions significant; age effects not significantly related to S-A axis but correlated with the main measure's age effects. · Sensitivity analysis; Intrinsic timescale estimated using lag-1…; Short- and long-lag contributions to intrinsic…; Figure legends