Fig. 3: Multivariate power changes with probe uncertainty during stimulus encoding.

a, b Topographies of stimulus-evoked power changes relative to pre-stimulus baseline (a, see Supplementary Fig. 4a) and load-related power modulation (b). With increasing attentional demands, theta and “broadband” gamma power increased, whereas alpha rhythms desynchronized. Asterisks indicate the sensors across which data were averaged for presentation in c and d. Topographies indicate maximum (theta/gamma) or minimum (alpha range) bootstrap ratios (BSR) across time. c Temporal traces of band-limited power as a function of target load, extracted from the channels presented in a/b (mean ± within-subject SEM; n = 47 participants). d, e Multivariate loading pattern for d spectral power changes under uncertainty and e associated multivariate brain scores at different levels of target load (n = 47 participants; ***p = 8.6e−20; linear: b = 3.33, 95% CI = [2.82, 3.84], t(46) = 13.11, p = 3.9e−17). Black horizontal bars in panel d indicate discrete frequency ranges or sensors (shown in a/b). Data in d represent across-channel average BSR levels (each channel was first thresholded at a BSR of 3). These average BSRs thus provide a relative metric about how often the threshold was exceeded across channels, and every non-zero value in d indicates the presence of supra-threshold BSR values. Panel e indicates p values from two-tailed paired t-test; pairwise comparisons were Benjamini–Hochberg-adjusted for multiple comparisons. f, g Participants with stronger multivariate power modulation exhibit stronger drift rates for single targets (f; n = 47 participants, Pearson’s correlation) as well as stronger drift rate decreases under uncertainty (g). In g, dots represent linear model residuals (see “Methods”; n = 188: participants × target condition), colored by participant. Coupled changes across target conditions are indicated by the black line. We indicate the direction of main effects (first drift rate, then SPMC) via + and − (− = small decreases, −− = large decreases, + = small increases, ++ = large increases). SPMC spectral power modulation component. Source data are provided as a Source Data file.