We conducted the same analysis as in human EEG (Fig. 2) in a previously published dataset (n=15 independent subjects for all panels; for experimental details, please refer to the original publication, ref. 33) with unpredictable fixation period durations (range 0.7 s-1.3 s). Decoding analyses were applied separately for data aligned to the onset of fixation (Fn, graded shading indicates range of possible stimulus onset times, upper panels) and aligned to the onset of the stimulus (Sn, graded shading indicates possible fixation onset times, lower panels). a, Tuning to previous-trial location (decoder trained in delay, 0.5s - 1.0s after stimulus onset) during previous-trial delay (left, stimulus aligned) vanishes in current-trial fixation (right, fixation onset aligned). No reactivation occurs. b, Average tuning reconstruction at different epochs for the delay decoder, indicated in a. c, Serial dependence separating trials with high (red curve, top quartile) from all other trials’ (black curve) decoding accuracy in early fixation (orange in a). Unlike in an experiment with predictable stimulus onset (Fig. 5), serial bias did not differ as a function of decoding strength. d, Difference in serial biases (Methods) between high-decoding and other trials were not significant at any time point in fixation. The black triangle marks the center of 0.2 s decoding window for the split in c. e-h, Parallel results were obtained when the analyses of panels a-d were run on data aligned to the time of stimulus onset instead of fixation onset. In d and h, time courses were smoothed using a squared filter of 5 samples. Periods with significant decoding in a,e are marked with black horizontal bars, indicating p<.001 in a two-sided bootstrap test. Shading indicates 95% C.I. in a,d,e,h, and ±s.e.m. in b,c,f,g.