Besides, time-frequency

decompositions of transient changes in EEG signals typically show low-frequency specificity, spanning frequencies across multiple octaves. Here, by contrast, the phasic modulation of decision weighing was fully circumscribed to the delta range ( Figure S5), consistent with a genuinely rhythmic process. Finally, we re-estimated delta phase using a non-Fourier-based approach, namely, the Hilbert transform, and obtained the same phasic modulation of decision weighting. To do so, we band-pass-filtered single-trial EEG signals between 1 and 4 Hz and estimated the analytic phase of the EEG signals at each time point from 0 to 1,000 ms following element k at parietal electrodes (see Experimental Procedures). The preferred phase with respect FRAX597 order to the decision weight wk shifted linearly over time from 100 to 750 ms following element k—hence spanning more than one delta cycle and confirming that the phasic modulation of decision weighting is not due to a single transient Roxadustat chemical structure change in EEG signals ( Figure 5C). Besides, entering simultaneously previous (k−1), current (k), and next (k+1) elements as separate

interaction terms showed overlapping influences of delta phase on the weighting of successive elements from 300 to 650 ms following element k (p < 0.05), with opposite preferred phases for current versus previous/next elements ( Figure 5D). Several features of the data strongly suggest that the phasic modulation of neural encoding and decision weighting was not occurring at a fixed subharmonic of the 4 Hz stimulation rate. Nevertheless, we sought to confirm that

the time courses of neural encoding (Figure 2) and decision weighting (Figure 3) also reflected endogenous cortical dynamics, rather than being mainly driven by the stimulation frequency f0. To do so, we obtained additional EEG data from an independent group of 17 participants who performed the same categorization task at a different stimulation rate of 3 Hz (see Supplemental Information). We compared the estimated neural encoding and decision weighting time courses between these two data sets (Figures 6 and S6). At both stimulation rates, the peak latencies of neural encoding and decision weighting did not differ significantly tuclazepam (paired t test, both p > 0.5). And critically, we found no difference in peak latencies for neural encoding and decision weighting between the two stimulation rates (two-sample t test; neural encoding: 508 ± 20 ms at 4 Hz, 552 ± 22 ms at 3 Hz, t30 = 1.4, p > 0.1; decision weighting: 518 ± 12 ms at 4 Hz, 532 ± 34 ms at 3 Hz, t30 < 1, p > 0.5). Furthermore, while the neural encoding and decision weighting profiles for element k peaked around the onset of element k+2 at a stimulation rate of 4 Hz (t test against 500 ms; neural encoding: t14 < 1, p > 0.5; decision weighting: t14 = 1.4, p > 0.