We linked our observations to the model as follows. (i) Observed phenomenon: M1 PAC was significantly and constantly higher in freezing trials than in non-freezing trials (Figs. 2 and 3) and was correlated with freezing severity during stable walking (Fig. 4). Reflected in the model: M1 PAC was indicative of the baseline occupation. When holding the dynamic fluctuation and bandwidth limit on, the higher the baseline occupation was, the higher the chance freezings were to occur. (ii) Observed phenomenon: freezings were more likely to occur during dual-task trials, which, however, were not associated with high PAC. Contrarily, if picking only the non-freezing trials, dual-tasks were accompanied with a lower PAC (Fig. 2D–F). Reflected in the model: a higher chance of freezing in dual-task trials was the result of the elevated dynamic fluctuation rather than the baseline occupation. While due to the larger fluctuation, only trials with low baseline occupation could avoid exceeding bandwidth limit, resulting in the observed low PAC in non-freezing dual-task trials. (iii) Observed phenomenon: stimulation significantly reduced PAC while simultaneously improving freezing. The STIM-induced reduction of PAC
