Figure 2.

Neural populations are thought to interact via sigmoidal activation functions, helping explain widespread FC decreases from resting to task states. A, Spiking model simulation results from Ito et al. (2020a), showing sigmoidal relationship between inputs and outputs of neural populations. B, Activity increases and decreases from resting state in the spiking model (Ito et al., 2020a) resulted in decreased variance and correlations in simulated excitatory neurons. Empirical results in both spiking populations and fMRI show that variance and correlations decrease as activity levels increase or decrease from resting state (He, 2013; Ito et al., 2020a). C, There is substantial evidence that biological neural populations have a sigmoidal relationship, which could help explain well known neural variability quenching effects from rest to task (He, 2013) as well as reductions in FC from rest to task (Ito et al., 2020a). The relationship between activity levels across neural populations (i.e., FC) changes as a function of overall activity levels. Figure adapted from Ito et al. (2020a).