Fig. 8:

Mean field model simulation results of non-evoked nociception and placebo/nocebo effects under the chronic pain condition. (A) Simulated midline envelope trace of ACC synaptic activation variable s in non-evoked nociception under naive (blue) and chronic pain (red) conditions, for an initial top-down expectation z(0) = 3.0. (B) Similar to panel A, except for z(0) = 4.5. At low z(0), the fraction of time above threshold during T_s (between the stimulus onset and withdrawal) was longer in the chronic pain condition; at high z(0), the fraction was similar between the two conditions. (C) Fraction of time during T_s that ACC synaptic activation variable was above the threshold (horizontal dashed line) for various top-down expectation z(0) in naive (blue) and chronic pain (red) conditions. The curve has a sigmoidal shape and shifts leftward from naive to chronic pain condition. 100 Monte Carlo trials were run with random z(0) ∈ [1.5, 5.0]. Mean and SEM for each group are plotted. (D) Comparison of average ACC synaptic activation in placebo/nocebo effects under naive (blue) and chronic pain (red) conditions for various initial top-down expectation z(0), where z(0) < 0 and z(0) > 0 represent the placebo and nocebo effects, respectively. The synaptic activation s of total ACC population increased monotonically, and shifted upward from the naive to chronic pain condition. (E) Similar to panel D, except for ACC subpopulations E_2-1 (w/ S1 input) and E_2-2 (w/o S1 input). The subpopulation E_2-1 had a similar shape of the total population, while E_2-2 did not increase much from the naive to chronic pain condition. 100 Monte Carlo trials were run with random z(0) ∈ [−4.0, 4.0]. Mean and SEM are plotted for each group.