Error bar plots of pyramidal (A) and dopaminergic midbrain (B) activity under stochastic mesocortical dynamics during delay interval.

The solid red (magenta) circles represent working memory-associated mean pyramidal (midbrain) activities and the blue error bars denote standard deviations around the mean activities at different dopamine releasability W34, in the presence of noisy circuit dynamics. The solid black circles represent pyramidal (midbrain) activities obtained from deterministic mesocortical dynamics and constitutes the signal profile. In the optimal region (green zone), the mean pyramidal (midbrain) activity is associated with least noisy fluctuations and coincides with the pyramidal (midbrain) activity of the signal profile. In the region of low dopamine releasability (left, red zone), the pyramidal (midbrain) activity shows dramatic fluctuations such that the mean activity significantly deviates away from the sustained-firing state and shifts towards the spontaneous-activity state. In the region of high dopamine releasability (right, red zone), there does not occur a noticeable deviation of the mean pyramidal (midbrain) activity from the sustained firing state, but, indeed contains significant fluctuations as compared to the optimal region. As evident, the pyramidal and midbrain activity demonstrates a tightly-linked response with regard to their relative noise content.