Static perceptual model: and .

<p>The agent is exposed to the same sequence of sensory inputs described in the reference scenario (see <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003094#pcbi-1003094-g002" target="_blank">Figure 2</a> for legends). (top) The posterior expectation of converges to 0.5, which is the true probability of across the three (low and high volatility) stages. The agent is unaware of unexpected changes in the environment. (bottom left) The posterior variance (estimation uncertainty) of asymptotically converges to zero across trials . Negative (red circle) and positive (blue circle) valences are indicated when elicited over the trial. The size of the circles is proportional to the surprise of the sensory input at trial . (bottom right) The change in the posterior variance of from trial to trial as a function of negative (red circle) and positive (blue circle) valences.</p

Dynamic perceptual model: , and .

<p>A simulation of 320 trials. The first (low volatility), second (high volatility) and third (low volatility) stages are separated by vertical dashed lines. (top) The agent's posterior expectation that (red line) after sensory input (green dots), is plotted over the true probability that (black line), which is unknown to the agent. (bottom left) The time course of the posterior variance of over trials. The size of the black circles is proportional to the surprise of sensory input at trial . (bottom right) The change in the posterior variance of from trial to trial as a function of the surprise of sensory input at trial .</p

Basic forms of emotion and the dynamics of free-energy.

<p>(top and bottom rows) Two hypothetical dynamics of free-energy and their corresponding basic forms of emotion. (left column) Free-energy plotted as a function of time. (middle column) The same free-energy and its first time-derivative (valence) as a function of time. (right column) The first and second time-derivatives of the same trajectory of free-energy as a function of time. Notice that the basic forms of emotion are mapped to specific quadrants in the first and second time-derivative spaces independently of the free-energy trajectory. The black arrows indicate the direction of increasing time. The background colours identify the basic forms of emotion elicited at each time point: <i>happiness</i> (dark blue), <i>unhappiness</i> (dark red), <i>hope</i> (light blue), <i>fear</i> (light red), <i>relief</i> (transition from dark red to light blue), <i>disappointment</i> (transition from dark blue to light red) and <i>surprise</i> (grey).</p

Boxplots of the mean posterior variance of state after the elicitation of <i>factive</i> (<i>happiness</i> or <i>unhappiness</i>) and <i>epistemic</i> (<i>fear</i> or <i>hope</i>) emotions and before the observation of the next sensory input.

<p>(left) Mean posterior variance during the low volatility stages of the reference scenario. (right) Mean posterior variance during the high volatility stages of the reference scenario. The mean was computed for each of 100 simulations of the reference scenario. In both the low and high volatility stages, the mean was on average higher for the <i>epistemic</i> (low volatility: M = 0.68, SD = 0.03; high volatility: M = 1.07, SD = 0.19) than the <i>factive</i> (low volatility: M = 0.58, SD = 0.02; high volatility: M = 0.69, SD = 0.06) emotions and it was also on average higher during the high (M = 0.88, SD = 0.24) than the low volatility (M = 0.63, SD = 0.06) stages.</p

Basic forms of emotion and the dynamics of free-energy.

a<p>First time-derivative of free-energy at time .</p>b<p>Second time-derivative of free-energy at time .</p>c<p>Negative value very close to zero.</p>d<p>Positive value very close to zero.</p

Static perceptual model with valence: and

<p><b>.</b> The agent is exposed to the same sequence of sensory inputs described in the reference scenario (see <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003094#pcbi-1003094-g002" target="_blank">Figure 2</a> for legends). Now, the agent becomes extremely reactive to unexpected changes in the environment. (top) The posterior expectation of changes more quickly and is closer to the true probability of at each stage. (bottom left) The posterior variance (estimation uncertainty) maintains a constant baseline during the first and third (low volatility) stages mainly defined by the mood, but it fluctuates more widely during the second (high volatility) stage. This clarifies the distinction between the low and high volatility stages. Negative (red circle) and positive (blue circle) valences are clearly associated with increases and decreases in uncertainty, respectively, and they become more intense during the second (high volatility) stage. (bottom right) The posterior variance of from trial to trial increases after negative valence but decreases after positive valence.</p

Static perceptual model with valence: and .

<p>The agent is exposed to the same sequence of sensory inputs described in the reference scenario (see <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003094#pcbi-1003094-g002" target="_blank">Figure 2</a> for legends). Now, the agent becomes reactive to unexpected changes in the environment. (top) The posterior expectation of fluctuates around the true probability of at each stage in a manner similar to the dynamic perceptual model (see <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003094#pcbi-1003094-g002" target="_blank">Figure 2</a>). (bottom left) The posterior variance (estimation uncertainty) maintains a constant baseline during the first and third (low volatility) stages mainly defined by the mood, but starts to show a tendency to fluctuate more freely during the second (high volatility) stage. (bottom right) The change in the posterior variance of from trial to trial as a function of negative (red circle) and positive (blue circle) valences is quite similar to the standard static model (see <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003094#pcbi-1003094-g003" target="_blank">Figure 3</a>), except for a small offset defined by the mood.</p

Characteristics of the sample population.

<p>Characteristics of the sample population.</p

Statistical parametric mapping (SPM) showing clusters in the left pregenual anterior cingulate cortex and the right ventral premotor cortex.

<p>There are significant differences in gray matter volume between the PTSD and control groups.</p