The Neural Basis of Event Simulation: An fMRI Study

<div><p>Event simulation (ES) is the situational inference process in which perceived event features such as objects, agents, and actions are associated in the brain to represent the whole situation. ES provides a common basis for various cognitive processes, such as perceptual prediction, situational understanding/prediction, and social cognition (such as mentalizing/trait inference). Here, functional magnetic resonance imaging was used to elucidate the neural substrates underlying important subdivisions within ES. First, the study investigated whether ES depends on different neural substrates when it is conducted explicitly and implicitly. Second, the existence of neural substrates specific to the future-prediction component of ES was assessed. Subjects were shown contextually related object pictures implying a situation and performed several picture–word-matching tasks. By varying task goals, subjects were made to infer the implied situation implicitly/explicitly or predict the future consequence of that situation. The results indicate that, whereas implicit ES activated the lateral prefrontal cortex and medial/lateral parietal cortex, explicit ES activated the medial prefrontal cortex, posterior cingulate cortex, and medial/lateral temporal cortex. Additionally, the left temporoparietal junction plays an important role in the future-prediction component of ES. These findings enrich our understanding of the neural substrates of the implicit/explicit/predictive aspects of ES-related cognitive processes.</p></div

Schematic depiction of a trial for each task and condition.

<p>In the Object task (cue “Same?”), the subject answered whether one of the three objects presented was congruent with the subsequently presented target word (i.e., object name). Three objects presented in the Con condition were contextually unrelated, and those in the Imp condition were contextually related and indicated a situation. In the Situation task (cue “Situation?”), the subject answered whether the target word was properly depicting the situation indicated by the object pictures. In the Future-prediction task (cue “After this?”), the subject answered whether the target word was properly depicting possible future events of the indicated situation.</p

Clusters of activation.

<p>Clusters with significant activation associated with implicit, explicit, or future prediction.</p><p>Significance level: p<0.001 with cluster correction for multiple comparisons (p<0.05).</p><p>(* p<0.001 uncorrected, **p<0.001 with cluster correction for multiple comparisons [p<0.06, k = 133]).</p>§<p>: activation peaks met the exclusion criteria described in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0096534#s2" target="_blank">Methods</a> & <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0096534#s3" target="_blank">Results</a> sections.</p><p>Size: Numbers of voxels. t value: maximum t value at the peak voxels.</p><p>x,y,z: MNI coordinates of peak voxel; TPJ: temporo-parietal junction.</p><p>dMPFC: dorsal medial prefrontal cortex; vMPFC: ventral medial prefrontal cortex.</p><p>ACC: anterior cingulate cortex.</p

Activation areas specific to the implicit and explicit event simulation (ES) processes.

<p>All voxels except for the regions described below are significant at a statistical threshold of <i>p</i><0.001, corrected to <i>p</i><0.05 for multiple comparisons using the cluster size, assuming the whole brain as the search volume. The result of the left parahippocampal cortex in the explicit ES process is thresholded at <i>p</i><0.001 (uncorrected). Error bars indicate standard deviations (SDs). IPL: inferior parietal lobule. PCC: posterior cingulate cortex. RSC: retrosplenial cortex. R: right. L: left. The coordinates in the Montreal Neurological Institute (MNI) standard space are indicated.</p

Activation areas specific to future prediction.

<p>The result is thresholded at <i>p</i><0.001, corrected to <i>p</i><0.06 (<i>k</i> = 133) for multiple comparisons. Error bars indicate SD. TPJ: temporoparietal junction. R: right. L: left. The coordinates in the MNI standard space are indicated.</p

Significant correlation between reaction time and the strength of high-gamma imaginary coherence or regional high-gamma power.

<p>(a) Reaction time <i>vs.</i> the strength of high-gamma imaginary coherence between the left IPS and the left MFG during the time window of 300 to 400 ms and (b) during the time window of 400 to 500 ms. (c) Reaction time <i>vs.</i> the strength of high-gamma imaginary coherence between the left IPS and the left MFG during the time window of 400 to 500 ms and (d) during the time window of 500 to 600 ms. (e) Reaction time <i>vs.</i> the high-gamma power in the left thalamus during the time window of 300 to 400 ms.</p

Time course of high-gamma power changes in each region of interest.

<p>Blue bars indicate significant differences between the non-target condition and the standard condition, while red bars indicate significant differences between the target condition and the standard condition (p<0.05, FDR corrected).</p

Time course of high-gamma power changes in response-locked analysis.

<p>Time course of high-gamma power changes in response-locked analysis.</p

High-gamma activity relevant to a 3-stimulus oddball task (p<0.05, FWE corrected).

<p>High-gamma activity relevant to a 3-stimulus oddball task (p<0.05, FWE corrected).</p

Experimental paradigm of 3-stimulus oddball task.

<p>Experimental paradigm of 3-stimulus oddball task.</p