RESUMEN
Studies on social cognition often use complex visual stimuli to asses neural processes attributed to abilities like "mentalizing" or "Theory of Mind" (ToM). During the processing of these stimuli, eye gaze, however, shapes neural signal patterns. Individual differences in neural operations on social cognition may therefore be obscured if individuals' gaze behavior differs systematically. These obstacles can be overcome by the combined analysis of neural signal and natural viewing behavior. Here, we combined functional magnetic resonance imaging (fMRI) with eye-tracking to examine effects of unconstrained gaze on neural ToM processes in healthy individuals with differing levels of emotional awareness, i.e. alexithymia. First, as previously described for emotional tasks, people with higher alexithymia levels look less at eyes in both ToM and task-free viewing contexts. Further, we find that neural ToM processes are not affected by individual differences in alexithymia per se. Instead, depending on alexithymia levels, gaze on critical stimulus aspects reversely shapes the signal in medial prefrontal cortex (MPFC) and anterior temporoparietal junction (TPJ) as distinct nodes of the ToM system. These results emphasize that natural selective attention affects fMRI patterns well beyond the visual system. Our study implies that, whenever using a task with multiple degrees of freedom in scan paths, ignoring the latter might obscure important conclusions.
