Causal contributions of the dorsolateral prefrontal cortex and temporoparietal junction to source and reality monitoring

Source and reality monitoring enable individuals to distinguish the origins of remembered information, including whether information was self- or other-generated and whether it was perceived or imagined. Although the dorsolateral prefrontal cortex (dlPFC) and temporoparietal junction (TPJ) have been implicated in these processes, their independent causal contributions remain unclear. We investigated whether focal transcranial direct current stimulation (f-tDCS) of the left dlPFC and left TPJ differentially modulates source and reality monitoring. One hundred participants were randomly assigned to receive anodal or sham stimulation of the left dlPFC or TPJ before completing an episodic memory task manipulating agent (self, experimenter), context (spoken, imagined), and emotional valence (positive, negative). Discrimination sensitivity (d⍰) and response criterion (c) were examined separately. For source monitoring, stimulation interacted with context and cortical region: anodal dlPFC stimulation was associated with a greater spoken-imagined difference in self-experimenter discrimination than sham stimulation, whereas no equivalent context-dependent effect emerged following TPJ stimulation. For reality monitoring, stimulation effects also differed by cortical target, with reduced spoken-imagined discrimination following anodal relative to sham TPJ stimulation and no significant effect of dlPFC stimulation. These effects were not accompanied by corresponding stimulation effects on response criterion. Independent of stimulation, source discrimination was substantially greater for spoken than imagined information, while reality-monitoring sensitivity was enhanced for self-generated relative to experimenter-generated negative information. Together, these findings provide evidence that the dlPFC and TPJ make dissociable contributions to source and reality monitoring, while highlighting the importance of contextual and affective features in determining how the origins of memories are evaluated.